Caret Movement Across Direction Boundaries

When a user presses the arrow keys to move the caret left or right across

characters on a line, TextEdit moves the caret uniformly in the direction of

the arrow. This sequence is unambiguous when a user moves the caret in the

middle of a style run. However, on direction boundaries, only the primary caret

moves uniformly in the direction of the arrows.

The next figure shows a sequence of two Right Arrow key presses and their

impact on caret display and movement in a mixed- directional line. If the

original caret position is 13 and the Right Arrow key is pressed, TextEdit

displays a dual caret at primary caret position 12 and secondary caret position

4, with the primary caret moving to the next position in the direction of the

arrow. If the Right Arrow key is pressed again, the new caret position is at

primary caret position 5.

Note: TextEdit currently deviates from this model for caret movement

in unstyled left-to-right text (displayed in a non-Roman font) on any

right-to-left script system. On the Arabic Script System, for example, it is

possible to display Roman characters from an Arabic font. If a user presses

the arrow keys to move through these characters, the caret moves in the

opposite direction of the arrow. Because of keyboard and font

synchronization, this situation is not common.

Caret movement across a direction boundary