gles2gsg: fix sRGB texture support

panda/src/gles2gsg/gles2gsg.h

@@ -100,9 +100,7 @@ typedef char GLchar;
 #define GL_RGBA16F GL_RGBA16F_EXT
 #define GL_RGB32F GL_RGB32F_EXT
 #define GL_RGBA32F GL_RGBA32F_EXT
-#define GL_SRGB GL_SRGB_EXT
 #define GL_SRGB_ALPHA GL_SRGB_ALPHA_EXT
-#define GL_SRGB8_ALPHA8 GL_SRGB8_ALPHA8_EXT
 #define GL_RGBA8 GL_RGBA8_OES
 #define GL_R8 GL_R8_EXT
 #define GL_RG8 GL_RG8_EXT
@@ -194,6 +192,9 @@ typedef char GLchar;
 #define GL_RGB9_E5 0x8C3D
 #define GL_UNSIGNED_INT_5_9_9_9_REV 0x8C3E
 #define GL_UNSIGNED_INT_10F_11F_11F_REV 0x8C3B
+#define GL_SRGB 0x8C40
+#define GL_SRGB8 0x8C41
+#define GL_SRGB8_ALPHA8 0x8C43
 #define GL_PRIMITIVE_RESTART_FIXED_INDEX 0x8D69
 #define GL_RED_INTEGER 0x8D94
 #define GL_RGB_INTEGER 0x8D98

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -10314,11 +10314,9 @@ get_internal_image_format(Texture *tex, bool force_sized) const {
 
 #ifndef OPENGLES_1
   case Texture::F_srgb:
-#ifndef OPENGLES
-    return GL_SRGB8;
-#endif
+    return _supports_texture_srgb ? GL_SRGB8 : GL_RGB8;
   case Texture::F_srgb_alpha:
-    return GL_SRGB8_ALPHA8;
+    return _supports_texture_srgb ? GL_SRGB8_ALPHA8 : GL_RGBA8;
 #endif
 #ifndef OPENGLES
   case Texture::F_sluminance:
@@ -12807,11 +12805,20 @@ upload_texture(CLP(TextureContext) *gtc, bool force, bool uses_mipmaps) {
     int num_levels = 1;
     CPTA_uchar image = tex->get_ram_mipmap_image(mipmap_bias);
 
+    bool can_generate = _supports_generate_mipmap;
+#if defined(OPENGLES) && !defined(OPENGLES_1)
+    // OpenGL ES doesn't support generating mipmaps for sRGB textures, so we
+    // have to do this on the CPU, unless we have a special extension.
+    if (internal_format == GL_SRGB8 || internal_format == GL_SRGB8_ALPHA8) {
+      can_generate = has_extension("GL_NV_generate_mipmap_sRGB");
+    }
+#endif
+
     if (image.is_null()) {
       // We don't even have a RAM image, so we have no choice but to let
       // mipmaps be generated on the GPU.
       if (uses_mipmaps) {
-        if (_supports_generate_mipmap) {
+        if (can_generate) {
           num_levels = tex->get_expected_num_mipmap_levels() - mipmap_bias;
           gtc->_generate_mipmaps = true;
         } else {
@@ -12827,7 +12834,7 @@ upload_texture(CLP(TextureContext) *gtc, bool force, bool uses_mipmaps) {
 
         if (num_levels <= 1) {
           // No RAM mipmap levels available.  Should we generate some?
-          if (!_supports_generate_mipmap || !driver_generate_mipmaps ||
+          if (!can_generate || !driver_generate_mipmaps ||
               image_compression != Texture::CM_off) {
             // Yes, the GL can't or won't generate them, so we need to.  Note
             // that some drivers (nVidia) will *corrupt memory* if you ask
@@ -12840,7 +12847,7 @@ upload_texture(CLP(TextureContext) *gtc, bool force, bool uses_mipmaps) {
         if (num_levels <= 1) {
           // We don't have mipmap levels in RAM.  Ask the GL to generate them
           // if it can.
-          if (_supports_generate_mipmap) {
+          if (can_generate) {
             num_levels = tex->get_expected_num_mipmap_levels() - mipmap_bias;
             gtc->_generate_mipmaps = true;
           } else {
@@ -14106,9 +14113,7 @@ do_extract_texture_data(CLP(TextureContext) *gtc) {
 
 #ifndef OPENGLES_1
   case GL_SRGB:
-#ifndef OPENGLES
   case GL_SRGB8:
-#endif
     format = Texture::F_srgb;
     break;
   case GL_SRGB_ALPHA: