[GRASSGUI] graphic overlays

[Michael Barton]

On 3/24/07 8:25 PM, "Glynn Clements" <glynn at gclements.plus.com> wrote:

> 
> Michael Barton wrote:
> 
>>>> I want to suggest that most or all graphic overlays be done via wxPython
>>>> rather than using GRASS d.* commands.
>>>> 
>>>> These are: north arrow, scale, grid (and geodetic lines maybe), and text.
>>>> We¹ll need someone to design some nice (and GRASS distinctive) north arrows
>>>> and scales.
>>>> 
>>>> I suggest that these be accessed through an item or items (popup checkbox
>>>> menu?) on the map display tool bar, rather than having them added as
>>>> layers.
>>>> They should be able to be turned on and off of course, as well as being
>>>> positioned with a mouse (the latter will be much easier if they are
>>>> wxPython
>>>> graphic objects). Each will need it¹s own dialog with options, but that
>>>> shouldn¹t be too difficult to do.
>>>> 
>>>> Vector labels could go either way<as something done from the map display
>>>> tool bar or as an independent layer.
>>>> 
>>>> Other opinions?
>>> 
>>> I suggest that this is implemented in such a way that the user can
>>> easily choose to use the equivalent d.* commands instead, so that the
>>> display contents can be exported as a script which can be used outside
>>> of the GUI (i.e. with an X/PNG monitor).
>> 
>> This kind of negates the idea (I thought you were promoting too) of using
>> native GUI functions for all 'decorations'.
> 
> FWIW, I don't support requiring the GUI in order to render anything
> which might reasonably appear on a printed map (labels, scale bar,
> legend etc).

I don't think we should necessarily limit the GUI to only being able to do
what plain GRASS command modules can do. The programming that goes into the
GUI is value added to anyone who uses this. Underneath, it is still just
running GRASS modules. So anyone who wants to script as creatively can get
the same results. But that doesn't mean that simply running a series of
GRASS commands will necessarily achieve the same result. Especially for
graphic rendering, a good GUI may well be able to some things that GRASS
outside the GUI cannot do. I don't see this as an issue. If people want to
use the features of the GUI they can. If they don't want to they don't have
to. If they want to recreate the GUI coding in another platform, that's fine
too. But a bash shell script may not be able to achieve what can be done in
a wxPython script.

> 
> These should all be achievable using d.* commands, and the GUI should
> provide a convenient interface to those commands (e.g. using the mouse
> to identify coordinates for placement).

This is fine as far as it goes. d.grid is fairly complete as is. However,
d.barscale is very limited in its style of north arrows and scales. And
there is no way to adjust the size of either. If someone wants to program in
a bunch of arrow and scale styles, along with ways of setting scale
parameters and arrow sizes, that's fine. But it may well be much easier to
to do this in the GUI than in a C module. I don't advocate getting rid of
d.barscale. But I don't think the GUI should be limited by its restrictions.
d.text is similarly limited. You can do quite a bit more with text in the
GUI, and do so more easily (e.g., built in font-setting dialogs that are
appropriate to whatever platform it's run on). For all of these, interactive
placing and moving with a mouse is difficult if we only use the d.* command
modules. While I can click and send coordinates to d.barscale (like we can
do in the TclTk GUI), I don't know how I could grab a north arrow with a
mouse and drag it to reposition it in another locale on the screen using
d.barscale. However, I can do that with wxPython generated graphics.

> 
>> It's not hard to add a layer
>> managers for d.grid, d.text, d.scalebar, etc. But it could clutter up the
>> main control more.
>> 
>> What if we could make it scriptable using wxPython graphic elements?
> 
> I'm not entirely sure what you mean by that.
> 
> But, essentially, I feel that it should be possible to save the
> contents of the display as a script which will work on a system with
> only core GRASS modules (no Python, no X server; can you render
> wxPython graphics into an image file on a system with no X server?).

NVIZ can be scripted, but you can't render an NVIZ image without NVIZ. I
don't see that as a problem. If you want to render a 2.5D or 4D image, you
need NVIZ. There is no way to render this using plain vanilla GRASS
commands. I wouldn't want to not have this tool simply because we couldn't
render its images with plain command line C modules.

I'm a very big advocate of GRASS's scripting potential. I've written a
number of scripts. And this scriptability is what makes it possible to wrap
the commands in a nice GUI. But as you've pointed out, there are limitations
to graphic output rendering from command-line modules alone. Continued
improvements to ps.map may be a way to achieve this. Perhaps it could be
made to render to a PNG or PPM file as well as a postscript one. Just some
thoughts.

Michael

__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton