move_cursor_visually

Description:

public void move_cursor_visually (bool strong, int old_index, int old_trailing, int direction, out int new_index, out int new_trailing)

Computes a new cursor position from an old position and a direction.

If direction is positive, then the new position will cause the strong or weak cursor to be displayed one position to right of where it was with the old cursor position. If direction is negative, it will be moved to the left.

In the presence of bidirectional text, the correspondence between logical and visual order will depend on the direction of the current run, and there may be jumps when the cursor is moved off of the end of a run.

Motion here is in cursor positions, not in characters, so a single call to this function may move the cursor over multiple characters when multiple characters combine to form a single grapheme.

Parameters:

this	a `PangoLayout`
strong	whether the moving cursor is the strong cursor or the weak cursor. The strong cursor is the cursor corresponding to text insertion in the base direction for the layout.
old_index	the byte index of the current cursor position
old_trailing	if 0, the cursor was at the leading edge of the grapheme indicated by `old_index`, if > 0, the cursor was at the trailing edge.
direction	direction to move cursor. A negative value indicates motion to the left
new_index	location to store the new cursor byte index. A value of -1 indicates that the cursor has been moved off the beginning of the layout. A value of g_maxint indicates that the cursor has been moved off the end of the layout.
new_trailing	number of characters to move forward from the location returned for `new_index` to get the position where the cursor should be displayed. This allows distinguishing the position at the beginning of one line from the position at the end of the preceding line. `new_index` is always on the line where the cursor should be displayed.