qt-everywhere-src-5.15.1/qtbase/tests/manual/rhi/hellominimalcrossgfxtriangle/main.cpp

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// This is a compact, minimal demo of deciding the backend at runtime while
// using the exact same shaders and rendering code without any branching
// whatsoever once the QWindow is up and the RHI is initialized.

#include <QGuiApplication>
#include <QCommandLineParser>
#include "hellowindow.h"

QString graphicsApiName(QRhi::Implementation graphicsApi)
{
    switch (graphicsApi) {
    case QRhi::Null:
        return QLatin1String("Null (no output)");
    case QRhi::OpenGLES2:
        return QLatin1String("OpenGL 2.x");
    case QRhi::Vulkan:
        return QLatin1String("Vulkan");
    case QRhi::D3D11:
        return QLatin1String("Direct3D 11");
    case QRhi::Metal:
        return QLatin1String("Metal");
    default:
        break;
    }
    return QString();
}

int main(int argc, char **argv)
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QGuiApplication app(argc, argv);

    QRhi::Implementation graphicsApi;
#if defined(Q_OS_WIN)
    graphicsApi = QRhi::D3D11;
#elif defined(Q_OS_MACOS) || defined(Q_OS_IOS)
    graphicsApi = QRhi::Metal;
#elif QT_CONFIG(vulkan)
    graphicsApi = QRhi::Vulkan;
#else
    graphicsApi = QRhi::OpenGLES2;
#endif

    QCommandLineParser cmdLineParser;
    cmdLineParser.addHelpOption();
    QCommandLineOption nullOption({ "n", "null" }, QLatin1String("Null"));
    cmdLineParser.addOption(nullOption);
    QCommandLineOption glOption({ "g", "opengl" }, QLatin1String("OpenGL (2.x)"));
    cmdLineParser.addOption(glOption);
    QCommandLineOption vkOption({ "v", "vulkan" }, QLatin1String("Vulkan"));
    cmdLineParser.addOption(vkOption);
    QCommandLineOption d3dOption({ "d", "d3d11" }, QLatin1String("Direct3D 11"));
    cmdLineParser.addOption(d3dOption);
    QCommandLineOption mtlOption({ "m", "metal" }, QLatin1String("Metal"));
    cmdLineParser.addOption(mtlOption);

    cmdLineParser.process(app);
    if (cmdLineParser.isSet(nullOption))
        graphicsApi = QRhi::Null;
    if (cmdLineParser.isSet(glOption))
        graphicsApi = QRhi::OpenGLES2;
    if (cmdLineParser.isSet(vkOption))
        graphicsApi = QRhi::Vulkan;
    if (cmdLineParser.isSet(d3dOption))
        graphicsApi = QRhi::D3D11;
    if (cmdLineParser.isSet(mtlOption))
        graphicsApi = QRhi::Metal;

    qDebug("Selected graphics API is %s", qPrintable(graphicsApiName(graphicsApi)));
    qDebug("This is a multi-api example, use command line arguments to override:\n%s", qPrintable(cmdLineParser.helpText()));

    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);
    fmt.setStencilBufferSize(8);
    QSurfaceFormat::setDefaultFormat(fmt);

#if QT_CONFIG(vulkan)
    QVulkanInstance inst;
    if (graphicsApi == QRhi::Vulkan) {
#ifndef Q_OS_ANDROID
        inst.setLayers({ "VK_LAYER_LUNARG_standard_validation" });
#else
        inst.setLayers({
                "VK_LAYER_GOOGLE_threading",
                "VK_LAYER_LUNARG_parameter_validation",
                "VK_LAYER_LUNARG_object_tracker",
                "VK_LAYER_LUNARG_core_validation",
                "VK_LAYER_LUNARG_image",
                "VK_LAYER_LUNARG_swapchain",
                "VK_LAYER_GOOGLE_unique_objects"});
#endif
        inst.setExtensions({ "VK_KHR_get_physical_device_properties2" });
        if (!inst.create()) {
            qWarning("Failed to create Vulkan instance, switching to OpenGL");
            graphicsApi = QRhi::OpenGLES2;
        }
    }
#endif

    HelloWindow w(graphicsApi);
#if QT_CONFIG(vulkan)
    if (graphicsApi == QRhi::Vulkan)
        w.setVulkanInstance(&inst);
#endif
    w.resize(1280, 720);
    w.setTitle(QCoreApplication::applicationName() + QLatin1String(" - ") + graphicsApiName(graphicsApi));
    w.show();

    int ret = app.exec();

    // Window::event() will not get invoked when the
    // PlatformSurfaceAboutToBeDestroyed event is sent during the QWindow
    // destruction. That happens only when exiting via app::quit() instead of
    // the more common QWindow::close(). Take care of it: if the QPlatformWindow
    // is still around (there was no close() yet), get rid of the swapchain
    // while it's not too late.
    if (w.handle())
        w.releaseSwapChain();

    return ret;
}