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⌂ ∞ ▽ The Sentinel on the BBC Micro

Gameplay: AbortWhenVisible

       Name: AbortWhenVisible                                        [Show more]
       Type: Subroutine
   Category: Gameplay
    Summary: Abort applying the tactics for this gameplay loop if updating the
             object on-screen will corrupt a screen pan

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ApplyTactics (Part 2 of 8) calls AbortWhenVisible
             * ApplyTactics (Part 6 of 8) calls AbortWhenVisible
             * DrainObjectEnergy calls AbortWhenVisible




 Arguments:

   A                    The number of the object to check



.AbortWhenVisible

 JSR CheckObjVisibility \ Check whether object A is visible and could therefore
                        \ be seen on-screen by the player

 BCS cvis1              \ If the C flag is clear then the object is partially
                        \ on-screen and we are about to repeat a screen pan, so
                        \ the object must not be updated or it could corrupt the
                        \ landscape view, so in this case fall through into
                        \ FinishEnemyTactics to stop applying tactics for this
                        \ gameplay loop
                        \
                        \ Otherwise the C flag is set so we can safely update
                        \ the object without fear of corrupting a screen pan,
                        \ so we can jump to cvis1 to return from the subroutine
                        \ without aborting the tactics routine