Re: Cairo clearing problem.

[Vlad Volodin <vest 84 gmail com>]

Hi, Carlos

Where do you use your drawing operation? As GTK suggested (like
GtkDrawingArea), you have to do it in "expose_event":

* The "expose_event" signal to handle redrawing the contents of the widget.

Here you can have several if's:
if (something)
   draw_lines();
else
   draw_other_lines();

"something" can be a simple enum, or gboolean, which is assigned
elsewhere. By the way, after changing it, you can send signals by
yourself, to redraw your widget.

Good luck,
Vlad Volodin

2009/5/8 Developer <csavoretti clubsanjorge com ar>:
> Hi all!
>
> Well, I'm having a problem with clearing a line.
>
> ---
> Â Â Â Âcairo_t *cr;
> Â Â Â Âcr = gdk_cairo_create (widget->window);
>
> Â Â Â Âcairo_set_source_rgba (cr, 0, 0, 0, 1);
>
> Â Â Â Âstatic const double dashed[] = { 3.0 };
> Â Â Â Âcairo_set_line_width (cr, 1.5);
> Â Â Â Âcairo_set_dash (cr, dashed, 1, 0);
>
> Â Â Â Âcairo_move_to (cr, RECTANGLE_GAP, RECTANGLE_GAP);
> Â Â Â Âcairo_rel_line_to (cr, width - (RECTANGLE_GAP * 2), 0);
> Â Â Â Âcairo_rel_line_to (cr, 0, height - (RECTANGLE_GAP * 2));
> Â Â Â Âcairo_rel_line_to (cr, -(width - (RECTANGLE_GAP * 2)), 0);
> Â Â Â Âcairo_close_path (cr);
> Â Â Â Âcairo_stroke (cr);
>
> Â Â Â Âcairo_destroy (cr);
> ---
>
> It intends to set a dotted rectangle around the
> border of a GtkVBox. Then, it must be erased
> without affecting the inner widgets.
>
> I thought that having the current path
> it could be used after to clear just that drawn
> in this path. Is there a way to do it?
>
> I've used gdk_window_clear (), but child widgets
> in the box are cleared also, which is undesired
> of course.
>
> Any suggestion ?
>
> Thanks in advance...
>
> Carlos Savoretti.
>
>
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