Make it possible to specify device extensions in a future proof manner

Follow the pattern of QQuickRenderTarget and QQuickGraphicsDevice.

This makes it possible to integrate with real world frameworks, such as
OpenXR, that, especially with Vulkan, expect this level of
configurability. (i.e. one pulls the list of extensions to be enabled on
the device, that then needs to be taken into account by Quick, otherwise
it will end up with a VkDevice that is not usable by OpenXR)

Same goes when integrating native Vulkan rendering into an application:
if certain extensions need to be enabled on the VkDevice, today that can
only be done with an environment variable which is not entirely ideal.

These issues are now solved by a new simple (and extensible) container
QQuickGraphicsConfiguration, which is associated with the QQuickWindow.
When applicable, the scene graph will then pick up the relevant settings.

Expand the related docs everywhere. Also rename the vulkanInstance() to
defaultVulkanInstance() to emphasize that it is the instance that is
used for normal QQuickWindows, and is not provided when redirecting
via QQuickRenderControl.

While we are at it, include another obvious candidate: the use-depth-buffer
flag. It turns out that Quick3D's Overlay render mode can be pretty
problematic if Quick writes to the depth buffer. In order to avoid
relying on environment variables (QSG_NO_DEPTH_BUFFER), we now provide
a proper API for controlling that as well.

Change-Id: Iefdb62c1f53de8bd34e3f0d393b00c5020d6188a
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

8 files changed, 33 insertions, 20 deletions

diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index 761f35bdd6..d550b2c66a 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -341,10 +341,13 @@ void QSGRenderContext::invalidate()
 {
 }
 
-void QSGRenderContext::prepareSync(qreal devicePixelRatio, QRhiCommandBuffer *cb)
+void QSGRenderContext::prepareSync(qreal devicePixelRatio,
+                                   QRhiCommandBuffer *cb,
+                                   const QQuickGraphicsConfiguration &config)
 {
     Q_UNUSED(devicePixelRatio);
     Q_UNUSED(cb);
+    Q_UNUSED(config);
 }
 
 void QSGRenderContext::beginNextFrame(QSGRenderer *renderer,
diff --git a/src/quick/scenegraph/qsgcontext_p.h b/src/quick/scenegraph/qsgcontext_p.h
index 650accd28d..fc3e3fc854 100644
--- a/src/quick/scenegraph/qsgcontext_p.h
+++ b/src/quick/scenegraph/qsgcontext_p.h
@@ -94,6 +94,7 @@ class QRhi;
 class QRhiRenderTarget;
 class QRhiRenderPassDescriptor;
 class QRhiCommandBuffer;
+class QQuickGraphicsConfiguration;
 
 Q_DECLARE_LOGGING_CATEGORY(QSG_LOG_TIME_RENDERLOOP)
 Q_DECLARE_LOGGING_CATEGORY(QSG_LOG_TIME_COMPILATION)
@@ -174,7 +175,10 @@ public:
 
     using RenderPassCallback = void (*)(void *);
 
-    virtual void prepareSync(qreal devicePixelRatio, QRhiCommandBuffer *cb);
+    virtual void prepareSync(qreal devicePixelRatio,
+                             QRhiCommandBuffer *cb,
+                             const QQuickGraphicsConfiguration &config);
+
     virtual void beginNextFrame(QSGRenderer *renderer,
                                 RenderPassCallback mainPassRecordingStart,
                                 RenderPassCallback mainPassRecordingEnd,
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext.cpp b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
index 1c7f6c5c59..6dbc20d9cb 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext.cpp
+++ b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
@@ -50,6 +50,7 @@
 #include <QtQuick/private/qsgcompressedtexture_p.h>
 
 #include <QtQuick/qsgrendererinterface.h>
+#include <QtQuick/qquickgraphicsconfiguration.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -62,6 +63,7 @@ QSGDefaultRenderContext::QSGDefaultRenderContext(QSGContext *context)
     , m_currentFrameCommandBuffer(nullptr)
     , m_currentFrameRenderPass(nullptr)
     , m_separateIndexBuffer(false)
+    , m_useDepthBufferFor2D(true)
 {
 }
 
