bugMyPaint - Bugs: bug #20730, Symmetry mode eats horizontal...

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bug #20730: Symmetry mode eats horizontal strokes of classic/kinfe brush with radius 1.10

Submitted by:  Libra Rian <zrzz>
Submitted on:  Tue Apr 9 16:38:54 2013  
Severity: 3 - NormalPriority: 5 - Normal
Status: Ready For TestPrivacy: Public
Assigned to: NoneOpen/Closed: Closed
Release: 819eae4Planned Release: None
Operating System: Lubuntu 12.10/Compiz

Tue Jun 24 21:33:17 2014, comment #3:

[This is a canned response, please forgive the broken formatting: it's one of the many things Gna! unfortunately does not do well.]

This bug tracker will shortly be moving to Github. As part of this process, we are reviewing old bug reports on gna.org.

This bug was marked as "Ready for Test" or "Works for Me" some time ago, but was still classified as Open and no feedback has been submitted since then.
I am therefore assuming that the problem has been fixed to everyone's satisfaction (or was't reproducible by anybody else).

If you believe that this bug still affects the most recent git master of MyPaint (and thus the next release), please feel free to open a new issue on
Github about it. Our new issue trackers are:


Andrew Chadwick <achadwick>
Project Administrator
Mon Apr 22 00:56:43 2013, comment #2:

Cool bug! Thanks for the fix: tested and pushed.


Andrew Chadwick <achadwick>
Project Administrator
Sat Apr 20 06:15:36 2013, comment #1:


Symmetry mode is broken due type conversion. Look at draw_dab(brushlib/mypaint-tiled-surface.c:587). When applying symmetry mode it converts float x to int symm_x. And that breaks things

Fix in this commit


Libra Rian <zrzz>
Tue Apr 9 16:38:54 2013, original submission:

Funny thing that is triggered under very specific conditions:

1) Launch mypaint
2) Select classic/knife brush, decrease radius to 1.10
3) Turn on symmetry mode
4) Draw line as horizontal as you can. Mouse or tablet - does not matter.

Symmetry mode will not reproduce horizontal lines correctly. Only horizontal lines. And only for radius=1.10. Other lines and radiuses are fine.

Now interesting part: open brush settings(Ctrl-B), click "update last stroke" and change brush radius. Horizontal stroke with radius != 1.10 will be symmetrically drawn more correctly.

Attach has two screenshots where I update radius. Notice that at radius=1.10 stroke in symmetry-drawn part is invisible.

Libra Rian <zrzz>


Attached Files


Depends on the following items: None found

Items that depend on this one: None found


Carbon-Copy List
  • -unavailable- added by achadwick (Posted a comment)
  • -unavailable- added by zrzz (Submitted the item)

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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Tue Jun 24 21:33:17 2014achadwickOpen/ClosedOpen=>Closed
    Mon Apr 22 00:56:43 2013achadwickStatusNone=>Ready For Test
    Tue Apr 9 16:38:54 2013zrzzAttached File-=>Added 2013-04-09-232438_1280x960_scrot.png, #17726
      Attached File-=>Added 2013-04-09-232456_1280x960_scrot.png, #17727
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