Flashing black background when resizing a form Root › Technical support › Troubleshooting This topic has 3 replies, 2 voices, and was last updated 7 years, 4 months ago by Support. Viewing 4 posts - 1 through 4 (of 4 total) Author Posts July 8, 2017 at 11:05 am #37534 LasseParticipant Use your demo: 1. Set MainUnit's PanelContainer.Align = alClient 2. Set UnitFrameTabControl's frame Align = alClient 3. Run the demo. 4. Go to Examples of components -> Inherited from VCL -> Tabbed controls 5. Resize the application, everything is smooth 6. Change Extended borders mode to false 7. Now that same resizing (5) is flashing black background Can I avoid this somehow when not using extended borders mode? July 13, 2017 at 11:20 am #56893 SupportKeymaster Hello These black rectangles are shown when but size of the control is changed, background is not rendered yet. Extended borders solves this issue. July 15, 2017 at 11:35 am #56911 LasseParticipant I managed to solve this when not using extended borders mode: Code: procedure TBaseForm.FormCreate(Sender: TObject); begin inherited; SetClassLong(Handle, GCL_HBRBACKGROUND, GetSysColorBrush(COLOR_WINDOW)); end; July 17, 2017 at 3:54 am #56913 SupportKeymaster Thank you, I didn't knew this feature. Author Posts Viewing 4 posts - 1 through 4 (of 4 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Log In Root › Technical support › Troubleshooting