opengl: Fixes for sRGB framebuffer support.

This changes the default for SDL_GL_FRAMEBUFFER_SRGB_CAPABLE to -1 (for
"don't care"). Minor ABI break, but technically this never worked correctly.

Fixes #13055.

include/SDL3/SDL_video.h

@@ -490,7 +490,7 @@ typedef enum SDL_GLAttr
     SDL_GL_CONTEXT_FLAGS,               /**< some combination of 0 or more of elements of the SDL_GLContextFlag enumeration; defaults to 0. */
     SDL_GL_CONTEXT_PROFILE_MASK,        /**< type of GL context (Core, Compatibility, ES). See SDL_GLProfile; default value depends on platform. */
     SDL_GL_SHARE_WITH_CURRENT_CONTEXT,  /**< OpenGL context sharing; defaults to 0. */
-    SDL_GL_FRAMEBUFFER_SRGB_CAPABLE,    /**< requests sRGB capable visual; defaults to 0. */
+    SDL_GL_FRAMEBUFFER_SRGB_CAPABLE,    /**< requests sRGB-capable visual if 1. Defaults to -1 ("don't care"). This is a request; GL drivers might not comply! */
     SDL_GL_CONTEXT_RELEASE_BEHAVIOR,    /**< sets context the release behavior. See SDL_GLContextReleaseFlag; defaults to FLUSH. */
     SDL_GL_CONTEXT_RESET_NOTIFICATION,  /**< set context reset notification. See SDL_GLContextResetNotification; defaults to NO_NOTIFICATION. */
     SDL_GL_CONTEXT_NO_ERROR,

src/video/SDL_video.c

@@ -4948,7 +4948,7 @@ void SDL_GL_ResetAttributes(void)
     }
 
     _this->gl_config.flags = 0;
-    _this->gl_config.framebuffer_srgb_capable = 0;
+    _this->gl_config.framebuffer_srgb_capable = -1;
     _this->gl_config.no_error = 0;
     _this->gl_config.release_behavior = SDL_GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH;
     _this->gl_config.reset_notification = SDL_GL_CONTEXT_RESET_NO_NOTIFICATION;

src/video/windows/SDL_windowsopengl.c

@@ -512,6 +512,13 @@ void WIN_GL_InitExtensions(SDL_VideoDevice *_this)
         _this->gl_data->HAS_WGL_ARB_create_context_no_error = true;
     }
 
+    // Check for WGL_ARB_framebuffer_sRGB
+    if (HasExtension("WGL_ARB_framebuffer_sRGB", extensions)) {
+        _this->gl_data->HAS_WGL_ARB_framebuffer_sRGB = true;
+    } else if (HasExtension("WGL_EXT_framebuffer_sRGB", extensions)) {  // same thing.
+        _this->gl_data->HAS_WGL_ARB_framebuffer_sRGB = true;
+    }
+
     /* Check for WGL_ARB_pixel_format_float */
     _this->gl_data->HAS_WGL_ARB_pixel_format_float =
         HasExtension("WGL_ARB_pixel_format_float", extensions);
@@ -532,9 +539,6 @@ static int WIN_GL_ChoosePixelFormatARB(SDL_VideoDevice *_this, int *iAttribs, fl
     int pixel_format = 0;
     unsigned int matching;
 
-    int qAttrib = WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB;
-    int srgb = 0;
-
     hwnd =
         CreateWindow(SDL_Appname, SDL_Appname, (WS_POPUP | WS_DISABLED), 0, 0,
                      10, 10, NULL, NULL, SDL_Instance, NULL);
@@ -556,7 +560,11 @@ static int WIN_GL_ChoosePixelFormatARB(SDL_VideoDevice *_this, int *iAttribs, fl
                                                     &matching);
 
