Support surrounding-text retrieval.

Unlike the GtkIMContext API, IBus automatically retrieves
surrounding-text when certain events occurred to the
client ("before filter_keypress", for example).  This makes the
engine API simpler but causes periodical emission of D-Bus
signals for updating surrounding-text information, which is
unwanted for typical engines.

For this reason, the surrounding-text support is currently
disabled by default.  To enable it, pass
--enable-surrounding-text to configure.  Also, even
surrounding-text support is compiled in, IBus does not start
polling until an engine requests surrounding-text using
ibus_engine_get_surrounding_text().  To make the function work
for the first time, clients should retrieve
initial surrounding-text when the engine is enabled (see ibus_im_context_focus_in() and
_ibus_context_enabled_cb() in client/gtk2/ibusimcontext.c).

BUG=Issue#778
TEST=manual

Review URL: http://codereview.appspot.com/4276082
Patch from Daiki Ueno <daiki.ueno@gmail.com>.

1 files changed, 101 insertions, 12 deletions

diff --git a/client/gtk2/ibusimcontext.c b/client/gtk2/ibusimcontext.c
index 0cb9c313..dcd356f3 100644
--- a/client/gtk2/ibusimcontext.c
+++ b/client/gtk2/ibusimcontext.c
@@ -24,6 +24,7 @@
 #  include <config.h>
 #endif
 
+#include <string.h>
 #include <gtk/gtk.h>
 #include <gdk/gdkkeysyms.h>
 #include <ibus.h>
@@ -114,6 +115,12 @@ static void     ibus_im_context_set_cursor_location
 static void     ibus_im_context_set_use_preedit
                                             (GtkIMContext           *context,
                                              gboolean               use_preedit);
+static void     ibus_im_context_set_surrounding
+                                            (GtkIMContext  *slave,
+                                             const gchar   *text,
+                                             gint           len,
+                                             gint           cursor_index);
+
 
 /* static methods*/
 static void     _create_input_context       (IBusIMContext      *context);
@@ -132,14 +139,16 @@ static void     _slave_preedit_start_cb     (GtkIMContext       *slave,
                                              IBusIMContext       *context);
 static void     _slave_preedit_end_cb       (GtkIMContext       *slave,
                                              IBusIMContext       *context);
-static void     _slave_retrieve_surrounding_cb
+static gboolean _slave_retrieve_surrounding_cb
                                             (GtkIMContext       *slave,
-                                             IBusIMContext       *context);
-static void     _slave_delete_surrounding_cb
+                                             IBusIMContext      *context);
+static gboolean _slave_delete_surrounding_cb
                                             (GtkIMContext       *slave,
-                                             gint               offset_from_cursor,
-                                             guint              nchars,
-                                             IBusIMContext       *context);
+                                             gint                offset_from_cursor,
+                                             guint               nchars,
+                                             IBusIMContext      *context);
+static void     _request_surrounding_text   (IBusIMContext      *context,
+                                             gboolean            force);
 static void     _create_fake_input_context  (void);
 
 
@@ -251,6 +260,28 @@ _process_key_event_done (GObject      *object,
 }
 
 
+/* emit "retrieve-surrounding" glib signal of GtkIMContext, if
+ * context->caps has IBUS_CAP_SURROUNDING_TEXT and the current IBus
+ * engine needs surrounding-text.
+ *
+ * if "force" is TRUE, emit the signal regardless of whether the
+ * engine needs surrounding-text.
+ */
+static void
+_request_surrounding_text (IBusIMContext *context, gboolean force)
+{
+    if (context->enable &&
+        (context->caps & IBUS_CAP_SURROUNDING_TEXT) != 0 &&
+        (force ||
+         ibus_input_context_needs_surrounding_text (context->ibuscontext))) {
+        gboolean return_value;
+        IDEBUG ("requesting surrounding text");
+        g_signal_emit (context, _signal_retrieve_surrounding_id, 0,
+                       &return_value);
+    }
+}
+
+
 static gint
 _key_snooper_cb (GtkWidget   *widget,
                  GdkEventKey *event,
@@ -337,6 +368,8 @@ _key_snooper_cb (GtkWidget   *widget,
 
     } while (0);
 
+    _request_surrounding_text (ibusimcontext, FALSE);
+
     if (ibusimcontext != NULL) {
         ibusimcontext->time = event->time;
     }
@@ -414,6 +447,7 @@ ibus_im_context_class_init (IBusIMContextClass *class)
     im_context_class->set_client_window = ibus_im_context_set_client_window;
     im_context_class->set_cursor_location = ibus_im_context_set_cursor_location;
     im_context_class->set_use_preedit = ibus_im_context_set_use_preedit;
+    im_context_class->set_surrounding = ibus_im_context_set_surrounding;
     gobject_class->finalize = ibus_im_context_finalize;
 
     _signal_commit_id =
@@ -545,7 +579,11 @@ ibus_im_context_init (GObject *obj)
     ibusimcontext->ibuscontext = NULL;
     ibusimcontext->has_focus = FALSE;
     ibusimcontext->time = GDK_CURRENT_TIME;
+#ifdef ENABLE_SURROUNDING
     ibusimcontext->caps = IBUS_CAP_PREEDIT_TEXT | IBUS_CAP_FOCUS | IBUS_CAP_SURROUNDING_TEXT;
+#else
+    ibusimcontext->caps = IBUS_CAP_PREEDIT_TEXT | IBUS_CAP_FOCUS;
+#endif
 
