Handle window resizing on the render thread in D3D11 and D3D12

This prevents crashing when a separate thread is being used for rendering

Discussion and sample code in https://github.com/libsdl-org/SDL/issues/8528

src/render/direct3d11/SDL_render_d3d11.c

@@ -138,6 +138,7 @@ typedef struct
     ID3D11SamplerState *nearestPixelSampler;
     ID3D11SamplerState *linearSampler;
     D3D_FEATURE_LEVEL featureLevel;
+    SDL_bool pixelSizeChanged;
 
     /* Rasterizers */
     ID3D11RasterizerState *mainRasterizer;
@@ -1036,8 +1037,10 @@ void D3D11_Trim(SDL_Renderer *renderer)
 
 static void D3D11_WindowEvent(SDL_Renderer *renderer, const SDL_WindowEvent *event)
 {
+    D3D11_RenderData *data = (D3D11_RenderData *)renderer->driverdata;
+
     if (event->type == SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED) {
-        D3D11_UpdateForWindowSizeChange(renderer);
+        data->pixelSizeChanged = SDL_TRUE;
     }
 }
 
@@ -2094,6 +2097,11 @@ static int D3D11_RunCommandQueue(SDL_Renderer *renderer, SDL_RenderCommand *cmd,
     D3D11_RenderData *rendererData = (D3D11_RenderData *)renderer->driverdata;
     const int viewportRotation = D3D11_GetRotationForCurrentRenderTarget(renderer);
 
+    if (rendererData->pixelSizeChanged) {
+        D3D11_UpdateForWindowSizeChange(renderer);
+        rendererData->pixelSizeChanged = SDL_FALSE;
+    }
+
     if (rendererData->currentViewportRotation != viewportRotation) {
         rendererData->currentViewportRotation = viewportRotation;
         rendererData->viewportDirty = SDL_TRUE;

src/render/direct3d12/SDL_render_d3d12.c

@@ -174,6 +174,7 @@ typedef struct
     ID3D12GraphicsCommandList2 *commandList;
     DXGI_SWAP_EFFECT swapEffect;
     UINT swapFlags;
+    SDL_bool pixelSizeChanged;
 
     /* Descriptor heaps */
     ID3D12DescriptorHeap *rtvDescriptorHeap;
@@ -1386,8 +1387,10 @@ static HRESULT D3D12_UpdateForWindowSizeChange(SDL_Renderer *renderer)
 
 static void D3D12_WindowEvent(SDL_Renderer *renderer, const SDL_WindowEvent *event)
 {
+    D3D12_RenderData *data = (D3D12_RenderData *)renderer->driverdata;
+
     if (event->type == SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED) {
-        D3D12_UpdateForWindowSizeChange(renderer);
+        data->pixelSizeChanged = SDL_TRUE;
     }
 }
 
@@ -2562,6 +2565,11 @@ static int D3D12_RunCommandQueue(SDL_Renderer *renderer, SDL_RenderCommand *cmd,
     D3D12_RenderData *rendererData = (D3D12_RenderData *)renderer->driverdata;
     const int viewportRotation = D3D12_GetRotationForCurrentRenderTarget(renderer);
 
+    if (rendererData->pixelSizeChanged) {
+        D3D12_UpdateForWindowSizeChange(renderer);
+        rendererData->pixelSizeChanged = SDL_FALSE;
+    }
+
     if (rendererData->currentViewportRotation != viewportRotation) {
         rendererData->currentViewportRotation = viewportRotation;
         rendererData->viewportDirty = SDL_TRUE;