currently everytime that seleciton start, selection end, caret position, caret bias is changed the decoration shapes are re-done

for example,
textNode.setImpl_caretPosition(caretOffset);
textNode.setImpl_caretBias(true);
textNode.setImpl_selectionStart(anchorOffset);
textNode.setImpl_selectionEnd(anchorOffset);

causes the caret and selection shape to be redone 4 times each


these shapes should be only done when
getImpl_selectionShape() or getImpl_caretShape() are called.