[GRASS5] embedding GRASS display into my app

[David Piasecki]

Will I be able to have responsive user control in moving vector objects 
if I use PNG? It seems like it would respond rather slow if every time 
I edit a road or point of interest in the graphical display, it's got 
to re-render the layer as a PNG, and I've got to import it again. Or 
perhaps this is faster than I realize. If you think it will work, then 
I can write my application in anything! What do you think?

David


On Apr 6, 2004, at 6:16 PM, Glynn Clements wrote:

>
> David Piasecki wrote:
>
>> I want to write an application that uses GRASS as the back end to an
>> application I plan to write. I need to embed the GRASS display into my
>> application. I haven't started yet, though C++ would be easiest for 
>> me.
>> If I have to learn Tcl/Tk, that's fine too. From what I understand, I
>> should be able to modify the XDRIVER in GRASS to handle events in my
>> application's main window, and I should be able to use TkSteal to
>> actually embed the graphics display for GRASS into my application's
>> main window. I'm not exactly clear on how to do all this considering
>> I'm new to GRASS and Tcl/Tk. I found a paper online saying it has been
>> done, but I haven't heard of anyone else that's done it, and I haven't
>> seen any documentation on how to do it. Any help you could provide
>> would be greatly appreciated.
>
> XDRIVER can be made to use an existing X window by setting the
> environment variable XDRIVER_WINDOW to the XID of the existing window.
> The value can be in any format acceptable to sscanf("%i"), i.e.
> decimal, hex preceded by "0x", or octal preceded by "0".
>
> However, note that X doesn't allow multiple clients to select
> ButtonPress events for a given window, so the Get_location_with_*
> functions (used by d.where, d.what.* etc) won't work if those events
> have already been selected by the program which creates the window.
>
> An alternative approach for a front-end would be to use the PNG driver
> for all graphical output, and have your program display the PNG
> images.
>
> This is likely to be somewhat tidier than either embedding the XDRIVER
> window (which is highly X-specific; this won't work with e.g. the
> "generic" Windows port), or trying to use the XDRIVER code (which uses
> the "raw" Xlib API).
>
> It is also more flexible. E.g. if you want to support "layers",
> rendering each layer as a separate PNG file then composing them in
> your program may be preferable to re-rendering the entire set whenever
> a layer is added, removed or changed.
>
> -- 
> Glynn Clements <glynn.clements at virgin.net>