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Bug 312147 - antialiased hex grid drawn incorrectly
antialiased hex grid drawn incorrectly
Status: RESOLVED FIXED
Product: dia
Classification: Other
Component: general
CVS head
Other Linux
: Normal normal
: 0.95
Assigned To: Dia maintainers
Dia maintainers
Depends on:
Blocks:
 
 
Reported: 2005-07-31 18:41 UTC by Roland Stigge
Modified: 2006-01-29 18:48 UTC
See Also:
GNOME target: ---
GNOME version: ---

Attachments
C implementation of bresenham (1.93 KB, text/x-csrc)
2005-11-15 15:52 UTC, Lars Clausen 		Details

Description Roland Stigge 2005-07-31 18:41:18 UTC 
Distribution/Version: Debian

A Debian user reported the following:

====================================================================
Steps to reproduce:
- Start dia
- Turn off dynamic grid and turn on hex grid. Hex grid drawn correctly.
- Turn on antialiasing. Hex grid drawn incorrectly.

See attached screenshot.

Both vanilla dia and dia-gnome exhibit this effect.

I also couldn't help but notice that the 'Hex grid size' value has
absolutely no effect on the size of the hex grid.
====================================================================

I can reproduce this here.

See also: http://bugs.debian.org/319981
Comment 1 Lars Clausen 2005-09-13 20:14:51 UTC 
Confirmed, looks slanted to the right.
Comment 2 Lars Clausen 2005-11-15 15:51:04 UTC 
Marking as confirmed.  Seems the draw_pixel_line function in render_libart is
only used non-horizontally/vertically in this one case, and thus is poorly
tested.  It's also awfully complex.

If anybody wants to poke at the algorithm, it is attached.
Comment 3 Lars Clausen 2005-11-15 15:52:05 UTC 
Created attachment 54784 [details]
C implementation of bresenham
Comment 4 Hans Breuer 2006-01-29 18:48:48 UTC 
2006-01-29  Hans Breuer  <hans@breuer.org>

	* app/render_libart.c(draw_line) : make setting the pixel side-effect
	free; account for it in now (less) magic increments. Fixes bug #312147