如何解决错误:无效使用不完整类型' GdkSurface {aka struct _GdkSurface} ' ?<

Question

关于incomplete type错误的问题已经在这里经常被问到，但是那里提供的所有解决方案对我的情况没有帮助。添加前向声明是没有意义的，因为GdkSurface已经在Gdk头文件中被前向声明了。包括适当的头已经完成了。在产生错误的代码部分+之后包括。

#include <gdkmm/display.h>
#include <gdkmm/surface.h>
extern "C" {
#include <gdk/x11/gdkx.h>
#include <gdk/gdk.h>
}
extern "C" {
void surface_move(Gdk::Surface* psurface, int x, int y) {
#ifdef GDK_WINDOWING_X11
GdkSurface* surface = psurface->gobj();
GdkSurface *impl = GDK_X11_SURFACE(surface);
XMoveWindow(GDK_SURFACE_XDISPLAY (surface), GDK_SURFACE_XID (surface), x * impl->surface_scale, y * impl->surface_scale);
#endif
}
}

以下是完整的错误:

src/utils.cpp: In function ‘void Gdk::surface_move(Gdk::Surface*, int, int)’:
src/utils.cpp:9:83: error: invalid use of incomplete type ‘GdkSurface {aka struct _GdkSurface}’
(GDK_SURFACE_XDISPLAY (surface), GDK_SURFACE_XID (surface), x * impl->surface_scale, y * impl->surface_scale);
^~
In file included from /home/user/.local/built/include/gtk-4.0/gdk/gdkapplaunchcontext.h:29:0,
from /home/user/.local/built/include/gtk-4.0/gdk/gdk.h:30,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/enums.h:29,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/event.h:29,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/display.h:30,
from ./include/libgdp/utils.hpp:3,
from src/utils.cpp:1:
/home/user/.local/built/include/gtk-4.0/gdk/gdktypes.h:97:16: note: forward declaration of ‘GdkSurface {aka struct _GdkSurface}’
typedef struct _GdkSurface             GdkSurface;
^~~~~~~~~~~
src/utils.cpp:9:108: error: invalid use of incomplete type ‘GdkSurface {aka struct _GdkSurface}’
rface), GDK_SURFACE_XID (surface), x * impl->surface_scale, y * impl->surface_scale);
^~
In file included from /home/user/.local/built/include/gtk-4.0/gdk/gdkapplaunchcontext.h:29:0,
from /home/user/.local/built/include/gtk-4.0/gdk/gdk.h:30,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/enums.h:29,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/event.h:29,
from /home/user/.local/built/include/gtkmm-4.0/gdkmm/display.h:30,
from ./include/libgdp/utils.hpp:3,
from src/utils.cpp:1:
/home/user/.local/built/include/gtk-4.0/gdk/gdktypes.h:97:16: note: forward declaration of ‘GdkSurface {aka struct _GdkSurface}’
typedef struct _GdkSurface             GdkSurface;
^~~~~~~~~~~

我用JHbuild构建了Gdk, Gtk, Gdkmm和Gtkmm。

Answer 1

似乎这种类型在设计上是GDK私有的(只提供了前向声明)。来自GDK4文档:

GdkSurfacestruct只包含私有字段，不应该包含私有字段可直接访问

请参阅此处查看其定义的头文件(未分发)。这就是为什么你会得到这些错误，你所拥有的只是一个传递指针和引用的前向声明。禁止对数据成员的所有访问。

要解决这个问题，您必须使用在表面(公共)上工作的函数，例如gdk_surface_get_scale_factor或类似的函数，而不是尝试直接访问数据成员。