vk_swapchain: Silence TOCTOU race condition
It's possible that the window is resized from the moment we ask for its size to the moment a swapchain is created, causing validation issues. To workaround this Vulkan issue request the capabilities again just before creating the swapchain, making the race condition less likely.
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@ -141,11 +141,6 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
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const vk::SurfaceFormatKHR surface_format{ChooseSwapSurfaceFormat(formats, srgb)};
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const vk::SurfaceFormatKHR surface_format{ChooseSwapSurfaceFormat(formats, srgb)};
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const vk::PresentModeKHR present_mode{ChooseSwapPresentMode(present_modes)};
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const vk::PresentModeKHR present_mode{ChooseSwapPresentMode(present_modes)};
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extent = ChooseSwapExtent(capabilities, width, height);
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current_width = extent.width;
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current_height = extent.height;
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current_srgb = srgb;
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u32 requested_image_count{capabilities.minImageCount + 1};
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u32 requested_image_count{capabilities.minImageCount + 1};
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if (capabilities.maxImageCount > 0 && requested_image_count > capabilities.maxImageCount) {
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if (capabilities.maxImageCount > 0 && requested_image_count > capabilities.maxImageCount) {
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@ -153,10 +148,9 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
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}
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}
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vk::SwapchainCreateInfoKHR swapchain_ci(
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vk::SwapchainCreateInfoKHR swapchain_ci(
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{}, surface, requested_image_count, surface_format.format, surface_format.colorSpace,
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{}, surface, requested_image_count, surface_format.format, surface_format.colorSpace, {}, 1,
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extent, 1, vk::ImageUsageFlagBits::eColorAttachment, {}, {}, {},
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vk::ImageUsageFlagBits::eColorAttachment, {}, {}, {}, capabilities.currentTransform,
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capabilities.currentTransform, vk::CompositeAlphaFlagBitsKHR::eOpaque, present_mode, false,
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vk::CompositeAlphaFlagBitsKHR::eOpaque, present_mode, false, {});
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{});
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const u32 graphics_family{device.GetGraphicsFamily()};
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const u32 graphics_family{device.GetGraphicsFamily()};
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const u32 present_family{device.GetPresentFamily()};
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const u32 present_family{device.GetPresentFamily()};
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@ -169,9 +163,18 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
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swapchain_ci.imageSharingMode = vk::SharingMode::eExclusive;
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swapchain_ci.imageSharingMode = vk::SharingMode::eExclusive;
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}
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}
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// Request the size again to reduce the possibility of a TOCTOU race condition.
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const auto updated_capabilities = physical_device.getSurfaceCapabilitiesKHR(surface, dld);
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swapchain_ci.imageExtent = ChooseSwapExtent(updated_capabilities, width, height);
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// Don't add code within this and the swapchain creation.
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const auto dev{device.GetLogical()};
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const auto dev{device.GetLogical()};
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swapchain = dev.createSwapchainKHRUnique(swapchain_ci, nullptr, dld);
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swapchain = dev.createSwapchainKHRUnique(swapchain_ci, nullptr, dld);
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extent = swapchain_ci.imageExtent;
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current_width = extent.width;
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current_height = extent.height;
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current_srgb = srgb;
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images = dev.getSwapchainImagesKHR(*swapchain, dld);
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images = dev.getSwapchainImagesKHR(*swapchain, dld);
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image_count = static_cast<u32>(images.size());
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image_count = static_cast<u32>(images.size());
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image_format = surface_format.format;
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image_format = surface_format.format;
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