Add notes on the PGTK S-SPC vs SPC confusion

1 files changed, 36 insertions, 0 deletions

diff --git a/itches/emacs/tracker.org b/itches/emacs/tracker.org
index 122c311..96c6bc7 100644
--- a/itches/emacs/tracker.org
+++ b/itches/emacs/tracker.org
@@ -63,6 +63,42 @@ when ranking fonts; it'd be nice if Emacs's ~find-font~ did so too.
 :Role:           author
 :PatchApplied:   t
 :END:
+***** TODO [[bug:56653]] =S-SPC= recognized as =SPC=
+Reported multiple times; see merged bug reports.  Something in the
+bowels of =GtkIMContext=.  Emacs's PGTK code does this:
+
+#+begin_src c
+/* pgtkterm.c: key_press_event */
+	  if (pgtk_im_filter_keypress (f, &event->key))
+	    return TRUE;
+        /* else keep processing */
+#+end_src
+
+Input methods seem to accept =S-SPC= and call
+=pgtkim.c:im_context_commit_cb= with the string =" "=, thereby losing
+the information that we have a shift modifier.
+
+Debugging notes on Debian 11 (GTK 3.24.24) using [[./pgtk-shift-space.c][this small
+reproducer]]:
+
+#+begin_src sh
+gcc -g $(pkg-config --cflags gtk+-3.0) pgtk-shift-space.c $(pkg-config --libs gtk+-3.0)
+export DEBUGINFOD_URLS=https://debuginfod.debian.net
+#+end_src
+
+Then break on =show_commit=, and help GDB find GTK code with
+~directory […gtk-3.24.24 checkout…]/gtk~.
+
+=gtkimcontextsimple.c:no_sequence_matches= is the last frame to know
+about the =GdkEventKey= event that includes the shift modifier; so
+presumably that function should refrain from calling
+=gtkimcontextsimple.c:gtk_im_context_simple_commit_char= if it sees
+modifiers?
+
+Or =pgtkim.c:im_context_commit_cb= should check its context and
+refrain from enqueueing =" "=; there is no straightforward way for
+that function to signal =pgtkterm.c:key_press_event= that the IM
+commit was "aborted" though…
 **** DONE [[bug:41584]] org-indent-mode's line-prefix text property flickers near overlays
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 :Role:           author