Dragging the if block produces weird results


Grabbing the `if` block from the toolbox results in a noticeable delay. If the mouse is held still for the delay, all is well. If the mouse is moved during the delay, then the offsets of various shadow and connectors are incorrect by an amount roughly proportional to the mouse movement, as in the screen shot.

It's as if there's some very excessive computation that gets run when the block is grabbed; and furthermore, that the current mouse position is sometimes grabbed before that computation, and sometimes after, resulting in incorrect offsets for some components.

`if` ブロックの toolbox ドラッグパスから始め、マウスを動かしている間の遅延を再現します。シャドウとコネクタのオフセットの挙動を追跡します。移動を伴うドラッグでこれらのオフセットが不正な状態のままにならなくなれば完了です。プロジェクトの既存のテストパスが回帰テストに対応している場合は、回帰テストも追加します。

索引モデルが issue の本文から書いたものです。