@@ -150,9 +152,12 @@ void QSGDefaultRenderContext::invalidate()
     emit invalidated();
 }
 
-void QSGDefaultRenderContext::prepareSync(qreal devicePixelRatio, QRhiCommandBuffer *cb)
+void QSGDefaultRenderContext::prepareSync(qreal devicePixelRatio,
+                                          QRhiCommandBuffer *cb,
+                                          const QQuickGraphicsConfiguration &config)
 {
     m_currentDevicePixelRatio = devicePixelRatio;
+    m_useDepthBufferFor2D = config.isDepthBufferEnabledFor2D();
 
     // we store the command buffer already here, in case there is something in
     // an updatePaintNode() implementation that leads to needing it (for
@@ -277,11 +282,6 @@ void QSGDefaultRenderContext::initializeRhiShader(QSGMaterialShader *shader, QSh
     QSGMaterialShaderPrivate::get(shader)->prepare(shaderVariant);
 }
 
-bool QSGDefaultRenderContext::separateIndexBuffer() const
-{
-    return m_separateIndexBuffer;
-}
-
 void QSGDefaultRenderContext::preprocess()
 {
     for (auto it = m_glyphCaches.begin(); it != m_glyphCaches.end(); ++it) {
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext_p.h b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
index 35a0695dab..a110172a6f 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext_p.h
+++ b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
@@ -90,7 +90,10 @@ public:
     void initialize(const QSGRenderContext::InitParams *params) override;
     void invalidate() override;
 
-    void prepareSync(qreal devicePixelRatio, QRhiCommandBuffer *cb) override;
+    void prepareSync(qreal devicePixelRatio,
+                     QRhiCommandBuffer *cb,
+                     const QQuickGraphicsConfiguration &config) override;
+
     void beginNextFrame(QSGRenderer *renderer,
                         RenderPassCallback mainPassRecordingStart,
                         RenderPassCallback mainPassRecordingEnd,
@@ -116,8 +119,8 @@ public:
     virtual void initializeRhiShader(QSGMaterialShader *shader, QShader::Variant shaderVariant);
 
     int maxTextureSize() const override { return m_maxTextureSize; }
-    bool separateIndexBuffer() const;
-
+    bool separateIndexBuffer() const { return m_separateIndexBuffer; }
+    bool useDepthBufferFor2D() const { return m_useDepthBufferFor2D; }
     int msaaSampleCount() const { return m_initParams.sampleCount; }
 
     QRhiCommandBuffer *currentFrameCommandBuffer() const {
@@ -152,6 +155,7 @@ protected:
     QRhiRenderPassDescriptor *m_currentFrameRenderPass;
     qreal m_currentDevicePixelRatio;
     bool m_separateIndexBuffer;
+    bool m_useDepthBufferFor2D;
 };
 
 QT_END_NAMESPACE
diff --git a/src/quick/scenegraph/qsgrenderloop.cpp b/src/quick/scenegraph/qsgrenderloop.cpp
index c025e8d9af..8388fa9576 100644
--- a/src/quick/scenegraph/qsgrenderloop.cpp
+++ b/src/quick/scenegraph/qsgrenderloop.cpp
@@ -107,7 +107,7 @@ void QSGRenderLoop::cleanup()
     s_instance = nullptr;
 
 #ifdef ENABLE_DEFAULT_BACKEND
-    QSGRhiSupport::cleanupVulkanInstance();
+    QSGRhiSupport::cleanupDefaultVulkanInstance();
     QSGRhiProfileConnection::instance()->cleanup();
 #endif
 }
diff --git a/src/quick/scenegraph/qsgrhilayer.cpp b/src/quick/scenegraph/qsgrhilayer.cpp
index 9d3db8354d..0e7eb1932e 100644
--- a/src/quick/scenegraph/qsgrhilayer.cpp
+++ b/src/quick/scenegraph/qsgrhilayer.cpp
@@ -352,9 +352,9 @@ void QSGRhiLayer::grab()
         return;
 
