path: root/examples/quick/rendercontrol/rendercontrol.pro
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authorLaszlo Agocs <laszlo.agocs@qt.io>2020-01-15 09:08:24 +0100
committerLaszlo Agocs <laszlo.agocs@qt.io>2020-04-11 18:23:55 +0200
commit400d176760de84626500787674b1ece387b25893 (patch)
treedbb8b5fd50440e6c01d6b940fe1692ba8e6a1f5c /examples/quick/rendercontrol/rendercontrol.pro
parent654959e2e2b74855036f949a9c23c9d9c7a614ac (diff)
Allow redirecting QRhi-based rendering via QQuickRenderControl
Implement the Qt 6 TODO for using an externally-provided render target when rendering the scene via QRhi. And say hello to QQuickRenderTarget. This class exists to allow potentially extending later what a "render target" consists of. Instead of hard-coding taking a single void * in the setRenderTarget() function, it takes a (implicitly shared, d-pointered) QQuickRenderTarget, which in turn can be created via static factory functions - of which new ones can be added later on. The new version of QQuickWindow::setRenderTarget() takes a QQuickRenderTarget. QQuickRenderControl gets a new initialize() variant, and a few extra functions (beginFrame(), endFrame()). This allows it to, by using QSGRhiSupport internally, create a QRhi under the hood. As a bonus, this also fixes an existing scenegraph resource leak when destroying the QQuickRenderControl. The qquickrendercontrol autotest is extended, with a QRhi-based test case that is executed for all of the QRhi backends that succeed to initialize. This is the internal verification. In addition, there is a Vulkan-based one that creates its own VkDevice, VkImage, and friends, and then uses Qt Quick with the same Vulkan device, targeting the VkImage. This test verifies the typical application use case. (sadly, life is too short to waste it on writing Vulkan boilerplate for an on-screen version of this, but we have the D3D11 example instead) What QQuickRenderControl loses, when used in combination with QRhi, is the grab() function. This never made much sense as a public API: QQuickWindow::grabWindow() call this when the window is associated with a rendercontrol, so as a public API QQuickRenderControl::grab() is redundant, because one gets the same result via the standard QQuickWindow API. It is now made private. More importantly, reading back the content is no longer supported, unless the 'software' backend is in use. The reasoning here is that, if the client of the API manages and provides the render target (as abstracted by QQuickRenderTarget), it is then expected to be capable of reading back the content in whatever way it sees fit, because it owns and manages the resource (e.g. the texture) in the first place. Providing fragile convenience functions for this is not reasonable anymore, and was questionable even with OpenGL, given that it is not future proof - what if the target is suddenly a floating point texture, for instance? The software backend case makes sense because that relies on private APIs - and has no render target concept either - so there the same cannot be achieved by applications by relying on public APIs only. Another new class is QQuickGraphicsDevice. This is very similar to QQuickRenderTarget, it is a simple container capable of holding a set of of native objects, mostly in the form of void*s, with future extensibility thanks to the static factory functions. (examples of native object sets would be a ID3D11Device + ID3D11DeviceContext, or a QOpenGLContext, or a MTLDevice + MTLCommandQueue, or a number of Vulkan device-related objects, etc.) This allows one to specify that the QRhi created under the hood (either by QQuickRenderControl or by the render loop) should use an existing graphics device (i.e. it is basically a public wrapper for values that go into a QRhi*InitParams under the hood). QQuickRenderTarget and QQuickGraphicsDevice are both demonstrated in a new example: rendercontrol_d3d11. We choose D3D11 because it is reasonably simple to set up a renderer with a window, and, because there is known user demand for Qt Quick - external D3D engine interop. Passing in the custom engine's own ID3D11Device and ID3D11DeviceContext is essential: the texture (ID3D11Texture2D) Qt Quick is targeting would not be usable if Qt Quick's QRhi was using a different ID3D11Device. Task-number: QTBUG-78595 Change-Id: I5dfe7f6cf1540daffc2f11136be114a08e87202b Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org> Reviewed-by: Andy Nichols <andy.nichols@qt.io>
Diffstat (limited to 'examples/quick/rendercontrol/rendercontrol.pro')
1 files changed, 6 insertions, 1 deletions
diff --git a/examples/quick/rendercontrol/rendercontrol.pro b/examples/quick/rendercontrol/rendercontrol.pro
index cdb431c8fd..d49be63c50 100644
--- a/examples/quick/rendercontrol/rendercontrol.pro
+++ b/examples/quick/rendercontrol/rendercontrol.pro
@@ -1,4 +1,9 @@
TEMPLATE = subdirs
+win32 {
+ SUBDIRS += \
+ rendercontrol_d3d11