Related: tdf#155266 force flush after drawing native scrollbars

When scrolling on some Intel Macs either via dragging
the scrollbar thumb or via swiping the trackpad with two
fingers, final repaint of scrollbars doesn't appear to
get flushed to the screen. It appears that scrollbars
aren't updated and repainted until after a batch of
native scroll events have been dispatched. On slower
machines, this lag is long enough that any pending
forced flushes have already been done so when the timer
that repaints scrollbars finally fires, the repainted
scrollbars won't get flushed to the native window until
the next normal flush which may not occur until seconds
later.

Change-Id: Iadef6812cd2495a28347560caae81f604c908b51
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/160440
Tested-by: Jenkins
Reviewed-by: Patrick Luby <plubius@libreoffice.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/vcl/osx/salnativewidgets.cxx b/vcl/osx/salnativewidgets.cxx
index 8a7e81fd5d86..a50735bf4628 100644
--- a/vcl/osx/salnativewidgets.cxx
+++ b/vcl/osx/salnativewidgets.cxx
@@ -757,6 +757,22 @@ bool AquaGraphicsBackendBase::performDrawNativeControl(ControlType nType,
 
                     CGContextRestoreGState(context);
 
+                    // Related: tdf#155266 force flush after drawing native scrollbars
+                    // When scrolling on some Intel Macs either via dragging
+                    // the scrollbar thumb or via swiping the trackpad with two
+                    // fingers, final repaint of scrollbars doesn't appear to
+                    // get flushed to the screen. It appears that scrollbars
+                    // aren't updated and repainted until after a batch of
+                    // native scroll events have been dispatched. On slower
+                    // machines, this lag is long enough that any pending
+                    // forced flushes have already been done so when the timer
+                    // that repaints scrollbars finally fires, the repainted
+                    // scrollbars won't get flushed to the native window until
+                    // the next normal flush which may not occur until seconds
+                    // later.
+                    if (mpFrame && nType == ControlType::Scrollbar)
+                        mpFrame->mbForceFlush = true;
+
                     bOK = true;
 
                     [pBar release];