diff options
| -rw-r--r-- | src/gui/rhi/qrhivulkan.cpp | 44 |
1 files changed, 34 insertions, 10 deletions
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp index b1fc8d222c..df721eb3a0 100644 --- a/src/gui/rhi/qrhivulkan.cpp +++ b/src/gui/rhi/qrhivulkan.cpp @@ -1425,21 +1425,45 @@ bool QRhiVulkan::recreateSwapChain(QRhiSwapChain *swapChain) ? VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR : surfaceCaps.currentTransform; + // This looks odd but matches how platforms work in practice. + // + // On Windows with NVIDIA for example, the only supportedCompositeAlpha + // value reported is OPAQUE, nothing else. Yet transparency works + // regardless, as long as the native window is set up correctly, so that's + // not something we need to handle here. + // + // On Linux with Intel and Mesa and running on xcb reports, on one + // particular system, INHERIT+PRE_MULTIPLIED. Tranparency works, regardless, + // presumably due to setting INHERIT. + // + // On the same setup with Wayland instead of xcb we see + // OPAQUE+PRE_MULTIPLIED reported. Here transparency won't work unless + // PRE_MULTIPLIED is set. + // + // Therefore our rules are: + // - Prefer INHERIT over OPAQUE. + // - Then based on the request, try the requested alpha mode, but if + // that's not reported as supported, try also the other (PRE/POST, + // POST/PRE) as that is better than nothing. This is not different from + // some other backends, e.g. D3D11 with DirectComposition there is also + // no control over being straight or pre-multiplied. Whereas with + // WGL/GLX/EGL we never had that sort of control. + VkCompositeAlphaFlagBitsKHR compositeAlpha = (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR) ? VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR : VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR; - if (swapChainD->m_flags.testFlag(QRhiSwapChain::SurfaceHasPreMulAlpha) - && (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR)) - { - compositeAlpha = VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR; - } - - if (swapChainD->m_flags.testFlag(QRhiSwapChain::SurfaceHasNonPreMulAlpha) - && (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR)) - { - compositeAlpha = VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR; + if (swapChainD->m_flags.testFlag(QRhiSwapChain::SurfaceHasPreMulAlpha)) { + if (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR) + compositeAlpha = VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR; + else if (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR) + compositeAlpha = VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR; + } else if (swapChainD->m_flags.testFlag(QRhiSwapChain::SurfaceHasNonPreMulAlpha)) { + if (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR) + compositeAlpha = VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR; + else if (surfaceCaps.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR) + compositeAlpha = VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR; } VkImageUsageFlags usage = VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT; |