gtk draw "expose-event" and redraw
- by warem
I want to use expose-event to draw something then update or redraw. That's to say, there are a drawing area and a button in window. When clicking button, the drawing area will be redrawn accordingly. My problems are
Following code worked but it only had a drawing area no button. If I add the button(cancel the comment for button), nothing is drawn. What's the reason?
In the following code, if I changed gtk_container_add (GTK_CONTAINER (box), canvas); to gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0);, nothing is drawn. Usually we use gtk_box_pack_start to add something into box. Why doesn't it work this time?
The function build_ACC_axis refreshed drawing area and prepared for new draw. I google it but I didn't know if it worked. Could you please comment on it?
If the source file is test.c, then compilation is
gcc -o test test.c `pkg-config --cflags --libs gtk+-2.0`
The code is below:
#include <gtk/gtk.h>
#include <glib.h>
static void draw (GdkDrawable *d, GdkGC *gc)
{
/* Draw with GDK */
gdk_draw_line (d, gc, 0, 0, 50, 50);
gdk_draw_line (d, gc, 50, 50, 50, 150);
gdk_draw_line (d, gc, 50, 150, 0, 200);
gdk_draw_line (d, gc, 200, 0, 150, 50);
gdk_draw_line (d, gc, 150, 50, 150, 150);
gdk_draw_line (d, gc, 150, 150, 200, 200);
gdk_draw_line (d, gc, 50, 50, 150, 50);
gdk_draw_line (d, gc, 50, 150, 150, 150);
}
static gboolean expose_cb (GtkWidget *canvas, GdkEventExpose *event, gpointer user_data)
{
GdkGC *gc;
gc = gdk_gc_new (canvas->window);
draw (canvas->window, gc);
g_object_unref (gc);
return FALSE;
}
void build_ACC_axis (GtkWidget *button, GtkWidget *widget)
{
GdkRegion *region;
GtkWidget *canvas = g_object_get_data(G_OBJECT(widget), "plat_GA_canvas");
region = gdk_drawable_get_visible_region(canvas->window);
gdk_window_invalidate_region(canvas->window, region, TRUE);
gtk_widget_queue_draw(canvas);
/* gdk_window_process_updates(canvas->window, TRUE); */
gdk_region_destroy (region);
}
int main (int argc, char **argv)
{
GtkWidget *window;
GtkWidget *canvas, *box, *button;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
g_signal_connect (G_OBJECT (window), "destroy", G_CALLBACK (gtk_main_quit), NULL);
box = gtk_vbox_new(FALSE, 0);
gtk_container_add (GTK_CONTAINER (window), box);
canvas = gtk_drawing_area_new ();
g_object_set_data(G_OBJECT(window), "plat_GA_canvas", canvas);
/* gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0); */
gtk_container_add (GTK_CONTAINER (box), canvas);
g_signal_connect (G_OBJECT (canvas), "expose-event", G_CALLBACK (expose_cb), NULL);
/* button = gtk_button_new_with_label ("ok");
gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 0);
|+ gtk_container_add (GTK_CONTAINER (box), button); +|
gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(build_ACC_axis), window); */
gtk_widget_show_all (window);
gtk_main ();
}
