[clutter] actor: Ensure allocation adjustment is safe against zero sizes

[Emmanuele Bassi <ebassi src gnome org>]

commit e72a1a44e6e339c55acecba67e2f99412982b832
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri May 15 12:34:53 2015 +0100

    actor: Ensure allocation adjustment is safe against zero sizes
    
    We already copy with negative end results, but there's no point in doing
    the work in the first place.

 clutter/clutter-actor.c |   30 ++++++++++++++++++++++++++----
 1 files changed, 26 insertions(+), 4 deletions(-)
---
diff --git a/clutter/clutter-actor.c b/clutter/clutter-actor.c
index 2032567..cffc61b 100644
--- a/clutter/clutter-actor.c
+++ b/clutter/clutter-actor.c
@@ -9203,10 +9203,25 @@ adjust_for_margin (float  margin_start,
                    float *allocated_start,
                    float *allocated_end)
 {
-  *minimum_size -= (margin_start + margin_end);
-  *natural_size -= (margin_start + margin_end);
-  *allocated_start += margin_start;
-  *allocated_end -= margin_end;
+  float min_size = *minimum_size;
+  float nat_size = *natural_size;
+  float start = *allocated_start;
+  float end = *allocated_end;
+
+  min_size = MAX (min_size - (margin_start + margin_end), 0);
+  nat_size = MAX (nat_size - (margin_start + margin_end), 0);
+
+  *minimum_size = min_size;
+  *natural_size = nat_size;
+
+  start += margin_start;
+  end -= margin_end;
+
+  if (end - start >= 0)
+    {
+      *allocated_start = start;
+      *allocated_end = end;
+    }
 }
 
 static inline void
@@ -9217,6 +9232,9 @@ adjust_for_alignment (ClutterActorAlign  alignment,
 {
   float allocated_size = *allocated_end - *allocated_start;
 
+  if (allocated_size <= 0.f)
+    return;
+
   switch (alignment)
     {
     case CLUTTER_ACTOR_ALIGN_FILL:
@@ -9805,6 +9823,10 @@ clutter_actor_adjust_allocation (ClutterActor    *self,
 
   clutter_actor_box_get_size (allocation, &alloc_width, &alloc_height);
 
+  /* There's no point in trying to adjust a zero-sized actor */
+  if (alloc_width == 0.f && alloc_height == 0.f)
+    return;
+
   /* we want to hit the cache, so we use the public API */
   req_mode = clutter_actor_get_request_mode (self);