Repetitive d.rast calls for wx0 monitor from command line

[hcho]

I was drawing 168 raster maps on the wx monitor from a shell script:

#!/bin/sh
maps=`g.mlist rast pattern="n[0-9]*w[0-9]*_1" sep=,`
g.region rast=$maps res=00:01:00
d.erase
for i in `echo $maps | sed 's/,/ /g'`
do
        d.rast $i
done

after starting and selecting a wx monitor. I'm getting the following error messages and not all the raster maps are displayed:

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ERROR: No graphics device selected. Use d.mon to select graphics device.
ERROR: No graphics device selected. Use d.mon to select graphics device.
ERROR: No graphics device selected. Use d.mon to select graphics device.
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I digged into the wx monitor script (gui/wxpython/mapdisp/main.py DMonMap.Render) and found that it unsets MONITOR (because GRASS_RENDER_IMMEDIATE doesn't like monitors) before calling d.rast and then restores it:

        currMon = grass.gisenv()['MONITOR']

        RunCommand('g.gisenv',
                   unset = 'MONITOR') # GRASS_RENDER_IMMEDIATE doesn't like monitors

        ret = Map.Render(self, *args, **kwargs)

        RunCommand('g.gisenv',
                    set = 'MONITOR=%s' % currMon)

So far, so good. Unfortunately, the wx monitor is running in a different process than d.rast calls from command line. Many d.rast calls cannot see the MONITOR variable while the monitor is rendering existing maps, which causes the above error.