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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\example hellovulkantriangle
\meta installpath vulkan
\ingroup examples-vulkan
\title Hello Vulkan Triangle Example
\brief Shows the basics of rendering with QVulkanWindow and the Vulkan API.
\examplecategory {Graphics}
The \e{Hello Vulkan Triangle Example} creates a full graphics pipeline,
including a vertex and fragment shader, to render a triangle.
\image hellovulkantriangle.png
\section1 Startup
Each Qt application using Vulkan will have to have a \c{Vulkan instance}
which encapsulates application-level state and initializes a Vulkan library.
A QVulkanWindow must always be associated with a QVulkanInstance and hence
the example performs instance creation before the window. The
QVulkanInstance object must also outlive the window.
\snippet hellovulkantriangle/main.cpp 0
The example enables validation layers, when supported. When the requested
layers are not present, the request will be ignored. Additional layers and
extensions can be enabled in a similar manner.
\snippet hellovulkantriangle/main.cpp 1
Once the instance is ready, it is time to create a window. Note that \c w
lives on the stack and is declared after \c inst.
\section1 The QVulkanWindow Subclass
To add custom functionality to a QVulkanWindow, subclassing is used. This
follows the existing patterns from QOpenGLWindow and QOpenGLWidget.
However, QVulkanWindow utilizes a separate QVulkanWindowRenderer object.
The QVulkanWindow subclass reimplements the factory function
QVulkanWindow::createRenderer(). This simply returns a new instance of the
QVulkanWindowRenderer subclass. In order to be able to access various
Vulkan resources via the window object, a pointer to the window is passed
and stored via the constructor.
\snippet hellovulkantriangle/main.cpp 2
\section1 The Actual Rendering
QVulkanWindow subclasses queue their draw calls in their reimplementation
of QVulkanWindowRenderer::startNextFrame(). Once done, they are required to
call back QVulkanWindow::frameReady(). The example has no asynchronous
command generation, so the frameReady() call is made directly from
startNextFrame(). To get continuous updates, the example simply invokes
QWindow::requestUpdate() in order to schedule a repaint.
The example also demonstrates multisample antialiasing. Based on the
supported sample counts reported by QVulkanWindow::supportedSampleCounts()
the example chooses between 8x, 4x, or no multisampling. Once configured
via QVulkanWindow::setSamples(), QVulkanWindow takes care of the rest: the
additional multisample color buffers are created automatically, and
resolving into the swapchain buffers is performed at the end of the default
render pass for each frame.
\include examples-run.qdocinc
*/
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