3ce280e825
Now the viewport rendering thread will lock the main thread while it is exporting objects to render data. This is not ideal if you have big scenes that might block the UI, but Cycles does the same, and it's fairly quick because the same evaluated mesh can be used as for viewport drawing. It's the only way to get things stable until the thread safe dependency graph is here. This adds a mechanism to the job system for jobs to lock the main thread, using a new 'ticket mutex lock' which is a mutex lock that gives priority to the first thread that tries to lock the mutex. Still to solve: undo/redo crashes.