[dbo@grendel.wustl.edu: [GNOME] GnomeCanvas interface]

[Federico Mena Quintero <federico nuclecu unam mx>]

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Return-Path: <dbo@grendel.wustl.edu>
To: federico@nuclecu.unam.mx
Subject: [GNOME] GnomeCanvas interface
Reply-To: David Ogilvie <david.ogilvie@yale.edu>
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Date: Fri, 17 Jul 1998 15:10:33 -0400
From: David Ogilvie <dbo@grendel.wustl.edu>

Sorry to forward this directly to you, but I don't have access to the mailing 
list, and don't want to subscribe.  If you could forward it to gnome-list (and 
repond, preferably!) that'd be appreciated.

Here are some comments and questions about the GnomeCanvas widget:

There needs to be some sort of gnome_canvas_item_configure for objects derived 
from GnomeCanvasItem.  I'm thinking here specifically of a GnomePlot widget, 
where the logical thing to do seems to be to derive various parts from the 
GnomeCanvasGroup.  Unfortunately, one cannot do this right now.

Is there any need for the code that does:
   gnome_canvas_group_child_bounds (group, NULL);

   if (item->parent)
     gnome_canvas_group_child_bounds (GNOME_CANVAS_GROUP (item->parent), item);

or is this a remnent of an older design (seen all over in gnome-canvas.c)?  it 
looks like gnome_canvas_group_child_bounds() calls its parent itself.

passing 0 to gnome_canvas_item_raise() to raise an item to the top makes no 
sense.  This means that if there was a dialog allowing raising and lowering of 
items, the value 0 would have to be disallowed or checked for seperately (and 
one might want to allow altering several variables at once, in which case 
allowing 0 would make sense.)  seems like seperate functions 
gnome_canvas_item_raise_to_{top,bottom} would be better.

there needs to be a way to pass GdkColors instead of strings to creating 
items.  In fact, I would argue for this being the default, since most apps 
should allow configuration of the colors used, meaning that they would have to 
use a color selection box anyway.  It seems like one rarely wants a fixed 
color except in early prototyping.  It's also more efficient to use a 
GdkColor, of course.  Perhaps one should allow both?

Isn't using the GtkObject system going to get really slow when there are 
several hundred or thousand objects?  Someone should write up a test for this 
at least, and stick it in test-gnome.  Just stick up a bunch of rectangles 
every second, or something.

Is there a reason why the interface uses the gnome_item_new to create all 
items, instead of having a per item creation call, such as gnome_rect_new 
(GnomeCanvas *canvas, GdkColor *fill_color, etc...)?  This seems easier from a 
programmer's point of view, and its not that much extra code.  Of course 
language bindings still need the get/set stuff.

hm... I think that's about it.  Hope this is helpful.

- -david






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