Add a QRhiSwapChain::NoVSync flag

examples/rhi/shared/examplefw.h

@@ -449,6 +449,8 @@ int main(int argc, char **argv)
     fmt.setStencilBufferSize(8);
     if (sampleCount > 1)
         fmt.setSamples(sampleCount);
+    if (scFlags.testFlag(QRhiSwapChain::NoVSync))
+        fmt.setSwapInterval(0);
     QSurfaceFormat::setDefaultFormat(fmt);
 
     // Vulkan setup.

examples/rhi/triquadcube/triquadcube.cpp

@@ -68,6 +68,7 @@
 //#define USE_MSAA
 //#define USE_SRGB_SWAPCHAIN
 //#define READBACK_SWAPCHAIN
+//#define NO_VSYNC
 
 struct {
     TriangleRenderer triRenderer;
@@ -104,6 +105,13 @@ void preInit()
 #ifdef USE_SRGB_SWAPCHAIN
     scFlags |= QRhiSwapChain::sRGB;
 #endif
+
+#ifdef NO_VSYNC
+    scFlags |= QRhiSwapChain::NoVSync;
+#endif
+
+    // For OpenGL some of these are incorporated into the QSurfaceFormat by
+    // examplefw.h after returning from here as that is out of the RHI's control.
 }
 
 void Window::customInit()

src/rhi/qrhi.h

@@ -871,7 +871,8 @@ public:
         SurfaceHasPreMulAlpha = 1 << 0,
         SurfaceHasNonPreMulAlpha = 1 << 1,
         sRGB = 1 << 2,
-        UsedAsTransferSource = 1 << 3 // will be read back
+        UsedAsTransferSource = 1 << 3, // will be read back
+        NoVSync = 1 << 4
     };
     Q_DECLARE_FLAGS(Flags, Flag)
 

src/rhi/qrhid3d11.cpp

@@ -620,9 +620,8 @@ QRhi::FrameOpResult QRhiD3D11::endFrame(QRhiSwapChain *swapChain)
     // this must be done before the Present
     QRHI_PROF_F(endSwapChainFrame(swapChain, swapChainD->frameCount + 1));
 
-    const UINT swapInterval = 1;
     const UINT presentFlags = 0;
-    HRESULT hr = swapChainD->swapChain->Present(swapInterval, presentFlags);
+    HRESULT hr = swapChainD->swapChain->Present(swapChainD->swapInterval, presentFlags);
     if (FAILED(hr))
         qWarning("Failed to present: %s", qPrintable(comErrorMessage(hr)));
 
@@ -2820,6 +2819,7 @@ bool QD3D11SwapChain::buildOrResize()
     currentFrameSlot = 0;
     frameCount = 0;
     ds = m_depthStencil ? QRHI_RES(QD3D11RenderBuffer, m_depthStencil) : nullptr;
+    swapInterval = m_flags.testFlag(QRhiSwapChain::NoVSync) ? 0 : 1;
 
     QD3D11ReferenceRenderTarget *rtD = QRHI_RES(QD3D11ReferenceRenderTarget, &rt);
     rtD->d.rp = QRHI_RES(QD3D11RenderPassDescriptor, m_renderPassDesc);

src/rhi/qrhid3d11_p.h

@@ -428,6 +428,7 @@ struct QD3D11SwapChain : public QRhiSwapChain
     QD3D11RenderBuffer *ds = nullptr;
     ID3D11Query *timestampDisjointQuery[BUFFER_COUNT];
     ID3D11Query *timestampQuery[BUFFER_COUNT * 2];
+    UINT swapInterval = 1;
 };
 
 class QRhiD3D11 : public QRhiImplementation

src/rhi/qrhimetal.mm

@@ -2557,6 +2557,9 @@ bool QMetalSwapChain::buildOrResize()
     if (m_flags.testFlag(UsedAsTransferSource))
         d->layer.framebufferOnly = NO;
 
+    if (m_flags.testFlag(NoVSync))
+        d->layer.displaySyncEnabled = NO;
+
     m_currentPixelSize = surfacePixelSize();
     pixelSize = m_currentPixelSize;
 

src/rhi/qrhivulkan.cpp

@@ -744,8 +744,6 @@ bool QRhiVulkan::createTransientImage(VkFormat format,
     return true;
 }
 
-static const VkPresentModeKHR presentMode = VK_PRESENT_MODE_FIFO_KHR;
-
 VkFormat QRhiVulkan::optimalDepthStencilFormat()
 {
     if (optimalDsFormat != VK_FORMAT_UNDEFINED)
@@ -1010,8 +1008,14 @@ bool QRhiVulkan::recreateSwapChain(QRhiSwapChain *swapChain)
     if (swapChainD->supportsReadback && swapChainD->m_flags.testFlag(QRhiSwapChain::UsedAsTransferSource))
         usage |= VK_IMAGE_USAGE_TRANSFER_SRC_BIT;
 
