tests: Fix GPU tests crashing when window is minimized

test/testgpu_simple_clear.c

@@ -87,6 +87,7 @@ SDL_AppResult SDL_AppIterate(void *appstate)
         return SDL_APP_FAILURE;
     }
 
+    if (swapchainTexture != NULL) {
         const double currentTime = (double)SDL_GetPerformanceCounter() / SDL_GetPerformanceFrequency();
         SDL_GPURenderPass *renderPass;
         SDL_GPUColorTargetInfo color_target_info;
@@ -103,6 +104,10 @@ SDL_AppResult SDL_AppIterate(void *appstate)
         SDL_EndGPURenderPass(renderPass);
 
         SDL_SubmitGPUCommandBuffer(cmdbuf);
+    } else {
+        /* Swapchain is unavailable, cancel work */
+        SDL_CancelGPUCommandBuffer(cmdbuf);
+    }
 
     frames++;
 

test/testgpu_spinning_cube.c

@@ -346,6 +346,12 @@ Render(SDL_Window *window, const int windownum)
         quit(2);
     }
 
+    if (swapchainTexture == NULL) {
+        /* Swapchain is unavailable, cancel work */
+        SDL_CancelGPUCommandBuffer(cmd);
+        return;
+    }
+
     /*
     * Do some rotation with Euler angles. It is not a fixed axis as
     * quaternions would be, but the effect is cool.