[gtk/matthiasc/for-master] imcontext: Enable font fallback for preedit

[Matthias Clasen <matthiasc src gnome org>]

commit 05fe2441a7e93f3d1ebf25bfe8e6c945925da0c9
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Feb 17 22:08:43 2021 -0500

    imcontext: Enable font fallback for preedit
    
    Not doing so only invites hexboxes.
    
    Fixes: #3678

 gtk/gtkimcontextsimple.c  | 9 ++++++++-
 gtk/gtkimcontextwayland.c | 3 +++
 2 files changed, 11 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkimcontextsimple.c b/gtk/gtkimcontextsimple.c
index 701e433c19..b8fec2f384 100644
--- a/gtk/gtkimcontextsimple.c
+++ b/gtk/gtkimcontextsimple.c
@@ -945,7 +945,14 @@ gtk_im_context_simple_get_preedit_string (GtkIMContext   *context,
 
       if (s->len)
         {
-          PangoAttribute *attr = pango_attr_underline_new (PANGO_UNDERLINE_SINGLE);
+          PangoAttribute *attr;
+
+          attr = pango_attr_underline_new (PANGO_UNDERLINE_SINGLE);
+          attr->start_index = 0;
+          attr->end_index = s->len;
+          pango_attr_list_insert (*attrs, attr);
+
+          attr = pango_attr_fallback_new (TRUE);
           attr->start_index = 0;
           attr->end_index = s->len;
           pango_attr_list_insert (*attrs, attr);
diff --git a/gtk/gtkimcontextwayland.c b/gtk/gtkimcontextwayland.c
index 77264087eb..c5e0093584 100644
--- a/gtk/gtkimcontextwayland.c
+++ b/gtk/gtkimcontextwayland.c
@@ -610,6 +610,9 @@ gtk_im_context_wayland_get_preedit_string (GtkIMContext   *context,
         *attrs = pango_attr_list_new ();
       pango_attr_list_insert (*attrs,
                               pango_attr_underline_new (PANGO_UNDERLINE_SINGLE));
+      /* enable fallback, since IBus will send us things like ⎄ */
+      pango_attr_list_insert (*attrs,
+                              pango_attr_fallback_new (TRUE));
       if (context_wayland->current_preedit.cursor_begin
           != context_wayland->current_preedit.cursor_end)
         {