[gnome-builder] libide: stay pinned to bottom of buffer during inserts

[Christian Hergert <chergert src gnome org>]

commit c3968d44c8220d11561cfb0b69c344bc6bedb869
Author: Christian Hergert <christian hergert me>
Date:   Sun Mar 8 22:59:26 2015 -0700

    libide: stay pinned to bottom of buffer during inserts
    
    If we are already at the bottom of the buffer, then keep the view pinned
    to the bottom of the buffer. Otherwise we get into a situation where we
    constantly have to keep scrolling down. Pretty handy when writing new
    functions at the bottom of the document.
    
    If someone wants to make this an option, I'm fine with that, but this
    should be the default.

 libide/ide-source-view.c |  128 ++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 125 insertions(+), 3 deletions(-)
---
diff --git a/libide/ide-source-view.c b/libide/ide-source-view.c
index 65b37d0..2cfad5b 100644
--- a/libide/ide-source-view.c
+++ b/libide/ide-source-view.c
@@ -240,6 +240,81 @@ ide_source_view_unblock_handlers (IdeSourceView *self)
     }
 }
 
+static gboolean
+ide_source_view_get_at_bottom (IdeSourceView *self)
+{
+  GtkAdjustment *vadj;
+  gdouble value;
+  gdouble page_size;
+  gdouble upper;
+
+  g_assert (IDE_IS_SOURCE_VIEW (self));
+
+  vadj = gtk_scrollable_get_vadjustment (GTK_SCROLLABLE (self));
+  value = gtk_adjustment_get_value (vadj);
+  upper = gtk_adjustment_get_upper (vadj);
+  page_size = gtk_adjustment_get_page_size (vadj);
+
+  return ((value + page_size) == upper);
+}
+
+static void
+ide_source_view_scroll_to_bottom__changed_cb (GtkAdjustment *vadj,
+                                              GParamSpec    *pspec,
+                                              gpointer       user_data)
+{
+  gdouble page_size;
+  gdouble upper;
+  gdouble value;
+
+  g_assert (GTK_IS_ADJUSTMENT (vadj));
+
+  g_signal_handlers_disconnect_by_func (vadj,
+                                        G_CALLBACK (ide_source_view_scroll_to_bottom__changed_cb),
+                                        NULL);
+
+  page_size = gtk_adjustment_get_page_size (vadj);
+  upper = gtk_adjustment_get_upper (vadj);
+  value = upper - page_size;
+
+  gtk_adjustment_set_value (vadj, value);
+}
+
+static void
+ide_source_view_scroll_to_bottom (IdeSourceView *self)
+{
+  GtkAdjustment *vadj;
+  gdouble page_size;
+  gdouble upper;
+  gdouble value;
+  gdouble new_value;
+
+  g_assert (IDE_IS_SOURCE_VIEW (self));
+
+  vadj = gtk_scrollable_get_vadjustment (GTK_SCROLLABLE (self));
+  upper = gtk_adjustment_get_upper (vadj);
+  page_size = gtk_adjustment_get_page_size (vadj);
+  value = gtk_adjustment_get_value (vadj);
+  new_value = upper - page_size;
+
+  if (new_value == value)
+    {
+      /*
+       * HACK:
+       *
+       * GtkTextView wont calculate the new heights until an idle handler.
+       * So wait until that happens and then jump.
+       */
+      g_signal_connect (vadj,
+                        "notify::upper",
+                        G_CALLBACK (ide_source_view_scroll_to_bottom__changed_cb),
+                        NULL);
+      return;
+    }
+
+  gtk_adjustment_set_value (vadj, new_value);
+}
+
 static void
 get_rect_for_iters (GtkTextView       *text_view,
                     const GtkTextIter *iter1,
@@ -1332,14 +1407,19 @@ ide_source_view_do_indent (IdeSourceView *self,
   GtkWidget *widget = (GtkWidget *)self;
   GtkTextBuffer *buffer;
   GtkTextMark *insert;
+  g_autofree gchar *indent = NULL;
   GtkTextIter begin;
   GtkTextIter end;
-  gchar *indent;
+  gboolean at_bottom;
   gint cursor_offset = 0;
 
+  IDE_ENTRY;
+
   g_assert (IDE_IS_SOURCE_VIEW (self));
   g_assert (event);
 
+  at_bottom = ide_source_view_get_at_bottom (self);
+
   buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (self));
 
   /*
@@ -1371,10 +1451,15 @@ ide_source_view_do_indent (IdeSourceView *self,
       if (!gtk_text_iter_equal (&begin, &end))
         gtk_text_buffer_delete (buffer, &begin, &end);
       gtk_text_buffer_insert (buffer, &begin, indent, -1);
-      g_free (indent);
       gtk_text_buffer_end_user_action (buffer);
 
