The FocusOnKeyAction subroutine - The Sentinel on the BBC Micro

       Name: FocusOnKeyAction                                        [Show more]
       Type: Subroutine
   Category: Keyboard
    Summary: Tell the game to start focusing effort on the action that has been
             initiated, such as a pan of the landscape, absorb, transfer etc.
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * CheckForKeyPresses calls FocusOnKeyAction
             * PerformHyperspace calls FocusOnKeyAction
             * ProcessActionKeys (Part 1 of 2) calls FocusOnKeyAction
             * ProcessGameplay calls FocusOnKeyAction
             * CheckForKeyPresses calls via focu1


 Other entry points:

   focu1                Store the current setting of focusOnKeyAction in the
                        previousFocus variable so we can detect (in the
                        ProcessGameplay routine) whether the player is still
                        holding down a pan key after we finish scrolling the
                        screen for the previous pan... and then return from the
                        subroutine


.FocusOnKeyAction

 LDA #%10000000         \ Set bit 7 of focusOnKeyAction to tell the game to
 STA focusOnKeyAction   \ focus effort on implementing the key action that has
                        \ just been initiated, such as a pan of the landscape
                        \ view, absorb, transfer and so on

 STA doNotDitherObject  \ Set bit 7 of doNotDitherObject to disable updating of
                        \ objects on-screen using a dithered effect, so we don't
                        \ dither any object changes onto the screen while we are
                        \ focusing on processing the action, which itself might
                        \ need to update the screen when it's done

.focu1

 LDA focusOnKeyAction   \ Set previousFocus = focusOnKeyAction so we can detect
 STA previousFocus      \ whether the value of focusOnKeyAction changes
                        \
                        \ This is used by the ProcessGameplay routine to detect
                        \ whether the player is still holding the same pan key
                        \ down after we finish scrolling the screen for the pan

 RTS                    \ Return from the subroutine

[X]

Variable doNotDitherObject in workspace Main variable workspace

Controls whether the DitherScreenBuffer routine can update an object on the screen using a dithered effect

[X]

Variable focusOnKeyAction in workspace Main variable workspace

A flag that determines whether the game should focus effort on implementing a key action, such as a pan of the landscape view

[X]

Variable previousFocus in workspace Main variable workspace

The previous setting of focusOnKeyAction, so we can detect (in the ProcessGameplay routine) whether the player is still holding down a pan key after we finish scrolling the screen for the previous pan

Keyboard: FocusOnKeyAction