LSL Wiki Mirror 10-5-2006: llTakeControls

llTakeControls(integer controls, integer accept, integer pass_on)

The control functions allow an object to respond to user interface input that normally controls the avatar. For example, this allows creation of a scripted vehicle that moves in response to the keyboard commands that normally move the avatar. Also, an gun can be created that fires in response to mouse button activity.

The controls parameter is an integer bitfield which is used to specify which user-interface controls the script is interested in. Possible values are:

Constant	Value	Description
`CONTROL_FWD`	0x00000001	forward control (W or up arrow)
`CONTROL_BACK`	0x00000002	back control (S or down arrow)
`CONTROL_LEFT`	0x00000004	move left control (shift + A or left arrow)
`CONTROL_RIGHT`	0x00000008	move right control (shift + D or right arrow)
`CONTROL_UP`	0x00000010	up control (E or PgUp)
`CONTROL_DOWN`	0x00000020	down control (C or PgDn)
`CONTROL_ROT_LEFT`	0x00000100	rotate left control (A or left arrow)
`CONTROL_ROT_RIGHT`	0x00000200	rotate right control ( D or right arrow)
`CONTROL_LBUTTON`	0x10000000	left mouse button control
`CONTROL_ML_LBUTTON`	0x40000000	left mouse button control with the avatar in MouseLook See ^Note

To filter multiple button presses, combine these values using the | (bitwise OR) operator. (See below for an example.)

The accept and pass_on parameters take a TRUE or FALSE value and have different effects:

`accept`	`pass_on`	effect
0	0	only specified controls functional...no script events
0	1	no apparent effect (all controls functional)...no script events
1	0	other controls functional no events...specified controls non-functional but generate events
1	1	all controls normal...specified controls also generate events

An object must have permission to take controls. Call llGetPermissions to see if the object has the PERMISSION_TAKE_CONTROLS permission. If it does not, you must first call llRequestPermissions to request permissions from the user.

After this function has been called and depending on the other parameters, the scripts's control event handler will be invoked whenever a specified input is received. The code you place in the control event handler determines how your object behaves in response to captured user input.

Each call to this function replaces the settings for any previous call. Unfortunately, that means a script can't completely control some inputs and let others continue to function while getting events. Fortunately there's a small glitch that is extremely handy since we can't rotate an avatar with a script. See below for more info.

When done with the controls (for example, when an attachment is removed) it is a good idea to clean up with a call to llReleaseControls.

CONTROL_ML_LBUTTON will cause a "Mouselook" button to appear on the bottom of the SL window, but only if pass_on is set to FALSE.

llTakeControls(CONTROL_ML_LBUTTON, TRUE, FALSE); // this works.
llTakeControls(CONTROL_ML_LBUTTON, TRUE, TRUE); // this doesn't.

Note: There seems to be a bug when taking CONTROL_ML_LBUTTON where it does not produce a MouseLook button after re-attaching even though permitted. Solution:

llReleaseControls();
llRequestPermissions(llGetOwner(), PERMISSION_TAKE_CONTROLS);
llTakeControls(CONTROL_ML_LBUTTON,TRUE,FALSE);

Example (see ExampleControls for a functioning script):

run_time_permissions(integer perms)
    {
        integer desired_controls = 
                CONTROL_FWD |
                CONTROL_BACK |
                CONTROL_LEFT |
                CONTROL_RIGHT |
                CONTROL_ROT_LEFT |
                CONTROL_ROT_RIGHT |
                CONTROL_UP |
                CONTROL_DOWN |
                CONTROL_LBUTTON |
                CONTROL_ML_LBUTTON; 

        if (perms & PERMISSION_TAKE_CONTROLS) {
            llTakeControls(desired_controls, TRUE, FALSE);
        }
    }

Taking Complete Control

There is a handy glitch that can be used to work around a major shortcoming of the control() system. There are many reasons why you might want to grab all the user input and not allow the standard av motion to take effect. For example, creating a custom movement solution.

The problem is that avs can not be scripted to rotate so normally using this function to grab all the input controls with accept set to 1 and pass to 0 will prevent a user from turning their av in normal non-mouselook view. You can leave out the right and left rotations but then you won't get events for them.

The trick is to make two calls to this function with the correct parameters. Using the following example, you'll take complete control (no normal movement) of all input except for left and right rotation which will behave normally and also generate control() events:

run_time_permissions(integer perms) {
        if (perms & PERMISSION_TAKE_CONTROLS) {
            llTakeControls(1, 1, 0); // glitch the rotation
            llTakeControls(desired_controls, 1, 0);
        }
    }

Hopefully if a 'fix' is made that changes this, the fix will include the functionality we all want and need.

Functions | Agent/Avatar | Control