Routines
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47964: Clear Play Area
Used by the routines at GameComplete, ShowAmulet, HandlerPoems, GameOver_1UP_Messaging, EnterRoomBelow, InitialiseGame, SwitchPlayer and HandlerGameMenu.
Clears the top third of the screen, but only from below the banner. The banner is left untouched.
Before After
clear-before clear-after
ClearPlayArea 47964 LD HL,16448 HL=16448(screen buffer).
Here D contains the value to be written (0) and E holds the number of rows of pixels to act on (the full height of a character block).
47967 LD DE,8 DE=0008.
B holds the number of columns (i.e. 32 == full width of the screen), and C is a counter for how many rows to clear (i.e. the top third would usually be 8 rows, but the banner takes up two - hence this initialises to 6).
47970 LD BC,8198 BC=8198.
ClearPlayArea_ClearLine 47973 PUSH BC Stash BC and HL on the stack.
47974 PUSH HL
ClearPlayArea_ClearLine_Start 47975 PUSH BC Stash BC on the stack.
ClearPlayArea_ClearLine_Loop 47976 LD (HL),D Write 0 (D) to the screen (HL).
47977 INC L Move "right" onto the next column.
47978 DJNZ ClearPlayArea_ClearLine_Loop Decrease the width counter by one and loop back to ClearPlayArea_ClearLine_Loop until counter is zero.
Resets the width counter ready for the next loop.
47980 POP BC Restore BC from the stack.
47981 DEC C Decrease the number of rows counter by one.
47982 JR NZ,ClearPlayArea_ClearLine_Start Jump back to ClearPlayArea_ClearLine_Start unless C is zero.
Resets the screen buffer to where the clearing started for this loop, then moves down one character block.
47984 POP HL Restore HL from the stack.
47985 INC H Increments H by one.
47986 POP BC Restore BC from the stack.
47987 DEC E Decrease the pixel row counter by one.
47988 JR NZ,ClearPlayArea_ClearLine Jump back to ClearPlayArea_ClearLine unless E is zero.
Clears the other two thirds of the screen, so now the screen only contains the banner.
47990 LD HL,18432 HL=18432(screen buffer).
47993 JP ResetScreen_FromAddress Jump to ResetScreen_FromAddress.
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