https://bugs.documentfoundation.org/show_bug.cgi?id=172399

--- Comment #3 from Patrick (volunteer) <[email protected]> ---
So the fact that Skia/Raster doesn't have the jitter that Skia/Metal does is
encouraging news. Usually Skia/Metal able to push pixels to a window much
faster than Skia/Raster so if Skia/Raster doesn't jitter, my first guess is
that the LibreOffice code isn't the bottleneck and most likely the bottleneck
is your machine's built-in GPU.

LibreOffice uses Google's Skia open source engine draw to the GPU. Their code
is a "black box" to me so I am not sure how to debug this. But one thing I do
know is that during window resizing, LibreOffice makes a temporary snapshot of
the window's contents while it handles the resizing.

So, during resizing, there are a large number of brief periods where a window's
memory usage is basically doubled. I wonder if a possible way to test that
theory would be if you did the following steps:

1. Launch LibreOffice, switch back to Skia/Metal, and restart
2. Open a new, empty Calc document and resize it to a very small size such as 5
cm x 5 cm
3. Rapidly resize the Calc window but keep it small during the resizing

Do you still see jitter with such a small window? If no, that my indicate that
the temporary snapshot (which are proportionate in memory size to the size of
the window) is overwhelming the GPU's available resources.

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