[Libreoffice-bugs] [Bug 104716] General performance problems - UI freezes, slow scrolling, etc. in files with big/complex images

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=104716

--- Comment #40 from Telesto <telesto at surfxs.nl> ---
Created attachment 136783
  --> https://bugs.documentfoundation.org/attachment.cgi?id=136783&action=edit
Bibisect log

The slow mouse scrolling for documents containing pngs's started with the LibO
4.3 branch.

1. Open attachment 129896
2. Scroll down.

I bibisected it to:

~/bibisect-43max$ git bisect bad
af3738481b95e4747478021f93aac10e80a35c52 is the first bad commit
commit af3738481b95e4747478021f93aac10e80a35c52
Author: Matthew Francis <mjay.francis at gmail.com>
Date:   Thu May 28 18:33:29 2015 +0800

    source-hash-3cf3700b7a903e88f5296076c40ae854bce91cdc

    commit 3cf3700b7a903e88f5296076c40ae854bce91cdc
    Author:     Jan Holesovsky <kendy at collabora.com>
    AuthorDate: Mon Jan 27 20:11:26 2014 +0100
    Commit:     Jan Holesovsky <kendy at collabora.com>
    CommitDate: Mon Jan 27 20:17:01 2014 +0100

fdo#74124: Scale the pictures before calling ImplDrawAlpha().

When the source and destination bitmap do not have the same size,
ImplDrawAlpha() does not use direct paint, but instead it gets the image from
the screen, blends it with the provided bitmap, and again draws it.

Unfortunately, the blending uses the most trivial (and ugly) way of scaling;
so to produce much better results, let's scale to the destination size before
even calling ImplDrawAlpha().

The sideeffect is that we use the direct paint in most cases now; so hopefully
it pays off to do the (a bit more expensive) scale first.

Change-Id: I3b6b275710220910709ae4345ad6be3d6e4bf79c
:040000 040000 d0f6eee0576c14affca0296f09caf1aff748a67c
8d9d2f4ebc8df18549ae3cc2fdccddc5856c6260 M    opt

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