[Libreoffice-ux-advise] [Bug 46988] VIEWING: Screen jumps when scrolling down with arrow keys

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=46988

--- Comment #25 from Michael Meeks <michael.meeks at collabora.com> ---
> LibreOffice Writer already supports a Smooth Scroll [1], that is disable
> by default. It does not completely remedy this, but it mostly functions

   Hmm, interesting. Of course - the real optimization with scroll is to
accelerate the big copy-area which happens when we scroll down I guess, and to
ensure we render only the 'new' content.

   Writer is however doing a ton of dumb stuff with OpenGL turned on, including
rendering to off-screen drawables and consuming lots of memory:

> But, it imposes additional overhead, and was even disabled for macOS builds
> due to the performance impact. Nor is it used on newer Android and iOS builds.

    Both Android & iOS do tiled rendering separately anyway; so it shouldn't be
used there.

> @Michael M, any thoughts on behavior of this and direction of the RFE? 

    I would be surprised if this particular piece of code did much good, and
I'd prefer to have faster, simpler code-paths there. Rendering and/or moving a
screen-full of pixels on the GPU should be so close to instant that there is
really no problem - so there must be some other silly here: perhaps key-event
handling priority vs. rendering, vs. typematic rate affecting how many events
we get queued, and ... that sort of thing I suspect =)

    The solution is just some engineering to timestamp the events, and time the
re-rendering sections, and do the fixing that becomes obvious from that I'd
imagine.

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