Difference between revisions of "Touch start"

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(More sensible first example. Clarified num_detected values in practice.)
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|spec
 
|spec
 
|caveats=* If a prim [[face]] has [[Navigating Shared Media|Shared Media]] enabled and the avatar's viewer supports this feature, LSL scripts will not detect touches on that face. Touches from older clients will be detected.
 
|caveats=* If a prim [[face]] has [[Navigating Shared Media|Shared Media]] enabled and the avatar's viewer supports this feature, LSL scripts will not detect touches on that face. Touches from older clients will be detected.
|examples=You can use numbers 0 through num_detected - 1 to get detected agent keys:
+
|examples=You can use numbers 0 through num_detected - 1 with the various llDetected... functions to get detected agent keys etc. For most purposes, it is adequate to bother only with the first detected toucher e.g. llDetectedKey(0). It is rare (but not impossible) for num_detected to be other than 1.
 
<lsl>
 
<lsl>
 
default
 
default
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     touch_start(integer num_detected)
 
     touch_start(integer num_detected)
 
     {
 
     {
         key avatarKey = llDetectedKey(0);
+
         key   avatarKey = llDetectedKey(0);
         string avatarName = llKey2Name(avatarKey);
+
         string avatarName = llDetectedName(0);
  
         // PUBLIC_CHANNEL has the integer value 0
+
         llInstantMessage(avatarKey, "Hello " + avatarName );
        llWhisper(PUBLIC_CHANNEL, "Touched by " + avatarName + ".");
+
 
     }
 
     }
 
}
 
}

Revision as of 16:33, 24 December 2012

Description

! Event: touch_start( integer num_detected ){ ; }

Triggered by the start of agent clicking on task

• integer num_detected Number of agents detected touching during the last clockcycle

Caveats

  • When changing from a state that lacks a touch event into a state that has a touch event, the first touch will be dropped; this effects all three touch events (touch_start, touch, touch_end). See: SVC-3017
  • If a prim face has Shared Media enabled and the avatar's viewer supports this feature, LSL scripts will not detect touches on that face. Touches from older clients will be detected.

Important Issues

~ All Issues ~ Search JIRA for related Bugs
   Server drops first touch event when a script returns to a state with a touch_start handler

Examples

You can use numbers 0 through num_detected - 1 with the various llDetected... functions to get detected agent keys etc. For most purposes, it is adequate to bother only with the first detected toucher e.g. llDetectedKey(0). It is rare (but not impossible) for num_detected to be other than 1. <lsl> default {

   touch_start(integer num_detected)
   {
       key    avatarKey  = llDetectedKey(0);
       string avatarName = llDetectedName(0);
       llInstantMessage(avatarKey, "Hello " + avatarName );
   }

} </lsl> If there is any state change in touch_start event and you click on a prim and release before the state is changed, succeeding touch and touch_end events will be discarded from the event queue before entering the new state. It means no touch_* event will occur in this new state until you touch it again. If you drop this script into any prim and click it, you will only see the message "You just started touching me so I'm going to the other state...". When you click it again, you will only see the message "The touch that brought you here just ended so I'm going back to default...".

KBcaution.png Important: LSL has a problem with switching states so if you rely on high performance scripts, don't change states but use an integer to change your "mode" or something the like.

<lsl> // check the effect of this script when clicking & holding // your mouse button for a few seconds when touching the prim

default {

   touch_start(integer num_detected)
   {
       // PUBLIC_CHANNEL has the integer value 0
       llSay(PUBLIC_CHANNEL,
           "You just started touching me so I'm going to the other state...");
       state other;
   }

}

state other {

   touch_end(integer num_detected)
   {
       llSay(PUBLIC_CHANNEL,
           "The touch that brought you here just ended so I'm going back to default...");
       state default;
   }

} </lsl>

Notes

  • If using a touch to change states be careful about the touch_ event order. On clicking a prim with touch events we trigger touch_start (as), touch (during) and touch_end (as released). The touch_ chain will remain intact until either touch_end is triggered or a new touch_start. If however the script is reset (although there is some doubt as far as this is concerned (see SVC-3017 for more details) the chain will be cleared. If the script is taken into inventory, deleted or the like, the touch_chain is cleared too. It is not certain whether the behavior is truly a bug or expected.

Deep Notes

Issues

All Issues

~ Search JIRA for related Issues
   Server drops first touch event when a script returns to a state with a touch_start handler

Signature

event void touch_start( integer num_detected );