GDK transient test

compile.sh

#!/bin/bash
set -ev
gcc -Wall -Werror -pedantic -std=c99 -g `pkg-config --cflags gdk-3.0` gdktransient.c `pkg-config --libs gdk-3.0` -o gdk 
./gdk

gdktransient.c

#include <glib.h>
#include <gdk/gdk.h>

GMainLoop *mainloop;
GdkWindow *win1, *win2;

static void event_func(GdkEvent *ev, gpointer data) {
    switch (ev->type) {
        case GDK_DELETE:
            gdk_window_destroy(gdk_event_get_window(ev));
            break;
        case GDK_EXPOSE: {
            GdkWindow *w = gdk_event_get_window(ev);
            gdk_window_begin_paint_region(w, ((GdkEventExpose *)ev)->region);
            cairo_t *cr = gdk_cairo_create(w);

            if (w == win1) {
                cairo_set_source_rgb(cr, 1, 1, 1);
            } else if (w == win2) {
                cairo_set_source_rgb(cr, 1, 0, 0);
            }

            cairo_rectangle(cr, 0, 0, gdk_window_get_width(w), gdk_window_get_height(w));
            cairo_fill(cr);
            cairo_destroy(cr);
            gdk_window_end_paint(w);
        }
        break;
        default:
            break;
    }
}

int main(int argc, char **argv) {
    gdk_init(&argc, &argv);

    GdkWindowAttr attr;
    attr.title = argv[0];
    attr.event_mask = GDK_EXPOSURE_MASK;
    attr.window_type = GDK_WINDOW_TOPLEVEL;
    attr.wclass = GDK_INPUT_OUTPUT;
    attr.width = 400;
    attr.height = 400;

    // Main (toplevel window)
    win1 = gdk_window_new(NULL, &attr, 0);

    // Transient window
    attr.width = attr.height = 200;
    win2 = gdk_window_new(NULL, &attr, 0);
    gdk_window_set_transient_for(win2, win1);
    
    gdk_event_handler_set(event_func, NULL, NULL);

    gdk_window_show(win1);
    gdk_window_show(win2);

    mainloop = g_main_loop_new(g_main_context_default(), FALSE);
    g_main_loop_run(mainloop);

    gdk_window_destroy(win2);
    gdk_window_destroy(win1);

    return 0;
}