GL: hook up EXT_texture_sRGB_RG8 for desktop GL as well.

Was browsing the extension registry looking for something else and found
this instead. It used to be ES catching up with desktop, now it's the
other way around.

doc/changelog.dox

@@ -88,6 +88,9 @@ See also:
     @webgl_extension{EXT,texture_norm16} ES and WebGL extensions, making
     normalized 16-bit texture and renderbuffer formats available on all
     platforms
+-   The @gl_extension{EXT,texture_sRGB_RG8} extension is now available on
+    desktop OpenGL as well, exposing a two-component sRGB format in addition to
+    the already present one-, three- and four-component formats
 -   Implemented @webgl_extension{WEBGL,blend_equation_advanced_coherent}
     extension, making advanced @ref GL::Renderer::BlendEquation values
     available on all platforms

doc/opengl-support.dox

@@ -323,6 +323,7 @@ Extension                                   | Status
 @gl_extension{EXT,debug_label}              | missing pipeline and sampler label
 @gl_extension{EXT,debug_marker}             | done
 @gl_extension{EXT,texture_sRGB_R8}          | done
+@gl_extension{EXT,texture_sRGB_RG8}         | done
 @gl_extension{GREMEDY,string_marker}        | done
 @gl_extension{NV,sample_locations}          | |
 @gl_extension{NV,fragment_shader_barycentric} | done (shading language only)

src/Magnum/GL/AbstractTexture.cpp

@@ -610,7 +610,7 @@ PixelFormat pixelFormatForInternalFormat(const TextureFormat internalFormat) {
         #ifndef MAGNUM_TARGET_GLES2
         case TextureFormat::RG8Snorm:
         #endif
-        #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_GLES2)
+        #ifndef MAGNUM_TARGET_GLES2
         case TextureFormat::SRG8:
         #endif
         #ifndef MAGNUM_TARGET_GLES2
@@ -917,14 +917,10 @@ PixelType pixelTypeForInternalFormat(const TextureFormat internalFormat) {
         case TextureFormat::Luminance:
         case TextureFormat::LuminanceAlpha:
         #endif
-        #ifndef MAGNUM_TARGET_WEBGL
+        #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
-        #ifndef MAGNUM_TARGET_GLES2
         case TextureFormat::SR8:
-        #endif
-        #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_GLES2)
         case TextureFormat::SRG8:
         #endif
-        #endif
         #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)
         case TextureFormat::SRGB:
         case TextureFormat::SRGBAlpha:

src/Magnum/GL/Context.cpp

@@ -98,6 +98,7 @@ constexpr Extension ExtensionList[]{
     Extensions::EXT::texture_filter_anisotropic{},
     Extensions::EXT::texture_mirror_clamp{},
     Extensions::EXT::texture_sRGB_R8{},
+    Extensions::EXT::texture_sRGB_RG8{},
     Extensions::EXT::texture_sRGB_decode{},
     Extensions::GREMEDY::string_marker{},
     Extensions::KHR::blend_equation_advanced{},

src/Magnum/GL/Extensions.h

@@ -242,8 +242,9 @@ namespace AMD {
     _extension(154,EXT,debug_label,                     GL210,  None) // #439
     _extension(155,EXT,debug_marker,                    GL210,  None) // #440
     _extension(156,EXT,texture_sRGB_R8,                 GL210,  None) // #534
+    _extension(157,EXT,texture_sRGB_RG8,                GL210,  None) // #555
 } namespace GREMEDY {
-    _extension(157,GREMEDY,string_marker,               GL210,  None) // #311
+    _extension(158,GREMEDY,string_marker,               GL210,  None) // #311
 } namespace KHR {
     _extension(160,KHR,texture_compression_astc_ldr,    GL210,  None) // #118
     _extension(161,KHR,texture_compression_astc_hdr,    GL210,  None) // #118

src/Magnum/GL/Implementation/pixelFormatMapping.hpp

@@ -59,12 +59,8 @@ _s(RGBA8Snorm)
 #ifndef MAGNUM_TARGET_GLES2
 #ifndef MAGNUM_TARGET_WEBGL
 _c(R8Srgb, Red, UnsignedByte, SR8)
-#ifdef MAGNUM_TARGET_GLES
 _c(RG8Srgb, RG, UnsignedByte, SRG8)
 #else
-_n(RG8Srgb, RG, UnsignedByte)
-#endif
-#else
 _n(R8Srgb, Red, UnsignedByte)
 _n(RG8Srgb, RG, UnsignedByte)
 #endif

src/Magnum/GL/Test/PixelFormatTest.cpp

@@ -311,8 +311,8 @@ void PixelFormatTest::mapTextureFormatUnsupported() {
     std::ostringstream out;
     Error redirectError{&out};
 
