drag

#include <stdio.h>
#include <X11/X.h>
#include <X11/Xlib.h>

int main ()
{
  Display* d = XOpenDisplay(0);
  Window w = XCreateSimpleWindow (d,  RootWindow(d, 0), 300, 300, 300, 300, 0,
      BlackPixel (d, 0), BlackPixel(d, 0));
  XMapWindow(d, w);
  XMoveResizeWindow(d, w, 300, 300, 300, 300);

  XSelectInput (d, w, ButtonPressMask|ButtonReleaseMask|PointerMotionMask);

  printf ("Display %x Window %x\n", d, (void*)w);

  int dragging=0;
  int ptr_x, ptr_y;
  int win_x = 300, win_y = 300;
  int win_h = 300, win_w = 300;
  int win_new_x, win_new_y;
  int win_new_h, win_new_w;
  int ptr_new_x, ptr_new_y;
  XWindowAttributes attr;
  Window child;

  while (1)
  {
    XEvent xev;
    XNextEvent(d, &xev);
    switch (xev.type)
    {
      case ButtonPress:
        printf ("Dragging!\n");
        dragging = 1;
        ptr_x = xev.xbutton.x;
        ptr_y = xev.xbutton.y;

        XGetWindowAttributes (d, w, &attr);
        XTranslateCoordinates(d, w, RootWindow(d, 0), 0, 0, &win_x, &win_y, &child);
        XTranslateCoordinates(d, w, RootWindow(d, 0), xev.xbutton.x, xev.xbutton.y, &ptr_x, &ptr_y, &child);
        win_w = attr.width;
        win_h = attr.height;

        printf ("Starting with x=%d y=%d w=%d h=%d\n", win_x, win_y, win_w, win_h);

        break;
      case ButtonRelease:
        printf ("Not Dragging!\n");
        dragging = 0;
        break;
      case MotionNotify:
        if (dragging)
        {
          int dx, dy;
          XTranslateCoordinates(d, w, RootWindow(d, 0), xev.xmotion.x, xev.xmotion.y, &ptr_new_x, &ptr_new_y, &child);
          dx = ptr_new_x - ptr_x;
          dy = ptr_new_y - ptr_y;
          printf ("dx = %d dy = %d\n", dx, dy);
          win_new_h = win_h - dy;
          win_new_w = win_w - dx;
          if (win_new_h < 100) win_new_h = 100;
          if (win_new_w < 100) win_new_w = 100;
          win_new_y = win_y + (win_h - win_new_h);
          win_new_x = win_x + (win_w - win_new_w);

          XMoveResizeWindow(d, w, win_new_x, win_new_y, win_new_w, win_new_h);
        }
    }
  }
}