RFR: 8273355: Lanai: Flickering on tooltip appearance IntelliJ IDEA 2021.2.1

[Alexey Ushakov]

On Mon, 13 Sep 2021 07:11:02 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> > in a normal state (when the window is created) we don't need to flush the layer content faster than DisplayLink provide.
> 
> But this is exactly related to the performance, no? When the RenderPerf test is executed it should check that delay between fillRect and the actual rendering is as small as possible. Can you please just confirm that the problem is in the "performance" of DisplayLink and unrelated to some broken rendering? I guess you can create two timestamps in NSWindow creation and in Layer callback(where we actually blit the content/ drawInXXXContext). How that timing is different for metal and OGL?

I did some measurements for Metal and OGL and didn't find any noticeable difference with the simple test (just showing the frame)
Metal
1631605170711 window appeared
1631605170723 rendering submitted
1631605170724 rendering complete
1631605170747 rendering submitted
1631605170747 rendering complete
OGL
1631605401836 rendering complete
1631605401838 rendering complete
1631605401843 window appeared
1631605401881 rendering complete

Metal has additional output because we can track two stages - submission and completion. Also, I saw the flickering with OGL too (if we have no match with content and window colors)

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PR: https://git.openjdk.java.net/jdk/pull/5373