Add notes on the PGTK S-SPC vs SPC confusion

2 files changed, 118 insertions, 0 deletions

diff --git a/itches/emacs/pgtk-shift-space.c b/itches/emacs/pgtk-shift-space.c
new file mode 100644
index 0000000..dcfef21
--- /dev/null
+++ b/itches/emacs/pgtk-shift-space.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+
+#include <gtk/gtk.h>
+
+static gboolean show_key (
+        GtkWidget *widget,
+        GdkEventKey *event,
+        gpointer data
+) {
+        int mods[] = {GDK_SHIFT_MASK, GDK_CONTROL_MASK, GDK_MOD1_MASK};
+        char* mods_names[] = {"shift", "control", "alt"};
+        char mods_desc[64] = {'\0'};
+
+        for (size_t i=0; i<sizeof(mods)/sizeof(mods[0]); i++)
+        {
+                if (! (event->state & mods[i]))
+                        continue;
+
+                if (mods_desc[0])
+                        strcat(mods_desc, ":");
+
+                strcat(mods_desc, mods_names[i]);
+        }
+        if (! mods_desc[0])
+                strcpy(mods_desc, "∅");
+
+        fprintf(stderr, "key pressed: '%d' (mods: %s)\n", event->keyval, mods_desc);
+
+        if (gtk_im_context_filter_keypress ((GtkIMContext*)data, event))
+                fprintf(stderr, "\t(handled by gtkim)\n");
+
+        return TRUE;
+}
+
+static void show_commit (
+        GtkIMContext *ctx,
+        gchar *str,
+        gpointer data
+) {
+        fprintf(stderr, "\tcommitting: \"%s\"\n", str);
+}
+
+static void
+activate (GtkApplication* app,
+          gpointer        user_data)
+{
+  GtkWidget *window;
+
+  window = gtk_application_window_new (app);
+  gtk_window_set_title (GTK_WINDOW (window), "Window");
+  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);
+  gtk_widget_show_all (window);
+
+  GtkIMContext *im_context = gtk_im_context_simple_new();
+  gtk_im_context_set_client_window(
+          im_context, gtk_widget_get_window(window)
+  );
+
+  gtk_widget_add_events (window, GDK_KEY_PRESS_MASK);
+
+  g_signal_connect (
+          G_OBJECT (window), "key_press_event", G_CALLBACK (show_key), im_context
+  );
+  g_signal_connect (
+          im_context, "commit", G_CALLBACK (show_commit), NULL
+  );
+}
+
+int
+main (int    argc,
+      char **argv)
+{
+  GtkApplication *app;
+  int status;
+
+  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
+  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
+  status = g_application_run (G_APPLICATION (app), argc, argv);
+  g_object_unref (app);
+
+  return status;
+}
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
 :PROPERTIES:
 :Role:           author