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[SOLVED] [Linux/X11 extension] would this ever cause an infinitie loop?

Discussion in 'Advanced Programming Discussion' started by Samuel Venable, Aug 12, 2019.

  1. Samuel Venable

    Samuel Venable Time Killer

    Joined:
    Sep 13, 2016
    Posts:
    1,292
    Code is pulled from another thread of mine:
    Code:
    /******************************************************************************
    
     MIT License
    
     Copyright © 2019 Samuel Venable
    
     Permission is hereby granted, free of charge, to any person obtaining a copy
     of this software and associated documentation files (the "Software"), to deal
     in the Software without restriction, including without limitation the rights
     to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     copies of the Software, and to permit persons to whom the Software is
     furnished to do so, subject to the following conditions:
    
     The above copyright notice and this permission notice shall be included in all
     copies or substantial portions of the Software.
    
     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     SOFTWARE.
    
    ******************************************************************************/
    
    #include "ShowBorder.h" // unimportant to the question at hand
    #include <X11/Xlib.h>
    #include <climits>
    
    typedef struct {
      unsigned long flags;
      unsigned long functions;
      unsigned long decorations;
      long inputMode;
      unsigned long status;
    } Hints;
    
    double window_get_showborder(void *hwnd) {
      Atom type;
      int format;
      unsigned long bytes;
      unsigned long items;
      unsigned char *data = NULL;
      bool ret = true;
      Display *d = XOpenDisplay(NULL);
      Window w = (Window)hwnd;
      Atom property = XInternAtom(d, "_MOTIF_WM_HINTS", False);
      if (XGetWindowProperty(d, w, property, 0, LONG_MAX, False, AnyPropertyType, &type, &format, &items, &bytes, &data) == Success && data != NULL) {
       Hints *hints = (Hints *)data;
       ret = hints->decorations;
       XFree(data);
      }
      XCloseDisplay(d);
      return ret;
    }
    
    double window_set_showborder(void *hwnd, double show, double clientx, double clienty) {
      Display *d = XOpenDisplay(NULL);
      Window w = (Window)hwnd;
      Atom aKWinRunning = XInternAtom(d, "KWIN_RUNNING", True);
      bool bKWinRunning = (aKWinRunning != None);
      XWindowAttributes wa;
      Window root, parent, *child; uint children;
      XWindowAttributes pwa;
      for (;;) {
       XGetWindowAttributes(d, w, &wa);
       XQueryTree(d, w, &root, &parent, &child, &children);
       XGetWindowAttributes(d, parent, &pwa);
       if ((bKWinRunning ? pwa.x : wa.x) || (bKWinRunning ? pwa.y : wa.y) || !window_get_showborder(hwnd))
         break;
      }
      static const int xoffset = bKWinRunning ? pwa.x : wa.x;
      static const int yoffset = bKWinRunning ? pwa.y : wa.y;
      Hints hints;
      Atom property = XInternAtom(d, "_MOTIF_WM_HINTS", False);
      hints.flags = 2;
      hints.decorations = show;
      XChangeProperty(d, w, property, property, 32, PropModeReplace, (unsigned char *)&hints, 5);
      int xpos = show ? clientx - xoffset : clientx;
      int ypos = show ? clienty - yoffset : clienty;
      XMoveResizeWindow(d, w, xpos, ypos, bKWinRunning ? wa.width : wa.width + xoffset, bKWinRunning ? wa.height : wa.height + yoffset);
      XCloseDisplay(d);
      return 0;
    }
    The for loop only breaks under one of two conditions, if the titlebar/border is greater than greater than zero by it's width or height, or, if the window decorations are turned off, which assumes the Window Manager is able to understand the _MOTIF_WM_HINTS atom.

    My concern is, would this ever create an infinite loop/hang on a Window Manager that:

    1) has no concept of Window Decorations (Raspberry Pi handhelds like GameShell come to mind).

    2) is a Window Manager which _MOTIF_WM_HINTS is not a recognized atom, and the border is not a child or parent window of the client area.

    3) is a Tiling Window Managers (i3, ratpoison, etc).

    The hope is, window_get_showborder() would return false in these particular cases, and thus the for loop would break, but im not sure if that would happen.

    Edit:

    I had my question answered by someone from a different community. No, this code shouldn't do what I was afraid of it doing, fortunately.
     
    Last edited: Aug 16, 2019

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