Using GtkPreview/gtk_preview_draw_row

[Eden Li <tile primenet com>]

I can't seem to get this GtkPreview to work right, and there is limited
documentation for it.  Here is a brief explanation of what I need and what
I get.

What I need to do is create a swatch of color that can be packed
like a GtkWidget.  I read the gtkcolorsel source and saw how it did this,
but when I put something similar to what it has into my code, it doesn't work.
All I get is a black square.  Here's what I'm doing currently:

-------

#define SWATCH_HEIGHT 15
#define SWATCH_WIDTH 20

( this is a function, it's argument is a GdkColor* called col )

guchar c[3], data[SWATCH_WIDTH * 3];
guint i, j, y, x;

/* see above about col */
c[0] = (guchar) (((gdouble)((gdouble)col->red / 65535.0)) * 255.0);
c[1] = (guchar) (((gdouble)((gdouble)col->green / 65535.0)) * 255.0);
c[2] = (guchar) (((gdouble)((gdouble)col->blue / 65535.0)) * 255.0);

swatch = gtk_preview_new (GTK_PREVIEW_COLOR);
gtk_container_add (GTK_CONTAINER (win), swatch);
gtk_preview_size (GTK_PREVIEW (swatch), SWATCH_WIDTH, SWATCH_HEIGHT);
gtk_preview_set_expand (GTK_PREVIEW (swatch), FALSE);

for (y = 0; y < SWATCH_HEIGHT; y++)
  for (x = 0, j = 0; x < SWATCH_WIDTH; x++)
    for (i = 0; i < 3; i++)
      data[j++] = c[i];

gtk_preview_draw_row (GTK_PREVIEW (swatch), data, 0, SWATCH_HEIGHT,
    SWATCH_WIDTH);
gtk_widget_queue_draw (swatch);
gtk_widget_show (swatch);

------------

I then return swatch from this function and pack it into a widget.  I've
tried isolating this into a simple test program (consisting of a window
and a preview) and swapping the order of the gtk_widget_show and
gtk_widget_queue_draw functions to no avail.  Can anyone offer any
insight?

BTW, I've already checked the values of c, they look correct (i.e. it's
not turning out to be all 0s).  I also tried setting data to all 50s,
and I still get just a black square.

Eden Li
tile@linuxgames.com