 
     // Create slave im context
@@ -642,6 +680,8 @@ ibus_im_context_filter_keypress (GtkIMContext *context,
         if (ibusimcontext->client_window == NULL && event->window != NULL)
             gtk_im_context_set_client_window ((GtkIMContext *)ibusimcontext, event->window);
 
+        _request_surrounding_text (ibusimcontext, FALSE);
+
         if (ibusimcontext != NULL) {
             ibusimcontext->time = event->time;
         }
@@ -721,6 +761,10 @@ ibus_im_context_focus_in (GtkIMContext *context)
                      g_object_ref (context),
                      (GDestroyNotify) g_object_unref);
 
+    /* retrieve the initial surrounding-text (regardless of whether
+     * the current IBus engine needs surrounding-text) */
+    _request_surrounding_text (ibusimcontext, TRUE);
+
     g_object_add_weak_pointer ((GObject *) context,
                                (gpointer *) &_focus_im_context);
     _focus_im_context = context;
@@ -899,12 +943,44 @@ ibus_im_context_set_use_preedit (GtkIMContext *context, gboolean use_preedit)
         else {
             ibusimcontext->caps &= ~IBUS_CAP_PREEDIT_TEXT;
         }
-        ibus_input_context_set_capabilities (ibusimcontext->ibuscontext, ibusimcontext->caps);
     }
     gtk_im_context_set_use_preedit (ibusimcontext->slave, use_preedit);
 }
 
 static void
+ibus_im_context_set_surrounding (GtkIMContext  *context,
+                                 const gchar   *text,
+                                 gint           len,
+                                 gint           cursor_index)
+{
+    g_return_if_fail (context != NULL);
+    g_return_if_fail (IBUS_IS_IM_CONTEXT (context));
+    g_return_if_fail (text != NULL);
+    g_return_if_fail (strlen (text) >= len);
+    g_return_if_fail (0 <= cursor_index && cursor_index <= len);
+
+    IBusIMContext *ibusimcontext = IBUS_IM_CONTEXT (context);
+
+    if (ibusimcontext->enable && ibusimcontext->ibuscontext) {
+        IBusText *ibustext;
+        guint cursor_pos;
+        gchar *p;
+
+        p = g_strndup (text, len);
+        cursor_pos = g_utf8_strlen (p, cursor_index);
+        ibustext = ibus_text_new_from_string (p);
+        g_free (p);
+        ibus_input_context_set_surrounding_text (ibusimcontext->ibuscontext,
+                                                 ibustext,
+                                                 cursor_pos);
+    }
+    gtk_im_context_set_surrounding (ibusimcontext->slave,
+                                    text,
+                                    len,
+                                    cursor_index);
+}
+
+static void
 _bus_connected_cb (IBusBus          *bus,
                    IBusIMContext    *ibusimcontext)
 {
@@ -923,6 +999,8 @@ _ibus_context_commit_text_cb (IBusInputContext *ibuscontext,
     IDEBUG ("%s", __FUNCTION__);
 
     g_signal_emit (ibusimcontext, _signal_commit_id, 0, text->text);
+
+    _request_surrounding_text (ibusimcontext, FALSE);
 }
 
 static gboolean
@@ -1217,6 +1295,8 @@ _ibus_context_show_preedit_text_cb (IBusInputContext   *ibuscontext,
     ibusimcontext->preedit_visible = TRUE;
     g_signal_emit (ibusimcontext, _signal_preedit_start_id, 0);
     g_signal_emit (ibusimcontext, _signal_preedit_changed_id, 0);
+
+    _request_surrounding_text (ibusimcontext, FALSE);
 }
 
 static void
@@ -1240,6 +1320,10 @@ _ibus_context_enabled_cb (IBusInputContext *ibuscontext,
     IDEBUG ("%s", __FUNCTION__);
 
     ibusimcontext->enable = TRUE;
+
+    /* retrieve the initial surrounding-text (regardless of whether
+     * the current IBus engine needs surrounding-text) */
+    _request_surrounding_text (ibusimcontext, TRUE);
 }
 
 static void
@@ -1417,17 +1501,21 @@ _slave_preedit_end_cb (GtkIMContext  *slave,
     g_signal_emit (ibusimcontext, _signal_preedit_end_id, 0);
 }
 
-static void
+static gboolean
 _slave_retrieve_surrounding_cb (GtkIMContext  *slave,
                                 IBusIMContext *ibusimcontext)
 {
+    gboolean return_value;
+
     if (ibusimcontext->enable && ibusimcontext->ibuscontext) {
-        return;
+        return FALSE;
     }
-    g_signal_emit (ibusimcontext, _signal_retrieve_surrounding_id, 0);
+    g_signal_emit (ibusimcontext, _signal_retrieve_surrounding_id, 0,
+                   &return_value);
+    return return_value;
 }
 
-static void
+static gboolean
 _slave_delete_surrounding_cb (GtkIMContext  *slave,
                               gint           offset_from_cursor,
                               guint          nchars,
@@ -1436,9 +1524,10 @@ _slave_delete_surrounding_cb (GtkIMContext  *slave,
     gboolean return_value;
 
     if (ibusimcontext->enable && ibusimcontext->ibuscontext) {
-        return;
+        return FALSE;
     }
     g_signal_emit (ibusimcontext, _signal_delete_surrounding_id, 0, offset_from_cursor, nchars, &return_value);
+    return return_value;
 }
 
 #ifdef OS_CHROMEOS