Mouse Selection

The user makes a primary selection with SELECT (the left mouse button). Pressing SELECT deselects any existing selection and moves the insertion cursor and the anchor to the position in the text where the button is pressed. Dragging SELECT selects all text between the anchor and the pointer position, deselecting any text outside the range.

The text selected is influenced by the resource XmNeditPolicy, which can be set to XmEDIT_LOGICAL or XmEDIT_VISUAL. If the XmNeditPolicy is set to XmEDIT_LOGICAL, and if the text selected is bi-directional, the selected text is not be contiguous visually and is a collection of segments. This is because the text in the logical buffer does not have a one-to-one correspondence with the display.

As a result, the contiguous buffer of logical characters of bi-directional text when rendered does not result in a continuous stream of characters. Conversely, when the XmNeditPolicy is set to XmEDIT_VISUAL, the text selected may be contiguous visually but is segmented in the logical buffer. So the sequence of selection, deletion, and insertion of bi-directional text at the same cursor point does not result in the same string.