rhi: Add a --transparent option to manual tests

This will also cause clearing to 0,0,0,0.

Essential in order to allow fast testing of window transparency
issues in combination with QRhi and the various backends.

Change-Id: Iee2763c1d06f1d3e5d59a9142abaf30fab1dc543
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/manual/rhi/shared/examplefw.h b/tests/manual/rhi/shared/examplefw.h
index 4bd087473b..220c3d0ff2 100644
--- a/tests/manual/rhi/shared/examplefw.h
+++ b/tests/manual/rhi/shared/examplefw.h
@@ -127,6 +127,7 @@ QRhiSwapChain::Flags scFlags = 0;
 QRhi::BeginFrameFlags beginFrameFlags = 0;
 QRhi::EndFrameFlags endFrameFlags = 0;
 int framesUntilTdr = -1;
+bool transparentBackground = false;
 
 class Window : public QWindow
 {
@@ -167,6 +168,8 @@ protected:
     QOffscreenSurface *m_fallbackSurface = nullptr;
 #endif
 
+    QColor m_clearColor;
+
     friend int main(int, char**);
 };
 
@@ -194,6 +197,8 @@ Window::Window()
     default:
         break;
     }
+
+    m_clearColor = transparentBackground ? Qt::transparent : QColor::fromRgbF(0.4f, 0.7f, 0.0f, 1.0f);
 }
 
 Window::~Window()
@@ -477,6 +482,9 @@ int main(int argc, char **argv)
     QCommandLineOption swOption(QLatin1String("software"), QLatin1String("Prefer a software renderer when choosing the adapter. "
                                                                          "Only applicable with some APIs and platforms."));
     cmdLineParser.addOption(swOption);
+    // Allow testing having a semi-transparent window.
+    QCommandLineOption transparentOption(QLatin1String("transparent"), QLatin1String("Make background transparent"));
+    cmdLineParser.addOption(transparentOption);
 
     cmdLineParser.process(app);
     if (cmdLineParser.isSet(nullOption))
@@ -493,6 +501,11 @@ int main(int argc, char **argv)
     qDebug("Selected graphics API is %s", qPrintable(graphicsApiName()));
     qDebug("This is a multi-api example, use command line arguments to override:\n%s", qPrintable(cmdLineParser.helpText()));
 
+    if (cmdLineParser.isSet(transparentOption)) {
+        transparentBackground = true;
+        scFlags |= QRhiSwapChain::SurfaceHasPreMulAlpha;
+    }
+
 #ifdef EXAMPLEFW_PREINIT
     void preInit();
     preInit();
@@ -508,6 +521,9 @@ int main(int argc, char **argv)
         fmt.setSwapInterval(0);
     if (scFlags.testFlag(QRhiSwapChain::sRGB))
         fmt.setColorSpace(QSurfaceFormat::sRGBColorSpace);
+    // Exception: The alpha size is not necessarily OpenGL specific.
+    if (transparentBackground)
+        fmt.setAlphaBufferSize(8);
     QSurfaceFormat::setDefaultFormat(fmt);
 
     // Vulkan setup.