RE: how to draw something on GtkDrawingArea when I click a button?
As a matter of fact. I would suggest using Cairo. Which will allow you to then
draw in any context (IE Printer, PDF, etc...)
/* Local Variables */
cairo_t *cr;/* Rendering context derived from widget */
/* Get the context to which we need to draw */
cr = gdk_cairo_create(widget->window);
/* Printer context would be:
cr = gtk_print_context_get_cairo_context(context)
where context is a GtkPrinterContext* */
/* If we have a valid context draw valid object */
if (cr != NULL){
/* Boarder rectangle */
cairo_rectangle(cr, 0.00, 0.00, 20.0 , 40.0 );
cairo_stroke(cr);
cairo_set_line_width(cr,line_width / 60);
/* Virtical Seporation lines */
cairo_move_to(cr, 20.0 , 40.0 );
cairo_line_to(cr, 40.0, 40.0);
cairo_stroke(cr);
/* Distroy the context we created */
cairo_destroy(cr);
}
EMAILING FOR THE GREATER GOOD
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> Subject: Re: how to draw something on GtkDrawingArea when I click a button?
> From: csaave...@gnome.org
> To: gtk-app-devel-list@gnome.org
> Date: Fri, 19 Mar 2010 08:46:33 +0200
>
> 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
>
> ___
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> gtk-app-devel-list@gnome.org
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Re: how to draw something on GtkDrawingArea when I click a button?
On Fri, Mar 19, 2010 at 2:46 PM, Claudio Saavedra 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
>
> ___
> gtk-app-devel-list mailing list
> gtk-app-devel-list@gnome.org
> http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
>
Thank you!
I solved my problem by following your instruction.
Thank you very much!!!
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Re: how to draw something on GtkDrawingArea when I click a button?
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
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Re: how to draw something on GtkDrawingArea when I click a button?
gdk_draw_line takes GdkDrawable as first parameter.
try using drawing_area->window instead.
--
Regards,
Amol
On Fri, 2010-03-19 at 13:34 +0800, Tolic Ma wrote:
> 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);
>
> }
>
> int main(int argc,char *argv[]){
>...
>g_signal_connect(button,"clicked",G_CALLBACK(click_button),NULL);
>...
> }*
> ___
> gtk-app-devel-list mailing list
> gtk-app-devel-list@gnome.org
> http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
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