tdf#172399 skip redrawing of old surface during live resize

During live resize on macOS, there is a flood of resize
events in quick succession so not only are most of the
newly created surfaces short lived, but preserving and
redrawing the original content drawn to the old surface
is unnecessary since AquaSalFrame::SendPaintEvent() is
is called after each resize event.

Change-Id: I60934d023a1303ffb898815a7787a30b1a163fba
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/208130
Tested-by: Jenkins
Reviewed-by: Patrick Luby <guibomacdev@gmail.com>

vcl/skia/gdiimpl.cxx

@@ -52,6 +52,10 @@
 #include <o3tl/sorted_vector.hxx>
 #include <rtl/math.hxx>
 
+#ifdef MACOSX
+#include <svdata.hxx>
+#endif
+
 using namespace SkiaHelper;
 
 namespace
@@ -555,8 +559,22 @@ void SkiaSalGraphicsImpl::checkSurface()
             sk_sp<SkImage> snapshot;
             if (!isOffscreen())
             {
-                flushDrawing();
-                snapshot = makeCheckedImageSnapshot(mSurface);
+#ifdef MACOSX
+                // tdf#172399 skip redrawing of old surface during live resize
+                // During live resize on macOS, there is a flood of resize
+                // events in quick succession so not only are most of the
+                // newly created surfaces short lived, but preserving and
+                // redrawing the original content drawn to the old surface
+                // is unnecessary since AquaSalFrame::SendPaintEvent() is
+                // is called after each resize event.
+                if (!ImplGetSVData()->mpWinData->mbIsLiveResize)
+                {
+#endif
+                    flushDrawing();
+                    snapshot = makeCheckedImageSnapshot(mSurface);
+#ifdef MACOSX
+                }
+#endif
             }
 
             destroySurface();