February 23, 2007
Using the Linden Scripting LanguageControls and Displays
You probably don't want to interact with an object via text and clicks alone. Flying a jet across a sim will be tough if you have to type "up" over and over again. Likewise, no one wants to watch your slide show if it is just text describing the pictures you put inside.
Taking Control
A scripted object can take over the normal movement controls from an avatar. This makes it easy to create guns that shoot when you click the mouse, or a car that drives when you use the arrow keys.
A script needs to request permission to take over the controls from the avatar. In the special case of attachments and vehicles, permission is granted automatically, but the script still needs to make the request. The following example is a portion of a very basic gun script:
default
{
// If we attach the gun, request permissions; if we detach, release
control.
attach(key attachedAgent)
{
if (attachedAgent != NULL_KEY)
{
llRequestPermissions(llGetOwner(), PERMISSION_TAKE_CONTROLS);
}
else
{
llReleaseControls();
}
}
// When permission is granted, the run_time_permissions event is triggered
// Use this as a cue to take controls.
run_time_permissions(integer permissions)
{
if (permissions == PERMISSION_TAKE_CONTROLS)
{
//We want to take the left mouse button in mouselook.
llTakeControls(CONTROL_ML_LBUTTON, TRUE, FALSE);
}
}
control(key name, integer levels, integer edges)
{
// After taking controls, if those controls are used, take the
appropriate action.
if ( ((edges & CONTROL_ML_LBUTTON) == CONTROL_ML_LBUTTON)
&&((levels & CONTROL_ML_LBUTTON) == CONTROL_ML_LBUTTON) )
{
// If left mouse button is pressed, fire
fire();
}
}
}
Display
Scripts can also control the appearance of an object. Probably the most used example of this is changing textures for things like slide shows. To change a texture, it is easiest to use a texture in the object's inventory. If you have a bunch of great snapshots, you can drop them into a box with the following script to watch them display:
integer i;
default
{
state_entry()
{
// Change image every 10 seconds
llSetTimerEvent(10.0);
}
timer()
{
if(i |
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