// Bindings for the Orca platform
//
// See: [[ https://orca-app.dev ]]

package orca

import "core:c"

char :: c.char

// currently missing in the api.json
pool :: struct {
	arena: arena,
	freeList: list,
	blockSize: u64,
}

UNICODE_BASIC_LATIN :: unicode_range { 0x0000, 127 }
UNICODE_C1_CONTROLS_AND_LATIN_1_SUPPLEMENT :: unicode_range { 0x0080, 127 }
UNICODE_LATIN_EXTENDED_A :: unicode_range { 0x0100, 127 }
UNICODE_LATIN_EXTENDED_B :: unicode_range { 0x0180, 207 }
UNICODE_IPA_EXTENSIONS :: unicode_range { 0x0250, 95 }
UNICODE_SPACING_MODIFIER_LETTERS :: unicode_range { 0x02b0, 79 }
UNICODE_COMBINING_DIACRITICAL_MARKS :: unicode_range { 0x0300, 111 }
UNICODE_GREEK_COPTIC :: unicode_range { 0x0370, 143 }
UNICODE_CYRILLIC :: unicode_range { 0x0400, 255 }
UNICODE_CYRILLIC_SUPPLEMENT :: unicode_range { 0x0500, 47 }
UNICODE_ARMENIAN :: unicode_range { 0x0530, 95 }
UNICODE_HEBREW :: unicode_range { 0x0590, 111 }
UNICODE_ARABIC :: unicode_range { 0x0600, 255 }
UNICODE_SYRIAC :: unicode_range { 0x0700, 79 }
UNICODE_THAANA :: unicode_range { 0x0780, 63 }
UNICODE_DEVANAGARI :: unicode_range { 0x0900, 127 }
UNICODE_BENGALI_ASSAMESE :: unicode_range { 0x0980, 127 }
UNICODE_GURMUKHI :: unicode_range { 0x0a00, 127 }
UNICODE_GUJARATI :: unicode_range { 0x0a80, 127 }
UNICODE_ORIYA :: unicode_range { 0x0b00, 127 }
UNICODE_TAMIL :: unicode_range { 0x0b80, 127 }
UNICODE_TELUGU :: unicode_range { 0x0c00, 127 }
UNICODE_KANNADA :: unicode_range { 0x0c80, 127 }
UNICODE_MALAYALAM :: unicode_range { 0x0d00, 255 }
UNICODE_SINHALA :: unicode_range { 0x0d80, 127 }
UNICODE_THAI :: unicode_range { 0x0e00, 127 }
UNICODE_LAO :: unicode_range { 0x0e80, 127 }
UNICODE_TIBETAN :: unicode_range { 0x0f00, 255 }
UNICODE_MYANMAR :: unicode_range { 0x1000, 159 }
UNICODE_GEORGIAN :: unicode_range { 0x10a0, 95 }
UNICODE_HANGUL_JAMO :: unicode_range { 0x1100, 255 }
UNICODE_ETHIOPIC :: unicode_range { 0x1200, 383 }
UNICODE_CHEROKEE :: unicode_range { 0x13a0, 95 }
UNICODE_UNIFIED_CANADIAN_ABORIGINAL_SYLLABICS :: unicode_range { 0x1400, 639 }
UNICODE_OGHAM :: unicode_range { 0x1680, 31 }
UNICODE_RUNIC :: unicode_range { 0x16a0, 95 }
UNICODE_TAGALOG :: unicode_range { 0x1700, 31 }
UNICODE_HANUNOO :: unicode_range { 0x1720, 31 }
UNICODE_BUHID :: unicode_range { 0x1740, 31 }
UNICODE_TAGBANWA :: unicode_range { 0x1760, 31 }
UNICODE_KHMER :: unicode_range { 0x1780, 127 }
UNICODE_MONGOLIAN :: unicode_range { 0x1800, 175 }
UNICODE_LIMBU :: unicode_range { 0x1900, 79 }
UNICODE_TAI_LE :: unicode_range { 0x1950, 47 }
UNICODE_KHMER_SYMBOLS :: unicode_range { 0x19e0, 31 }
UNICODE_PHONETIC_EXTENSIONS :: unicode_range { 0x1d00, 127 }
UNICODE_LATIN_EXTENDED_ADDITIONAL :: unicode_range { 0x1e00, 255 }
UNICODE_GREEK_EXTENDED :: unicode_range { 0x1f00, 255 }
UNICODE_GENERAL_PUNCTUATION :: unicode_range { 0x2000, 111 }
UNICODE_SUPERSCRIPTS_AND_SUBSCRIPTS :: unicode_range { 0x2070, 47 }
UNICODE_CURRENCY_SYMBOLS :: unicode_range { 0x20a0, 47 }
UNICODE_COMBINING_DIACRITICAL_MARKS_FOR_SYMBOLS :: unicode_range { 0x20d0, 47 }
UNICODE_LETTERLIKE_SYMBOLS :: unicode_range { 0x2100, 79 }
UNICODE_NUMBER_FORMS :: unicode_range { 0x2150, 63 }
UNICODE_ARROWS :: unicode_range { 0x2190, 111 }
UNICODE_MATHEMATICAL_OPERATORS :: unicode_range { 0x2200, 255 }
UNICODE_MISCELLANEOUS_TECHNICAL :: unicode_range { 0x2300, 255 }
UNICODE_CONTROL_PICTURES :: unicode_range { 0x2400, 63 }
UNICODE_OPTICAL_CHARACTER_RECOGNITION :: unicode_range { 0x2440, 31 }
UNICODE_ENCLOSED_ALPHANUMERICS :: unicode_range { 0x2460, 159 }
UNICODE_BOX_DRAWING :: unicode_range { 0x2500, 127 }
UNICODE_BLOCK_ELEMENTS :: unicode_range { 0x2580, 31 }
UNICODE_GEOMETRIC_SHAPES :: unicode_range { 0x25a0, 95 }
UNICODE_MISCELLANEOUS_SYMBOLS :: unicode_range { 0x2600, 255 }
UNICODE_DINGBATS :: unicode_range { 0x2700, 191 }
UNICODE_MISCELLANEOUS_MATHEMATICAL_SYMBOLS_A :: unicode_range { 0x27c0, 47 }
UNICODE_SUPPLEMENTAL_ARROWS_A :: unicode_range { 0x27f0, 15 }
UNICODE_BRAILLE_PATTERNS :: unicode_range { 0x2800, 255 }
UNICODE_SUPPLEMENTAL_ARROWS_B :: unicode_range { 0x2900, 127 }
UNICODE_MISCELLANEOUS_MATHEMATICAL_SYMBOLS_B :: unicode_range { 0x2980, 127 }
UNICODE_SUPPLEMENTAL_MATHEMATICAL_OPERATORS :: unicode_range { 0x2a00, 255 }
UNICODE_MISCELLANEOUS_SYMBOLS_AND_ARROWS :: unicode_range { 0x2b00, 255 }
UNICODE_CJK_RADICALS_SUPPLEMENT :: unicode_range { 0x2e80, 127 }
UNICODE_KANGXI_RADICALS :: unicode_range { 0x2f00, 223 }
UNICODE_IDEOGRAPHIC_DESCRIPTION_CHARACTERS :: unicode_range { 0x2ff0, 15 }
UNICODE_CJK_SYMBOLS_AND_PUNCTUATION :: unicode_range { 0x3000, 63 }
UNICODE_HIRAGANA :: unicode_range { 0x3040, 95 }
UNICODE_KATAKANA :: unicode_range { 0x30a0, 95 }
UNICODE_BOPOMOFO :: unicode_range { 0x3100, 47 }
UNICODE_HANGUL_COMPATIBILITY_JAMO :: unicode_range { 0x3130, 95 }
UNICODE_KANBUN_KUNTEN :: unicode_range { 0x3190, 15 }
UNICODE_BOPOMOFO_EXTENDED :: unicode_range { 0x31a0, 31 }
UNICODE_KATAKANA_PHONETIC_EXTENSIONS :: unicode_range { 0x31f0, 15 }
UNICODE_ENCLOSED_CJK_LETTERS_AND_MONTHS :: unicode_range { 0x3200, 255 }
UNICODE_CJK_COMPATIBILITY :: unicode_range { 0x3300, 255 }
UNICODE_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A :: unicode_range { 0x3400, 6591 }
UNICODE_YIJING_HEXAGRAM_SYMBOLS :: unicode_range { 0x4dc0, 63 }
UNICODE_CJK_UNIFIED_IDEOGRAPHS :: unicode_range { 0x4e00, 20911 }
UNICODE_YI_SYLLABLES :: unicode_range { 0xa000, 1167 }
UNICODE_YI_RADICALS :: unicode_range { 0xa490, 63 }
UNICODE_HANGUL_SYLLABLES :: unicode_range { 0xac00, 11183 }
UNICODE_HIGH_SURROGATE_AREA :: unicode_range { 0xd800, 1023 }
UNICODE_LOW_SURROGATE_AREA :: unicode_range { 0xdc00, 1023 }
UNICODE_PRIVATE_USE_AREA :: unicode_range { 0xe000, 6399 }
UNICODE_CJK_COMPATIBILITY_IDEOGRAPHS :: unicode_range { 0xf900, 511 }
UNICODE_ALPHABETIC_PRESENTATION_FORMS :: unicode_range { 0xfb00, 79 }
UNICODE_ARABIC_PRESENTATION_FORMS_A :: unicode_range { 0xfb50, 687 }
UNICODE_VARIATION_SELECTORS :: unicode_range { 0xfe00, 15 }
UNICODE_COMBINING_HALF_MARKS :: unicode_range { 0xfe20, 15 }
UNICODE_CJK_COMPATIBILITY_FORMS :: unicode_range { 0xfe30, 31 }
UNICODE_SMALL_FORM_VARIANTS :: unicode_range { 0xfe50, 31 }
UNICODE_ARABIC_PRESENTATION_FORMS_B :: unicode_range { 0xfe70, 143 }
UNICODE_HALFWIDTH_AND_FULLWIDTH_FORMS :: unicode_range { 0xff00, 239 }
UNICODE_SPECIALS :: unicode_range { 0xfff0, 15 }
UNICODE_LINEAR_B_SYLLABARY :: unicode_range { 0x10000, 127 }
UNICODE_LINEAR_B_IDEOGRAMS :: unicode_range { 0x10080, 127 }
UNICODE_AEGEAN_NUMBERS :: unicode_range { 0x10100, 63 }
UNICODE_OLD_ITALIC :: unicode_range { 0x10300, 47 }
UNICODE_GOTHIC :: unicode_range { 0x10330, 31 }
UNICODE_UGARITIC :: unicode_range { 0x10380, 31 }
UNICODE_DESERET :: unicode_range { 0x10400, 79 }
UNICODE_SHAVIAN :: unicode_range { 0x10450, 47 }
UNICODE_OSMANYA :: unicode_range { 0x10480, 47 }
UNICODE_CYPRIOT_SYLLABARY :: unicode_range { 0x10800, 63 }
UNICODE_BYZANTINE_MUSICAL_SYMBOLS :: unicode_range { 0x1d000, 255 }
UNICODE_MUSICAL_SYMBOLS :: unicode_range { 0x1d100, 255 }
UNICODE_TAI_XUAN_JING_SYMBOLS :: unicode_range { 0x1d300, 95 }
UNICODE_MATHEMATICAL_ALPHANUMERIC_SYMBOLS :: unicode_range { 0x1d400, 1023 }
UNICODE_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B :: unicode_range { 0x20000, 42719 }
UNICODE_CJK_COMPATIBILITY_IDEOGRAPHS_SUPPLEMENT :: unicode_range { 0x2f800, 543 }
UNICODE_TAGS :: unicode_range { 0xe0000, 127 }
UNICODE_VARIATION_SELECTORS_SUPPLEMENT :: unicode_range { 0xe0100, 239 }
UNICODE_SUPPLEMENTARY_PRIVATE_USE_AREA_A :: unicode_range { 0xf0000, 65533 }
UNICODE_SUPPLEMENTARY_PRIVATE_USE_AREA_B  :: unicode_range { 0x100000, 65533 }

file_write_slice :: proc(file: file, slice: []char) -> u64 {
	return file_write(file, u64(len(slice)), raw_data(slice))
}

file_read_slice :: proc(file: file, slice: []char) -> u64 {
	return file_read(file, u64(len(slice)), raw_data(slice))
}
////////////////////////////////////////////////////////////////////////////////
// Utility data structures and helpers used throughout the Orca API.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Types and helpers for vectors and matrices.
////////////////////////////////////////////////////////////////////////////////