     if (!m_renderer) {
-        static const bool useDepth = qEnvironmentVariableIsEmpty("QSG_NO_DEPTH_BUFFER");
-        static const QSGRendererInterface::RenderMode renderMode = useDepth ? QSGRendererInterface::RenderMode2D
-                                                                            : QSGRendererInterface::RenderMode2DNoDepthBuffer;
+        const bool useDepth = m_context->useDepthBufferFor2D();
+        const QSGRendererInterface::RenderMode renderMode = useDepth ? QSGRendererInterface::RenderMode2D
+                                                                     : QSGRendererInterface::RenderMode2DNoDepthBuffer;
         m_renderer = m_context->createRenderer(renderMode);
         connect(m_renderer, SIGNAL(sceneGraphChanged()), this, SLOT(markDirtyTexture()));
     }
diff --git a/src/quick/scenegraph/qsgrhisupport.cpp b/src/quick/scenegraph/qsgrhisupport.cpp
index 618e1f1411..aa5661fc94 100644
--- a/src/quick/scenegraph/qsgrhisupport.cpp
+++ b/src/quick/scenegraph/qsgrhisupport.cpp
@@ -60,7 +60,7 @@ QT_BEGIN_NAMESPACE
 QVulkanInstance *s_vulkanInstance = nullptr;
 #endif
 
-QVulkanInstance *QSGRhiSupport::vulkanInstance()
+QVulkanInstance *QSGRhiSupport::defaultVulkanInstance()
 {
 #if QT_CONFIG(vulkan)
     QSGRhiSupport *inst = QSGRhiSupport::instance();
@@ -97,7 +97,7 @@ QVulkanInstance *QSGRhiSupport::vulkanInstance()
 #endif
 }
 
-void QSGRhiSupport::cleanupVulkanInstance()
+void QSGRhiSupport::cleanupDefaultVulkanInstance()
 {
 #if QT_CONFIG(vulkan)
     delete s_vulkanInstance;
@@ -537,7 +537,8 @@ QOffscreenSurface *QSGRhiSupport::maybeCreateOffscreenSurface(QWindow *window)
 // must be called on the render thread
 QRhi *QSGRhiSupport::createRhi(QQuickWindow *window, QOffscreenSurface *offscreenSurface)
 {
-    const QQuickGraphicsDevice &customDev(QQuickWindowPrivate::get(window)->customDeviceObjects);
+    QQuickWindowPrivate *wd = QQuickWindowPrivate::get(window);
+    const QQuickGraphicsDevice &customDev(wd->customDeviceObjects);
     const QQuickGraphicsDevicePrivate *customDevD = QQuickGraphicsDevicePrivate::get(&customDev);
 
     QRhi *rhi = nullptr;
@@ -580,6 +581,7 @@ QRhi *QSGRhiSupport::createRhi(QQuickWindow *window, QOffscreenSurface *offscree
             qWarning("No QVulkanInstance set for QQuickWindow, this is wrong.");
         if (window->handle()) // only used for vkGetPhysicalDeviceSurfaceSupportKHR and that implies having a valid native window
             rhiParams.window = window;
+        rhiParams.deviceExtensions = wd->graphicsConfig.deviceExtensions();
         if (customDevD->type == QQuickGraphicsDevicePrivate::Type::DeviceObjects) {
             QRhiVulkanNativeHandles importDev;
             importDev.physDev = reinterpret_cast<VkPhysicalDevice>(customDevD->u.deviceObjects.physicalDevice);
diff --git a/src/quick/scenegraph/qsgrhisupport_p.h b/src/quick/scenegraph/qsgrhisupport_p.h
index 9e81706f41..24cd787afc 100644
--- a/src/quick/scenegraph/qsgrhisupport_p.h
+++ b/src/quick/scenegraph/qsgrhisupport_p.h
@@ -104,8 +104,8 @@ class Q_QUICK_PRIVATE_EXPORT QSGRhiSupport
 public:
     static void configure(QSGRendererInterface::GraphicsApi api);
     static QSGRhiSupport *instance();
-    static QVulkanInstance *vulkanInstance();
-    static void cleanupVulkanInstance();
+    static QVulkanInstance *defaultVulkanInstance();
+    static void cleanupDefaultVulkanInstance();
 
     bool isRhiEnabled() const { return m_enableRhi; }
     QRhi::Implementation rhiBackend() const { return m_rhiBackend; }