RFR: 8270874: JFrame paint artifacts when dragged from standard monitor to HiDPI monitor

[Sergey Bylokhov]

On Mon, 15 Nov 2021 10:00:37 GMT, Jayathirth D V <jdv at openjdk.org> wrote:

> Please correct my understanding. Does this refined repaint logic apply even for overlapping Windows? What happens when 2 windows are overlapping and we move top window slowly? Any performance/power impact?

Initially, this code was used just for that, to make a fast blit of the content from the Swing back buffer to the native window, when some other window is moved over the Swing and damaged it (the fix for the "grey rectangle" JDK-4967886). But since Windows Vista the Windows itself maintain such doublebuffer and the content is not damaged when windows overlap, so this callback is not called.

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PR: https://git.openjdk.java.net/jdk/pull/6339