// A 2D vector type.
vec2 :: [2]f32

// A 3D vector type.
vec3 :: [3]f32

// A 2D integer vector type.
vec2i :: [2]i32

// A 4D vector type.
vec4 :: [4]f32

// A 2-by-3 matrix.
mat2x3 :: [6]f32

// An axis-aligned rectangle.
rect :: struct { x, y, w, h: f32 }

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Check if two 2D vectors are equal.
	vec2_equal :: proc(v0: vec2, v1: vec2) -> bool ---
	// Multiply a 2D vector by a scalar.
	vec2_mul :: proc(f: f32, v: vec2) -> vec2 ---
	// Add two 2D vectors
	vec2_add :: proc(v0: vec2, v1: vec2) -> vec2 ---
	// Transforms a vector by an affine transformation represented as a 2x3 matrix.
	mat2x3_mul :: proc(m: mat2x3, p: vec2) -> vec2 ---
	// Multiply two affine transformations represented as 2x3 matrices. Both matrices are treated as 3x3 matrices with an implicit `(0, 0, 1)` bottom row
	mat2x3_mul_m :: proc(lhs: mat2x3, rhs: mat2x3) -> mat2x3 ---
	// Invert an affine transform represented as a 2x3 matrix.
	mat2x3_inv :: proc(x: mat2x3) -> mat2x3 ---
	// Return a 2x3 matrix representing a rotation.
	mat2x3_rotate :: proc(radians: f32) -> mat2x3 ---
	// Return a 2x3 matrix representing a translation.
	mat2x3_translate :: proc(x: f32, y: f32) -> mat2x3 ---
	// Return a 2x3 matrix representing a scale.
	mat2x3_scale :: proc(x: f32, y: f32) -> mat2x3 ---
}

////////////////////////////////////////////////////////////////////////////////
// API for sampling the system clock.
////////////////////////////////////////////////////////////////////////////////

clock_kind :: enum u32 {
	// A clock incrementing monotonically.
	MONOTONIC = 0,
	// A clock incrementing monotonically during uptime.
	UPTIME = 1,
	// A clock driven by the platform time.
	DATE = 2,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	clock_time :: proc(clock: clock_kind) -> f64 ---
}

////////////////////////////////////////////////////////////////////////////////
// Helpers for logging, asserting and aborting.
////////////////////////////////////////////////////////////////////////////////

// Constants allowing to specify the level of logging verbosity.
log_level :: enum u32 {
	// Only errors are logged.
	ERROR = 0,
	// Only warnings and errors are logged.
	WARNING = 1,
	// All messages are logged.
	INFO = 2,
	COUNT = 3,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	/*
	Abort the application, showing an error message.
	
	This function should not be called directly by user code, which should use the `OC_ABORT` macro instead, as the macro takes care of filling in the source location parameters of the function.
	*/
	abort_ext :: proc(file: cstring, function: cstring, line: i32, fmt: cstring, #c_vararg args: ..any) -> ! ---
	/*
	Tigger a failed assertion. This aborts the application, showing the failed assertion and an error message.
	
	This function should not be called directly by user code, which should use the `OC_ASSERT` macro instead. The macro checks the assert condition and calls the function if it is false. It also takes care of filling in the source location parameters of the function.
	*/
	assert_fail :: proc(file: cstring, function: cstring, line: i32, src: cstring, fmt: cstring, #c_vararg args: ..any) -> ! ---
	// Set the logging verbosity.
	log_set_level :: proc(level: log_level) ---
	/*
	Log a message to the console.
	
	This function should not be called directly by user code, which should use the `oc_log_XXX` family of macros instead. The macros take care of filling in the message level and source location parameters of the function.
	*/
	log_ext :: proc(level: log_level, function: cstring, file: cstring, line: i32, fmt: cstring, #c_vararg args: ..any) ---
}

////////////////////////////////////////////////////////////////////////////////
// Types and helpers for doubly-linked lists.
////////////////////////////////////////////////////////////////////////////////

// An element of an intrusive doubly-linked list.
list_elt :: struct {
	// Points to the previous element in the list.
	prev: ^list_elt,
	// Points to the next element in the list.
	next: ^list_elt,
}

// A doubly-linked list.
list :: struct {
	// Points to the first element in the list.
	first: ^list_elt,
	// Points to the last element in the list.
	last: ^list_elt,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Check if a list is empty.
	list_empty :: proc(list: list) -> bool ---
	// Zero-initializes a linked list.
	list_init :: proc(list: ^list) ---
	// Insert an element in a list after a given element.
	list_insert :: proc(list: ^list, afterElt: ^list_elt, elt: ^list_elt) ---
	// Insert an element in a list before a given element.
	list_insert_before :: proc(list: ^list, beforeElt: ^list_elt, elt: ^list_elt) ---
	// Remove an element from a list.
	list_remove :: proc(list: ^list, elt: ^list_elt) ---
	// Add an element at the end of a list.
	list_push_back :: proc(list: ^list, elt: ^list_elt) ---
	// Remove the last element from a list.
	list_pop_back :: proc(list: ^list) -> ^list_elt ---
	// Add an element at the beginning of a list.
	list_push_front :: proc(list: ^list, elt: ^list_elt) ---
	// Remove the first element from a list.
	list_pop_front :: proc(list: ^list) -> ^list_elt ---
}

////////////////////////////////////////////////////////////////////////////////
// Base allocator and memory arenas.
////////////////////////////////////////////////////////////////////////////////

// The prototype of a procedure to reserve memory from the system.
mem_reserve_proc :: proc "c" (_context: ^base_allocator, size: u64) -> rawptr

// The prototype of a procedure to modify a memory reservation.
mem_modify_proc :: proc "c" (_context: ^base_allocator, ptr: rawptr, size: u64)

// A structure that defines how to allocate memory from the system.
base_allocator :: struct {
	// A procedure to reserve memory from the system.
	reserve: mem_reserve_proc,
	// A procedure to commit memory from the system.
	commit: mem_modify_proc,
	// A procedure to decommit memory from the system.
	decommit: mem_modify_proc,
	// A procedure to release memory previously reserved from the system.
	release: mem_modify_proc,
}

// A contiguous chunk of memory managed by a memory arena.
arena_chunk :: struct {
	listElt: list_elt,
	ptr: cstring,
	offset: u64,
	committed: u64,
	cap: u64,
}

// A memory arena, allowing to allocate memory in a linear or stack-like fashion.
arena :: struct {
	// An allocator providing memory pages from the system
	base: ^base_allocator,
	// A list of `oc_arena_chunk` chunks.
	chunks: list,
	// The chunk new memory allocations are pulled from.
	currentChunk: ^arena_chunk,
}

// This struct provides a way to store the current offset in a given arena, in order to reset the arena to that offset later. This allows using arenas in a stack-like fashion, e.g. to create temporary "scratch" allocations
arena_scope :: struct {
	// The arena which offset is stored.
	arena: ^arena,
	// The arena chunk to which the offset belongs.
	chunk: ^arena_chunk,
	// The offset to rewind the arena to.
	offset: u64,
}

// Options for arena creation.
arena_options :: struct {
	// The base allocator to use with this arena
	base: ^base_allocator,
	// The amount of memory to reserve up-front when creating the arena.
	reserve: u64,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Initialize a memory arena.
	arena_init :: proc(arena: ^arena) ---
	// Initialize a memory arena with additional options.
	arena_init_with_options :: proc(arena: ^arena, options: ^arena_options) ---
	// Release all resources allocated to a memory arena.
	arena_cleanup :: proc(arena: ^arena) ---
	// Allocate a zero initialized block of memory from an arena.
	arena_push :: proc(arena: ^arena, size: u64) -> rawptr ---
	// Allocate an aligned, zero initialized block of memory from an arena.
	arena_push_aligned :: proc(arena: ^arena, size: u64, alignment: u32) -> rawptr ---
	// Allocate a block of memory from an arena.
	arena_push_uninitialized :: proc(arena: ^arena, size: u64) -> rawptr ---
	// Allocate an aligned block of memory from an arena.
	arena_push_aligned_uninitialized :: proc(arena: ^arena, size: u64, alignment: u32) -> rawptr ---
	// Reset an arena. All memory that was previously allocated from this arena is released to the arena, and can be reallocated by later calls to `oc_arena_push` and similar functions. No memory is actually released _to the system_.
	arena_clear :: proc(arena: ^arena) ---
	// Begin a memory scope. This creates an `oc_arena_scope` object that stores the current offset of the arena. The arena can later be reset to that offset by calling `oc_arena_scope_end`, releasing all memory that was allocated within the scope to the arena.
	arena_scope_begin :: proc(arena: ^arena) -> arena_scope ---
	// End a memory scope. This resets an arena to the offset it had when the scope was created. All memory allocated within the scope is released back to the arena.
	arena_scope_end :: proc(scope: arena_scope) ---
	/*
	Begin a scratch scope. This creates a memory scope on a per-thread, global "scratch" arena. This allows easily creating temporary memory for scratch computations or intermediate results, in a stack-like fashion.
	
