port: allow user to disable framebuffer use

port/fast3d/gfx_opengl.cpp

@@ -921,7 +921,9 @@ static void gfx_opengl_init(void) {
         // maybe replace this with sysFatalError, though the GLSL compiler will cause that later anyway
     }
 
-    if (!gfx_opengl_supports_framebuffers()) {
+    if (!gfx_framebuffers_enabled) {
+        sysLogPrintf(LOG_WARNING, "GL: framebuffer effects disabled by user");
+    } else if (!gfx_opengl_supports_framebuffers()) {
         sysLogPrintf(LOG_WARNING, "GL: GL_ARB_framebuffer_object unsupported, framebuffer effects disabled");
         gfx_framebuffers_enabled = false;
     }

port/fast3d/gfx_pc.cpp

@@ -2688,6 +2688,11 @@ extern "C" void gfx_init(struct GfxWindowManagerAPI* wapi, struct GfxRenderingAP
     game_framebuffer = gfx_rapi->create_framebuffer();
     game_framebuffer_msaa_resolved = gfx_rapi->create_framebuffer();
 
+    if (gfx_msaa_level > 1 && !gfx_framebuffers_enabled) {
+        sysLogPrintf(LOG_WARNING, "F3D: MSAA set to %d, but framebuffers are not available; disabling", gfx_msaa_level);
+        gfx_msaa_level = 1;
+    }
+
     for (int i = 0; i < 16; i++) {
         segmentPointers[i] = 0;
     }

port/src/video.c

@@ -33,6 +33,8 @@ s32 videoInit(void)
 	const s32 h = configGetInt("Video.DefaultHeight", 480);
 	const bool fs = configGetInt("Video.DefaultFullscreen", false);
 
+	gfx_framebuffers_enabled = (bool)configGetIntClamped("Video.FramebufferEffects", 1, 0, 1);
+
 	gfx_msaa_level = configGetInt("Video.MSAA", 0);
 	if (gfx_msaa_level < 1 || gfx_msaa_level > 16) {
 		gfx_msaa_level = 1;