RE: Scrolling a Cairo drawing-area or Gtk layout

[Roger Matthews <roger matthews hotmail com>]

Hi Damien Caliste, Jim Charlton, and Pramithesh,                   that has worked and here is the code I 
used:window2 = gtk_window_new(GTK_WINDOW_TOPLEVEL);gtk_window_set_default_size(GTK_WINDOW(window2), 1000, 
800);grid2 = gtk_grid_new();darea = gtk_drawing_area_new();gtk_widget_set_size_request(darea, 3000, 
2000);gtk_grid_attach(GTK_GRID (grid2), darea, 0, 0, 1, 1);g_signal_connect(G_OBJECT(darea), "draw", 
G_CALLBACK(on_draw_event), NULL);g_signal_connect(G_OBJECT(darea), "destroy", G_CALLBACK(gtk_widget_destroy), 
NULL);swin2 = gtk_scrolled_window_new(NULL, NULL);gtk_container_set_border_width(GTK_CONTAINER (swin2), 
5);gtk_container_add(GTK_CONTAINER (swin2), grid2);box2 = gtk_box_new (TRUE, 5);gtk_box_pack_start (GTK_BOX 
(box2), swin2, TRUE, TRUE, 5);gtk_container_add (GTK_CONTAINER (window2), box2);gtk_widget_show_all (window2);



> Date: Mon, 27 Jul 2015 10:10:27 +0200
> From: damien caliste cea fr
> To: gtk-app-devel-list gnome org
> Subject: Re: Scrolling a Cairo drawing-area or Gtk layout
>
> Hello,
>
> Le 21/07/2015, Roger Matthews <roger matthews hotmail com> a écrit :
> > which results from a simple straight line equation, and*/ /* that
> > extends beyond the bounds of the window.
> Reading your code quickly, it seems to me that, you're drawing indeed
> the line outside the drawing area, *but* the drawing area has the size
> of your window, so GTK is not displaying any scrollbars.
>
> In my opinion, you should :
> - in main, declare your drawing area to a fixed size (let say
>   1200×1200) and declare your window size at 600×400 as you're doing ;
> - in the drawing method (do_drawing()), don't use the window size, but
>   the drawing size as bounds from your drwaing commands. It's useless
>   to draw lines or whatever outside the cairo drawing area, they will
>   be cropped anyway. So don't reach for the top level there, use the
>   size of the widget itself.
>
> As a schemme :
> - your implementation : |#####|
> - the way to do it : |----######----------------|
>   - # means GTK scrollview, - means drawing area
>   - call cairo drawing primitives in the coordinates of the drawing area
>     (-), but not outside.
>
> Damien.
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