The story about line wrapping is mainly that, you:
· Break the text into runs.
· Calculate BiDi at paragraph level.
· Shape every run to get its length and possible line breaking points.
· Arrange the runs (now only have length, height, text isnide it and some breaking properties — glyphs and glyph positions are dropped) into lines.
Such process is called “measuring”. And the real text display is delayed until a line become visible: you fetch out the text runs in the line and do the real display.
In most times (like appending text) you do not to do much recalculation.
In most times (like appending text) you do not to do much recalculation.