	If you must return results in an arena passed by the caller, and you also use a scratch arena to do intermediate computations, beware that the results arena could itself be a scatch arena. In this case, you have to be careful not to intermingle your scratch computations with the final result, or clear your result entirely. You can either:
	
	- Allocate memory for the result upfront and call `oc_scratch_begin` afterwards, if possible.
	- Use `oc_scratch_begin_next()` and pass it the result arena, to get a scratch arena that does not conflict with it.
	*/
	scratch_begin :: proc() -> arena_scope ---
	// Begin a scratch scope that does not conflict with a given arena. See `oc_scratch_begin()` for more details about when to use this function.
	scratch_begin_next :: proc(used: ^arena) -> arena_scope ---
}

////////////////////////////////////////////////////////////////////////////////
// String slices and string lists.
////////////////////////////////////////////////////////////////////////////////

// A type representing a string of bytes.
str8 :: string

// A type representing an element of a string list.
str8_elt :: struct {
	// The string element is linked into its parent string list through this field.
	listElt: list_elt,
	// The string for this element.
	string: str8,
}

// A type representing a string list.
str8_list :: struct {
	// A linked-list of `oc_str8_elt`.
	list: list,
	// The number of elements in `list`.
	eltCount: u64,
	// The total length of the string list, which is the sum of the lengths over all elements.
	len: u64,
}

// A type describing a string of 16-bits characters (typically used for UTF-16).
str16 :: distinct []u16

// A type representing an element of an `oc_str16` list.
str16_elt :: struct {
	// The string element is linked into its parent string list through this field.
	listElt: list_elt,
	// The string for this element.
	string: str16,
}

str16_list :: struct {
	// A linked-list of `oc_str16_elt`.
	list: list,
	// The number of elements in `list`.
	eltCount: u64,
	// The total length of the string list, which is the sum of the lengths over all elements.
	len: u64,
}

// A type describing a string of 32-bits characters (typically used for UTF-32 codepoints).
str32 :: distinct []rune

// A type representing an element of an `oc_str32` list.
str32_elt :: struct {
	// The string element is linked into its parent string list through this field.
	listElt: list_elt,
	// The string for this element.
	string: str32,
}

str32_list :: struct {
	// A linked-list of `oc_str32_elt`.
	list: list,
	// The number of elements in `list`.
	eltCount: u64,
	// The total length of the string list, which is the sum of the lengths over all elements.
	len: u64,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Make a string from a bytes buffer and a length.
	str8_from_buffer :: proc(len: u64, buffer: [^]char) -> str8 ---
	// Make a string from a slice of another string. The resulting string designates some subsequence of the input string.
	str8_slice :: proc(s: str8, start: u64, end: u64) -> str8 ---
	// Pushes a copy of a buffer to an arena, and makes a string refering to that copy.
	str8_push_buffer :: proc(arena: ^arena, len: u64, buffer: [^]char) -> str8 ---
	// Pushes a copy of a C null-terminated string to an arena, and makes a string referring to that copy.
	str8_push_cstring :: proc(arena: ^arena, str: cstring) -> str8 ---
	// Copy the contents of a string on an arena and make a new string referring to the copied bytes.
	str8_push_copy :: proc(arena: ^arena, s: str8) -> str8 ---
	// Make a copy of a string slice. This function copies a subsequence of the input string onto an arena, and returns a new string referring to the copied content.
	str8_push_slice :: proc(arena: ^arena, s: str8, start: u64, end: u64) -> str8 ---
	// Lexicographically compare the contents of two strings.
	str8_cmp :: proc(s1: str8, s2: str8) -> i32 ---
	// Create a null-terminated C-string from an `oc_str8` string.
	str8_to_cstring :: proc(arena: ^arena, string: str8) -> cstring ---
	// Push a string element to the back of a string list. This creates a `oc_str8_elt` element referring to the contents of the input string, and links that element at the end of the string list.
	str8_list_push :: proc(arena: ^arena, list: ^str8_list, str: str8) ---
	// Build a string from a null-terminated format string an variadic arguments, and append it to a string list.
	str8_list_pushf :: proc(arena: ^arena, list: ^str8_list, format: cstring, #c_vararg args: ..any) ---
	// Build a string by combining the elements of a string list with a prefix, a suffix, and separators.
	str8_list_collate :: proc(arena: ^arena, list: str8_list, prefix: str8, separator: str8, suffix: str8) -> str8 ---
	// Build a string by joining the elements of a string list.
	str8_list_join :: proc(arena: ^arena, list: str8_list) -> str8 ---
	/*
	Split a list into a string list according to separators.
	
	No string copies are made. The elements of the resulting string list refer to subsequences of the input string.
	*/
	str8_split :: proc(arena: ^arena, str: str8, separators: str8_list) -> str8_list ---
	// Make an `oc_str16` string from a buffer of 16-bit characters.
	str16_from_buffer :: proc(len: u64, buffer: [^]u16) -> str16 ---
	// Make an `oc_str16` string from a slice of another `oc_str16` string.
	str16_slice :: proc(s: str16, start: u64, end: u64) -> str16 ---
	// Copy the content of a 16-bit character buffer on an arena and make a new `oc_str16` referencing the copied contents.
	str16_push_buffer :: proc(arena: ^arena, len: u64, buffer: [^]u16) -> str16 ---
	// Copy the contents of an `oc_str16` string and make a new string referencing the copied contents.
	str16_push_copy :: proc(arena: ^arena, s: str16) -> str16 ---
	// Copy a slice of an `oc_str16` string an make a new string referencing the copies contents.
	str16_push_slice :: proc(arena: ^arena, s: str16, start: u64, end: u64) -> str16 ---
	// Push a string element to the back of a string list. This creates a `oc_str16_elt` element referring to the contents of the input string, and links that element at the end of the string list.
	str16_list_push :: proc(arena: ^arena, list: ^str16_list, str: str16) ---
	// Build a string by joining the elements of a string list.
	str16_list_join :: proc(arena: ^arena, list: str16_list) -> str16 ---
	/*
	Split a list into a string list according to separators.
	
	No string copies are made. The elements of the resulting string list refer to subsequences of the input string.
	*/
	str16_split :: proc(arena: ^arena, str: str16, separators: str16_list) -> str16_list ---
	// Make an `oc_str32` string from a buffer of 32-bit characters.
	str32_from_buffer :: proc(len: u64, buffer: [^]u32) -> str32 ---
	// Make an `oc_str32` string from a slice of another `oc_str32` string.
	str32_slice :: proc(s: str32, start: u64, end: u64) -> str32 ---
	// Copy the content of a 32-bit character buffer on an arena and make a new `oc_str32` referencing the copied contents.
	str32_push_buffer :: proc(arena: ^arena, len: u64, buffer: [^]u32) -> str32 ---
	// Copy the contents of an `oc_str32` string and make a new string referencing the copied contents.
	str32_push_copy :: proc(arena: ^arena, s: str32) -> str32 ---
	// Copy a slice of an `oc_str32` string an make a new string referencing the copies contents.
	str32_push_slice :: proc(arena: ^arena, s: str32, start: u64, end: u64) -> str32 ---
	// Push a string element to the back of a string list. This creates a `oc_str32_elt` element referring to the contents of the input string, and links that element at the end of the string list.
	str32_list_push :: proc(arena: ^arena, list: ^str32_list, str: str32) ---
	// Build a string by joining the elements of a string list.
	str32_list_join :: proc(arena: ^arena, list: str32_list) -> str32 ---
	/*
	Split a list into a string list according to separators.
	
	No string copies are made. The elements of the resulting string list refer to subsequences of the input string.
	*/
	str32_split :: proc(arena: ^arena, str: str32, separators: str32_list) -> str32_list ---
}

////////////////////////////////////////////////////////////////////////////////
// UTF8 encoding/decoding.
////////////////////////////////////////////////////////////////////////////////

// A unicode codepoint.
utf32 :: rune

// This enum declares the possible return status of UTF8 decoding/encoding operations.
utf8_status :: enum u32 {
	// The operation was successful.
	OK = 0,
	// The operation unexpectedly encountered the end of the utf8 sequence.
	OUT_OF_BOUNDS = 1,
	// A continuation byte was encountered where a leading byte was expected.
	UNEXPECTED_CONTINUATION_BYTE = 2,
	// A leading byte was encountered in the middle of the encoding of utf8 codepoint.
	UNEXPECTED_LEADING_BYTE = 3,
	// The utf8 sequence contains an invalid byte.
	INVALID_BYTE = 4,
	// The operation encountered an invalid utf8 codepoint.
	INVALID_CODEPOINT = 5,
	// The utf8 sequence contains an overlong encoding of a utf8 codepoint.
	OVERLONG_ENCODING = 6,
}

// A type representing the result of decoding of utf8-encoded codepoint.
utf8_dec :: struct {
	// The status of the decoding operation. If not `OC_UTF8_OK`, it describes the error that was encountered during decoding.
	status: utf8_status,
	// The decoded codepoint.
	codepoint: utf32,
	// The size of the utf8 sequence encoding that codepoint.
	size: u32,
}

// A type representing a contiguous range of unicode codepoints.
unicode_range :: struct {
	// The first codepoint of the range.
	firstCodePoint: utf32,
	// The number of codepoints in the range.
	count: u32,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Get the size of a utf8-encoded codepoint for the first byte of the encoded sequence.
	utf8_size_from_leading_char :: proc(leadingChar: char) -> u32 ---
	// Get the size of the utf8 encoding of a codepoint.
	utf8_codepoint_size :: proc(codePoint: utf32) -> u32 ---
	utf8_codepoint_count_for_string :: proc(string: str8) -> u64 ---
	// Get the length of the utf8 encoding of a sequence of unicode codepoints.
	utf8_byte_count_for_codepoints :: proc(codePoints: str32) -> u64 ---
	// Get the offset of the next codepoint after a given offset, in a utf8 encoded string.
	utf8_next_offset :: proc(string: str8, byteOffset: u64) -> u64 ---
	// Get the offset of the previous codepoint before a given offset, in a utf8 encoded string.
	utf8_prev_offset :: proc(string: str8, byteOffset: u64) -> u64 ---
	// Decode a utf8 encoded codepoint.
	utf8_decode :: proc(string: str8) -> utf8_dec ---
	// Decode a codepoint at a given offset in a utf8 encoded string.
	utf8_decode_at :: proc(string: str8, offset: u64) -> utf8_dec ---
	// Encode a unicode codepoint into a utf8 sequence.
	utf8_encode :: proc(dst: cstring, codePoint: utf32) -> str8 ---
	// Decode a utf8 string to a string of unicode codepoints using memory passed by the caller.
	utf8_to_codepoints :: proc(maxCount: u64, backing: ^utf32, string: str8) -> str32 ---
	// Encode a string of unicode codepoints into a utf8 string using memory passed by the caller.
	utf8_from_codepoints :: proc(maxBytes: u64, backing: cstring, codePoints: str32) -> str8 ---
	// Decode a utf8 encoded string to a string of unicode codepoints using an arena.
	utf8_push_to_codepoints :: proc(arena: ^arena, string: str8) -> str32 ---
	// Encode a string of unicode codepoints into a utf8 string using an arena.
	utf8_push_from_codepoints :: proc(arena: ^arena, codePoints: str32) -> str8 ---
}

////////////////////////////////////////////////////////////////////////////////
// Input, windowing, dialogs.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Application events.
////////////////////////////////////////////////////////////////////////////////

// This enum defines the type events that can be sent to the application by the runtime. This determines which member of the `oc_event` union field is active.
event_type :: enum u32 {
	// No event. That could be used simply to wake up the application.
	NONE = 0,
	// A modifier key event. This event is sent when a key such as <kbd>Alt</kbd>, <kbd>Control</kbd>, <kbd>Command</kbd> or <kbd>Shift</kbd> are pressed, released, or repeated. The `key` field contains the event's details.
	KEYBOARD_MODS = 1,
	// A key event. This event is sent when a normal key is pressed, released, or repeated. The `key` field contains the event's details.
	KEYBOARD_KEY = 2,
	// A character input event. This event is sent when an input character is produced by the keyboard. The `character` field contains the event's details.
	KEYBOARD_CHAR = 3,
	// A mouse button event. This is event sent when one of the mouse buttons is pressed, released, or clicked. The `key` field contains the event's details.
	MOUSE_BUTTON = 4,
	// A mouse move event. This is event sent when the mouse is moved. The `mouse` field contains the event's details.
	MOUSE_MOVE = 5,
	// A mouse wheel event. This is event sent when the mouse wheel is moved (or when a trackpad is scrolled). The `mouse` field contains the event's details.
	MOUSE_WHEEL = 6,
	// A mouse enter event. This event is sent when the mouse enters the application's window. The `mouse` field contains the event's details.
	MOUSE_ENTER = 7,
	// A mouse leave event. This event is sent when the mouse leaves the application's window.
	MOUSE_LEAVE = 8,
	// A clipboard paste event. This event is sent when the user uses the paste shortcut while the application window has focus.
	CLIPBOARD_PASTE = 9,
	// A resize event. This event is sent when the application's window is resized. The `move` field contains the event's details.
	WINDOW_RESIZE = 10,
	// A move event. This event is sent when the window is moved. The `move` field contains the event's details.
	WINDOW_MOVE = 11,
	// A focus event. This event is sent when the application gains focus.
	WINDOW_FOCUS = 12,
	// An unfocus event. This event is sent when the application looses focus.
	WINDOW_UNFOCUS = 13,
	// A hide event. This event is sent when the application's window is hidden or minimized.
	WINDOW_HIDE = 14,
	// A show event. This event is sent when the application's window is shown or de-minimized.
	WINDOW_SHOW = 15,
	// A close event. This event is sent when the window is about to be closed.
	WINDOW_CLOSE = 16,
	// A path drop event. This event is sent when the user drops files onto the application's window. The `paths` field contains the event's details.
	PATHDROP = 17,
	// A frame event. This event is sent when the application should render a frame.
	FRAME = 18,
	// A quit event. This event is sent when the application has been requested to quit.
	QUIT = 19,
}

