Re: [PATCH] Fix rendering issues on window managers without _NET_WM_STATE

[Omar Polo]

Tom Gillespie <tgbugs@gmail.com> writes:

> Hi,
>     This patch fixes a bug that occurs when running Emacs in a window
> manager that does not set _NET_WM_STATE. The patch is simplest fix
> that restores expected behavior for window managers that do not set
> _NET_WM_STATE, but I have no idea whether there are other issues that
> may be occurring.
>
> I'm guessing that there are also likely issues with other logic in the
> MapNotify case that uses not_hidden for window managers that does not
> set _NET_WM_STATE.
>
> Thus, the more complex solution, which I am not knowledgeable enough
> to implement correctly, is to fix x_get_current_wm_state so that it
> works on window managers that do not set _NET_WM_STATE.
>
> I am unfamiliar with this section of the code, so my explanation may
> be off and a sanity check would be appreciated. Best,
> Tom
>
>
> A description of the bug for the record.
>
> The bug manifests as frames rendering as solid background after
> changing desktops on window managers that do not set _NET_WM_STATE.
>
> When changing desktops and returning to a desktop with Emacs frames,
> any frame that is not focused will render the whole frame as only the
> background color for the current theme.
>
> I have run a git bisect and found that the first bad commit is
> 483c5e953c12a95382bef4a3b6769a680c32fe86 Fix two GTK3 event handling
> issues.
>
> I think that the bug is occurring because 483c5e953c1 changed calls to
> SET_FRAME_VISIBLE and friends from being unconditional to being
> conditional on not_hidden, which returns incorrect information when
> _NET_WM_STATE is not set (I think).
>
> I encountered the bug on fluxbox but the behavior should happen for
> any window manager that does not set _NET_WM_STATE.

I can confirm that the bug was present also with cwm and that your patch
fixes it, thanks!!

> It should be possible to reproduce the bug using the following steps.
> Run a window manager that does not set _NET_WM_STATE, e.g. fluxbox.
> In a terminal run the following and when the newly built Emacs
> launches alt-tab to the terminal window, and then leave and return to
> the desktop with the Emacs frame.
> #+begin_src bash
> pushd ~/git/emacs
> git checkout 483c5e953c12a95382bef4a3b6769a680c32fe86
> git clean -dfx && ./autogen.sh && ./configure && make && \
> src/emacs -q
> #+end_src