-    qDebug("Creating new swapchain of %d buffers, size %dx%d",
-           reqBufferCount, swapChainD->pixelSize.width(), swapChainD->pixelSize.height());
+    VkPresentModeKHR presentMode = swapChainD->m_flags.testFlag(QRhiSwapChain::NoVSync)
+            ? VK_PRESENT_MODE_IMMEDIATE_KHR
+            : VK_PRESENT_MODE_FIFO_KHR;
+    if (!swapChainD->supportedPresentationModes.contains(presentMode))
+        presentMode = VK_PRESENT_MODE_FIFO_KHR;
+
+    qDebug("Creating new swapchain of %d buffers, size %dx%d, presentation mode %d",
+           reqBufferCount, swapChainD->pixelSize.width(), swapChainD->pixelSize.height(), presentMode);
 
     VkSwapchainKHR oldSwapChain = swapChainD->sc;
     VkSwapchainCreateInfoKHR swapChainInfo;
@@ -4494,7 +4498,12 @@ bool QVkSwapChain::ensureSurface()
                     rhiD->inst->getInstanceProcAddr("vkGetPhysicalDeviceSurfaceCapabilitiesKHR"));
         rhiD->vkGetPhysicalDeviceSurfaceFormatsKHR = reinterpret_cast<PFN_vkGetPhysicalDeviceSurfaceFormatsKHR>(
                     rhiD->inst->getInstanceProcAddr("vkGetPhysicalDeviceSurfaceFormatsKHR"));
-        if (!rhiD->vkGetPhysicalDeviceSurfaceCapabilitiesKHR || !rhiD->vkGetPhysicalDeviceSurfaceFormatsKHR) {
+        rhiD->vkGetPhysicalDeviceSurfacePresentModesKHR = reinterpret_cast<PFN_vkGetPhysicalDeviceSurfacePresentModesKHR>(
+                    rhiD->inst->getInstanceProcAddr("vkGetPhysicalDeviceSurfacePresentModesKHR"));
+        if (!rhiD->vkGetPhysicalDeviceSurfaceCapabilitiesKHR
+                || !rhiD->vkGetPhysicalDeviceSurfaceFormatsKHR
+                || !rhiD->vkGetPhysicalDeviceSurfacePresentModesKHR)
+        {
             qWarning("Physical device surface queries not available");
             return false;
         }
@@ -4525,6 +4534,12 @@ bool QVkSwapChain::ensureSurface()
 
     samples = rhiD->effectiveSampleCount(m_sampleCount);
 
+    quint32 presModeCount = 0;
+    rhiD->vkGetPhysicalDeviceSurfacePresentModesKHR(rhiD->physDev, surface, &presModeCount, nullptr);
+    QVector<VkPresentModeKHR> presModes(presModeCount);
+    rhiD->vkGetPhysicalDeviceSurfacePresentModesKHR(rhiD->physDev, surface, &presModeCount, presModes.data());
+    supportedPresentationModes = presModes;
+
     return true;
 }
 

src/rhi/qrhivulkan_p.h

@@ -292,6 +292,7 @@ struct QVkSwapChain : public QRhiSwapChain
     VkColorSpaceKHR colorSpace = VK_COLOR_SPACE_SRGB_NONLINEAR_KHR;
     QVkRenderBuffer *ds = nullptr;
     VkSampleCountFlagBits samples = VK_SAMPLE_COUNT_1_BIT;
+    QVector<VkPresentModeKHR> supportedPresentationModes;
     VkDeviceMemory msaaImageMem = VK_NULL_HANDLE;
     QVkReferenceRenderTarget rtWrapper;
     QVkCommandBuffer cbWrapper;
@@ -497,6 +498,7 @@ public:
     PFN_vkQueuePresentKHR vkQueuePresentKHR;
     PFN_vkGetPhysicalDeviceSurfaceCapabilitiesKHR vkGetPhysicalDeviceSurfaceCapabilitiesKHR = nullptr;
     PFN_vkGetPhysicalDeviceSurfaceFormatsKHR vkGetPhysicalDeviceSurfaceFormatsKHR;
+    PFN_vkGetPhysicalDeviceSurfacePresentModesKHR vkGetPhysicalDeviceSurfacePresentModesKHR;
 
     VkPipelineCache pipelineCache = VK_NULL_HANDLE;
     struct DescriptorPoolData {

todo.txt

-d3d: timestamp query
 prof report api (fed by a cbor stream)
 mtl: report readback temp buf
 multiwindow_threaded should demo pulling out the device and importing to another rhi
@@ -52,6 +51,8 @@ dxc for d3d as an alternative to fxc?
 hlsl -> dxc -> spirv -> spirv-cross hmmm...
 
 +++ done
+allow requesting no-vsync present mode where applicable
+d3d: timestamp query
 vk: timestamp query
 prof: report readback temp buf
 merge offscreen examples into one