Support non-integer pixel-ratio in QQuickWidget

Non-integer pixel-ratios always resulted in blurry rendering when
QQuickWidget was used, but not with QQuickWindow. Fixed by reading qreal
accessor of devicePixelRatio instead.

Change-Id: I49f5efcf2da2efc090c00017e68c99c857cd84ef
Task-number: QTBUG-61502
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 8 insertions, 6 deletions

diff --git a/src/quickwidgets/qquickwidget.cpp b/src/quickwidgets/qquickwidget.cpp
index 2e8623f508..2c3c72d5f1 100644
--- a/src/quickwidgets/qquickwidget.cpp
+++ b/src/quickwidgets/qquickwidget.cpp
@@ -913,9 +913,9 @@ void QQuickWidget::createFramebufferObject()
     d->offscreenWindow->setGeometry(globalPos.x(), globalPos.y(), width(), height());
 
     if (d->useSoftwareRenderer) {
-        const QSize imageSize = size() * devicePixelRatio();
+        const QSize imageSize = size() * devicePixelRatioF();
         d->softwareImage = QImage(imageSize, QImage::Format_ARGB32_Premultiplied);
-        d->softwareImage.setDevicePixelRatio(devicePixelRatio());
+        d->softwareImage.setDevicePixelRatio(devicePixelRatioF());
         return;
     }
 
@@ -960,7 +960,7 @@ void QQuickWidget::createFramebufferObject()
         format.setInternalTextureFormat(GL_SRGB8_ALPHA8_EXT);
 #endif
 
-    const QSize fboSize = size() * devicePixelRatio();
+    const QSize fboSize = size() * devicePixelRatioF();
 
     // Could be a simple hide - show, in which case the previous fbo is just fine.
     if (!d->fbo || d->fbo->size() != fboSize) {
@@ -1181,7 +1181,7 @@ void QQuickWidget::resizeEvent(QResizeEvent *e)
     // Software Renderer
     if (d->useSoftwareRenderer) {
         needsSync = true;
-        if (d->softwareImage.size() != size() * devicePixelRatio()) {
+        if (d->softwareImage.size() != size() * devicePixelRatioF()) {
             createFramebufferObject();
         }
     } else {
@@ -1191,7 +1191,7 @@ void QQuickWidget::resizeEvent(QResizeEvent *e)
             // during hide - resize - show sequences and also during application exit.
             if (!d->fbo && !d->offscreenWindow->openglContext())
                 return;
-            if (!d->fbo || d->fbo->size() != size() * devicePixelRatio()) {
+            if (!d->fbo || d->fbo->size() != size() * devicePixelRatioF()) {
                 needsSync = true;
                 createFramebufferObject();
             }
@@ -1607,10 +1607,12 @@ void QQuickWidget::paintEvent(QPaintEvent *event)
             //Paint everything
             painter.drawImage(rect(), d->softwareImage);
         } else {
+            QTransform transform;
+            transform.scale(devicePixelRatioF(), devicePixelRatioF());
             //Paint only the updated areas
             const auto rects = d->updateRegion.rects();
             for (auto targetRect : rects) {
-                auto sourceRect = QRect(targetRect.topLeft() * devicePixelRatio(), targetRect.size() * devicePixelRatio());
+                auto sourceRect = transform.mapRect(QRectF(targetRect));
                 painter.drawImage(targetRect, d->softwareImage, sourceRect);
             }
             d->updateRegion = QRegion();