-    textureFormat(Magnum::PixelFormat::RG8Srgb);
+    textureFormat(Magnum::PixelFormat::Depth16UnormStencil8UI);
-    CORRADE_COMPARE(out.str(), "GL::textureFormat(): format PixelFormat::RG8Srgb is not supported on this target\n");
+    CORRADE_COMPARE(out.str(), "GL::textureFormat(): format PixelFormat::Depth16UnormStencil8UI is not supported on this target\n");
     #endif
 }
 

src/Magnum/GL/TextureFormat.cpp

@@ -63,14 +63,10 @@ Debug& operator<<(Debug& debug, const TextureFormat value) {
         #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
         _c(RGBA8)
         #endif
-        #ifndef MAGNUM_TARGET_WEBGL
+        #if !defined(MAGNUM_TARGET_WEBGL) && !defined(MAGNUM_TARGET_GLES2)
-        #ifndef MAGNUM_TARGET_GLES2
         _c(SR8)
-        #endif
-        #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_GLES2)
         _c(SRG8)
         #endif
-        #endif
         #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)
         _c(SRGB)
         #endif

src/Magnum/GL/TextureFormat.h

@@ -195,8 +195,7 @@ enum class TextureFormat: GLenum {
     #endif
     #endif
 
-    #ifndef MAGNUM_TARGET_WEBGL
+    #if !defined(MAGNUM_TARGET_WEBGL) && !defined(MAGNUM_TARGET_GLES2)
-    #ifndef MAGNUM_TARGET_GLES2
     /**
      * sRGB-encoded red component, normalized unsigned byte.
      * @requires_extension Extension @gl_extension{EXT,texture_sRGB_R8}
@@ -208,23 +207,19 @@ enum class TextureFormat: GLenum {
      * @m_since{2019,10}
      */
     SR8 = GL_SR8_EXT,
-    #endif
 
-    #if (defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_GLES2)) || defined(DOXYGEN_GENERATING_OUTPUT)
     /**
      * sRGB-encoded red and green component, normalized unsigned byte.
+     * @requires_extension Extension @gl_extension{EXT,texture_sRGB_RG8}
      * @requires_es_extension OpenGL ES 3.0 and extension
      *      @gl_extension{EXT,texture_sRGB_RG8}
      * @requires_gles One- and two-component sRGB texture formats are not
      *      available in WebGL, use @ref TextureFormat::SRGB8 or
-     *      @ref TextureFormat::SRGB8Alpha8 instead. Only
+     *      @ref TextureFormat::SRGB8Alpha8 instead.
-     *      @ref TextureFormat::SR8, @ref TextureFormat::SRGB8 or
-     *      @ref TextureFormat::SRGB8Alpha8 is available in desktop OpenGL.
      * @m_since{2019,10}
      */
     SRG8 = GL_SRG8_EXT,
     #endif
-    #endif
 
     #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)
     /**

src/MagnumExternal/OpenGL/GL/extensions.txt

@@ -34,6 +34,7 @@ extension EXT_shader_integer_mix                optional
 extension EXT_debug_label                       optional
 extension EXT_debug_marker                      optional
 extension EXT_texture_sRGB_R8                   optional
+extension EXT_texture_sRGB_RG8                  optional
 extension GREMEDY_string_marker                 optional
 extension KHR_texture_compression_astc_ldr      optional
 # extension KHR_texture_compression_astc_hdr    optional

src/MagnumExternal/OpenGL/GL/flextGL.h

@@ -1716,6 +1716,10 @@ typedef void (APIENTRY *GLDEBUGPROC)(GLenum source,GLenum type,GLuint id,GLenum
 
 #define GL_SR8_EXT 0x8FBD
 
+/* GL_EXT_texture_sRGB_RG8 */
+
+#define GL_SRG8_EXT 0x8FBE
+
 /* GL_KHR_texture_compression_astc_ldr */
 
 #define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0