// This enum describes the actions that can happen to a key.
key_action :: enum u32 {
	// No action happened on that key.
	NO_ACTION = 0,
	// The key was pressed.
	PRESS = 1,
	// The key was released.
	RELEASE = 2,
	// The key was maintained pressed at least for the system's key repeat period.
	REPEAT = 3,
}

// A code representing a key's physical location. This is independent of the system's keyboard layout.
scan_code :: enum u32 {
	UNKNOWN = 0,
	SPACE = 32,
	APOSTROPHE = 39,
	COMMA = 44,
	MINUS = 45,
	PERIOD = 46,
	SLASH = 47,
	_0 = 48,
	_1 = 49,
	_2 = 50,
	_3 = 51,
	_4 = 52,
	_5 = 53,
	_6 = 54,
	_7 = 55,
	_8 = 56,
	_9 = 57,
	SEMICOLON = 59,
	EQUAL = 61,
	LEFT_BRACKET = 91,
	BACKSLASH = 92,
	RIGHT_BRACKET = 93,
	GRAVE_ACCENT = 96,
	A = 97,
	B = 98,
	C = 99,
	D = 100,
	E = 101,
	F = 102,
	G = 103,
	H = 104,
	I = 105,
	J = 106,
	K = 107,
	L = 108,
	M = 109,
	N = 110,
	O = 111,
	P = 112,
	Q = 113,
	R = 114,
	S = 115,
	T = 116,
	U = 117,
	V = 118,
	W = 119,
	X = 120,
	Y = 121,
	Z = 122,
	WORLD_1 = 161,
	WORLD_2 = 162,
	ESCAPE = 256,
	ENTER = 257,
	TAB = 258,
	BACKSPACE = 259,
	INSERT = 260,
	DELETE = 261,
	RIGHT = 262,
	LEFT = 263,
	DOWN = 264,
	UP = 265,
	PAGE_UP = 266,
	PAGE_DOWN = 267,
	HOME = 268,
	END = 269,
	CAPS_LOCK = 280,
	SCROLL_LOCK = 281,
	NUM_LOCK = 282,
	PRINT_SCREEN = 283,
	PAUSE = 284,
	F1 = 290,
	F2 = 291,
	F3 = 292,
	F4 = 293,
	F5 = 294,
	F6 = 295,
	F7 = 296,
	F8 = 297,
	F9 = 298,
	F10 = 299,
	F11 = 300,
	F12 = 301,
	F13 = 302,
	F14 = 303,
	F15 = 304,
	F16 = 305,
	F17 = 306,
	F18 = 307,
	F19 = 308,
	F20 = 309,
	F21 = 310,
	F22 = 311,
	F23 = 312,
	F24 = 313,
	F25 = 314,
	KP_0 = 320,
	KP_1 = 321,
	KP_2 = 322,
	KP_3 = 323,
	KP_4 = 324,
	KP_5 = 325,
	KP_6 = 326,
	KP_7 = 327,
	KP_8 = 328,
	KP_9 = 329,
	KP_DECIMAL = 330,
	KP_DIVIDE = 331,
	KP_MULTIPLY = 332,
	KP_SUBTRACT = 333,
	KP_ADD = 334,
	KP_ENTER = 335,
	KP_EQUAL = 336,
	LEFT_SHIFT = 340,
	LEFT_CONTROL = 341,
	LEFT_ALT = 342,
	LEFT_SUPER = 343,
	RIGHT_SHIFT = 344,
	RIGHT_CONTROL = 345,
	RIGHT_ALT = 346,
	RIGHT_SUPER = 347,
	MENU = 348,
	COUNT = 349,
}

// A code identifying a key. The physical location of the key corresponding to a given key code depends on the system's keyboard layout.
key_code :: enum u32 {
	UNKNOWN = 0,
	SPACE = 32,
	APOSTROPHE = 39,
	COMMA = 44,
	MINUS = 45,
	PERIOD = 46,
	SLASH = 47,
	_0 = 48,
	_1 = 49,
	_2 = 50,
	_3 = 51,
	_4 = 52,
	_5 = 53,
	_6 = 54,
	_7 = 55,
	_8 = 56,
	_9 = 57,
	SEMICOLON = 59,
	EQUAL = 61,
	LEFT_BRACKET = 91,
	BACKSLASH = 92,
	RIGHT_BRACKET = 93,
	GRAVE_ACCENT = 96,
	A = 97,
	B = 98,
	C = 99,
	D = 100,
	E = 101,
	F = 102,
	G = 103,
	H = 104,
	I = 105,
	J = 106,
	K = 107,
	L = 108,
	M = 109,
	N = 110,
	O = 111,
	P = 112,
	Q = 113,
	R = 114,
	S = 115,
	T = 116,
	U = 117,
	V = 118,
	W = 119,
	X = 120,
	Y = 121,
	Z = 122,
	WORLD_1 = 161,
	WORLD_2 = 162,
	ESCAPE = 256,
	ENTER = 257,
	TAB = 258,
	BACKSPACE = 259,
	INSERT = 260,
	DELETE = 261,
	RIGHT = 262,
	LEFT = 263,
	DOWN = 264,
	UP = 265,
	PAGE_UP = 266,
	PAGE_DOWN = 267,
	HOME = 268,
	END = 269,
	CAPS_LOCK = 280,
	SCROLL_LOCK = 281,
	NUM_LOCK = 282,
	PRINT_SCREEN = 283,
	PAUSE = 284,
	F1 = 290,
	F2 = 291,
	F3 = 292,
	F4 = 293,
	F5 = 294,
	F6 = 295,
	F7 = 296,
	F8 = 297,
	F9 = 298,
	F10 = 299,
	F11 = 300,
	F12 = 301,
	F13 = 302,
	F14 = 303,
	F15 = 304,
	F16 = 305,
	F17 = 306,
	F18 = 307,
	F19 = 308,
	F20 = 309,
	F21 = 310,
	F22 = 311,
	F23 = 312,
	F24 = 313,
	F25 = 314,
	KP_0 = 320,
	KP_1 = 321,
	KP_2 = 322,
	KP_3 = 323,
	KP_4 = 324,
	KP_5 = 325,
	KP_6 = 326,
	KP_7 = 327,
	KP_8 = 328,
	KP_9 = 329,
	KP_DECIMAL = 330,
	KP_DIVIDE = 331,
	KP_MULTIPLY = 332,
	KP_SUBTRACT = 333,
	KP_ADD = 334,
	KP_ENTER = 335,
	KP_EQUAL = 336,
	LEFT_SHIFT = 340,
	LEFT_CONTROL = 341,
	LEFT_ALT = 342,
	LEFT_SUPER = 343,
	RIGHT_SHIFT = 344,
	RIGHT_CONTROL = 345,
	RIGHT_ALT = 346,
	RIGHT_SUPER = 347,
	MENU = 348,
	COUNT = 349,
}

keymod_flag :: enum u32 {
	ALT = 0,
	SHIFT,
	CTRL,
	CMD,
	MAIN_MODIFIER,
}
keymod_flags :: bit_set[keymod_flag; u32]

// A code identifying a mouse button.
mouse_button :: enum u32 {
	LEFT = 0,
	RIGHT = 1,
	MIDDLE = 2,
	EXT1 = 3,
	EXT2 = 4,
	BUTTON_COUNT = 5,
}

// A structure describing a key event or a mouse button event.
key_event :: struct {
	// The action that was done on the key.
	action: key_action,
	// The scan code of the key. Only valid for key events.
	scanCode: scan_code,
	// The key code of the key. Only valid for key events.
	keyCode: key_code,
	// The button of the mouse. Only valid for mouse button events.
	button: mouse_button,
	// Modifier flags indicating which modifier keys where pressed at the time of the event.
	mods: keymod_flags,
	// The number of clicks that where detected for the button. Only valid for mouse button events.
	clickCount: u8,
}

// A structure describing a character input event.
char_event :: struct {
	// The unicode codepoint of the character.
	codepoint: utf32,
	// The utf8 sequence of the character.
	sequence: [8]char,
	// The utf8 sequence length.
	seqLen: u8,
}

// A structure describing a mouse move or a mouse wheel event. Mouse coordinates have their origin at the top-left corner of the window, with the y axis going down.
mouse_event :: struct {
	// The x coordinate of the mouse.
	x: f32,
	// The y coordinate of the mouse.
	y: f32,
	// The delta from the last x coordinate of the mouse, or the scroll value along the x coordinate.
	deltaX: f32,
	// The delta from the last y coordinate of the mouse, or the scoll value along the y  coordinate.
	deltaY: f32,
	// Modifier flags indicating which modifier keys where pressed at the time of the event.
	mods: keymod_flags,
}

// A structure describing a window move or resize event.
move_event :: struct {
	// The position and dimension of the frame rectangle, i.e. including the window title bar and border.
	frame: rect,
	// The position and dimension of the content rectangle, relative to the frame rectangle.
	content: rect,
}

// A structure describing an event sent to the application.
event :: struct {
	// The window in which this event happened.
	window: window,
	// The type of the event. This determines which member of the event union is active.
	type: event_type,
	using _: struct #raw_union {
		key: key_event,
		character: char_event,
		mouse: mouse_event,
		move: move_event,
		paths: str8_list,
	},
}

// This enum describes the kinds of possible file dialogs.
file_dialog_kind :: enum u32 {
	// The file dialog is a save dialog.
	SAVE = 0,
	// The file dialog is an open dialog.
	OPEN = 1,
}

// A type for flags describing various file dialog options.
// File dialog flags.
file_dialog_flag :: enum u32 {
	// This dialog allows selecting files.
	FILES = 0,
	// This dialog allows selecting directories.
	DIRECTORIES,
	// This dialog allows selecting multiple items.
	MULTIPLE,
	// This dialog allows creating directories.
	CREATE_DIRECTORIES,
}
file_dialog_flags :: bit_set[file_dialog_flag; u32]

// A structure describing a file dialog.
file_dialog_desc :: struct {
	// The kind of file dialog, see `oc_file_dialog_kind`.
	kind: file_dialog_kind,
	// A combination of file dialog flags used to enable file dialog options.
	flags: file_dialog_flags,
	// The title of the dialog, displayed in the dialog title bar.
	title: str8,
	// Optional. The label of the OK button, e.g. "Save" or "Open".
	okLabel: str8,
	// Optional. A file handle to the root directory for the dialog. If set to zero, the root directory is the application's default data directory.
	startAt: file,
	// Optional. The path of the starting directory of the dialog, relative to its root directory. If set to nil, the dialog starts at its root directory.
	startPath: str8,
	// A list of file extensions used to restrict which files can be selected in this dialog. An empty list allows all files to be selected. Extensions should be provided without a leading dot.
	filters: str8_list,
}

