Re: Unsolved clipping problem

[Tor Lillqvist <tml iki fi>]

Tintin72 writes:
> Do you think is there a way to improve/optimise my code and remove this
> problem ?

Yes. Thanks to Mitch on #gimp for this hint: You should set the
background of the window instead of trying to paint the background
yourself in the expose_event handler. Below is your sample program
corrected. Now I don't see any artefacts while scrolling any longer.

--tml

#include <gtk/gtk.h> 
#define WIDTH 500 
#define HEIGHT 300 

typedef struct APPLICATION 
{ 
  GtkWidget *pWin; 
  GtkWidget *pDrawArea; 
  GtkWidget *pVBox; 
  GtkWidget *pScrollBar; 

}APPLICATION; 

static gboolean draw_cb(GtkWidget *drawArea, GdkEventExpose *event, gpointer
userData) 
{ 
   PangoContext *pContext = gtk_widget_get_pango_context(drawArea); 
   PangoLayout *pLayout = pango_layout_new(pContext); 
   int i; 
   for(i = 0; i < 30; i++) 
    { 
      pango_layout_set_text (pLayout, g_strdup_printf ("Test clipping %d", i), -1); 
      gdk_draw_layout (drawArea->window, drawArea->style->fg_gc[GTK_WIDGET_STATE(drawArea)], 0,i * 15, 
pLayout); 
    } 
   g_object_unref(pLayout); 
   return FALSE; 
} 

int main (int argc, char *argv[]) 
{ 
  APPLICATION myApp; 
  gtk_init(&argc, &argv); 

  myApp.pWin = gtk_window_new(GTK_WINDOW_TOPLEVEL); 
  gtk_window_set_default_size(GTK_WINDOW(myApp.pWin), WIDTH, HEIGHT); 
  g_signal_connect(G_OBJECT(myApp.pWin), "destroy", G_CALLBACK(gtk_main_quit), NULL); 
  myApp.pVBox = gtk_vbox_new(FALSE, 0); 
  gtk_container_add(GTK_CONTAINER(myApp.pWin), myApp.pVBox); 
  myApp.pScrollBar = gtk_scrolled_window_new(NULL,NULL); 
  gtk_box_pack_start(GTK_BOX(myApp.pVBox), myApp.pScrollBar, TRUE, TRUE, 0); 
  myApp.pDrawArea = gtk_drawing_area_new ();
  gtk_widget_modify_bg (GTK_WIDGET(myApp.pDrawArea), GTK_STATE_NORMAL, 
&GTK_WIDGET(myApp.pDrawArea)->style->white);
  gtk_widget_set_size_request (myApp.pDrawArea,
                               myApp.pWin->allocation.width, 500); 
 
  g_signal_connect(G_OBJECT(myApp.pDrawArea),"expose_event",G_CALLBACK(draw_cb),
&myApp); 
 
  gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(myApp.pScrollBar), myApp.pDrawArea); 
  gtk_window_set_title(GTK_WINDOW(myApp.pWin), "GTK-Win"); 
  gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(myApp.pScrollBar), 
GTK_POLICY_NEVER,GTK_POLICY_AUTOMATIC); 

  gtk_widget_show_all (myApp.pWin); 
  gtk_main (); 
  return 0; 
}