Improved error message for unsupported texture format

src/video/SDL_renderer_gl.c

@@ -760,7 +760,8 @@ GL_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture)
 
     if (!convert_format(renderdata, texture->format, &internalFormat,
                         &format, &type)) {
-        SDL_SetError("Unsupported texture format");
+        SDL_SetError("Texture format %s not supported by OpenGL",
+                     SDL_GetPixelFormatName(texture->format));
         return -1;
     }
     if (texture->format == SDL_PIXELFORMAT_UYVY &&

src/video/SDL_renderer_gles.c

@@ -408,7 +408,8 @@ GLES_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture)
         type = GL_UNSIGNED_SHORT_4_4_4_4;
         break;
     default:
-        SDL_SetError("Unsupported by OpenGL ES texture format");
+        SDL_SetError("Texture format %s not supported by OpenGL ES",
+                     SDL_GetPixelFormatName(texture->format));
         return -1;
     }