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wasm: propagate QWindow format to backing store 

Qt backing store images should have alpha iff that was
requested by the QWindow's surface format. This changes
wasm to be in line with the other platforms, and enables
use of transparency for Qt windows.

Change beginPaint() to clear the backing store only
if the format/image has alpha. This is also established
behavior Qt's backing stores.

Change-Id: Idafe658e24d864f7c4f9e68ee39cb409982b5852
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: David Skoland <david.skoland@qt.io>
bb10
Morten Sørvig 2022-04-12 12:43:07 +02:00
parent e629efc82c
commit c78925f487
1 changed files with 10 additions and 5 deletions
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15
src/plugins/platforms/wasm/qwasmbackingstore.cpp
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@ -156,17 +156,22 @@ void QWasmBackingStore::beginPaint(const QRegion &region)
resize(backingStore()->size(), backingStore()->staticContents());
QPainter painter(&m_image);
painter.setCompositionMode(QPainter::CompositionMode_Source);
const QColor blank = Qt::transparent;
for (const QRect &rect : region)
painter.fillRect(rect, blank);
if (m_image.hasAlphaChannel()) {
painter.setCompositionMode(QPainter::CompositionMode_Source);
const QColor blank = Qt::transparent;
for (const QRect &rect : region)
painter.fillRect(rect, blank);
}
}
void QWasmBackingStore::resize(const QSize &size, const QRegion &staticContents)
{
Q_UNUSED(staticContents);
m_image = QImage(size * window()->devicePixelRatio(), QImage::Format_RGB32);
QImage::Format format = window()->format().hasAlpha() ?
QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32;
m_image = QImage(size * window()->devicePixelRatio(), format);
m_image.setDevicePixelRatio(window()->devicePixelRatio());
m_recreateTexture = true;
}