render: Update the size/scale/viewport on moves, in addition to resizes.

For OpenGL this means resetting the viewport state shadowing flag too.

Fixes #1504

src/render/SDL_render.c

@@ -698,7 +698,17 @@ SDL_RendererEventWatch(void *userdata, SDL_Event *event)
                 renderer->WindowEvent(renderer, &event->window);
             }
 
-            if (event->window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
+            /* In addition to size changes, we also want to do this block for
+             * moves as well, for two reasons:
+             *
+             * 1. The window could be moved to a new display, which has a new
+             *    DPI and therefore a new window/drawable ratio
+             * 2. For whatever reason, the viewport can get messed up during
+             *    window movement (this has been observed on macOS), so this is
+             *    also a good opportunity to force viewport updates
+             */
+            if (event->window.event == SDL_WINDOWEVENT_SIZE_CHANGED ||
+                event->window.event == SDL_WINDOWEVENT_MOVED) {
                 /* Make sure we're operating on the default render target */
                 SDL_Texture *saved_target = SDL_GetRenderTarget(renderer);
                 if (saved_target) {