From 97df931b43afcfb02f87a0812dd663c273e88287 Mon Sep 17 00:00:00 2001
From: Bill Hollings <bill.hollings@brenwill.com>
Date: Wed, 15 Aug 2018 13:14:43 -0400
Subject: [PATCH] vkGetPhysicalDeviceFormatProperties() return
 VK_FORMAT_FEATURE_VERTEX_BUFFER_BIT if supported, even if other format
 properties are not.

---
 MoltenVK/MoltenVK/API/mvk_datatypes.h     | 19 ++++++++++---------
 MoltenVK/MoltenVK/GPUObjects/MVKDevice.h  |  2 +-
 MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm |  6 ++----
 MoltenVK/MoltenVK/Vulkan/mvk_datatypes.mm |  4 ++--
 4 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/MoltenVK/MoltenVK/API/mvk_datatypes.h b/MoltenVK/MoltenVK/API/mvk_datatypes.h
index 0be95ce1..c02676bc 100644
--- a/MoltenVK/MoltenVK/API/mvk_datatypes.h
+++ b/MoltenVK/MoltenVK/API/mvk_datatypes.h
@@ -165,17 +165,18 @@ size_t mvkMTLPixelFormatBytesPerLayer(MTLPixelFormat mtlFormat, size_t bytesPerR
 /** 
  * Returns the default properties for the specified Vulkan format.
  *
- * Not all MTLPixelFormats returned by this function are supported by all GPU's,
- * and, as a result, MoltenVK may return a different value from the 
- * vkGetPhysicalDeviceFormatProperties() function than is returned here.
+ * Not all MTLPixelFormats returned by this function are supported by all GPU's, and, as a
+ * result, MoltenVK may return a different value from the vkGetPhysicalDeviceFormatProperties()
+ * function than is returned here. Use the vkGetPhysicalDeviceFormatProperties() function to
+ * return the properties for a particular GPU.
  *
- * Not all macOS GPU's support the MTLPixelFormatDepth24Unorm_Stencil8 
- * (VK_FORMAT_D24_UNORM_S8_UINT) pixel format. On an macOS device that has more 
- * than one GPU, one of the GPU's may support that format, while another may not.
- * Use the vkGetPhysicalDeviceFormatProperties() function to return the properties
- * for a particular GPU.
+ * Setting assumeGPUSupportsDefault to true allows the default format properties to be returned.
+ * The assumeGPUSupportsDefault flag can be set to false if it is already known that the format
+ * is not supported by a particular GPU for images, in which case all of the returned properties
+ * will be disabled, except possibly VK_FORMAT_FEATURE_VERTEX_BUFFER_BIT, which may be supported
+ * for the format even without image support.
  */
-VkFormatProperties mvkVkFormatProperties(VkFormat vkFormat);
+VkFormatProperties mvkVkFormatProperties(VkFormat vkFormat, bool assumeGPUSupportsDefault = true);
 
 /** Returns the name of the specified Vulkan format. */
 const char* mvkVkFormatName(VkFormat vkFormat);
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.h b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.h
index b40fe42d..7f5a8931 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.h
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.h
@@ -81,7 +81,7 @@ public:
 	/** Populates the specified structure with the properties of this device. */
 	void getProperties(VkPhysicalDeviceProperties* properties);
 
-	/** Returns whether the specified format is supported. */
+	/** Returns whether the specified format is supported on this device. */
 	bool getFormatIsSupported(VkFormat format);
 
 	/** Populates the specified structure with the format properties of this device. */
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
index db8fad1e..66da7007 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
@@ -85,11 +85,9 @@ bool MVKPhysicalDevice::getFormatIsSupported(VkFormat format) {
 	return true;
 }
 
-void MVKPhysicalDevice::getFormatProperties(VkFormat format,
-                                            VkFormatProperties* pFormatProperties) {
-	static VkFormatProperties noFmtFeats = { 0, 0, 0 };
+void MVKPhysicalDevice::getFormatProperties(VkFormat format, VkFormatProperties* pFormatProperties) {
     if (pFormatProperties) {
-		*pFormatProperties = getFormatIsSupported(format) ? mvkVkFormatProperties(format) : noFmtFeats;
+		*pFormatProperties = mvkVkFormatProperties(format, getFormatIsSupported(format));
 	}
 }
 
diff --git a/MoltenVK/MoltenVK/Vulkan/mvk_datatypes.mm b/MoltenVK/MoltenVK/Vulkan/mvk_datatypes.mm
index 7e4e878e..3e67654a 100644
--- a/MoltenVK/MoltenVK/Vulkan/mvk_datatypes.mm
+++ b/MoltenVK/MoltenVK/Vulkan/mvk_datatypes.mm
@@ -594,9 +594,9 @@ MVK_PUBLIC_SYMBOL size_t mvkMTLPixelFormatBytesPerLayer(MTLPixelFormat mtlFormat
     return mvkCeilingDivide(texelRowsPerLayer, formatDescForMTLPixelFormat(mtlFormat).blockTexelSize.height) * bytesPerRow;
 }
 
-MVK_PUBLIC_SYMBOL VkFormatProperties mvkVkFormatProperties(VkFormat vkFormat) {
+MVK_PUBLIC_SYMBOL VkFormatProperties mvkVkFormatProperties(VkFormat vkFormat, bool assumeGPUSupportsDefault) {
 	const MVKFormatDesc& fmtDesc = formatDescForVkFormat(vkFormat);
-	if (fmtDesc.isSupported()) {
+	if (assumeGPUSupportsDefault && fmtDesc.isSupported()) {
 		return fmtDesc.properties;
 	} else {
 		// If texture format is unsupported, vertex buffer format may still be.