Re: [C source] What is gravity and the change_gravity argument?

[Eli Zaretskii <eliz@gnu.org>]

> From: Akib Azmain Turja <akib@disroot.org>
> Date: Fri, 08 Jul 2022 18:40:16 +0600
> 
> In src/termhooks.h, I found the following two members of struct
> terminal:
> 
> --8<---------------cut here---------------start------------->8---
>   /* This hook is called to change the size of frame F's native
>    (underlying) window.  If CHANGE_GRAVITY, change to top-left-corner
>    window gravity for this size change and subsequent size changes.
>    Otherwise we leave the window gravity unchanged.  */
>   void (*set_window_size_hook) (struct frame *f, bool change_gravity,
>                                 int width, int height);
> 
>   /* CHANGE_GRAVITY is 1 when calling from Fset_frame_position,
>    to really change the position, and 0 when calling from
>    *_make_frame_visible (in that case, XOFF and YOFF are the current
>    position values).  It is -1 when calling from gui_set_frame_parameters,
>    which means, do adjust for borders but don't change the gravity.  */
> 
>   void (*set_frame_offset_hook) (struct frame *f, register int xoff,
>                                  register int yoff, int change_gravity);
> --8<---------------cut here---------------end--------------->8---
> 
> X and PGTK uses that 'change_gravity' argument, I can't understand what
> they are doing with them.  I searched the internet and found several
> answers[1], but couldn't make any sense.

Try this:

  https://tronche.com/gui/x/xlib/window/attributes/gravity.html