Added {EXT_texture_compression,WEBGL_compressed_texture}_s3tc_srgb extensions.

And silently the definitions from EXT_texture_sRGB (core since GL 2.1) as
that's where definitions for sRGB S3TC formats are hiding on desktop.

doc/opengl-support.dox

@@ -454,6 +454,7 @@ Extension                                   | Status
 @gl_extension{EXT,sRGB_write_control}       | done
 @gl_extension{EXT,texture_compression_s3tc} | done
 @gl_extension{EXT,shader_integer_mix}       | done (shading language only)
+@gl_extension{EXT,texture_compression_s3tc_srgb} | |
 @gl_extension2{KHR,texture_compression_astc_hdr,KHR_texture_compression_astc_hdr} | done
 @gl_extension2{KHR,blend_equation_advanced_coherent,KHR_blend_equation_advanced} | done
 @gl_extension{KHR,context_flush_control}    | |
@@ -523,6 +524,7 @@ Extension                                   | Status
 @webgl_extension{EXT,color_buffer_float}    | |
 @webgl_extension{OES,texture_float_linear}  | done
 @webgl_extension{WEBGL,compressed_texture_s3tc} | done
+@webgl_extension{WEBGL,compressed_texture_s3tc_srgb} |
 
 @section opengl-unsupported Unsupported OpenGL features
 

src/Magnum/GL/Context.cpp

@@ -249,7 +249,8 @@ constexpr Extension ExtensionList[]{
     _extension(EXT,color_buffer_float),
     #endif
     _extension(OES,texture_float_linear),
-    _extension(WEBGL,compressed_texture_s3tc)};
+    _extension(WEBGL,compressed_texture_s3tc),
+    _extension(WEBGL,compressed_texture_s3tc_srgb)};
 constexpr Extension ExtensionListES300[]{
     #ifdef MAGNUM_TARGET_GLES2
     _extension(ANGLE,instanced_arrays),
@@ -298,6 +299,7 @@ constexpr Extension ExtensionList[]{
     _extension(EXT,shader_integer_mix),
     #endif
     _extension(EXT,polygon_offset_clamp),
+    _extension(EXT,texture_compression_s3tc_srgb),
     _extension(KHR,texture_compression_astc_hdr),
     _extension(KHR,blend_equation_advanced_coherent),
     _extension(KHR,context_flush_control),

src/Magnum/GL/Extensions.h

@@ -301,6 +301,7 @@ namespace ANGLE {
     _extension(19,WEBGL,color_buffer_float,         GLES200,    None) // #14
     _extension(20,WEBGL,draw_buffers,               GLES200, GLES300) // #18
     #endif
+    _extension(21,WEBGL,compressed_texture_s3tc_srgb, GLES200,  None) // #32
 } namespace MAGNUM {
     _extension(30,MAGNUM,shader_vertex_id,          GLES300, GLES300)
 }
@@ -397,6 +398,7 @@ namespace ANDROID {
     _extension( 60,EXT,primitive_bounding_box,      GLES310, GLES320) // #186
     #endif
     _extension( 61,EXT,polygon_offset_clamp,        GLES200,    None) // #252
+    _extension( 62,EXT,texture_compression_s3tc_srgb, GLES200,  None) // #289
 } namespace KHR {
     _extension( 70,KHR,texture_compression_astc_ldr,GLES200, GLES320) // #117
     _extension( 71,KHR,texture_compression_astc_hdr,GLES200,    None) // #117

src/MagnumExternal/OpenGL/GL/extensions.txt

@@ -4,6 +4,9 @@
 
 version 4.6 core
 
+# Need this only for sRGB S3TC definitions, everything else is core since 2.1
+extension EXT_texture_sRGB                      optional
+
 extension AMD_transform_feedback3_lines_triangles optional
 extension AMD_vertex_shader_layer               optional
 extension AMD_shader_trinary_minmax             optional

src/MagnumExternal/OpenGL/GL/flextGL.h

@@ -1596,6 +1596,25 @@ typedef void (APIENTRY *GLDEBUGPROC)(GLenum source,GLenum type,GLuint id,GLenum
 #define GL_TRANSFORM_FEEDBACK_OVERFLOW 0x82EC
 #define GL_TRANSFORM_FEEDBACK_STREAM_OVERFLOW 0x82ED
 
