Michael Meeks <> changed:

           What    |Removed                     |Added
                 CC|                            |
            Summary|VIEWING: Scrolling becomes  |Non-accelerated image
                   |slow when pictures appear   |scaling under Linux ...

--- Comment #35 from Michael Meeks <> ---
Thanks for the trace - as expected this looks like it is down to the drawing
layer re-scaling images very regularly; and I imagine that we re-scale the
entire image no matter how little of it we want to actually render too ;-) [ a
better VCL rendering API / Impl. might improve that ? ] Either way - Armin is
the expert here.

I see 39bn pcycles in your trace - of which:

18.7bn are from scaleNonPaletteGeneral2 - on GetPixelForN32BitTcBgra - which we
could write an accelerated C++ version for I guess.

This is from the threaded method (why you have 4 CPUs at 100% ;-)

And another 8.9bn pcycles from the main thread - doing some of that work too.

I attach a pretty picture of where that comes from. It is possible that by
intersecting with the VCL clipping region we could do something more optimal
and quick here I guess wrt. reducing the amount of image data we operate on.


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