vk: make default render target independent of call order (#9065)

Author: poweifeng

filament/backend/src/vulkan/VulkanDriver.cpp

@@ -206,6 +206,11 @@ VulkanDriver::VulkanDriver(VulkanPlatform* platform, VulkanContext& context,
     : mPlatform(platform),
       mResourceManager(driverConfig.handleArenaSize, driverConfig.disableHandleUseAfterFreeCheck,
               driverConfig.disableHeapHandleTags),
+      // Note that we always create the default rendertarget before createDefaultRenderTarget(). We
+      // swap the content later when createDefaultRenderTarget() is called.  This frees
+      // createDefaultRenderTarget() from being ordered with makeCurrent().
+      mDefaultRenderTarget(
+              fvkmemory::resource_ptr<VulkanRenderTarget>::construct(&mResourceManager)),
       mAllocator(createAllocator(mPlatform->getInstance(), mPlatform->getPhysicalDevice(),
               mPlatform->getDevice())),
       mContext(context),
@@ -698,8 +703,11 @@ void VulkanDriver::destroyProgram(Handle<HwProgram> ph) {
 }
 
 void VulkanDriver::createDefaultRenderTargetR(Handle<HwRenderTarget> rth, int) {
-    assert_invariant(!mDefaultRenderTarget);
-    auto renderTarget = resource_ptr<VulkanRenderTarget>::make(&mResourceManager, rth);
+    assert_invariant(mDefaultRenderTarget); // Default render target should already exist.
+
+    auto renderTarget = resource_ptr<VulkanRenderTarget>::make(&mResourceManager, rth,
+            std::move(std::move(*mDefaultRenderTarget.get())));
+
     mDefaultRenderTarget = renderTarget;
 }
 
@@ -775,6 +783,7 @@ void VulkanDriver::destroyRenderTarget(Handle<HwRenderTarget> rth) {
 
     auto rt = resource_ptr<VulkanRenderTarget>::cast(&mResourceManager, rth);
     if (UTILS_UNLIKELY(rt == mDefaultRenderTarget)) {
+        // Note that this should only happen on driver shutdown.
         mDefaultRenderTarget = {};
     } else {
         rt.dec();

filament/backend/src/vulkan/VulkanHandles.h

@@ -308,6 +308,15 @@ struct VulkanRenderTarget : private HwRenderTarget, fvkmemory::Resource {
     // Creates a special "default" render target (i.e. associated with the swap chain)
     explicit VulkanRenderTarget();
 
+    VulkanRenderTarget(VulkanRenderTarget&& target) {
+        swap(std::move(target));
+    }
+
+    VulkanRenderTarget& operator=(VulkanRenderTarget&& target) {
+        swap(std::move(target));
+        return *this;
+    }
+
     void transformClientRectToPlatform(VkRect2D* bounds) const;
 
     void transformViewportToPlatform(VkViewport* bounds) const;
@@ -355,6 +364,12 @@ struct VulkanRenderTarget : private HwRenderTarget, fvkmemory::Resource {
     void emitBarriersEndRenderPass(VulkanCommandBuffer& commands);
 
 private:
+    void swap(VulkanRenderTarget&& target) {
+        std::swap(mOffscreen, target.mOffscreen);
+        std::swap(mProtected, target.mProtected);
+        std::swap(mInfo, target.mInfo);
+    }
+
     struct Auxiliary {
         static constexpr int8_t UNDEFINED_INDEX = -1;
 
@@ -368,7 +383,7 @@ struct VulkanRenderTarget : private HwRenderTarget, fvkmemory::Resource {
         int8_t msaaDepthIndex = UNDEFINED_INDEX;
         int8_t msaaIndex = UNDEFINED_INDEX;
     };
-    bool const mOffscreen;
+    bool mOffscreen;
     bool mProtected;
 
     std::unique_ptr<Auxiliary> mInfo;