I have added the drawing of green rectangle in configure_event_cb() code
where I am creating the surface.
Now, when I run this I get BOTH the green rectangle and blue rectangle on
the main window.
I assume since I am not calling cairo_set_source_surface() in
configure_event_cb() that means the green rectangle is being drawn on main
window and NOT on offscreen surface, whereas
in expose_event(), since I am calling cairo_set_source_surface() and
drawing blue rectangle on that surface, it is getting drawn on offscreen.
Please confirm and second my understanding.
Thank you all for your help.
#include <gtk/gtk.h>
static cairo_surface_t *surface = NULL;
static gboolean
configure_event_cb (GtkWidget *widget, GdkEventConfigure *event, gpointer
data)
{
cairo_t *cr;
g_print("configure event: %d, %d\n", event->width, event->height);
if (surface)
cairo_surface_destroy(surface);
surface = gdk_window_create_similar_surface (event->window,
CAIRO_CONTENT_COLOR,
event->width,
event->height);
cr = cairo_create(surface);
cairo_set_source_rgb(cr, 0, 0, 0);
cairo_paint(cr);
cairo_set_source_rgb(cr, 0, 1, 0);
cairo_rectangle(cr, 100, 100, 200, 200);
cairo_stroke(cr);
return FALSE;
}
static gboolean
expose_event_offscr (GtkWidget *widget,GdkEventExpose *event, gpointer
data)
{
g_print("draw event offscr\n");
cairo_t *cr = gdk_cairo_create(widget->window);
cairo_set_source_surface(cr, surface, 0, 0);
cairo_paint(cr);
cairo_set_source_rgb(cr, 0, 0, 1);
cairo_rectangle(cr, 300, 300, 200, 200);
cairo_stroke(cr);
return TRUE;
}
int
main(int argc,
char **argv)
{
GtkWidget *window,
*area;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_default_size (GTK_WINDOW (window), 1200, 800);
g_signal_connect (window, "destroy", gtk_main_quit, NULL);
area = gtk_drawing_area_new();
g_signal_connect (area, "expose-event",
G_CALLBACK (expose_event_offscr), NULL);
g_signal_connect (area, "configure-event",
G_CALLBACK(configure_event_cb), NULL);
gtk_container_add (GTK_CONTAINER (window), area);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
On Fri, Aug 10, 2012 at 2:38 PM, Jean Brefort
<[email protected]>wrote:
> I suppose that surface is the offscreen scene. In that case, ther bule
> rectangle should not be drawn during the expose event callback, but when
> you build surface. Then you can use the code in my previous message,
> replacing the blue color by green color.
>
> Hope this helps.
>
> Le vendredi 10 août 2012 à 14:34 +0530, Prasanta Sadhukhan a écrit :
> > Thanks for your code. This draws a blue rectangle on a black
> > background and the offscreen surface contents is rendered on main
> > window.
> > But I also would like to draw green rectangle in main window so after
> > final rendering of offscreen contents (the blue rectangle) on main
> > window, I would get both blue and green rectangles on main window.
> > Can you please clarify how can I achieve that (both offscreen & main
> > window contents being shown on main window)?
> >
> > Thanks in advance!!
> >
> > Regards
> > Prasanta
> >
> > On Fri, Aug 10, 2012 at 2:22 PM, Jean Brefort
> > <[email protected]> wrote:
> > You should use something like:
> >
> > cairo_set_source_surface(cr, surface, 0, 0);
> > cairo_paint(cr).
> > cairo_set_source_rgb(cr, 0, 0, 1);
> > cairo_rectangle(cr, 300,300, 200, 200);
> > cairo_stroke(cr);
> >
> >
> > This will paint the window with surface as source and then
> > draw a blue
> > rectangle.
> >
> > Le vendredi 10 août 2012 à 14:09 +0530, Prasanta Sadhukhan a
> > écrit :
> > >
> > >
> > > On Fri, Aug 10, 2012 at 1:22 PM, Jean Brefort
> > > <[email protected]> wrote:
> > > This code is quite strange. Your call to
> > > cairo_set_source_surface() is
> > > not useful since you use cairo_set_source_rgb() just
> > after.
> > > You should
> > > call cairo_paint() just after
> > cairo_set_source_surface() if
> > > you want it
> > > to have any effect.
> > >
> > > If I do not call cairo_set_source_rgb(cr, 0, 0, 1); how
> > will get a
> > > blue rectangle?
> > > Just having these is giving me a window with black
> > background.
> > > cairo_set_source_surface(cr, surface, 0, 0);
> > > cairo_rectangle(cr, 300,300, 200, 200);
> > > cairo_stroke(cr);
> > > cairo_paint(cr).
> > >
> > > Can you please clarify?
> > > As I told, I would like to get a blue rectangle in offscreen
> > surface
> > > and a green rectangle in main visible surface so after final
> > rendering
> > > of offscreen contents on main window, I would get both
> > rectangles on
> > > main window.
> > >
> > > Regards
> > > Prasanta
> > >
> > > Hope it helps,
> > > Jean
> > >
> > > Le vendredi 10 août 2012 à 13:07 +0530, Prasanta
> > Sadhukhan a
> > > écrit :
> > > > expose_event (GtkWidget *widget,GdkEventExpose
> > *event,
> > > gpointer
> > > > data)
> > > > {
> > > > g_print("draw event main\n");
> > > >
> > > > cairo_t *cr = gdk_cairo_create(widget->window);
> > > > // draw blue rectangle into offscreen
> > > > cairo_set_source_surface(cr, surface, 0, 0);
> > > > cairo_set_source_rgb(cr, 0, 0, 1);
> > > > cairo_rectangle(cr, 300, 300, 200, 200);
> > > > cairo_stroke(cr);
> > > > cairo_paint(cr);
> > > >
> > > > //draw green rectangle onto main window
> > > > cairo_set_source_rgb(cr, 0, 1, 0);
> > > > cairo_rectangle(cr, 100, 100, 200, 200);
> > > > cairo_stroke(cr)
> > > > }
> > > >
> > > >
> > > >
> > >
> > >
> > > _______________________________________________
> > > gtk-list mailing list
> > > [email protected]
> > > https://mail.gnome.org/mailman/listinfo/gtk-list
> > >
> >
> >
> >
> >
>
>
>
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