Remove GLES2/WebGL1 support. (#821)

notable changes:

- depth/stencil images are now regular gl textures
- SG_PIXELFORMAT_DEPTH now resolves to GL_DEPTH_COMPONENT32F
- sg_gl_context_desc and sg_desc.gl removed
- in sg_begin_pass() only use glClearBuffer functions
- in sg_end_pass() MSAA resolve now does glInvalidateFramebuffer() on the MSAA buffer
- sg_features: instancing, multiple_render_targets, msaa_render_targets, imagetype_3d, imagetype_array removed
- sapp_desc.gl_force_gles2 removed
- sapp_gles2() function removed
- any GLES3-to-GLES2 fallbacks removed

1 files changed, 56 insertions, 51 deletions

diff --git a/util/sokol_fontstash.h b/util/sokol_fontstash.h
index 049d5e11..9bf406fc 100644
--- a/util/sokol_fontstash.h
+++ b/util/sokol_fontstash.h
@@ -20,7 +20,6 @@
     used by sokol_gfx.h and sokol_app.h):
 
     SOKOL_GLCORE33
-    SOKOL_GLES2
     SOKOL_GLES3
     SOKOL_D3D11
     SOKOL_METAL
@@ -283,7 +282,7 @@ SOKOL_FONTSTASH_API_DECL uint32_t sfons_rgba(uint8_t r, uint8_t g, uint8_t b, ui
 /*
     Embedded source code compiled with:
 
-    sokol-shdc -i sfons.glsl -o sfons.h -l glsl330:glsl100:hlsl4:metal_macos:metal_ios:metal_sim:wgpu -b
+    sokol-shdc -i sfons.glsl -o sfons.h -l glsl330:glsl300es:hlsl4:metal_macos:metal_ios:metal_sim:wgpu -b
 
     (not that for Metal and D3D11 byte code, sokol-shdc must be run
     on macOS and Windows)
@@ -366,52 +365,58 @@ static const char _sfons_fs_source_glsl330[195] = {
     0x79,0x29,0x2e,0x78,0x29,0x20,0x2a,0x20,0x63,0x6f,0x6c,0x6f,0x72,0x3b,0x0a,0x7d,
     0x0a,0x0a,0x00,
 };
-#elif defined(SOKOL_GLES2) || defined(SOKOL_GLES3)
-static const char _sfons_vs_source_glsl100[430] = {
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+#elif defined(SOKOL_GLES3)
+static const char _sfons_vs_source_glsl300es[481] = {
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+    0x00,
 };
-static const char _sfons_fs_source_glsl100[233] = {
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+static const char _sfons_fs_source_glsl300es[268] = {
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+    0x20,0x63,0x6f,0x6c,0x6f,0x72,0x3b,0x0a,0x7d,0x0a,0x0a,0x00,
 };
 #elif defined(SOKOL_METAL)
 static const uint8_t _sfons_vs_bytecode_metal_macos[3417] = {
@@ -1651,7 +1656,7 @@ static const uint8_t fs_bytecode_wgpu[1000] = {
 static const char* _sfons_vs_source_dummy = "";
 static const char* _sfons_fs_source_dummy = "";
 #else
-#error "Please define one of SOKOL_GLCORE33, SOKOL_GLES2, SOKOL_GLES3, SOKOL_D3D11, SOKOL_METAL, SOKOL_WGPU or SOKOL_DUMMY_BACKEND!"
+#error "Please define one of SOKOL_GLCORE33, SOKOL_GLES3, SOKOL_D3D11, SOKOL_METAL, SOKOL_WGPU or SOKOL_DUMMY_BACKEND!"
 #endif
 
 typedef struct _sfons_t {
@@ -1729,9 +1734,9 @@ static int _sfons_render_create(void* user_ptr, int width, int height) {
         #if defined(SOKOL_GLCORE33)
             shd_desc.vs.source = _sfons_vs_source_glsl330;
             shd_desc.fs.source = _sfons_fs_source_glsl330;
-        #elif defined(SOKOL_GLES2) || defined(SOKOL_GLES3)
-            shd_desc.vs.source = _sfons_vs_source_glsl100;
-            shd_desc.fs.source = _sfons_fs_source_glsl100;
+        #elif defined(SOKOL_GLES3)
+            shd_desc.vs.source = _sfons_vs_source_glsl300es;
+            shd_desc.fs.source = _sfons_fs_source_glsl300es;
         #elif defined(SOKOL_METAL)
             shd_desc.vs.entry = "main0";
             shd_desc.fs.entry = "main0";