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rhiwindow: Set DPR on image texture to ensure DPR-agnostic drawing

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Otherwise the 20x20 margins will produce different layouts depending
on the DPR, which is not what we want.

Pick-to: 6.7
Change-Id: I4153d0843ef51c8e0f60d7d5166b153d45201c95
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
This commit is contained in:
Tor Arne Vestbø 2024-04-10 14:51:44 +02:00
parent 8d84f7643b
commit a78938e0f6
2 changed files with 10 additions and 4 deletions
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5
examples/gui/doc/src/rhiwindow.qdoc
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@ -427,6 +427,11 @@
QRhiShaderResourceBindings, continue to be valid all the time. It is only
the underlying native resources that come and go over time.
Note also that we set a device pixel ratio on the image that matches
the window that we're drawing into. This ensures that the drawing code
can be DPR-agnostic, producing the same layout regardless of the DPR,
while also taking advantage of the additional pixels for improved fidelity.
\snippet rhiwindow/rhiwindow.cpp ensure-texture
Once a QImage is generated and the QPainter-based drawing into it has

9
examples/gui/rhiwindow/rhiwindow.cpp
View File

@ -281,17 +281,18 @@ void HelloWindow::ensureFullscreenTexture(const QSize &pixelSize, QRhiResourceUp
m_texture->create();
QImage image(pixelSize, QImage::Format_RGBA8888_Premultiplied);
image.setDevicePixelRatio(devicePixelRatio());
//! [ensure-texture]
QPainter painter(&image);
painter.fillRect(QRectF(QPointF(0, 0), pixelSize), QColor::fromRgbF(0.4f, 0.7f, 0.0f, 1.0f));
painter.fillRect(QRectF(QPointF(0, 0), size()), QColor::fromRgbF(0.4f, 0.7f, 0.0f, 1.0f));
painter.setPen(Qt::transparent);
painter.setBrush({ QGradient(QGradient::DeepBlue) });
painter.drawRoundedRect(QRectF(QPointF(20, 20), pixelSize - QSize(40, 40)), 16, 16);
painter.drawRoundedRect(QRectF(QPointF(20, 20), size() - QSize(40, 40)), 16, 16);
painter.setPen(Qt::black);
QFont font;
font.setPixelSize(0.05 * qMin(pixelSize.width(), pixelSize.height()));
font.setPixelSize(0.05 * qMin(width(), height()));
painter.setFont(font);
painter.drawText(QRectF(QPointF(60, 60), pixelSize - QSize(120, 120)), 0,
painter.drawText(QRectF(QPointF(60, 60), size() - QSize(120, 120)), 0,
QLatin1String("Rendering with QRhi to a resizable QWindow.\nThe 3D API is %1.\nUse the command-line options to choose a different API.")
.arg(graphicsApiName()));
painter.end();