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GUI: draw framebuffer updates without temporary pixmaps #745

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GUI: draw framebuffer updates without temporary pixmaps #745

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28 changes: 11 additions & 17 deletions src/VBox/Frontends/VirtualBox/src/runtime/UIFrameBuffer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1441,31 +1441,25 @@ void UIFrameBufferPrivate::drawImageRect(QPainter &painter, const QImage &image,
int iContentsShiftX, int iContentsShiftY,
double dDevicePixelRatio)
{
/* Calculate offset: */
const size_t offset = (rect.x() + iContentsShiftX) * image.depth() / 8 +
(rect.y() + iContentsShiftY) * image.bytesPerLine();

/* Restrain boundaries: */
const int iSubImageWidth = qMin(rect.width(), image.width() - rect.x() - iContentsShiftX);
const int iSubImageHeight = qMin(rect.height(), image.height() - rect.y() - iContentsShiftY);
if ( iSubImageWidth <= 0
|| iSubImageHeight <= 0)
return;

/* Create sub-image (no copy involved): */
QImage subImage = QImage(image.bits() + offset,
iSubImageWidth, iSubImageHeight,
image.bytesPerLine(), image.format());

/* Create sub-pixmap on the basis of sub-image above (1st copy involved): */
QPixmap subPixmap = QPixmap::fromImage(subImage);
/* Take the device-pixel-ratio into account: */
subPixmap.setDevicePixelRatio(dDevicePixelRatio);

/* Which point we should draw corresponding sub-pixmap? */
/* Which point we should draw the image at? */
QPoint paintPoint = rect.topLeft();
/* Take the device-pixel-ratio into account: */
paintPoint /= dDevicePixelRatio;

/* Draw sub-pixmap: */
painter.drawPixmap(paintPoint, subPixmap);
/* Draw directly from the source image to avoid materializing a temporary pixmap for every update rectangle. */
const QRect sourceRect(rect.x() + iContentsShiftX, rect.y() + iContentsShiftY,
iSubImageWidth, iSubImageHeight);
const QRectF targetRect(QPointF(paintPoint),
QSizeF((double)iSubImageWidth / dDevicePixelRatio,
(double)iSubImageHeight / dDevicePixelRatio));
painter.drawImage(targetRect, image, sourceRect);
}

/* static */
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