Function: plock

Syntax

plock ({<num>})

Type

point

Returns

The 3-D point on a graphic primitive closest to the mouse position. The user may indicate a graphic primitive within any active graphic window.

The rules for how the system decides on a successful hit are as follows:

1) Only graphic primitives which are members of the window’s pick_group are examined. On window creation, a window’s pick_group is the all group.

2) Only graphic primitives which satisfy the selection criteria in window’s pick_filter are examined. On window creation, a window’s pick_filter is undefined implying no filter.

3) Only graphic primitives which are within the window’s pick_tolerance of the mouse position are examined. A window’s pick_tolerance is measured in pixels with a value of 10 on window creation.

Parameters

• <num>
  A tolerance to be used in preference to the window’s pick_tolerance. This tolerance is in screen pixels.

When a hit is successful, the system numeric found is set to one and the system epointer this is set to point to the graphic primitive which was "hit". On failure, found is set to zero, and this is set to null.

Confirmation of the selected point is given on the monitor. This message is a level 6 message and can be suppressed by using a lower value of err_level, e.g.

err_level = 5

See Also