But existing frames do, correct?
yes. When I set  ‘frame-resize-pixelwise’ to t only newly created frames work properly. 

> What happens when you explicitly call ‘x-wm-set-size-hint’ for such an
>existing frame?  After having customized ‘frame-resize-pixelwise’ to t,
>obviously.
The frame magically starts to resize properly O_O

On 2 October 2016 at 12:26, martin rudalics <rudalics@gmx.at> wrote:
Please do CC to 24583@debbugs.gnu.org as I asked before.  This might be
of interest for other people as well.

> Yes new frame doesn't glitch.

But existing frames do, correct?

What happens when you explicitly call ‘x-wm-set-size-hint’ for such an
existing frame?  After having customized ‘frame-resize-pixelwise’ to t,
obviously.

martin