Added copyright lines for files I've edited this year.

[synfig.git] / synfig-core / trunk / src / synfig / layer_pastecanvas.cpp

diff --git a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
index edc3d0b..b161412 100644 (file)
--- a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
+++ b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
@@ -6,7 +6,7 @@
 **
 **     \legal
 **     Copyright (c) 2002-2005 Robert B. Quattlebaum Jr., Adrian Bentley
-**     Copyright (c) 2007 Chris Moore
+**     Copyright (c) 2007, 2008 Chris Moore
 **
 **     This package is free software; you can redistribute it and/or
 **     modify it under the terms of the GNU General Public License as
@@ -341,16 +341,42 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
 
        Color::BlendMethod blend_method(get_blend_method());
        const Rect full_bounding_rect(canvas->get_context().get_full_bounding_rect());
+
        bool blend_using_straight = false; // use 'straight' just for the central blit
 
+       // sometimes the user changes the parameters while we're
+       // rendering, causing our pasted canvas' bounding box to shrink
+       // and no longer overlap with our tile.  if that has happened,
+       // let's just stop now - we'll be refreshing soon anyway
+       //! \todo shouldn't a mutex ensure this isn't needed?
+       // http://synfig.org/images/d/d2/Bbox-change.sifz is an example
+       // that shows this happening - open the encapsulation, select the
+       // 'shade', and toggle the 'invert' parameter quickly.
+       // Occasionally you'll see:
+       //   error: Context::accelerated_render(): Layer "shade" threw a bad_alloc exception!
+       // where the shade layer tries to allocate itself a canvas of
+       // negative proportions, due to changing bounding boxes.
+       if (!etl::intersect(desc.get_rect(), full_bounding_rect))
+       {
+               warning("%s:%d bounding box shrank while rendering?", __FILE__, __LINE__);
+               return true;
+       }
+
+       // we have rendered what's under us, if necessary
        if(context->empty())
        {
+               // if there's nothing under us, and we're blending 'onto', then we've finished
                if (Color::is_onto(blend_method)) return true;
-               if (blend_method==Color::BLEND_COMPOSITE) blend_method=Color::BLEND_STRAIGHT;
+
+               // there's nothing under us, so using straight blending is
+               // faster than and equivalent to using composite, but we don't
+               // want to blank the surrounding areas
+               if (blend_method==Color::BLEND_COMPOSITE) blend_using_straight = true;
        }
 
        if (!etl::intersect(context.get_full_bounding_rect(),full_bounding_rect+origin))
        {
+               // if there's no intersection between the context and our surface, and we're rendering 'onto', then we're done
                if (Color::is_onto(blend_method)) return true;
 
                /* 'straight' is faster than 'composite' and has the same