Cursor position and movement in Bidi Input.

Question

In the case of Bidi input, where both RTL and LTR types languages can be mixed together, what should be the cursor position? And what should be the movement of the cursor with Home and End buttons?

At first, I thought that the cursor should always be placed where the next character is going to be placed. I mean for next e the cursor should be like (assuming | as the cursor)-

peac|سلام

But in many places, it is like-

|peacسلام

One advantage in the later approach is, when the language mode will be RTL again, the cursor position will be same. While in the first approach, it has jump to the left-most.

And should the behaviors of Home and End key change with RTL and LTR? Or should it remain same?

Answer 1

I have always been of the opinion that there should be minimal jumping around in the text when moving the caret. It makes it so confusing to work with a mixture of RTL and LTR text.

This is the approach, even though it is not very standard, that I would take.

Start with the cursor at the beginning

|peacسلام

If you press the right arrow key, move the caret right.

p|eacسلام
pe|acسلام
pea|cسلام
peac|سلام
peacسلا|م
peacسل|ام
peacس|لام
peacسلام|

This makes it so that there is no jumping and the arrow keys behave sensibly. Even if I am reading from right to left, the left arrow should still move me left in the text and the right arrow should still move me right in the text. Selecting text should behave the same way.

If I add a new character, if I am in LTR mode it should append a character to the right of where the caret is and then move the caret right. If I am in RTL mode, it should append a character to the left of where the caret is and move the caret left.

If I press Enter, if the text on this line is aligned LTR, all the text to the right of the caret should be moved to the next line, and if it is aligned RTL, it the text left of the caret should be moved to the next line:

peacسلا|م
peacم //Enter is pressed
سلا

               pea|cسلام
Enter is pressed\\ cسلام
                    pea

If the line is in LTR mode, Home and End should go to the very left and to the very right of the line, respectively. In RTL mode, they should instead go to the very right and very left.