c - 无法使用 GTK3 更改光标

Question

我正在尝试使用 GTK3 动态更改窗口的光标，但 gtk_widget_get_parent_window 似乎不起作用。

有人可以指出我做错了什么吗？谢谢!

// https://developer.gnome.org/gtk3/stable/gtk-getting-started.html
// minimal example
#include <gtk/gtk.h>

static void
activate (GtkApplication* app,
          gpointer        user_data)
{
  GtkWidget *window;

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Window");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  // Here \/\/\/\/\/ .
  GdkWindow* w = gtk_widget_get_parent_window(window);
  GdkCursor* c = gdk_cursor_new_for_display(gdk_display_get_default(), GDK_WATCH);
  gdk_window_set_cursor(w, c);
  //      /\/\/\/\/\ .

  gtk_widget_show_all (window);
}

int
main (int    argc,
      char **argv)
{
  GtkApplication *app;
  int status;

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}

(main.exe:16508): Gdk-CRITICAL **: gdk_window_set_cursor: assertion 'GDK_IS_WINDOW (window)' failed

我正在使用 GTK 3.16 和 msys2

非常感谢。

Answer 1

扩展@andlabs 评论

任何更改光标的尝试都需要在小部件被添加到小部件层次结构之后完成，或者在 GTK 术语中实现。

在为小部件触发 realize 事件之前调用 gtk_widget_get_parent_window() 甚至 gtk_widget_get_window() 将导致 NULL 指针两种情况。

与@andlabs 一样，结合使用 gtk_widget_get_window() 和 GtkWindow 会更安全。

解决方案。

static GdkWindow* G_WINDOW = 0;
static GdkCursor* G_CURSOR = 0;

// call after WindowRealize()
void changecursor()
{
     assert(G_WINDOW != NULL);
     gdk_window_set_cursor(G_WINDOW, G_CURSOR);
}

static void WindowRealize(GtkWidget *window, gpointer data)
{
    G_CURSOR_HAND = gdk_cursor_new_for_display(gdk_display_get_default(), GDK_HAND2);
    G_WINDOW = gtk_widget_get_window(window);
}

static void activate(GtkApplication* app,gpointer user_data)
{
    GtkWidget *window = gtk_application_window_new(app);
    ...
    g_signal_connect(window, "realize", G_CALLBACK(WindowRealize), NULL);
    gtk_widget_show_all (window);
}