#632: Thematic Maps
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Reporter: voncasec | Owner: grass-dev@lists.osgeo.org
Type: defect | Status: new
Priority: normal | Milestone: 6.4.0
Component: default | Version: 6.4.0 RCs
Keywords: | Platform: Linux
Cpu: Unspecified |
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Hi everyone, I have noticed what seems to me to be a bug with displaying
thematic map layers in Grass 6.4 RC4 using Ubuntu 8.10.
When a thematic layer is displayed based on the attributes of a point
file, the initial thematic map display seems fine (i.e. the graduated
point symbols correspond with the locations of the point data in x,y
space). However, if I zoom in or out of the data or pan to a different
region, the thematic map layer does not zoom or pan with the the vector
layers or raster layers also being displayed, the graduated symbols seem
fixed to the display not associated with the point file that was used to
create it.
I spent sometime to look into this issue and consider using FloatCanvas http://trac.paulmcnett.com/floatcanvas/wiki to fixed this bug. However, If
we use FloatCanvas to display maps, that means probably a lot of codes in
gui/wxpython/gui_modules/mapdisp.py, mapdisp_windows.py ,wxgui_utils and
render.py has to be change. Anyone know how much effort this might cause?
And I just sent an email to FloatCanvas mailing list to ask whether does
FloatCanavas support multilayer.
Any suggestion?
Thanks
Replying to [comment:4 yytsui]:
> I spent sometime to look into this issue and consider using FloatCanvas
> http://trac.paulmcnett.com/floatcanvas/wiki to fixed this bug. However,
If we use FloatCanvas to display maps, that means probably a lot of codes
in gui/wxpython/gui_modules/mapdisp.py, mapdisp_windows.py ,wxgui_utils
and render.py has to be change. Anyone know how much effort this might
cause? And I just sent an email to
probably quite a lot of work. If you start I would suggest to make a fork
of wxGUI in grass-addons and later to merge it into trunk.
I looked at FloatCanvas quite a while ago. It is nice, but it is much
simpler that we need for GRASS. The GRASS canvas does what FloatCanvas
does, but a lot more.
d.vect.thematic was written (by me and enhanced by others) as a shell
script wrapper around d.vect. When it was written, all GRASS displays
still used d.mon via an xterm. It still works in the display environment
of TclTk and wxPython canvases, but not as well.
We could add the newer module d.thematic.area to the layer tree
selections. I've done that for GRASS 7. I don't know if that would be
permitted for GRASS 6.4 as it is sort of a feature change (though it
shouldn't break anything). We could also enhance d.vect.thematic by
'Pythonizing' it. Glynn has done that for GRASS 7, but I haven't yet had
the chance to test it.
Ultimately, we are aware that we need to create a new and improved Python
script or an extended C module. As of a few days ago, I think that the C
module seems to be the direction we are headed. Any help would be
appreciated.