Fix crash with non-integer Qt scaling

We could end up dropping visible blocks during scrolling if only one
pixel line was left and the viewport got rounding one line too small.

Task-number: QTBUG-68699
Change-Id: I1ab646f23d8dd4911b32d02df68c80d6a8d78651
Reviewed-by: Michal Klocek <michal.klocek@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/core/delegated_frame_node.cpp b/src/core/delegated_frame_node.cpp
index eed407a09..c0f515ad8 100644
--- a/src/core/delegated_frame_node.cpp
+++ b/src/core/delegated_frame_node.cpp
@@ -852,7 +852,8 @@ void DelegatedFrameNode::commit(ChromiumCompositorData *chromiumCompositorData,
     QScopedPointer<DelegatedNodeTreeHandler> nodeHandler;
 
     const QSizeF viewportSizeInPt = apiDelegate->screenRect().size();
-    const QSize viewportSize = (viewportSizeInPt * devicePixelRatio).toSize();
+    const QSizeF viewportSizeF = viewportSizeInPt * devicePixelRatio;
+    const QSize viewportSize(std::ceil(viewportSizeF.width()), std::ceil(viewportSizeF.height()));
 
     // We first compare if the render passes from the previous frame data are structurally
     // equivalent to the render passes in the current frame data. If they are, we are going