Question

我正在使用C和GTK3 +编写程序。我想使用键盘更改鼠标光标行为。目前，每当鼠标悬停绘图区域时，我的代码都会使鼠标光标从“默认”变为“十字准线”：

#include <cairo.h>
#include <gtk/gtk.h>

/* gcc example_mouse_cursor.c `pkg-config --cflags gtk+-3.0 --libs --libs cairo gtk+-3.0` -lm -o example && ./example */

static void do_drawing(cairo_t *);


struct {
  int count;
  double coordx[100];
  double coordy[100];
} glob;


static gboolean on_draw_event(GtkWidget *widget, cairo_t *cr, 
    gpointer user_data)
{
  do_drawing(cr);

  return FALSE;
}


static void do_drawing(cairo_t *cr)
{
  cairo_set_source_rgb(cr, 0, 0, 0);
  cairo_set_line_width(cr, 0.5);

  int i, j;
  for (i = 0; i <= glob.count - 1; i++ ) {
      for (j = 0; j <= glob.count - 1; j++ ) {
          cairo_move_to(cr, glob.coordx[i], glob.coordy[i]);
          cairo_line_to(cr, glob.coordx[j], glob.coordy[j]);
      }
  }

  glob.count = 0;
  cairo_stroke(cr);    
}


static gboolean on_crossing (GtkWidget *darea, GdkEvent *event)
{
  GdkCursor *cursor;
  GdkDisplay *display = gtk_widget_get_display (darea);

  switch (gdk_event_get_event_type (event))
    {
    case GDK_ENTER_NOTIFY:
      cursor = gdk_cursor_new_from_name (display, "crosshair");
      break;

    case GDK_LEAVE_NOTIFY:
      cursor = gdk_cursor_new_from_name (display, "default");
      break;
    default:
      break;  
    }
  // Assign the cursor to the window
  gdk_window_set_cursor (gtk_widget_get_window (darea), cursor);

// Release the reference on the cursor
  g_object_unref (cursor);  

  return TRUE;  
}

static gboolean clicked(GtkWidget *widget, GdkEventButton *event,
    gpointer user_data)
{
    if (event->button == 1) {
        glob.coordx[glob.count] = event->x;
        glob.coordy[glob.count++] = event->y;
    }

    if (event->button == 3) {
        gtk_widget_queue_draw(widget);
    }

    return TRUE;
}



gboolean keyboard_press (GtkWidget *window, GdkEventKey *event, gpointer data){

  /*Do something if 'b' key is pressed */
  if (event->keyval == GDK_KEY_b)
  {
    printf("'b' key pressed!\n");
  }
  return TRUE;     
};


int main(int argc, char *argv[])
{
  GtkWidget *window;
  GtkWidget *darea;


  glob.count = 0;

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  darea = gtk_drawing_area_new();
  gtk_container_add(GTK_CONTAINER(window), darea);

  gtk_widget_set_has_window (GTK_WIDGET (darea), TRUE);


  gtk_widget_add_events (GTK_WIDGET (darea), (GDK_ENTER_NOTIFY_MASK | GDK_LEAVE_NOTIFY_MASK) );
  gtk_widget_add_events(window, GDK_BUTTON_PRESS_MASK);

  g_signal_connect (darea, "enter-notify-event", G_CALLBACK (on_crossing), NULL);
  g_signal_connect (darea, "leave-notify-event", G_CALLBACK (on_crossing), NULL);
  g_signal_connect (G_OBJECT(window), "key_press_event", G_CALLBACK (keyboard_press), NULL); 
  g_signal_connect(G_OBJECT(darea), "draw", G_CALLBACK(on_draw_event), NULL); 
  g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);  

  g_signal_connect(window, "button-press-event", 
      G_CALLBACK(clicked), NULL);

  gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
  gtk_window_set_default_size(GTK_WINDOW(window), 400, 300); 
  gtk_window_set_title(GTK_WINDOW(window), "Lines");

  gtk_widget_show_all(window);

  gtk_main();

  return 0;
}

我希望能够在按下'b'键时禁用鼠标悬停行为（'让鼠标光标在任何地方保持'默认'）。如果用户再次按下“b”键，则再次启用光标更改bahaviour。

我可以从键盘上获取信号，在函数 gboolean keyboard_press（）中实现，但我不知道如何在此函数中更改鼠标光标行为。有没有办法解除信号：

g_signal_connect (darea, "enter-notify-event", G_CALLBACK (on_crossing), NULL);
g_signal_connect (darea, "leave-notify-event", G_CALLBACK (on_crossing), NULL);

在 gboolean keyboard_press（）函数内？我找到g_signal_handler_disconnect()，但我不知道如何使用它。

你会怎么做？

由于

使用键盘更改GTK3鼠标光标的行为

0 个答案: