[GRASS5] PNG driver problem

David Piasecki piasecda at nv.doe.gov
Mon Aug 23 08:36:19 EDT 2004

I am using the PNG graphics driver in a C++ application that I am 
writing. At the click of a button, I can zoom in and out by starting 
the PNG driver, sending region and display commands to GRASS, and 
stopping the PNG driver. When I behave like a normal user, it seems to 
work just fine. However, when I try to break my code by clicking the 
zoom button about 30-50 times in quick succession, I will eventually 
get the message that the PNG driver is already running, even though the 
output to the terminal window has verified that the PNG driver has 
terminated. Is it possible to get such an error message if "d.mon 
start=PNG" is called too quickly after "d.mon stop=PNG"?

If it turns out that GRASS cannot accept commands to start the PNG 
graphics driver so quickly after it's been stopped, I'll have to put 
something in my code that ensures the user doesn't click zoom too fast.


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