On Fri, Mar 19, 2010 at 2:46 PM, Claudio Saavedra <csaave...@gnome.org>wrote:
> El vie, 19-03-2010 a las 13:34 +0800, Tolic Ma escribió:
> > Hi,everyone!
> >
> > I want to draw something on GtkDrawingArea when I click a GtkButton,but I
> > don't know how to do this...
> >
> > this is my code(it doesn't work...):
> >
> > *void click_button(void){
> >
> >
> >
> gdk_draw_line(drawing_area,drawing_area->style->white_gc,x,y,width+x,height+y);
> >
> > }
>
> You shouldn't draw directly in your callback for the button. Instead,
> you should call gtk_widget_queue_draw() to tell GTK+ to schedule a paint
> of the widget.
>
> How will the widget be painted? GTK+ will tell your code that the widget
> needs to be painted by emitting the GtkWidget::expose-event signal.
> Then, you should connect to that signal and paint in your callback.
>
> Last but no least, don't forget to paint to the GdkWindow of the drawing
> area, since that's the drawable.
>
> More or less (untested code, just for clarity):
>
> *void
> click_button(GtkButton *button, gpointer data)
> {
> button_clicked = TRUE;
> gtk_widget_queue_draw (drawing_area);
> ...
> }
>
> gboolean
> expose_drawing_area (GtkWidget *area,
> GdkExposureEvent *event,
> gpointer data)
> {
> ...
> if (button_clicked) {
> gdk_draw_line(drawing_area->window,
> drawing_area->style->white_gc,x,y,width+x,height+y);
> }
> ...
> }
>
> int main(int argc,char *argv[]){
> ...
> g_signal_connect(button,"clicked",G_CALLBACK(click_button),NULL);
>
> g_signal_connect(drawing_area,"expose-event",G_CALLBACK(expose_drawing_area),NULL);
> ...
> }
>
>
> Claudio
>
> --
> Claudio Saavedra <csaave...@gnome.org>
>
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>
Thank you!
I solved my problem by following your instruction.
Thank you very much!!!
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