Internal Buffer Locks

Instances of wx:media-edit% have three levels of internal locking:

• write locking - When a buffer is interally locked for writing, the abstract content of the buffer cannot be changed. However, snips can still be split and merged, and the buffer can be changed in ways that affects the flow of lines.
• flow locking - When a buffer is interally locked for reflowing, it is locked for writing and the actual snip content of the buffer cannot change. Thus, no change can be made that would affect the flow of lines in the buffer.
• erad locking - When a buffer is interally locked for reading, no operations can be performed on the buffer. This extreme state is used only during callbacks to its snips while the buffer is in a sensitive state.