From: dooglus <dooglus@1f10aa63-cdf2-0310-b900-c93c546f37ac>
Date: Mon, 4 Feb 2008 18:41:06 +0000 (+0000)
Subject: Added some comments.  Fixed a crash when composite-blending a pastecanvas onto an... 
X-Git-Url: https://git.pterodactylus.net/?a=commitdiff_plain;h=5335d36efe2ec34b99cf1d6fa65c0c4c2a5d199b;p=synfig.git

Added some comments.  Fixed a crash when composite-blending a pastecanvas onto an empty canvas.


git-svn-id: http://svn.voria.com/code@1579 1f10aa63-cdf2-0310-b900-c93c546f37ac
---

diff --git a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
index edc3d0b..e632f26 100644
--- a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
+++ b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
@@ -343,14 +343,21 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
 	const Rect full_bounding_rect(canvas->get_context().get_full_bounding_rect());
 	bool blend_using_straight = false; // use 'straight' just for the central blit
 
+	// 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