Strk and me had a discussion about display lists and jumping between frames.
We discovered that this problem does not just knock out invalidated bounds but is actually a very serious bug in Gnash.
-- The problem:
When looping back (for example, gotoAndPlay(_currentframe-1); ) Gnash resets the sprite's display list and reconstructs it by executing all frame tags again until the target frame.
This causes *everything* in the target frame to become new instances. Now, when looping back to a frame that still contains the same sprite instance this instance will be re-created, causing all ActionScript variables and other stateful information to be lost and actions in the first frame of that instance to be executed!
yes, it's not correct to reset display list when jump back. And this will cause some unnecessary re-creations. The previous implementation was using "reverse execution". eg. gotoAndPlay(N) (suppose N < current frame) will reverse execute frame tags from frame N to current frame. But the concept of "reverse execution" is also bogus and fails on some existing testcases.
With other words: jumping between frames leads to lots of problems.
more specifically, jumping back leads to lots of problems.
As a side effect set_invalidated() is called without need, but this is now a secondary problem.
Jumping to frame 0 is a special case because it has a dedicated _frame0_chars display list. However, this can't be a solution.
-- The solution we're discussing:
Generally we would need to get rid of the recreation mechanism. goto_frame() should be able to build the correct display list without browsing through all frames.
We need to improve the recreation mechanism when jump back, in other words, only re-create those need to be re-created. eg. characters removed at current frame but appears at target frame. We need to scan all frame tags from frame0 to target frame to find out which placement tags are responsible for handling(ADD, MOVE) this character.
This way goto_frame() can do a before/after comparison and destroy/create sprite instances as needed, including correct ActionScript execution and invalidated bounds calculation.
One way is to keep a DisplayList for *each* frame of a sprite. This most probably would eat lots of RAM.
This is a simple way, but costs too much memory. And the "DisplayList " might be changed at any time when executing action scripts. That means you need to maintain lots of DisplayLists for a single sprite. In sprite_instance::goto_frame() resetDisplayList() clears all static characters placed from frame1 to current frame when jump back. Instead of doing that, I think we should just clear static characters placed from target frame to current frame. This might solve some problems above. _______________________________________________ Gnash-dev mailing list [email protected] http://lists.gnu.org/mailman/listinfo/gnash-dev
