[gtk/unintrusive-compose-preedit: 8/8] imwayland: Tweak preedit text

[Matthias Clasen <matthiasc src gnome org>]

commit d84a028455cadbf146e4cd234f57dc1df2e69cd6
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Feb 18 11:31:04 2021 -0500

    imwayland: Tweak preedit text
    
    Tweak the preedit text we get from IBus (via the compositor) to
    match what GtkIMContextSimple produces for Compose sequences now.
    
    This provides a unified experience.

 gtk/gtkimcontextwayland.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkimcontextwayland.c b/gtk/gtkimcontextwayland.c
index 915ad9e854..397909064d 100644
--- a/gtk/gtkimcontextwayland.c
+++ b/gtk/gtkimcontextwayland.c
@@ -570,6 +570,38 @@ gtk_im_context_wayland_set_client_widget (GtkIMContext *context,
     }
 }
 
+/* We want a unified experience between GtkIMContextSimple and IBus / Wayland
+ * when it comes to Compose sequences. IBus initial implementation of preedit
+ * for Compose sequences shows U+2384, which has been described as 'distracting'.
+ * This function tries to detect this case, and tweaks the text to match what
+ * GtkIMContextSimple produces.
+ */
+static char *
+tweak_preedit (const char *text)
+{
+  GString *s;
+  guint len;
+
+  s = g_string_new ("");
+
+  len = g_utf8_strlen (text, -1);
+
+  for (const char *p = text; *p; p = g_utf8_next_char (p))
+    {
+      gunichar ch = g_utf8_get_char (p);
+
+      if (ch == 0x2384)
+        {
+          if (len == 1 || p > text)
+            g_string_append (s, "·");
+        }
+      else
+        g_string_append_unichar (s, ch);
+    }
+
+  return g_string_free (s, FALSE);
+}
+
 static void
 gtk_im_context_wayland_get_preedit_string (GtkIMContext   *context,
                                            char          **str,
@@ -599,7 +631,7 @@ gtk_im_context_wayland_get_preedit_string (GtkIMContext   *context,
     context_wayland->current_preedit.text ? context_wayland->current_preedit.text : "";
 
   if (str)
-    *str = g_strdup (preedit_str);
+    *str = tweak_preedit (preedit_str);
   if (cursor_pos)
     *cursor_pos = g_utf8_strlen (preedit_str,
                                  context_wayland->current_preedit.cursor_begin);