// An enum identifying the button clicked by the user when a file dialog returns.
file_dialog_button :: enum u32 {
	// The user clicked the "Cancel" button, or closed the dialog box.
	CANCEL = 0,
	// The user clicked the "OK" button.
	OK = 1,
}

// A structure describing the result of a file dialog.
file_dialog_result :: struct {
	// The button clicked by the user.
	button: file_dialog_button,
	// The path that was selected when the user clicked the OK button. If the dialog box had the `OC_FILE_DIALOG_MULTIPLE` flag set, this is the first file of the list of selected paths.
	path: str8,
	// If the dialog box had the `OC_FILE_DIALOG_MULTIPLE` flag set and the user clicked the OK button, this list contains the selected paths.
	selection: str8_list,
}

// An opaque handle identifying a window.
window :: distinct u64

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Set the title of the application's window.
	window_set_title :: proc(title: str8) ---
	// Set the size of the application's window.
	window_set_size :: proc(size: vec2) ---
	// Request the system to quit the application.
	request_quit :: proc() ---
	// Convert a scancode to a keycode, according to current keyboard layout.
	scancode_to_keycode :: proc(scanCode: scan_code) -> key_code ---
}

////////////////////////////////////////////////////////////////////////////////
// Application user input.
////////////////////////////////////////////////////////////////////////////////

key_state :: struct {
	lastUpdate: u64,
	transitionCount: u32,
	repeatCount: u32,
	down: bool,
	sysClicked: bool,
	sysDoubleClicked: bool,
	sysTripleClicked: bool,
}

keyboard_state :: struct {
	keys: [349]key_state,
	mods: keymod_flags,
}

mouse_state :: struct {
	lastUpdate: u64,
	posValid: bool,
	pos: vec2,
	delta: vec2,
	wheel: vec2,
	using _: struct #raw_union {
		buttons: [5]key_state,
		using _: struct {
			left: key_state,
			right: key_state,
			middle: key_state,
			ext1: key_state,
			ext2: key_state,
		},
	},
}

BACKING_SIZE :: 64

text_state :: struct {
	lastUpdate: u64,
	backing: [64]utf32,
	codePoints: str32,
}

clipboard_state :: struct {
	lastUpdate: u64,
	pastedText: str8,
}

input_state :: struct {
	frameCounter: u64,
	keyboard: keyboard_state,
	mouse: mouse_state,
	text: text_state,
	clipboard: clipboard_state,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	input_process_event :: proc(arena: ^arena, state: ^input_state, event: ^event) ---
	input_next_frame :: proc(state: ^input_state) ---
	key_down :: proc(state: ^input_state, key: key_code) -> bool ---
	key_press_count :: proc(state: ^input_state, key: key_code) -> u8 ---
	key_release_count :: proc(state: ^input_state, key: key_code) -> u8 ---
	key_repeat_count :: proc(state: ^input_state, key: key_code) -> u8 ---
	key_down_scancode :: proc(state: ^input_state, key: scan_code) -> bool ---
	key_press_count_scancode :: proc(state: ^input_state, key: scan_code) -> u8 ---
	key_release_count_scancode :: proc(state: ^input_state, key: scan_code) -> u8 ---
	key_repeat_count_scancode :: proc(state: ^input_state, key: scan_code) -> u8 ---
	mouse_down :: proc(state: ^input_state, button: mouse_button) -> bool ---
	mouse_pressed :: proc(state: ^input_state, button: mouse_button) -> u8 ---
	mouse_released :: proc(state: ^input_state, button: mouse_button) -> u8 ---
	mouse_clicked :: proc(state: ^input_state, button: mouse_button) -> bool ---
	mouse_double_clicked :: proc(state: ^input_state, button: mouse_button) -> bool ---
	mouse_position :: proc(state: ^input_state) -> vec2 ---
	mouse_delta :: proc(state: ^input_state) -> vec2 ---
	mouse_wheel :: proc(state: ^input_state) -> vec2 ---
	input_text_utf32 :: proc(arena: ^arena, state: ^input_state) -> str32 ---
	input_text_utf8 :: proc(arena: ^arena, state: ^input_state) -> str8 ---
	// Put a string in the clipboard.
	clipboard_set_string :: proc(string: str8) ---
	clipboard_pasted :: proc(state: ^input_state) -> bool ---
	clipboard_pasted_text :: proc(state: ^input_state) -> str8 ---
	key_mods :: proc(state: ^input_state) -> keymod_flags ---
}

////////////////////////////////////////////////////////////////////////////////
// File input/output.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// API for opening, reading and writing files.
////////////////////////////////////////////////////////////////////////////////

// An opaque handle identifying an opened file.
file :: distinct u64

// The type of file open flags describing file open options.
// Flags for the `oc_file_open()` function.
file_open_flag :: enum u16 {
	// Open the file in 'append' mode. All writes append data at the end of the file.
	APPEND = 0,
	// Truncate the file to 0 bytes when opening.
	TRUNCATE,
	// Create the file if it does not exist.
	CREATE,
	// If the file is a symlink, open the symlink itself instead of following it.
	SYMLINK,
	// If the file is a symlink, the call to open will fail.
	NO_FOLLOW,
	// Reserved.
	RESTRICT,
}
file_open_flags :: bit_set[file_open_flag; u16]

// This enum describes the access permissions of a file handle.
file_access_flag :: enum u16 {
	// The file handle can be used for reading from the file.
	READ = 0,
	// The file handle can be used for writing to the file.
	WRITE,
}
file_access :: bit_set[file_access_flag; u16]

// This enum is used in `oc_file_seek()` to specify the starting point of the seek operation.
file_whence :: enum u32 {
	// Set the file position relative to the beginning of the file.
	SET = 0,
	// Set the file position relative to the end of the file.
	END = 1,
	// Set the file position relative to the current position.
	CURRENT = 2,
}

// A type used to identify I/O requests.
io_req_id :: u64

// A type used to identify I/O operations.
// This enum declares all I/O operations.
io_op :: enum u32 {
	// ['Open a file at a path relative to a given root directory.', '', "    - `handle` is the handle to the root directory. If it is nil, the application's default directory is used.", '    - `size` is the size of the path, in bytes.', '    - `buffer` points to an array containing the path of the file to open, relative to the directory identified by `handle`.', '    - `open` contains the permissions and flags for the open operation.']
	OPEN_AT = 0,
	// ['Close a file handle.', '', '    - `handle` is the handle to close.']
	CLOSE = 1,
	// ['Get status information for a file handle.', '', '    - `handle` is the handle to stat.', '    - `size` is the size of the result buffer. It should be at least `sizeof(oc_file_status)`.', '    - `buffer` is the result buffer.']
	FSTAT = 2,
	// ['Move the file position in a file.', '', '    - `handle` is the handle of the file.', '    - `offset` specifies the offset of the new position, relative to the base position specified by `whence`.', '    - `whence` determines the base position for the seek operation.']
	SEEK = 3,
	// ['Read data from a file.', '', '    - `handle` is the handle of the file.', '    - `size` is the number of bytes to read.', '    - `buffer` is the result buffer. It should be big enough to hold `size` bytes.']
	READ = 4,
	// ['Write data to a file.', '', '    - `handle` is the handle of the file.', '    - `size` is the number of bytes to write.', '    - `buffer` contains the data to write to the file.']
	WRITE = 5,
	// ['Get the error attached to a file handle.', '', '    - `handle` is the handle of the file.']
	OC_OC_IO_ERROR = 6,
}

// A structure describing an I/O request.
io_req :: struct {
	// An identifier for the request. You can set this to any value you want. It is passed back in the `oc_io_cmp` completion and can be used to match requests and completions.
	id: io_req_id,
	// The requested operation.
	op: io_op,
	// A file handle used by some operations.
	handle: file,
	// An offset used by some operations.
	offset: i64,
	// A size indicating the capacity of the buffer pointed to by `buffer`, in bytes.
	size: u64,
	using _: struct #raw_union {
		buffer: [^]char,
		unused: u64,
	},
	using _: struct #raw_union {
		using open: struct {
			// The access permissions requested on the file to open.
			rights: file_access,
			// The options to use when opening the file.
			flags: file_open_flags,
		},
		whence: file_whence,
	},
}

// A type identifying an I/O error.
// This enum declares all I/O error values.
io_error :: enum u32 {
	// No error.
	OK = 0,
	// An unexpected error happened.
	UNKNOWN = 1,
	// The request had an invalid operation.
	OP = 2,
	// The request had an invalid handle.
	HANDLE = 3,
	// The operation was not carried out because the file handle has previous errors.
	PREV = 4,
	// The request contained wrong arguments.
	ARG = 5,
	// The operation requires permissions that the file handle doesn't have.
	PERM = 6,
	// The operation couldn't complete due to a lack of space in the result buffer.
	SPACE = 7,
	// One of the directory in the path does not exist or couldn't be traversed.
	NO_ENTRY = 8,
	// The file already exists.
	EXISTS = 9,
	// The file is not a directory.
	NOT_DIR = 10,
	// The file is a directory.
	DIR = 11,
	// There are too many opened files.
	MAX_FILES = 12,
	// The path contains too many symbolic links (this may be indicative of a symlink loop).
	MAX_LINKS = 13,
	// The path is too long.
	PATH_LENGTH = 14,
	// The file is too large.
	FILE_SIZE = 15,
	// The file is too large to be opened.
	OVERFLOW = 16,
	// The file is locked or the device on which it is stored is not ready.
	NOT_READY = 17,
	// The system is out of memory.
	MEM = 18,
	// The operation was interrupted by a signal.
	INTERRUPT = 19,
	// A physical error happened.
	PHYSICAL = 20,
	// The device on which the file is stored was not found.
	NO_DEVICE = 21,
	// One element along the path is outside the root directory subtree.
	WALKOUT = 22,
}

// A structure describing the completion of an I/O operation.
io_cmp :: struct {
	// The request ID as passed in the `oc_io_req` request that generated this completion.
	id: io_req_id,
	// The error value for the operation.
	error: io_error,
	using _: struct #raw_union {
		result: i64,
		size: u64,
		offset: i64,
		handle: file,
	},
}

// An enum identifying the type of a file.
file_type :: enum u32 {
	// The file is of unknown type.
	UNKNOWN = 0,
	// The file is a regular file.
	REGULAR = 1,
	// The file is a directory.
	DIRECTORY = 2,
	// The file is a symbolic link.
	SYMLINK = 3,
	// The file is a block device.
	BLOCK = 4,
	// The file is a character device.
	CHARACTER = 5,
	// The file is a FIFO pipe.
	FIFO = 6,
	// The file is a socket.
	SOCKET = 7,
}

// A type describing file permissions.
file_perm_flag :: enum u16 {
	OTHER_EXEC = 0,
	OTHER_WRITE,
	OTHER_READ,
	GROUP_EXEC,
	GROUP_WRITE,
	GROUP_READ,
	OWNER_EXEC,
	OWNER_WRITE,
	OWNER_READ,
	STICKY_BIT,
	SET_GID,
	SET_UID,
}
file_perm :: bit_set[file_perm_flag; u16]

datestamp :: struct {
	seconds: i64,
	fraction: u64,
}

file_status :: struct {
	uid: u64,
	type: file_type,
	perm: file_perm,
	size: u64,
	creationDate: datestamp,
	accessDate: datestamp,
	modificationDate: datestamp,
}

