[pahlevan]

Description

Window::buildSwapchain() waits for device idle and clears _frames and _indices, but keeps _availableSemaphores and appends a fresh set. Each rebuild therefore retains another swapchain's acquire semaphores. The stale set can include a semaphore signaled by a VK_SUBOPTIMAL_KHR acquisition; reusing it after the rebuild can trigger VUID-vkAcquireNextImageKHR-semaphore-01286.

Clear the acquire semaphore pool alongside the old frames and indices, after vkDeviceWaitIdle. The existing initialization resets _availableSemaphoreIndex and creates one fresh acquire semaphore per new image. No API or dependency changes.

Type of change

• Bug fix (non-breaking change)

How Has This Been Tested?

• Built upstream master e4718bf078a26930e0b6f5932d2537b689fa3969 before and after the change with MSVC x64, Ninja, RelWithDebInfo, shader compiler support disabled.
• A standalone native-window probe fails before the fix on the first rebuild: 6 acquire semaphores for 3 images. With the fix, all 16 rebuilds retain exactly 3 for 3 images.
• Backported the same one-line change to downstream's pinned 599a8c5c61cbb993079261b2ada99bd843badf5b. Its separate Qt/Vulkan probe alternates window dimensions 16 times, presents and reads back after each resize. With Khronos validation enabled it completes with 10 validation errors before, 0 after, including the acquire semaphore VUID above. This downstream validation result is distinct from the standalone test of current master.

Test environment: Windows x64, Intel UHD 770, MSVC 14.51, Vulkan SDK 1.4.313.2.

The standalone Windows reproduction links only VSG:

#include <vsg/all.h>
#include <vsg/platform/win32/Win32_Window.h>
#include <iostream>

class ProbeWindow : public vsg::Inherit<vsgWin32::Win32_Window, ProbeWindow>
{
public:
    using Inherit::Inherit;
    size_t acquireSemaphoreCount() const { return _availableSemaphores.size(); }
};

int main()
{
    auto traits = vsg::WindowTraits::create();
    traits->width = 640;
    traits->height = 480;
    traits->debugLayer = true;
    auto window = ProbeWindow::create(traits);
    window->getOrCreateSwapchain();
    for (int i = 0; i < 16; ++i)
    {
        window->resize();
        std::cout << window->acquireSemaphoreCount() << " / "
                  << window->frames().size() << '\n';
        if (window->acquireSemaphoreCount() != window->frames().size()) return 1;
    }
    return 0;
}

Build the snippet as a C++ executable linked to vsg::vsg. Calling resize() intentionally rebuilds the swapchain even with unchanged dimensions, so semaphore retention is deterministic without mouse input or application data.