SPFUNC

Assign a callback to a sprite. A callback can be assigned using either a label or a user-defined function name. If a label is used, the callback works like `GOSUB`. If a function is used, it works like `CALL`. A callback cannot take any arguments or return any values. A sprite can only have one callback at a time. All sprite callbacks are called in batch by `CALL SPRITE`, in order of sprite ID. During a callback, `CALLIDX` returns the ID of the associated sprite. * Set ```sbsyntax SPFUNC spriteID%, callback$ ``` |* Input | Description | | `spriteID%` | ID of the target sprite. | | `callback$` | A string containing the name of the callback. Can be a label or a user-defined function.\ The name can also start with a slot number, e.g. `0:@FOO` or `1:BAR` to specify a label or function in a specific slot. | * Clear Remove the callback from the sprite. ```sbsyntax SPFUNC spriteID% ``` |* Input | Description | | `spriteID%` | ID of the target sprite. | * Examples ```sb4 'use a DEF as a callback SPFUNC 0,"CALLBACK" CALL SPRITE DEF CALLBACK 'prints the current sprite ID PRINT CALLIDX() END ``` ```sb4 'use a label as a callback SPFUNC 0,@CALLBACK CALL SPRITE END @CALLBACK 'prints the current sprite ID PRINT CALLIDX() RETURN ``` ```sb4 'clear a callback SPFUNC 0 CALL SPRITE 'nothing happens! ``` ```sb4 'CALLIDX example with multiple sprites FOR I=0 TO 9 SPSET I,0 SPFUNC I,"CALLBACK" NEXT I CALL SPRITE DEF CALLBACK 'prints the current sprite ID PRINT CALLIDX() END ```