Re: Whether a struct window *w is a live/valid window.

[Keith David Bershatsky]

Thank you, Alan, for confirming that a reasonable approach to checking whether 
the window is alive/valid is to use:

    if (w != NULL && NILP (w->contents))

The drawing method for glyphs that I am familiar with is as follows:

draw_glyphs

  FRAME_RIF (f)->draw_glyph_string (s);

    font->driver->draw

Those series of events do not occur when the vertical scroll bar is removed.  
The scroll bar removal is processed in the span of just one (1) gdb step; i.e., 
"s".

ns_read_socket ... [NSAPP run];

The calls to "draw_glyphs ... font->driver->draw" have already occurred and the 
window has already been properly updated (with fake cursors) *before* 
"ns_read_socket ... [NSAPP run]" is processed.  Does "ns_read_socket ... [NSAPP 
run]" have a sort of "selective photographic memory" of the glyphs, but not the 
fake cursors that were created with NSRectFill?

http://www.lawlist.com/images/after_03_10_2019.png