       /*
+       * Keep our selves pinned to the bottom of the document if that makes sense.
+       */
+      if (at_bottom)
+        ide_source_view_scroll_to_bottom (self);
+
+      /*
        * Place the cursor, as it could be somewhere within our indent text.
        */
       gtk_text_buffer_get_iter_at_mark (buffer, &begin, insert);
@@ -1384,6 +1469,8 @@ ide_source_view_do_indent (IdeSourceView *self,
         gtk_text_iter_backward_chars (&begin, ABS (cursor_offset));
       gtk_text_buffer_select_range (buffer, &begin, &begin);
     }
+
+  IDE_EXIT;
 }
 
 static gboolean
@@ -1821,6 +1908,7 @@ ide_source_view_real_insert_at_cursor_and_indent (IdeSourceView *self,
   IdeSourceViewPrivate *priv = ide_source_view_get_instance_private (self);
   GtkTextView *text_view = (GtkTextView *)self;
   GtkTextBuffer *buffer;
+  gboolean at_bottom;
   GdkEvent fake_event = { 0 };
   GString *gstr;
 
@@ -1831,6 +1919,8 @@ ide_source_view_real_insert_at_cursor_and_indent (IdeSourceView *self,
 
   buffer = gtk_text_view_get_buffer (text_view);
 
+  at_bottom = ide_source_view_get_at_bottom (self);
+
   /*
    * Ignore if there is nothing to do.
    */
@@ -1843,7 +1933,7 @@ ide_source_view_real_insert_at_cursor_and_indent (IdeSourceView *self,
   if (!priv->auto_indent || !priv->indenter)
     {
       g_signal_emit_by_name (self, "insert-at-cursor", str);
-      IDE_EXIT;
+      IDE_GOTO (maybe_scroll);
     }
 
   gtk_text_buffer_begin_user_action (buffer);
@@ -1889,6 +1979,10 @@ ide_source_view_real_insert_at_cursor_and_indent (IdeSourceView *self,
 
   gtk_text_buffer_end_user_action (buffer);
 
+maybe_scroll:
+  if (at_bottom)
+    ide_source_view_scroll_to_bottom (self);
+
   IDE_EXIT;
 }
 
@@ -2477,6 +2571,25 @@ ide_source_view_real_redo (GtkSourceView *source_view)
 }
 
 static void
+ide_source_view_real_insert_at_cursor (GtkTextView *text_view,
+                                       const gchar *str)
+{
+  IdeSourceView *self = (IdeSourceView *)text_view;
+  gboolean at_bottom;
+
+  g_assert (IDE_IS_SOURCE_VIEW (self));
+  g_assert (GTK_IS_TEXT_VIEW (text_view));
+  g_assert (str);
+
+  at_bottom = ide_source_view_get_at_bottom (self);
+
+  GTK_TEXT_VIEW_CLASS (ide_source_view_parent_class)->insert_at_cursor (text_view, str);
+
+  if (at_bottom)
+    ide_source_view_scroll_to_bottom (self);
+}
+
+static void
 ide_source_view_dispose (GObject *object)
 {
   IdeSourceView *self = (IdeSourceView *)object;
@@ -2619,6 +2732,7 @@ ide_source_view_class_init (IdeSourceViewClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+  GtkTextViewClass *text_view_class = GTK_TEXT_VIEW_CLASS (klass);
   GtkSourceViewClass *source_view_class = GTK_SOURCE_VIEW_CLASS (klass);
 
   object_class->constructed = ide_source_view_constructed;
@@ -2630,6 +2744,8 @@ ide_source_view_class_init (IdeSourceViewClass *klass)
   widget_class->key_press_event = ide_source_view_key_press_event;
   widget_class->query_tooltip = ide_source_view_query_tooltip;
 
+  text_view_class->insert_at_cursor = ide_source_view_real_insert_at_cursor;
+
   source_view_class->undo = ide_source_view_real_undo;
   source_view_class->redo = ide_source_view_real_redo;
 
@@ -3239,12 +3355,15 @@ ide_source_view_push_snippet (IdeSourceView    *self,
   GtkTextIter iter;
   gboolean has_more_tab_stops;
   gboolean insert_spaces;
+  gboolean at_bottom;
   gchar *line_prefix;
   guint tab_width;
 
   g_return_if_fail (IDE_IS_SOURCE_VIEW (self));
   g_return_if_fail (IDE_IS_SOURCE_SNIPPET (snippet));
 
+  at_bottom = ide_source_view_get_at_bottom (self);
+
   context = ide_source_snippet_get_context (snippet);
 
   if ((previous = g_queue_peek_head (priv->snippets)))
@@ -3302,6 +3421,9 @@ ide_source_view_push_snippet (IdeSourceView    *self,
     ide_source_view_pop_snippet (self);
 
   ide_source_view_invalidate_window (self);
+
+  if (at_bottom)
+    ide_source_view_scroll_to_bottom (self);
 }
 
 /**