// An type describing a list of enumerated files in a given directory.
file_list :: struct {
	list: list,
	eltCount: u64,
}

file_listdir_elt :: struct {
	listElt: list_elt,
	basename: str8,
	type: file_type,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Send a single I/O request and wait for its completion.
	io_wait_single_req :: proc(req: ^io_req) -> io_cmp ---
	// Returns a `nil` file handle
	file_nil :: proc() -> file ---
	// Test if a file handle is `nil`.
	file_is_nil :: proc(handle: file) -> bool ---
	// Open a file in the applications' default directory subtree.
	file_open :: proc(path: str8, rights: file_access, flags: file_open_flags) -> file ---
	// Open a file in a given directory's subtree.
	file_open_at :: proc(dir: file, path: str8, rights: file_access, flags: file_open_flags) -> file ---
	// Close a file.
	file_close :: proc(file: file) ---
	// Get the current position in a file.
	file_pos :: proc(file: file) -> i64 ---
	// Set the current position in a file.
	file_seek :: proc(file: file, offset: i64, whence: file_whence) -> i64 ---
	// Write data to a file.
	file_write :: proc(file: file, size: u64, buffer: [^]char) -> u64 ---
	// Read from a file.
	file_read :: proc(file: file, size: u64, buffer: [^]char) -> u64 ---
	// Get the last error on a file handle.
	file_last_error :: proc(handle: file) -> io_error ---
	file_get_status :: proc(file: file) -> file_status ---
	file_size :: proc(file: file) -> u64 ---
	file_open_with_request :: proc(path: str8, rights: file_access, flags: file_open_flags) -> file ---
	file_listdir :: proc(arena: ^arena, directory: str8) -> file_list ---
}

////////////////////////////////////////////////////////////////////////////////
// API for obtaining file capabilities through open/save dialogs.
////////////////////////////////////////////////////////////////////////////////

// An element of a list of file handles acquired through a file dialog.
file_open_with_dialog_elt :: struct {
	listElt: list_elt,
	file: file,
}

// A structure describing the result of a call to `oc_file_open_with_dialog()`.
file_open_with_dialog_result :: struct {
	// The button of the file dialog clicked by the user.
	button: file_dialog_button,
	// The file that was opened through the dialog. If the dialog had the `OC_FILE_DIALOG_MULTIPLE` flag set, this is equal to the first handle in the `selection` list.
	file: file,
	// If the dialog had the `OC_FILE_DIALOG_MULTIPLE` flag set, this list of `oc_file_open_with_dialog_elt` contains the handles of the opened files.
	selection: list,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Open files through a file dialog. This allows the user to select files outside the root directories currently accessible to the applications, giving them a way to provide new file capabilities to the application.
	file_open_with_dialog :: proc(arena: ^arena, rights: file_access, flags: file_open_flags, desc: ^file_dialog_desc) -> file_open_with_dialog_result ---
}

////////////////////////////////////////////////////////////////////////////////
// API for handling filesystem paths.
////////////////////////////////////////////////////////////////////////////////

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Get a string slice of the directory part of a path.
	path_slice_directory :: proc(path: str8) -> str8 ---
	// Get a string slice of the file name part of a path.
	path_slice_filename :: proc(path: str8) -> str8 ---
	// Split a path into path elements.
	path_split :: proc(arena: ^arena, path: str8) -> str8_list ---
	// Join path elements to form a path.
	path_join :: proc(arena: ^arena, elements: str8_list) -> str8 ---
	// Append a path to another path.
	path_append :: proc(arena: ^arena, parent: str8, relPath: str8) -> str8 ---
	// Test wether a path is an absolute path.
	path_is_absolute :: proc(path: str8) -> bool ---
}

////////////////////////////////////////////////////////////////////////////////
// 2D/3D rendering APIs.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// A 2D Vector Graphics API.
////////////////////////////////////////////////////////////////////////////////

// An opaque handle to a graphics surface.
surface :: distinct u64

// An opaque handle representing a rendering engine for the canvas API.
canvas_renderer :: distinct u64

// An opaque handle to a canvas context. Canvas contexts are used to hold contextual state about drawing commands, such as the current color or the current line width, and to record drawing commands. Once commands have been recorded, they can be rendered to a surface using `oc_canvas_render()`.
canvas_context :: distinct u64

// An opaque font handle.
font :: distinct u64

// An opaque image handle.
image :: distinct u64

// This enum describes possible blending modes for color gradient.
gradient_blend_space :: enum u32 {
	// The gradient colors are interpolated in linear space.
	LINEAR = 0,
	// The gradient colors are interpolated in sRGB space.
	SRGB = 1,
}

// An enum identifying possible color spaces.
color_space :: enum u32 {
	// A linear RGB color space.
	RGB = 0,
	// An sRGB color space.
	SRGB = 1,
}

// A struct representing a color.
color :: struct { using c: [4]f32, colorSpace: color_space }

// Stroke joint types.
joint_type :: enum u32 {
	// Miter joint.
	MITER = 0,
	// Bevel joint.
	BEVEL = 1,
	// Don't join path segments.
	NONE = 2,
}

// Cap types.
cap_type :: enum u32 {
	// Don't draw caps.
	NONE = 0,
	// Square caps.
	SQUARE = 1,
}

// A struct describing the metrics of a font.
font_metrics :: struct {
	// The ascent from the baseline to the top of the line (a positive value means the top line is above the baseline). 
	ascent: f32,
	// The descent from the baseline to the bottom line (a positive value means the bottom line is below the baseline). 
	descent: f32,
	// The gap between two lines of text.
	lineGap: f32,
	// The height of the lowercase character 'x'.
	xHeight: f32,
	// The height of capital letters.
	capHeight: f32,
	// The maximum character width.
	width: f32,
}

// A struct describing the metrics of a single glyph.
glyph_metrics :: struct {
	ink: rect,
	// The default amount from which to advance the cursor after drawing this glyph.
	advance: vec2,
}

// A struct describing the metrics of a run of glyphs.
text_metrics :: struct {
	// The bounding box of the inked portion of the text.
	ink: rect,
	// The logical bounding box of the text (including ascents, descents, and line gaps).
	logical: rect,
	// The amount from which to advance the cursor after drawing the text.
	advance: vec2,
}

// An opaque struct representing a rectangle atlas. This is used to allocate rectangular regions of an image to make texture atlases.
rect_atlas :: struct {}

// A struct describing a rectangular sub-region of an image.
image_region :: struct {
	// The image handle.
	image: image,
	// The rectangular region of the image.
	rect: rect,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Returns a `nil` surface handle.
	surface_nil :: proc() -> surface ---
	// Check if a surface handle is `nil`.
	surface_is_nil :: proc(surface: surface) -> bool ---
	// Destroy a graphics surface.
	surface_destroy :: proc(surface: surface) ---
	/*
	Get a surface's size.
	
