[Impeller] Port a recent Vulkan swapchain fence waiting fix to the AHB version of the swapchain#185763
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…B version of the swapchain WaitForFence should only wait if there is a pending frame presentation that will cause the fence to become signaled. This was fixed in the KHR swapchain by flutter@c5d0a84. This PR implements the same fix for the AHB swapchain and adds a unit test for AHBSwapchainVK.
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This pull request refactors SurfaceControl into an abstract base class to facilitate testing and introduces unit tests for the Android AHB swapchain. It also updates AHBFrameSynchronizerVK to track whether an acquire fence is pending, ensuring that fence waits only occur when a fence has actually been submitted. A high-severity issue was identified in the mock Vulkan implementation where vkEnumerateDeviceExtensionProperties could cause a buffer overflow by failing to validate the capacity of the output array and potentially missing null-termination for extension names.
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| uint32_t count = 0; | ||
| for (const std::string& ext : GetMockVulkanState().device_extensions) { | ||
| strncpy(pProperties[count].extensionName, ext.c_str(), | ||
| sizeof(VkExtensionProperties::extensionName)); | ||
| pProperties[count].specVersion = 0; | ||
| count++; | ||
| } |
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The current implementation of vkEnumerateDeviceExtensionProperties in the mock has a potential buffer overflow. It iterates through all device_extensions without checking if the provided pProperties array has enough capacity (indicated by *pPropertyCount). Additionally, strncpy is used without guaranteeing null-termination if the extension name length equals the buffer size.
According to the Vulkan specification, if pProperties is not NULL, *pPropertyCount structures should be written at most, and the function should return VK_INCOMPLETE if the buffer is too small.
uint32_t count = 0;
VkResult result = VK_SUCCESS;
for (const std::string& ext : GetMockVulkanState().device_extensions) {
if (count >= *pPropertyCount) {
result = VK_INCOMPLETE;
break;
}
snprintf(pProperties[count].extensionName,
sizeof(pProperties[count].extensionName), "%s", ext.c_str());
pProperties[count].specVersion = 0;
count++;
}
*pPropertyCount = count;
return result;
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Fixed this (and the similar implementations of vkEnumerateInstanceExtensionProperties and vkEnumerateInstanceLayerProperties)
gaaclarke
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Apr 29, 2026
| auto surface_control = | ||
| android::SurfaceControl::Create(window.GetHandle(), "ImpellerSurface"); | ||
| auto ahb_swapchain = | ||
| std::shared_ptr<AHBSwapchainVK>(new AHBSwapchainVK(context, // |
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std::make_shared? (I know sometimes that doesn't work because of friend)
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std::make_shared is not usable here because this is invoking a private constructor
| /// | ||
| explicit SurfaceControl(ANativeWindow* window, | ||
| const char* debug_name = nullptr); | ||
| static std::shared_ptr<SurfaceControl> Create( |
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Please make this return a std::unique_ptr, that can be implicitly cast to shared_ptr and doesn't force clients to have to make it shared.
| friend class SurfaceControl; | ||
|
|
||
| struct UniqueASurfaceControlTraits { | ||
| static ASurfaceControl* InvalidValue() { return nullptr; } |
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Just make this a field instead of a function?
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This must be a method to match the declaration of the fml::UniqueObjectTraits concept (see https://github.com/flutter/flutter/blob/master/engine/src/flutter/fml/unique_object.h)
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heads up, there are tidy errors |
gaaclarke
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Apr 29, 2026
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WaitForFence should only wait if there is a pending frame presentation that will cause the fence to become signaled.
This was fixed in the KHR swapchain by c5d0a84. This PR implements the same fix for the AHB swapchain and adds a unit test for AHBSwapchainVK.