core: Drain WebGPU render-thread cleanup jobs (#4367)

platform/android/MapLibreAndroid/src/cpp/android_webgpu_renderer_backend.cpp

@@ -310,6 +310,8 @@ AndroidWebGPURendererBackend::AndroidWebGPURendererBackend(ANativeWindow* window
 }
 
 AndroidWebGPURendererBackend::~AndroidWebGPURendererBackend() {
+    context.reset();
+
     if (impl) {
         if (impl->currentTextureView) {
             wgpuTextureViewRelease(impl->currentTextureView);

platform/glfw/glfw_webgpu_backend_impl.ipp

@@ -751,6 +751,8 @@ GLFWWebGPUBackend::~GLFWWebGPUBackend() {
     // Mark any in-flight frame as completed so tear-down logic can continue.
     frameInProgress.store(false, std::memory_order_release);
 
+    context.reset();
+
     {
         std::lock_guard<SpinLock> guard(textureStateLock);
 

platform/ios/src/MLNMapView+WebGPU.mm

@@ -231,6 +231,8 @@ MLNMapViewWebGPUImpl::MLNMapViewWebGPUImpl(MLNMapView* nativeView_)
 }
 
 MLNMapViewWebGPUImpl::~MLNMapViewWebGPUImpl() {
+  context.reset();
+
   if (!impl) return;
 
   if (impl->currentTextureView) {

src/mbgl/webgpu/context.cpp

@@ -53,10 +53,12 @@ Context::Context(RendererBackend& backend_)
       backend(backend_),
       globalUniformBuffers(std::make_unique<UniformBufferArray>()) {}
 
-Context::~Context() = default;
+Context::~Context() {
+    backend.getThreadPool().runRenderJobs(true /* closeQueue */);
+}
 
 void Context::beginFrame() {
-    // Begin a new frame - WebGPU command recording starts here
+    backend.getThreadPool().runRenderJobs();
 }
 
 void Context::endFrame() {
@@ -64,11 +66,11 @@ void Context::endFrame() {
 }
 
 void Context::performCleanup() {
-    // Clean up unused resources
+    backend.getThreadPool().runRenderJobs();
 }
 
 void Context::reduceMemoryUsage() {
-    // Free cached resources to reduce memory
+    backend.getThreadPool().runRenderJobs();
 }
 
 std::unique_ptr<gfx::OffscreenTexture> Context::createOffscreenTexture(Size size,

src/mbgl/webgpu/headless_backend.cpp

@@ -202,6 +202,7 @@ HeadlessBackend::HeadlessBackend(Size size_, SwapBehaviour swapBehaviour_, gfx::
 HeadlessBackend::~HeadlessBackend() {
     // Explicitly reset the renderable resource
     setResource(nullptr);
+    context.reset();
 
     if (impl) {
         // Clean up textures

src/mbgl/webgpu/renderer_backend.cpp

@@ -46,7 +46,9 @@ RendererBackend::RendererBackend(const gfx::ContextMode contextMode_)
     : gfx::RendererBackend(contextMode_),
       impl(std::make_unique<Impl>()) {}
 
-RendererBackend::~RendererBackend() = default;
+RendererBackend::~RendererBackend() {
+    context.reset();
+}
 
 void RendererBackend::activate() {
     // Activation logic if needed