[gtksourceview/gnome-3-20] view: connect to ::highlight-updated signal to update highlight

[Sébastien Wilmet <swilmet src gnome org>]

commit 03e78aeab3368a8291cc18b5d45cc663e6b17335
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon Jun 13 17:52:28 2016 +0200

    view: connect to ::highlight-updated signal to update highlight
    
    There was a good reason behind
    commit 949cd128064201935f90d999544e6a19f8e3baa6: the code was not clear.
    It was not evident to know why that code was useful.
    
    If the title of this commit doesn't make any sense, it's because the
    ::highlight-updated signal has a bad name. When the ContextEngine sends
    it, the _highlight_ is actually not yet updated.
    
    Now with the new implementation and the comment in the code, I hope
    it'll be a bit clearer. But it would be nice to do something about the
    signal name.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=767565

 gtksourceview/gtksourceview.c |   95 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 95 insertions(+), 0 deletions(-)
---
diff --git a/gtksourceview/gtksourceview.c b/gtksourceview/gtksourceview.c
index bf9b7df..97f95ff 100644
--- a/gtksourceview/gtksourceview.c
+++ b/gtksourceview/gtksourceview.c
@@ -1338,6 +1338,92 @@ gtk_source_view_finalize (GObject *object)
 }
 
 static void
+get_visible_region (GtkTextView *text_view,
+                   GtkTextIter *start,
+                   GtkTextIter *end)
+{
+       GdkRectangle visible_rect;
+
+       gtk_text_view_get_visible_rect (text_view, &visible_rect);
+
+       gtk_text_view_get_line_at_y (text_view,
+                                    start,
+                                    visible_rect.y,
+                                    NULL);
+
+       gtk_text_view_get_line_at_y (text_view,
+                                    end,
+                                    visible_rect.y + visible_rect.height,
+                                    NULL);
+
+       gtk_text_iter_backward_line (start);
+       gtk_text_iter_forward_line (end);
+}
+
+static void
+highlight_updated_cb (GtkSourceBuffer *buffer,
+                     GtkTextIter     *_start,
+                     GtkTextIter     *_end,
+                     GtkTextView     *text_view)
+{
+       GtkTextIter start;
+       GtkTextIter end;
+       GtkTextIter visible_start;
+       GtkTextIter visible_end;
+       GtkTextIter intersect_start;
+       GtkTextIter intersect_end;
+
+       start = *_start;
+       end = *_end;
+       gtk_text_iter_order (&start, &end);
+
+       get_visible_region (text_view, &visible_start, &visible_end);
+
+       if (gtk_text_iter_compare (&end, &visible_start) < 0 ||
+           gtk_text_iter_compare (&visible_end, &start) < 0)
+       {
+               return;
+       }
+
+       if (gtk_text_iter_compare (&start, &visible_start) < 0)
+       {
+               intersect_start = visible_start;
+       }
+       else
+       {
+               intersect_start = start;
+       }
+
+       if (gtk_text_iter_compare (&visible_end, &end) < 0)
+       {
+               intersect_end = visible_end;
+       }
+       else
+       {
+               intersect_end = end;
+       }
+
+       /* GtkSourceContextEngine sends the highlight-updated signal to notify
+        * the view, and in the view (here) we tell the ContextEngine to update
+        * the highlighting, but only in the visible area. It seems that the
+        * purpose is to reduce the number of tags that the ContextEngine
+        * applies to the buffer.
+        *
+        * A previous implementation of this signal handler queued a redraw on
+        * the view with gtk_widget_queue_draw_area(), instead of calling
+        * directly _gtk_source_buffer_update_highlight(). The ::draw handler
+        * also calls _gtk_source_buffer_update_highlight(), so this had the
+        * desired effect, but it was less clear.
+        * See the Git commit 949cd128064201935f90d999544e6a19f8e3baa6.
+        * And: https://bugzilla.gnome.org/show_bug.cgi?id=767565
+        */
+       _gtk_source_buffer_update_highlight (buffer,
+                                            &intersect_start,
+                                            &intersect_end,
+                                            FALSE);
+}
+
+static void
 source_mark_updated_cb (GtkSourceBuffer *buffer,
                        GtkSourceMark   *mark,
                        GtkTextView     *text_view)
@@ -1361,6 +1447,10 @@ remove_source_buffer (GtkSourceView *view)
        if (view->priv->source_buffer != NULL)
        {
                g_signal_handlers_disconnect_by_func (view->priv->source_buffer,
+                                                     highlight_updated_cb,
+                                                     view);
+
+               g_signal_handlers_disconnect_by_func (view->priv->source_buffer,
                                                      source_mark_updated_cb,
                                                      view);
 
@@ -1389,6 +1479,11 @@ set_source_buffer (GtkSourceView *view,
                view->priv->source_buffer = g_object_ref (buffer);
 
                g_signal_connect (buffer,
+                                 "highlight-updated",
+                                 G_CALLBACK (highlight_updated_cb),
+                                 view);
+
+               g_signal_connect (buffer,
                                  "source-mark-updated",
                                  G_CALLBACK (source_mark_updated_cb),
                                  view);