	The size is returned in device-independent "points". To get the size in pixels, multiply the size in points by the scaling factor returned by `oc_surface_contents_scaling()`.
	*/
	surface_get_size :: proc(surface: surface) -> vec2 ---
	// Get the scaling factor of a surface.
	surface_contents_scaling :: proc(surface: surface) -> vec2 ---
	// Bring a surface to the foreground, rendering it on top of other surfaces.
	surface_bring_to_front :: proc(surface: surface) ---
	// Send a surface to the background, rendering it below other surfaces.
	surface_send_to_back :: proc(surface: surface) ---
	// Checks if a surface is hidden.
	surface_get_hidden :: proc(surface: surface) -> bool ---
	// Set the hidden status of a surface.
	surface_set_hidden :: proc(surface: surface, hidden: bool) ---
	// Create a color using RGBA values.
	color_rgba :: proc(r: f32, g: f32, b: f32, a: f32) -> color ---
	// Create a current color using sRGBA values.
	color_srgba :: proc(r: f32, g: f32, b: f32, a: f32) -> color ---
	// Convert a color from one color space to another.
	color_convert :: proc(_color: color, colorSpace: color_space) -> color ---
	// Returns a `nil` canvas renderer handle.
	canvas_renderer_nil :: proc() -> canvas_renderer ---
	// Checks if a canvas renderer handle is `nil`.
	canvas_renderer_is_nil :: proc(renderer: canvas_renderer) -> bool ---
	// Create a canvas renderer.
	canvas_renderer_create :: proc() -> canvas_renderer ---
	// Destroy a canvas renderer.
	canvas_renderer_destroy :: proc(renderer: canvas_renderer) ---
	// Render canvas commands onto a surface.
	canvas_render :: proc(renderer: canvas_renderer, _context: canvas_context, surface: surface) ---
	// Present a canvas surface to the display.
	canvas_present :: proc(renderer: canvas_renderer, surface: surface) ---
	// Create a surface for rendering vector graphics.
	canvas_surface_create :: proc(renderer: canvas_renderer) -> surface ---
	// Returns a `nil` canvas context handle.
	canvas_context_nil :: proc() -> canvas_context ---
	// Checks if a canvas context handle is `nil`.
	canvas_context_is_nil :: proc(_context: canvas_context) -> bool ---
	// Create a canvas context.
	canvas_context_create :: proc() -> canvas_context ---
	// Destroy a canvas context
	canvas_context_destroy :: proc(_context: canvas_context) ---
	// Make a canvas context current in the calling thread. Subsequent canvas commands will refer to this context until another context is made current.
	canvas_context_select :: proc(_context: canvas_context) -> canvas_context ---
	// Set the multisample anti-aliasing sample count for the commands of a context.
	canvas_context_set_msaa_sample_count :: proc(_context: canvas_context, sampleCount: u32) ---
	// Return a `nil` font handle.
	font_nil :: proc() -> font ---
	// Check if a font handle is `nil`.
	font_is_nil :: proc(font: font) -> bool ---
	// Create a font from in-memory TrueType data.
	font_create_from_memory :: proc(mem: str8, rangeCount: u32, ranges: ^unicode_range) -> font ---
	// Create a font from a TrueType font file.
	font_create_from_file :: proc(file: file, rangeCount: u32, ranges: ^unicode_range) -> font ---
	// Create a font from a TrueType font file path.
	font_create_from_path :: proc(path: str8, rangeCount: u32, ranges: ^unicode_range) -> font ---
	// Destroy a font.
	font_destroy :: proc(font: font) ---
	// Get the glyph indices of a run of unicode code points in a given font.
	font_get_glyph_indices :: proc(font: font, codePoints: str32, backing: str32) -> str32 ---
	// Get the glyph indices of a run of unicode code points in a given font and push them on an arena.
	font_push_glyph_indices :: proc(arena: ^arena, font: font, codePoints: str32) -> str32 ---
	// Get the glyp index of a single codepoint in a given font.
	font_get_glyph_index :: proc(font: font, codePoint: utf32) -> u32 ---
	// Get a font's metrics for a given font size.
	font_get_metrics :: proc(font: font, emSize: f32) -> font_metrics ---
	// Get a font's unscaled metrics.
	font_get_metrics_unscaled :: proc(font: font) -> font_metrics ---
	// Get a scale factor to apply to unscaled font metrics to obtain a given 'm' size.
	font_get_scale_for_em_pixels :: proc(font: font, emSize: f32) -> f32 ---
	// Get text metrics for a run of unicode code points.
	font_text_metrics_utf32 :: proc(font: font, fontSize: f32, codepoints: str32) -> text_metrics ---
	// Get the text metrics for a utf8 string.
	font_text_metrics :: proc(font: font, fontSize: f32, text: str8) -> text_metrics ---
	// Returns a `nil` image handle.
	image_nil :: proc() -> image ---
	// Check if an image handle is `nil`.
	image_is_nil :: proc(a: image) -> bool ---
	// Create an uninitialized image.
	image_create :: proc(renderer: canvas_renderer, width: u32, height: u32) -> image ---
	// Create an image from an array of 8 bit per channel rgba values.
	image_create_from_rgba8 :: proc(renderer: canvas_renderer, width: u32, height: u32, pixels: [^]u8) -> image ---
	// Create an image from in-memory png, jpeg or bmp data.
	image_create_from_memory :: proc(renderer: canvas_renderer, mem: str8, flip: bool) -> image ---
	// Create an image from an image file. Supported formats are: png, jpeg or bmp.
	image_create_from_file :: proc(renderer: canvas_renderer, file: file, flip: bool) -> image ---
	// Create an image from an image file path. Supported formats are: png, jpeg or bmp.
	image_create_from_path :: proc(renderer: canvas_renderer, path: str8, flip: bool) -> image ---
	// Destroy an image.
	image_destroy :: proc(image: image) ---
	// Upload pixels to an image.
	image_upload_region_rgba8 :: proc(image: image, region: rect, pixels: [^]u8) ---
	// Get the size of an image.
	image_size :: proc(image: image) -> vec2 ---
	// Create a rectangle atlas.
	rect_atlas_create :: proc(arena: ^arena, width: i32, height: i32) -> ^rect_atlas ---
	// Allocate a rectangular region from an atlas.
	rect_atlas_alloc :: proc(atlas: ^rect_atlas, width: i32, height: i32) -> rect ---
	// Recycle a rectangular region that was previously allocated from an atlas.
	rect_atlas_recycle :: proc(atlas: ^rect_atlas, rect: rect) ---
	// Allocate an image region from an atlas and upload pixels to that region.
	image_atlas_alloc_from_rgba8 :: proc(atlas: ^rect_atlas, backingImage: image, width: u32, height: u32, pixels: [^]u8) -> image_region ---
	// Allocate an image region from an atlas and upload an image to it.
	image_atlas_alloc_from_memory :: proc(atlas: ^rect_atlas, backingImage: image, mem: str8, flip: bool) -> image_region ---
	// Allocate an image region from an atlas and upload an image to it.
	image_atlas_alloc_from_file :: proc(atlas: ^rect_atlas, backingImage: image, file: file, flip: bool) -> image_region ---
	// Allocate an image region from an atlas and upload an image to it.
	image_atlas_alloc_from_path :: proc(atlas: ^rect_atlas, backingImage: image, path: str8, flip: bool) -> image_region ---
	// Recycle an image region allocated from an atlas.
	image_atlas_recycle :: proc(atlas: ^rect_atlas, imageRgn: image_region) ---
	// Push a matrix on the transform stack.
	matrix_push :: proc(_matrix: mat2x3) ---
	// Multiply a matrix with the top of the transform stack, and push the result on the top of the stack.
	matrix_multiply_push :: proc(_matrix: mat2x3) ---
	// Pop a matrix from the transform stack.
	matrix_pop :: proc() ---
	// Get the top matrix of the transform stack.
	matrix_top :: proc() -> mat2x3 ---
	// Push a clip rectangle to the clip stack.
	clip_push :: proc(x: f32, y: f32, w: f32, h: f32) ---
	// Pop from the clip stack.
	clip_pop :: proc() ---
	// Get the clip rectangle from the top of the clip stack.
	clip_top :: proc() -> rect ---
	// Set the current color.
	set_color :: proc(_color: color) ---
	// Set the current color using linear RGBA values.
	set_color_rgba :: proc(r: f32, g: f32, b: f32, a: f32) ---
	// Set the current color using sRGBA values.
	set_color_srgba :: proc(r: f32, g: f32, b: f32, a: f32) ---
	// Set the current color gradient.
	set_gradient :: proc(blendSpace: gradient_blend_space, bottomLeft: color, bottomRight: color, topRight: color, topLeft: color) ---
	// Set the current line width.
	set_width :: proc(width: f32) ---
	// Set the current tolerance for the line width. Bigger values increase performance but allow more inconsistent stroke widths along a path.
	set_tolerance :: proc(tolerance: f32) ---
	// Set the current joint style.
	set_joint :: proc(joint: joint_type) ---
	// Set the maximum joint excursion. If a joint would extend past this threshold, the renderer falls back to a bevel joint.
	set_max_joint_excursion :: proc(maxJointExcursion: f32) ---
	// Set the current cap style.
	set_cap :: proc(cap: cap_type) ---
	// The the current font.
	set_font :: proc(font: font) ---
	// Set the current font size.
	set_font_size :: proc(size: f32) ---
	// Set the current text flip value. `true` flips the y-axis of text rendering commands.
	set_text_flip :: proc(flip: bool) ---
	// Set the current source image.
	set_image :: proc(image: image) ---
	// Set the current source image region.
	set_image_source_region :: proc(region: rect) ---
	// Get the current color
	get_color :: proc() -> color ---
	// Get the current line width.
	get_width :: proc() -> f32 ---
	// Get the current line width tolerance.
	get_tolerance :: proc() -> f32 ---
	// Get the current joint style.
	get_joint :: proc() -> joint_type ---
	// Get the current max joint excursion.
	get_max_joint_excursion :: proc() -> f32 ---
	// Get the current cap style.
	get_cap :: proc() -> cap_type ---
	// Get the current font.
	get_font :: proc() -> font ---
	// Get the current font size.
	get_font_size :: proc() -> f32 ---
	// Get the current text flip value.
	get_text_flip :: proc() -> bool ---
	// Get the current source image.
	get_image :: proc() -> image ---
	// Get the current image source region.
	get_image_source_region :: proc() -> rect ---
	// Get the current cursor position.
	get_position :: proc() -> vec2 ---
	// Move the cursor to a given position.
	move_to :: proc(x: f32, y: f32) ---
	// Add a line to the path from the current position to a new one.
	line_to :: proc(x: f32, y: f32) ---
	// Add a quadratic Bézier curve to the path from the current position to a new one.
	quadratic_to :: proc(x1: f32, y1: f32, x2: f32, y2: f32) ---
	// Add a cubic Bézier curve to the path from the current position to a new one.
	cubic_to :: proc(x1: f32, y1: f32, x2: f32, y2: f32, x3: f32, y3: f32) ---
	// Close the current path with a line.
	close_path :: proc() ---
	// Add the outlines of a glyph run to the path, using glyph indices.
	glyph_outlines :: proc(glyphIndices: str32) -> rect ---
	// Add the outlines of a glyph run to the path, using unicode codepoints.
	codepoints_outlines :: proc(string: str32) ---
	// Add the outlines of a glyph run to the path, using a utf8 string.
	text_outlines :: proc(string: str8) ---
	// Clear the canvas to the current color.
	clear :: proc() ---
	// Fill the current path.
	fill :: proc() ---
	// Stroke the current path.
	stroke :: proc() ---
	// Draw a filled rectangle.
	rectangle_fill :: proc(x: f32, y: f32, w: f32, h: f32) ---
	// Draw a stroked rectangle.
	rectangle_stroke :: proc(x: f32, y: f32, w: f32, h: f32) ---
	// Draw a filled rounded rectangle.
	rounded_rectangle_fill :: proc(x: f32, y: f32, w: f32, h: f32, r: f32) ---
	// Draw a stroked rounded rectangle.
	rounded_rectangle_stroke :: proc(x: f32, y: f32, w: f32, h: f32, r: f32) ---
	// Draw a filled ellipse.
	ellipse_fill :: proc(x: f32, y: f32, rx: f32, ry: f32) ---
	// Draw a stroked ellipse.
	ellipse_stroke :: proc(x: f32, y: f32, rx: f32, ry: f32) ---
	// Draw a filled circle.
	circle_fill :: proc(x: f32, y: f32, r: f32) ---
	// Draw a stroked circle.
	circle_stroke :: proc(x: f32, y: f32, r: f32) ---
	// Add an arc to the path.
	arc :: proc(x: f32, y: f32, r: f32, arcAngle: f32, startAngle: f32) ---
	// Draw a text line.
	text_fill :: proc(x: f32, y: f32, text: str8) ---
	// Draw an image.
	image_draw :: proc(image: image, rect: rect) ---
	// Draw a sub-region of an image.
	image_draw_region :: proc(image: image, srcRegion: rect, dstRegion: rect) ---
}

////////////////////////////////////////////////////////////////////////////////
// A surface for rendering using the GLES API.
////////////////////////////////////////////////////////////////////////////////

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	// Create a graphics surface for GLES rendering.
	gles_surface_create :: proc() -> surface ---
	// Make the GL context of the surface current.
	gles_surface_make_current :: proc(surface: surface) ---
	// Swap the buffers of a GLES surface.
	gles_surface_swap_buffers :: proc(surface: surface) ---
}

////////////////////////////////////////////////////////////////////////////////
// Graphical User Interface API.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// Graphical User Interface Core API.
////////////////////////////////////////////////////////////////////////////////

ui_axis :: enum u32 {
	X = 0,
	Y = 1,
	COUNT = 2,
}

ui_align :: enum u32 {
	START = 0,
	END = 1,
	CENTER = 2,
}

ui_size_kind :: enum u32 {
	CHILDREN = 0,
	TEXT = 1,
	PIXELS = 2,
	PARENT = 3,
	PARENT_MINUS_PIXELS = 4,
}

ui_size :: struct {
	kind: ui_size_kind,
	value: f32,
	relax: f32,
	minSize: f32,
}

ui_overflow :: enum u32 {
	CLIP = 0,
	ALLOW = 1,
	SCROLL = 2,
}

ui_attribute :: enum u32 {
	WIDTH = 0,
	HEIGHT = 1,
	AXIS = 2,
	MARGIN_X = 3,
	MARGIN_Y = 4,
	SPACING = 5,
	ALIGN_X = 6,
	ALIGN_Y = 7,
	FLOATING_X = 8,
	FLOATING_Y = 9,
	FLOAT_TARGET_X = 10,
	FLOAT_TARGET_Y = 11,
	OVERFLOW_X = 12,
	OVERFLOW_Y = 13,
	CONSTRAIN_X = 14,
	CONSTRAIN_Y = 15,
	COLOR = 16,
	BG_COLOR = 17,
	BORDER_COLOR = 18,
	FONT = 19,
	TEXT_SIZE = 20,
	BORDER_SIZE = 21,
	ROUNDNESS = 22,
	DRAW_MASK = 23,
	ANIMATION_TIME = 24,
	ANIMATION_MASK = 25,
	CLICK_THROUGH = 26,
	ATTRIBUTE_COUNT = 27,
}

ui_attribute_mask :: enum u32 {
	NONE = 0,
	SIZE_WIDTH = 1,
	SIZE_HEIGHT = 2,
	LAYOUT_AXIS = 4,
	LAYOUT_MARGIN_X = 8,
	LAYOUT_MARGIN_Y = 16,
	LAYOUT_SPACING = 32,
	LAYOUT_ALIGN_X = 64,
	LAYOUT_ALIGN_Y = 128,
	FLOATING_X = 256,
	FLOATING_Y = 512,
	FLOAT_TARGET_X = 1024,
	FLOAT_TARGET_Y = 2048,
	OVERFLOW_X = 4096,
	OVERFLOW_Y = 8192,
	CONSTRAIN_X = 16384,
	CONSTRAIN_Y = 32768,
	COLOR = 65536,
	BG_COLOR = 131072,
	BORDER_COLOR = 262144,
	FONT = 524288,
	FONT_SIZE = 1048576,
	BORDER_SIZE = 2097152,
	ROUNDNESS = 4194304,
	DRAW_MASK = 8388608,
	ANIMATION_TIME = 16777216,
	ANIMATION_MASK = 33554432,
	CLICK_THROUGH = 67108864,
}

