gdk_screen_get_default() returns null

gdk_screen_get_default() returns null

本文关键字：returns null default screen get gdk      更新时间：2023-10-16

请帮助此初学者的程序以获取GDK屏幕属性。我有一个小的C 程序来找出连接的显示单元。我在Linux Debian上使用C 。gdk_screen_get_default()不返回Screen对象。如果我不检查屏幕对象，则会发生以下错误。

错误 (过程：8023(：GDK-Critical **：GDK_SCREEN_GET_MONITOR_GEOMETRY：断言'gdk_is_screen(屏幕('失败

我浏览了相关的帖子，并将其用于以下代码片段。

感谢您的帮助。任何解决此问题的指针/准则都会有所帮助。

我有一个已连接的监视器，显示设置为

$ echo $XDG_CURRENT_DESKTOP
GNOME
$ echo $DISPLAY
:0

代码

    #include <gdk/gdk.h>
    #include <iostream>
    /*
    GTK version 3.14.5
    g++ getScreenInfo.cpp -o getScreenInfo `pkg-config gtk+-3.0 --cflags --libs`
    */
    int main()
    {
       GdkScreen *screen;
       screen = gdk_screen_get_default();           
       int num_monitors;
       int i;
       if (screen)
       {
          num_monitors = gdk_screen_get_n_monitors(screen);
          for (i = 0; i < num_monitors; i++)
          {
              GdkRectangle rect;
              gdk_screen_get_monitor_geometry (screen, i, &rect);
              std::cout << "monitor " << i << ": coordinates (" << rect.x << ","
              <<  rect.y << ", size (" << rect.width << "," << rect.height << ")"
              << std::endl;
           }
       }else
       {
            std::cout << "Couldn't obtain default screen object" << std::endl;
        }
    }

2017年4月27日编辑：已解决

  #include <iostream>
  #include <gdk/gdk.h>
  #include <gtk/gtk.h>
  /*
  GTK version 3.14.5
  To compile:
  g++ getScreenInfo.cpp -o getScreenInfo `pkg-config gtk+-3.0 --cflags --libs`
  */
  int main(int argc, char *argv[])
  {
    gtk_init(&argc, &argv);
    GdkScreen *screen = gdk_screen_get_default();

    int num_monitors;
    int i;
    if (screen)
    {
        num_monitors = gdk_screen_get_n_monitors(screen);
        for (i = 0; i < num_monitors; i++)
        {
            GdkRectangle rect;
            gdk_screen_get_monitor_geometry (screen, i, &rect);
            std::cout << "monitor " << i << ": offsets (" << rect.x << ","
            <<  rect.y << ", size (" << rect.width << "," << rect.height << ")"
            << std::endl;
        }
    }
    else
    {
        std::cout << "Couldn't obtain default screen object" << std::endl;
    }
    // To query primary display properties 
    guint monitor = gdk_screen_get_primary_monitor(screen);
    GdkRectangle screen_geometry = { 0, 0, 0, 0 };
    gdk_screen_get_monitor_geometry(screen, monitor, &screen_geometry);
    std::cout << screen_geometry.x << std::endl;
    std::cout << screen_geometry.y  << std::endl;
    std::cout << screen_geometry.width  << std::endl;
    std::cout << screen_geometry.height << std::endl;
  }

回答我自己的问题。

最后，弄清楚了分辨率。在获取屏幕之前，GTK_INIT((缺失。补充说，包括GTK/gtk.h的各自，现在代码看起来像

int main(int argc, char *argv[]) 
{ 
   gtk_init(&argc, &argv);                 // <---- added this
   GdkScreen *screen = gdk_screen_get_default(); 
   : 
   followed by rest of the code shared in the problem description above.
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