More sophisticated detection whether qis is supported.

src/common/sdl_blitter/BlitterFactory.cxx

@@ -27,10 +27,6 @@ unique_ptr<Blitter> BlitterFactory::createBlitter(FrameBufferSDL2& fb)
     throw runtime_error("BlitterFactory requires an initialized framebuffer!");
   }
 
-  SDL_RendererInfo info;
-
-  SDL_GetRendererInfo(fb.renderer(), &info);
-
-  return (info.flags & SDL_RENDERER_TARGETTEXTURE) ?
+  return HqBlitter::isSupported(fb) ?
     unique_ptr<Blitter>(new HqBlitter(fb)) : unique_ptr<Blitter>(new BilinearBlitter(fb));
 }

src/common/sdl_blitter/HqBlitter.cxx

@@ -36,6 +36,31 @@ HqBlitter::~HqBlitter()
   free();
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool HqBlitter::isSupported(FrameBufferSDL2 &fb)
+{
+  ASSERT_MAIN_THREAD;
+
+  if (!fb.isInitialized()) throw runtime_error("frambuffer not initialized");
+
+  SDL_RendererInfo info;
+
+  SDL_GetRendererInfo(fb.renderer(), &info);
+
+  if (!(info.flags & SDL_RENDERER_TARGETTEXTURE)) return false;
+
+  SDL_Texture* tex = SDL_CreateTexture(fb.renderer(), fb.pixelFormat().format, SDL_TEXTUREACCESS_TARGET, 16, 16);
+
+  if (!tex) return false;
+
+  int sdlError = SDL_SetRenderTarget(fb.renderer(), tex);
+  SDL_SetRenderTarget(fb.renderer(), nullptr);
+
+  SDL_DestroyTexture(tex);
+
+  return sdlError == 0;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void HqBlitter::reinitialize(
   SDL_Rect srcRect,
@@ -103,6 +128,8 @@ void HqBlitter::blit(SDL_Surface& surface)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void HqBlitter::blitToIntermediate()
 {
+  ASSERT_MAIN_THREAD;
+
   SDL_Rect r = mySrcRect;
   r.x = r.y = 0;
 

src/common/sdl_blitter/HqBlitter.hxx

@@ -28,6 +28,8 @@ class HqBlitter : public Blitter {
 
     HqBlitter(FrameBufferSDL2& fb);
 
+    static bool isSupported(FrameBufferSDL2 &fb);
+
     virtual ~HqBlitter();
 
     virtual void reinitialize(