vulkan: Add instance-level version getter

...as described in the Vulkan >= 1.1 spec. One can now call
supportedApiVersion() (before create(), similarly to the other
supported* functions) to determine the available Vulkan
(instance-level) version.

Fixes: QTBUG-90333
Change-Id: Ibe8482402b7f07e4abc48c88252ff0365e4e2faa
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

5 files changed, 59 insertions, 3 deletions

diff --git a/src/gui/vulkan/qbasicvulkanplatforminstance.cpp b/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
index 01d6179166..abb17e9d6d 100644
--- a/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
+++ b/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
@@ -135,6 +135,25 @@ void QBasicPlatformVulkanInstance::init(QLibrary *lib)
         return;
     }
 
+    // Do not rely on non-1.0 header typedefs here.
+    typedef VkResult (VKAPI_PTR *T_enumerateInstanceVersion)(uint32_t* pApiVersion);
+    // Determine instance-level version as described in the Vulkan 1.2 spec.
+    T_enumerateInstanceVersion enumerateInstanceVersion = reinterpret_cast<T_enumerateInstanceVersion>(
+        m_vkGetInstanceProcAddr(VK_NULL_HANDLE, "vkEnumerateInstanceVersion"));
+    if (enumerateInstanceVersion) {
+        uint32_t ver = 0;
+        if (enumerateInstanceVersion(&ver) == VK_SUCCESS) {
+            m_supportedApiVersion = QVersionNumber(VK_VERSION_MAJOR(ver),
+                                                   VK_VERSION_MINOR(ver),
+                                                   VK_VERSION_PATCH(ver));
+        } else {
+            m_supportedApiVersion = QVersionNumber(1, 0, 0);
+        }
+    } else {
+        // Vulkan 1.0
+        m_supportedApiVersion = QVersionNumber(1, 0, 0);
+    }
+
     uint32_t layerCount = 0;
     m_vkEnumerateInstanceLayerProperties(&layerCount, nullptr);
     if (layerCount) {
@@ -180,6 +199,11 @@ QVulkanInfoVector<QVulkanExtension> QBasicPlatformVulkanInstance::supportedExten
     return m_supportedExtensions;
 }
 
+QVersionNumber QBasicPlatformVulkanInstance::supportedApiVersion() const
+{
+    return m_supportedApiVersion;
+}
+
 void QBasicPlatformVulkanInstance::initInstance(QVulkanInstance *instance, const QByteArrayList &extraExts)
 {
     if (!m_vkGetInstanceProcAddr) {
diff --git a/src/gui/vulkan/qbasicvulkanplatforminstance_p.h b/src/gui/vulkan/qbasicvulkanplatforminstance_p.h
index 8c01af2a8f..39ce71b4d3 100644
--- a/src/gui/vulkan/qbasicvulkanplatforminstance_p.h
+++ b/src/gui/vulkan/qbasicvulkanplatforminstance_p.h
@@ -68,6 +68,7 @@ public:
 
     QVulkanInfoVector<QVulkanLayer> supportedLayers() const override;
     QVulkanInfoVector<QVulkanExtension> supportedExtensions() const override;
+    QVersionNumber supportedApiVersion() const override;
     bool isValid() const override;
     VkResult errorCode() const override;
     VkInstance vkInstance() const override;
@@ -99,6 +100,7 @@ private:
     VkResult m_errorCode;
     QVulkanInfoVector<QVulkanLayer> m_supportedLayers;
     QVulkanInfoVector<QVulkanExtension> m_supportedExtensions;
+    QVersionNumber m_supportedApiVersion;
     QByteArrayList m_enabledLayers;
     QByteArrayList m_enabledExtensions;
 
diff --git a/src/gui/vulkan/qplatformvulkaninstance.h b/src/gui/vulkan/qplatformvulkaninstance.h
index d9c219198f..b918632b57 100644
--- a/src/gui/vulkan/qplatformvulkaninstance.h
+++ b/src/gui/vulkan/qplatformvulkaninstance.h
@@ -69,6 +69,7 @@ public:
 
     virtual QVulkanInfoVector<QVulkanLayer> supportedLayers() const = 0;
     virtual QVulkanInfoVector<QVulkanExtension> supportedExtensions() const = 0;
+    virtual QVersionNumber supportedApiVersion() const = 0;
     virtual void createOrAdoptInstance() = 0;
     virtual bool isValid() const = 0;
     virtual VkResult errorCode() const = 0;
diff --git a/src/gui/vulkan/qvulkaninstance.cpp b/src/gui/vulkan/qvulkaninstance.cpp
index 31f971b570..e0f1b1a5f3 100644
--- a/src/gui/vulkan/qvulkaninstance.cpp
+++ b/src/gui/vulkan/qvulkaninstance.cpp
@@ -448,6 +448,28 @@ QVulkanInfoVector<QVulkanExtension> QVulkanInstance::supportedExtensions()
 }
 
 /*!
+    \return the version of instance-level functionality supported by the Vulkan
+    implementation.
+
+    In practice this is either the value returned from
+    vkEnumerateInstanceVersion, if that function is available (with Vulkan 1.1
+    and newer), or 1.0.
+
+    Applications that want to branch in their Vulkan feature and API usage
+    based on what Vulkan version is available at run time, can use this function
+    to determine what version to pass in to setApiVersion() before calling
+    create().
+
+    \note This function can be called before create().
+
+    \sa setApiVersion()
+ */
+QVersionNumber QVulkanInstance::supportedApiVersion()
+{
+    return d_ptr->ensureVulkan() ? d_ptr->platformInst->supportedApiVersion() : QVersionNumber();
+}
+
+/*!
     Makes QVulkanInstance adopt an existing VkInstance handle instead of
     creating a new one.
 
@@ -524,10 +546,9 @@ void QVulkanInstance::setExtensions(const QByteArrayList &extensions)
 }
 
 /*!
-    Specifies the Vulkan API against which the application expects to run.
+    Specifies the highest Vulkan API version the application is designed to use.
 
-    By default no \a vulkanVersion is specified, and so no version check is performed
-    during Vulkan instance creation.
+    By default \a vulkanVersion is 0, which maps to Vulkan 1.0.
 
     \note This function can only be called before create() and has no effect if
     called afterwards.
@@ -538,6 +559,13 @@ void QVulkanInstance::setExtensions(const QByteArrayList &extensions)
     as was mandated by the specification. Starting with Vulkan 1.1, the
     specification disallows this, the driver must accept any version without
     failing the instance creation.
+
+    Application developers are advised to familiarize themselves with the \c
+    apiVersion notes in
+    \l{https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VkApplicationInfo.html}{the
+    Vulkan specification}.
+
+    \sa supportedApiVersion()
  */
 void QVulkanInstance::setApiVersion(const QVersionNumber &vulkanVersion)
 {
diff --git a/src/gui/vulkan/qvulkaninstance.h b/src/gui/vulkan/qvulkaninstance.h
index 58948854b4..3e597f9c87 100644
--- a/src/gui/vulkan/qvulkaninstance.h
+++ b/src/gui/vulkan/qvulkaninstance.h
@@ -176,6 +176,7 @@ public:
 
     QVulkanInfoVector<QVulkanLayer> supportedLayers();
     QVulkanInfoVector<QVulkanExtension> supportedExtensions();
+    QVersionNumber supportedApiVersion();
 
     void setVkInstance(VkInstance existingVkInstance);