ui_layout_align :: [2]ui_align

ui_layout :: struct {
	axis: ui_axis,
	spacing: f32,
	margin: [2]f32,
	align: ui_layout_align,
	overflow: [2]ui_overflow,
	constrain: [2]bool,
}

ui_box_size :: [2]ui_size

ui_box_floating :: [2]bool

// These bits *disable* the corresponding element when they're set.
ui_draw_mask :: enum u32 {
	BACKGROUND = 1,
	BORDER = 2,
	TEXT = 4,
	PROC = 8,
}

ui_style :: struct {
	size: ui_box_size,
	layout: ui_layout,
	floating: ui_box_floating,
	floatTarget: vec2,
	_color: color,
	bgColor: color,
	borderColor: color,
	font: font,
	fontSize: f32,
	borderSize: f32,
	roundness: f32,
	drawMask: u32,
	animationTime: f32,
	animationMask: ui_attribute_mask,
	clickThrough: bool,
}

ui_context :: struct {}

ui_sig :: struct {
	box: ^ui_box,
	mouse: vec2,
	delta: vec2,
	wheel: vec2,
	lastPressedMouse: vec2,
	pressed: bool,
	released: bool,
	clicked: bool,
	doubleClicked: bool,
	tripleClicked: bool,
	rightPressed: bool,
	closed: bool,
	active: bool,
	hover: bool,
	focus: bool,
	pasted: bool,
}

ui_box_draw_proc :: proc "c" (arg0: ^ui_box, arg1: rawptr)

ui_key :: struct {
	hash: u64,
}

ui_box :: struct {
	listElt: list_elt,
	children: list,
	parent: ^ui_box,
	overlayElt: list_elt,
	overlay: bool,
	bucketElt: list_elt,
	key: ui_key,
	frameCounter: u64,
	keyString: str8,
	text: str8,
	tags: list,
	drawProc: ui_box_draw_proc,
	drawData: rawptr,
	rules: list,
	targetStyle: ^ui_style,
	style: ui_style,
	z: u32,
	floatPos: vec2,
	childrenSum: [2]f32,
	spacing: [2]f32,
	minSize: [2]f32,
	rect: rect,
	styleVariables: list,
	sig: ui_sig,
	fresh: bool,
	closed: bool,
	parentClosed: bool,
	dragging: bool,
	hot: bool,
	active: bool,
	scroll: vec2,
	pressedMouse: vec2,
	hotTransition: f32,
	activeTransition: f32,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	ui_context_create :: proc(defaultFont: font) -> ^ui_context ---
	ui_context_destroy :: proc(_context: ^ui_context) ---
	ui_get_context :: proc() -> ^ui_context ---
	ui_set_context :: proc(_context: ^ui_context) ---
	ui_process_event :: proc(event: ^event) ---
	ui_frame_begin :: proc(size: vec2) ---
	ui_frame_end :: proc() ---
	ui_draw :: proc() ---
	ui_input :: proc() -> ^input_state ---
	ui_frame_arena :: proc() -> ^arena ---
	ui_frame_time :: proc() -> f64 ---
	ui_box_begin_str8 :: proc(string: str8) -> ^ui_box ---
	ui_box_end :: proc() -> ^ui_box ---
	ui_box_set_draw_proc :: proc(box: ^ui_box, _proc: ui_box_draw_proc, data: rawptr) ---
	ui_box_set_text :: proc(box: ^ui_box, text: str8) ---
	ui_box_set_overlay :: proc(box: ^ui_box, overlay: bool) ---
	ui_box_set_closed :: proc(box: ^ui_box, closed: bool) ---
	ui_box_user_data_get :: proc(box: ^ui_box) -> cstring ---
	ui_box_user_data_push :: proc(box: ^ui_box, size: u64) -> cstring ---
	ui_box_request_focus :: proc(box: ^ui_box) ---
	ui_box_release_focus :: proc(box: ^ui_box) ---
	ui_box_get_sig :: proc(box: ^ui_box) -> ui_sig ---
	ui_set_draw_proc :: proc(_proc: ui_box_draw_proc, data: rawptr) ---
	ui_set_text :: proc(text: str8) ---
	ui_set_overlay :: proc(overlay: bool) ---
	ui_set_closed :: proc(closed: bool) ---
	ui_user_data_get :: proc() -> cstring ---
	ui_user_data_push :: proc(size: u64) -> cstring ---
	ui_request_focus :: proc() ---
	ui_release_focus :: proc() ---
	ui_get_sig :: proc() -> ui_sig ---
	ui_box_tag_str8 :: proc(box: ^ui_box, string: str8) ---
	ui_tag_str8 :: proc(string: str8) ---
	ui_tag_next_str8 :: proc(string: str8) ---
	ui_style_rule_begin :: proc(pattern: str8) ---
	ui_style_rule_end :: proc() ---
	ui_style_set_i32 :: proc(attr: ui_attribute, i: i32) ---
	ui_style_set_f32 :: proc(attr: ui_attribute, f: f32) ---
	ui_style_set_color :: proc(attr: ui_attribute, _color: color) ---
	ui_style_set_font :: proc(attr: ui_attribute, font: font) ---
	ui_style_set_size :: proc(attr: ui_attribute, size: ui_size) ---
	ui_style_set_var_str8 :: proc(attr: ui_attribute, var: str8) ---
	ui_style_set_var :: proc(attr: ui_attribute, var: cstring) ---
	ui_var_default_i32_str8 :: proc(name: str8, i: i32) ---
	ui_var_default_f32_str8 :: proc(name: str8, f: f32) ---
	ui_var_default_size_str8 :: proc(name: str8, size: ui_size) ---
	ui_var_default_color_str8 :: proc(name: str8, _color: color) ---
	ui_var_default_font_str8 :: proc(name: str8, font: font) ---
	ui_var_default_str8 :: proc(name: str8, src: str8) ---
	ui_var_default_i32 :: proc(name: cstring, i: i32) ---
	ui_var_default_f32 :: proc(name: cstring, f: f32) ---
	ui_var_default_size :: proc(name: cstring, size: ui_size) ---
	ui_var_default_color :: proc(name: cstring, _color: color) ---
	ui_var_default_font :: proc(name: cstring, font: font) ---
	ui_var_default :: proc(name: cstring, src: cstring) ---
	ui_var_set_i32_str8 :: proc(name: str8, i: i32) ---
	ui_var_set_f32_str8 :: proc(name: str8, f: f32) ---
	ui_var_set_size_str8 :: proc(name: str8, size: ui_size) ---
	ui_var_set_color_str8 :: proc(name: str8, _color: color) ---
	ui_var_set_font_str8 :: proc(name: str8, font: font) ---
	ui_var_set_str8 :: proc(name: str8, src: str8) ---
	ui_var_set_i32 :: proc(name: cstring, i: i32) ---
	ui_var_set_f32 :: proc(name: cstring, f: f32) ---
	ui_var_set_size :: proc(name: cstring, size: ui_size) ---
	ui_var_set_color :: proc(name: cstring, _color: color) ---
	ui_var_set_font :: proc(name: cstring, font: font) ---
	ui_var_set :: proc(name: cstring, src: cstring) ---
	ui_var_get_i32_str8 :: proc(name: str8) -> i32 ---
	ui_var_get_f32_str8 :: proc(name: str8) -> f32 ---
	ui_var_get_size_str8 :: proc(name: str8) -> ui_size ---
	ui_var_get_color_str8 :: proc(name: str8) -> color ---
	ui_var_get_font_str8 :: proc(name: str8) -> font ---
	ui_var_get_i32 :: proc(name: cstring) -> i32 ---
	ui_var_get_f32 :: proc(name: cstring) -> f32 ---
	ui_var_get_size :: proc(name: cstring) -> ui_size ---
	ui_var_get_color :: proc(name: cstring) -> color ---
	ui_var_get_font :: proc(name: cstring) -> font ---
	ui_theme_dark :: proc() ---
	ui_theme_light :: proc() ---
}

////////////////////////////////////////////////////////////////////////////////
// Graphical User Interface Widgets.
////////////////////////////////////////////////////////////////////////////////

ui_text_box_result :: struct {
	changed: bool,
	accepted: bool,
	text: str8,
	box: ^ui_box,
}

ui_edit_move :: enum u32 {
	NONE = 0,
	CHAR = 1,
	WORD = 2,
	LINE = 3,
}

ui_text_box_info :: struct {
	text: str8,
	defaultText: str8,
	cursor: i32,
	mark: i32,
	selectionMode: ui_edit_move,
	wordSelectionInitialCursor: i32,
	wordSelectionInitialMark: i32,
	firstDisplayedChar: i32,
	cursorBlinkStart: f64,
}

ui_select_popup_info :: struct {
	changed: bool,
	selectedIndex: i32,
	optionCount: i32 `fmt:"-"`,
	options: [^]str8 `fmt:"s,optionCount"`,
	placeholder: str8,
}

ui_radio_group_info :: struct {
	changed: bool,
	selectedIndex: i32,
	optionCount: i32 `fmt:"-"`,
	options: [^]str8 `fmt:"s,optionCount"`,
}

@(default_calling_convention="c", link_prefix="oc_")
foreign {
	ui_label :: proc(key: cstring, label: cstring) -> ui_sig ---
	ui_label_str8 :: proc(key: str8, label: str8) -> ui_sig ---
	ui_button :: proc(key: cstring, text: cstring) -> ui_sig ---
	ui_button_str8 :: proc(key: str8, text: str8) -> ui_sig ---
	ui_checkbox :: proc(key: cstring, checked: ^bool) -> ui_sig ---
	ui_checkbox_str8 :: proc(key: str8, checked: ^bool) -> ui_sig ---
	ui_slider :: proc(name: cstring, value: ^f32) -> ^ui_box ---
	ui_slider_str8 :: proc(name: str8, value: ^f32) -> ^ui_box ---
	ui_tooltip :: proc(key: cstring, text: cstring) ---
	ui_tooltip_str8 :: proc(key: str8, text: str8) ---
	ui_menu_bar_begin :: proc(key: cstring) ---
	ui_menu_bar_begin_str8 :: proc(key: str8) ---
	ui_menu_bar_end :: proc() ---
	ui_menu_begin :: proc(key: cstring, name: cstring) ---
	ui_menu_begin_str8 :: proc(key: str8, name: str8) ---
	ui_menu_end :: proc() ---
	ui_menu_button :: proc(key: cstring, text: cstring) -> ui_sig ---
	ui_menu_button_str8 :: proc(key: str8, text: str8) -> ui_sig ---
	ui_text_box :: proc(key: cstring, arena: ^arena, info: ^ui_text_box_info) -> ui_text_box_result ---
	ui_text_box_str8 :: proc(key: str8, arena: ^arena, info: ^ui_text_box_info) -> ui_text_box_result ---
	ui_select_popup :: proc(key: cstring, info: ^ui_select_popup_info) -> ui_select_popup_info ---
	ui_select_popup_str8 :: proc(key: str8, info: ^ui_select_popup_info) -> ui_select_popup_info ---
	ui_radio_group :: proc(key: cstring, info: ^ui_radio_group_info) -> ui_radio_group_info ---
	ui_radio_group_str8 :: proc(key: str8, info: ^ui_radio_group_info) -> ui_radio_group_info ---
}