CATransaction

Overview

  • CATransactionis unique in thread.
  • Implicit transaction is only uesd when there is no active transaction while change the layer tree.
  • CATransactioncapture layer tree changes just by mark the root layer.

Topics

  • +[CATransaction begin] just add 1 in specific var.
  • Change layer tree.
  • +[CATransaction commit] sub 1 in specific var. if var is 0, then commit actally. Ensure nested transaction are commited completely.

Tips

Change the layer follows 3 step.

  1. CA::Layer::begin_change(CA::Transaction*,unsigned int,objc_object*&)

    • call CA::Transaction::ensure_implicit() make sure that add an implicit transaction if there is no active transaction.
    • call -[CALayer actionForkKey:],find the CAAnimation correspond with the property. Store it to objc_object*&.

  2. Change property.

  3. CA::Layer::end_change(CA::Transaction,unsigned int,,objc_object\&),

    • call CA::Transaction::add_root() mark the root layer of the updated layer tree

    • call CA::Layer::add_animation() set CATransaction values to the animation(like duration,timingFunction.just guess.)

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