我应该如何使用X11，motif，DrawingArea和c ++来设置DrawingArea（X，Y）坐标（0,0）

Question

我正在尝试使用DrawingAreas，事情并没有按照我的预期运作。

#include <Xm/Xm.h>
#include <Xm/DrawingA.h>

main(int argc, char *argv[])
{
  Widget shell, workArea, box1;
  XtAppContext app;
  shell = XtVaAppInitialize(&app, "gp", NULL, 0, &argc, argv, NULL, XmNwidth, 500, XmNheight, 500, NULL);
  XtRealizeWidget(shell);

  workArea = XtCreateWidget("wa",xmDrawingAreaWidgetClass, shell, NULL, 0);
  XtVaSetValues(workArea, XmNbackground, 30000, NULL);

  box1 = XtCreateWidget("b1", xmDrawingAreaWidgetClass, workArea, NULL, 0);
  XtVaSetValues(box1, XmNx, 0, XmNy, 0, XmNwidth, 400, XmNheight, 400, NULL);

  XtManageChild(workArea);
  XtManageChild(box1);
  //XtAppMainLoop(app);
  XEvent event;
  Dimension x,y,w,h;
  while(1)
  {
    XtAppNextEvent(app, &event);
    if (event.type == EnterNotify)
    {
      XtVaGetValues(box1, XmNx, &x, XmNy, &y, XmNwidth, &w, XmNheight, &h, NULL);
      printf("(x,y,w,h) == (%d,%d,%d,%d)\n", x, y, w, h);
    }
    if (event.type == LeaveNotify)
    {
      XtVaSetValues(box1, XmNx, 0, XmNy, 0, XmNwidth, 400, XmNheight, 400, NULL);
      printf("tried to set (x,y,w,h) = (0,0,400,400)\n");
    }
    XtDispatchEvent(&event);
  }
}

当我进入窗口并使用指针离开窗口时，我得到输出：

(x,y,w,h) == (10,10,400,400)
(x,y,w,h) == (10,10,400,400)
tried to set (x,y,w,h) = (0,0,400,400)
tried to set (x,y,w,h) = (0,0,400,400)
(x,y,w,h) == (10,10,400,400)
(x,y,w,h) == (10,10,400,400)
tried to set (x,y,w,h) = (0,0,400,400)
tried to set (x,y,w,h) = (0,0,400,400)

为什么XtVaSetValues没有将box1设置为（X，Y）=（0,0）？ 如何在窗口内的（0,0）处完成绘图区域的放置？

我找到了答案，但没有提供它的声誉：

XtManageChild(box1);
XtUnmanageChild(box1);
XtVaSetValues(box1, XmNx, 0, XmNy, 0, XmNwidth, 400, XmNheight, 400, NULL);
XtMapWidget(box1);

Answer 1

看起来对XtManageChild（）的调用正在调用父级的change_managed过程：

xtmanpage

为了将（x，y）设置为（0,0），我必须确保不管理小部件：

XtManageChild(box1); // must be called once
XtUnmanageChild(box1); // unmanage to allow (0,0)
XtVaSetValues(box1, NmNx, 0, XmNy, 0, XmNwidth, 400, XmNheight, 400, NULL);
XtMapWidget(box1); // show the widget