Avoid some crashes when dragging windows partially offscreen. Possible (or

2007-04-03  Elijah Newren  <newren gmail com>

	Avoid some crashes when dragging windows partially offscreen.
	Possible (or at least partial) fix for #353513.

	* src/edge-resistance.c (apply_edge_resistance): be more careful
	about calls to find_index_of_edge_near_position() returning
	possibly invalid indices.  Also, add a warning comment to
	find_index_of_edge_near_position().

svn path=/branches/gnome-2-18/; revision=3148

2 files changed, 21 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 09426663..88958146 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2007-04-03  Elijah Newren  <newren gmail com>
+
+	Avoid some crashes when dragging windows partially offscreen.
+	Possible (or at least partial) fix for #353513.
+
+	* src/edge-resistance.c (apply_edge_resistance): be more careful
+	about calls to find_index_of_edge_near_position() returning
+	possibly invalid indices.  Also, add a warning comment to
+	find_index_of_edge_near_position().
+
 2007-03-31  Elijah Newren  <newren gmail com>
 
 	Clean up event mask handling and meta_create_offscreen_window, to
diff --git a/src/edge-resistance.c b/src/edge-resistance.c
index 3db21ab4..a536accc 100644
--- a/src/edge-resistance.c
+++ b/src/edge-resistance.c
@@ -62,6 +62,9 @@ struct MetaEdgeResistanceData
   ResistanceDataForAnEdge bottom_data;
 };
 
+/* !WARNING!: this function can return invalid indices (namely, either -1 or
+ * edges->len); this is by design, but you need to remember this.
+ */
 static int
 find_index_of_edge_near_position (const GArray *edges,
                                   int           position,
@@ -330,6 +333,7 @@ apply_edge_resistance (MetaWindow                *window,
                        gboolean                   keyboard_op)
 {
   int i, begin, end;
+  int last_edge;
   gboolean increasing = new_pos > old_pos;
   int      increment = increasing ? 1 : -1;
 
@@ -366,6 +370,13 @@ apply_edge_resistance (MetaWindow                *window,
   begin = find_index_of_edge_near_position (edges, old_pos,  increasing, xdir);
   end   = find_index_of_edge_near_position (edges, new_pos, !increasing, xdir);
 
+  /* begin and end can be outside the array index, if the window is partially
+   * off the screen
+   */
+  last_edge = edges->len - 1;
+  begin = CLAMP (begin, 0, last_edge);
+  end   = CLAMP (end,   0, last_edge);
+
   /* Loop over all these edges we're moving past/to. */
   i = begin;
   while ((increasing  && i <= end) ||