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Fix rotated Vulkan output on Android #119

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Merged
Try merged 2 commits into from
Oct 3, 2026
Merged

Fix rotated Vulkan output on Android #119

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1993d59
Let Android rotate untransformed Vulkan frames
Solessfir Oct 3, 2026
1057c9a
Use supported identity transforms on all platforms
Solessfir Oct 3, 2026
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2 changes: 2 additions & 0 deletions Engine/gapi/vulkan/vswapchain.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -390,6 +390,8 @@ VkResult VSwapchain::createSwapchain(VDevice& device, const SwapChainSupport& sw
}

createInfo.preTransform = swapChainSupport.capabilities.currentTransform;
if(swapChainSupport.capabilities.supportedTransforms & VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR)
createInfo.preTransform = VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR;

@Try Try Oct 3, 2026

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should it be just VkSurfaceTransformFlagBitsKHR(0) in all cases?

@Solessfir Solessfir Oct 3, 2026

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0 isn’t valid here; identity is VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR (1). We can remove the Android guard and prefer identity on all platforms, while retaining the supported-transform check and fallback.

@Try Try Oct 3, 2026

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Base on this guide here: https://docs.vulkan.org/samples/latest/samples/performance/surface_rotation/README.html
0 allowed.

Or more exact wording:

Ignore the preTransform field in VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR. This will not match the value returned by vkGetPhysicalDeviceSurfaceCapabilitiesKHR and therefore the Android Compositor will rotate the scene before presenting it to the display

Basically, as long as we letting composer do it's job we good.

@Solessfir Solessfir Oct 3, 2026

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Agreed on letting the compositor handle rotation. The linked sample uses VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR, not 0. I can remove the Android guard and use that selection across platforms, keeping the supported-transform check.

@Try Try Oct 3, 2026

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I can remove the Android guard and use that selection across platforms, keeping the supported-transform check.

Sounds good: VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR by default, if possible and currentTransform otherwise

@Solessfir Solessfir Oct 3, 2026

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Updated as suggested: prefer VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR when supported, otherwise use currentTransform. Removed the Android guard.

createInfo.compositeAlpha = alphaMode;
createInfo.presentMode = presentMode;
createInfo.clipped = VK_FALSE;
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