Re: Interface with 64 toggleable elements: what's the best way?

[Russell Shaw <rjshaw iprimus com au>]

Sean McAfee wrote:
> Russell Shaw <rjshaw@iprimus.com.au> wrote:
> 
>>Sean McAfee wrote:
>>
>>>My next idea was to represent the bits as pixmaps: an empty circle for
>>>a clear bit, and a filled circle for a set bit.  I want my program to
>>>be completely standalone, so now I'm trying to create a pair of
>>>textual xpm's that look like decent circles, which isn't completely
>>>trivial.
> 
>>It's much easier to create an outline and solid circle using
>>gdk_draw_arc() onto GdkPixmap at the start of your program.
> 
> D'oh!  That did sound much easier.
> 
> When I tried this approach, however, I ran into some difficulties.  In
> order to craete a GtkPixmap from a GdkPixmap, one needs a second GdkPixmap,
> the bit mask.  I searched high and low, but couldn't find any information on
> how one would go about creating a bit mask.  I finally had to jump into the
> source of the gdk_pixmap_create_from_xpm_d() function, the only standard
> function that returns a bit mask.  After some cutting and pasting, I came up
> with the following routine:
> 
> void
> circular_pixmap(GdkWindow *window, int size,
>                 GdkPixmap **image, GdkPixmap **mask)
> {
>     GdkColor mask_pattern;
>     GdkGC *image_gc, *mask_gc;
> 
>     *image = gdk_pixmap_new(window, size, size, -1);
>     *mask  = gdk_pixmap_new(window, size, size, 1);
> 
>     image_gc = gdk_gc_new(*image);
>     mask_gc  = gdk_gc_new(*mask);
> 
>     mask_pattern.pixel = 0;
>     gdk_gc_set_foreground(mask_gc, &mask_pattern);
>     gdk_draw_rectangle(*mask, mask_gc, TRUE, 0, 0, -1, -1);
>     mask_pattern.pixel = 1;
>     gdk_gc_set_foreground(mask_gc, &mask_pattern);
> 
>     gdk_draw_arc(*image, image_gc, TRUE, 0, 0, size, size, 0, 64*360);
>     gdk_draw_arc(*mask, mask_gc, TRUE, 0, 0, size, size, 0, 64*360);
> 
>     gdk_gc_destroy(image_gc);
>     gdk_gc_destroy(mask_gc);
> 
> }
> 
> This works, but damn if it doesn't seem awfully clunky.  Is there a better
> way to create a pixmap-plus-mask from scratch?
> 

GdkPixmap*
circular_pixmap(GtkWidget *widget, int size, GdkColor *color)
{
   GdkPixmap *dot=gdk_pixmap_new(widget,size,size,-1);
   GtkStyle *style=gtk_widget_get_style(widget);

   gdk_draw_rectangle(dot,style->bg_gc[NORMAL],TRUE,0,0,size,size);     // background

   GdkGC *gc=gdk_gc_new();
   gdk_gc_copy(gc,&(style->fg_gc[NORMAL]));
   gdk_colormap_alloc_color(gtk_widget_get_colormap(widget),color,TRUE,TRUE);
   gdk_gc_set_foreground(gc,color);

   gdk_draw_arc(dot,gc,TRUE,0,0,size,size,0,23040);   // foreground
   g_object_unref(gc);
   return dot;
}

Draw a pixmap instead of a bitmap. I thought there was
a way to extract a "plane" from a pixmap to use as a
bitmap, but can't recall. Ideally, there should be a
way to get a clear background like with a circular clip
region or something.