+/* GL_EXT_texture_sRGB */
+
+#define GL_SRGB_EXT 0x8C40
+#define GL_SRGB8_EXT 0x8C41
+#define GL_SRGB_ALPHA_EXT 0x8C42
+#define GL_SRGB8_ALPHA8_EXT 0x8C43
+#define GL_SLUMINANCE_ALPHA_EXT 0x8C44
+#define GL_SLUMINANCE8_ALPHA8_EXT 0x8C45
+#define GL_SLUMINANCE_EXT 0x8C46
+#define GL_SLUMINANCE8_EXT 0x8C47
+#define GL_COMPRESSED_SRGB_EXT 0x8C48
+#define GL_COMPRESSED_SRGB_ALPHA_EXT 0x8C49
+#define GL_COMPRESSED_SLUMINANCE_EXT 0x8C4A
+#define GL_COMPRESSED_SLUMINANCE_ALPHA_EXT 0x8C4B
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* GL_ARB_robustness */
 
 #define GL_NO_ERROR 0

src/MagnumExternal/OpenGL/GLES2/Emscripten/extensions.txt

@@ -25,3 +25,4 @@ extension EXT_disjoint_timer_query              optional
 # These are used as a base for WEBGL_* extensions
 extension EXT_color_buffer_float                optional
 extension EXT_texture_compression_s3tc          optional
+extension EXT_texture_compression_s3tc_srgb     optional

src/MagnumExternal/OpenGL/GLES2/extensions.txt

@@ -80,6 +80,7 @@ extension EXT_disjoint_timer_query              optional
 extension EXT_texture_sRGB_decode               optional
 extension EXT_sRGB_write_control                optional
 extension EXT_texture_compression_s3tc          optional
+extension EXT_texture_compression_s3tc_srgb     optional
 extension KHR_texture_compression_astc_hdr      optional
 extension KHR_blend_equation_advanced_coherent  optional
 extension KHR_context_flush_control             optional

src/MagnumExternal/OpenGL/GLES2/flextGL.h

@@ -987,6 +987,13 @@ typedef void (APIENTRY *GLDEBUGPROCKHR)(GLenum source,GLenum type,GLuint id,GLen
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* GL_KHR_texture_compression_astc_hdr */
 
 #define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0

src/MagnumExternal/OpenGL/GLES2/flextGLEmscripten.h

@@ -499,6 +499,13 @@ typedef khronos_uint64_t GLuint64;
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* Function prototypes */
 
 /* GL_ANGLE_instanced_arrays */

src/MagnumExternal/OpenGL/GLES2/flextGLWindowsDesktop.h

@@ -982,6 +982,13 @@ typedef void (APIENTRY *GLDEBUGPROCKHR)(GLenum source,GLenum type,GLuint id,GLen
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* GL_KHR_texture_compression_astc_hdr */
 
 #define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0

src/MagnumExternal/OpenGL/GLES3/Emscripten/extensions.txt

@@ -8,3 +8,4 @@ extension EXT_disjoint_timer_query              optional
 extension EXT_color_buffer_float                optional
 # These are used as a base for WEBGL_* extensions
 extension EXT_texture_compression_s3tc          optional
+extension EXT_texture_compression_s3tc_srgb     optional

src/MagnumExternal/OpenGL/GLES3/extensions.txt

@@ -45,6 +45,7 @@ extension EXT_disjoint_timer_query                  optional
 extension EXT_texture_sRGB_decode                   optional
 extension EXT_sRGB_write_control                    optional
 extension EXT_texture_compression_s3tc              optional
+extension EXT_texture_compression_s3tc_srgb         optional
 extension EXT_shader_integer_mix                    optional
 extension KHR_texture_compression_astc_hdr          optional
 extension KHR_blend_equation_advanced_coherent      optional

src/MagnumExternal/OpenGL/GLES3/flextGL.h

@@ -1526,6 +1526,13 @@ typedef void (APIENTRY *GLDEBUGPROCKHR)(GLenum source,GLenum type,GLuint id,GLen
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* GL_KHR_texture_compression_astc_hdr */
 
 #define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0

src/MagnumExternal/OpenGL/GLES3/flextGLEmscripten.h

@@ -738,6 +738,13 @@ typedef struct __GLsync *GLsync;
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* Function prototypes */
 
 /* GL_ES_VERSION_2_0 */

src/MagnumExternal/OpenGL/GLES3/flextGLWindowsDesktop.h

@@ -1518,6 +1518,13 @@ typedef void (APIENTRY *GLDEBUGPROCKHR)(GLenum source,GLenum type,GLuint id,GLen
 #define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
 #define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 
+/* GL_EXT_texture_compression_s3tc_srgb */
+
+#define GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+
 /* GL_KHR_texture_compression_astc_hdr */
 
 #define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0