             // Check whether we actually got an SRGB capable buffer
-            _this->gl_data->wglGetPixelFormatAttribivARB(hdc, pixel_format, 0, 1, &qAttrib, &srgb);
+            int srgb = 0;
+            if (_this->gl_data->HAS_WGL_ARB_framebuffer_sRGB) {
+                int qAttrib = WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB;
+                _this->gl_data->wglGetPixelFormatAttribivARB(hdc, pixel_format, 0, 1, &qAttrib, &srgb);
+            }
             _this->gl_config.framebuffer_srgb_capable = srgb;
         }
 
@@ -651,9 +659,9 @@ static bool WIN_GL_SetupWindowInternal(SDL_VideoDevice *_this, SDL_Window *windo
         *iAttr++ = WGL_TYPE_RGBA_FLOAT_ARB;
     }
 
-    if (_this->gl_config.framebuffer_srgb_capable) {
+    if ((_this->gl_config.framebuffer_srgb_capable >= 0) && _this->gl_data->HAS_WGL_ARB_framebuffer_sRGB) {
         *iAttr++ = WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB;
-        *iAttr++ = _this->gl_config.framebuffer_srgb_capable;
+        *iAttr++ = _this->gl_config.framebuffer_srgb_capable ? GL_TRUE : GL_FALSE;
     }
 
     /* We always choose either FULL or NO accel on Windows, because of flaky

src/video/windows/SDL_windowsopengl.h

@@ -66,6 +66,7 @@ struct SDL_GLDriverData
     bool HAS_WGL_ARB_create_context_no_error;
     bool HAS_WGL_ARB_pixel_format_float;
     bool HAS_WGL_EXT_create_context_es2_profile;
+    bool HAS_WGL_ARB_framebuffer_sRGB;
 
     /* Max version of OpenGL ES context that can be created if the
        implementation supports WGL_EXT_create_context_es2_profile.

src/video/x11/SDL_x11opengl.c

@@ -466,6 +466,13 @@ static void X11_GL_InitExtensions(SDL_VideoDevice *_this)
         _this->gl_data->HAS_GLX_ARB_create_context_no_error = true;
     }
 
+    // Check for GLX_ARB_framebuffer_sRGB
+    if (HasExtension("GLX_ARB_framebuffer_sRGB", extensions)) {
+        _this->gl_data->HAS_GLX_ARB_framebuffer_sRGB = true;
+    } else if (HasExtension("GLX_EXT_framebuffer_sRGB", extensions)) {   // same thing.
+        _this->gl_data->HAS_GLX_ARB_framebuffer_sRGB = true;
+    }
+
     if (context) {
         _this->gl_data->glXMakeCurrent(display, None, NULL);
         _this->gl_data->glXDestroyContext(display, context);
@@ -576,9 +583,9 @@ static int X11_GL_GetAttributes(SDL_VideoDevice *_this, Display *display, int sc
         attribs[i++] = GLX_RGBA_FLOAT_TYPE_ARB;
     }
 
-    if (_this->gl_config.framebuffer_srgb_capable) {
+    if ((_this->gl_config.framebuffer_srgb_capable >= 0) && _this->gl_data->HAS_GLX_ARB_framebuffer_sRGB) {
         attribs[i++] = GLX_FRAMEBUFFER_SRGB_CAPABLE_ARB;
-        attribs[i++] = True; // always needed, for_FBConfig or not!
+        attribs[i++] = _this->gl_config.framebuffer_srgb_capable ? True : False; // always needed, for_FBConfig or not!
     }
 
     if (_this->gl_config.accelerated >= 0 &&

src/video/x11/SDL_x11opengl.h

@@ -47,6 +47,7 @@ struct SDL_GLDriverData
     bool HAS_GLX_ARB_context_flush_control;
     bool HAS_GLX_ARB_create_context_robustness;
     bool HAS_GLX_ARB_create_context_no_error;
+    bool HAS_GLX_ARB_framebuffer_sRGB;
 
     /* Max version of OpenGL ES context that can be created if the
        implementation supports GLX_EXT_create_context_es2_profile.