Routines
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59515: Colourise Preview Grid
Used by the routines at DemoEntryPoint, Game_Initialisation and 54943.
This routine is identical to Colourise_PreviewGrid in the main game code.
Colours in the green checkerboard attribute pattern. Note, it doesn't alter the top row at all - only the rows which will have content in them.
Colourise_PreviewGrid 59515 LD B,4 Set a counter in B for 4 rows.
59517 LD DE,22678 DE=22678 (attribute buffer location).
59520 LD HL,59633 HL=AttributeData_PreviewGrid.
PreviewGrid_RowCounter_Loop 59523 PUSH BC Stash the row counter on the stack.
59524 LD B,2 Set a counter in B for 2 character blocks per square.
PreviewGrid_BlockCounter_Loop 59526 PUSH BC Stash the block counter and the attribute reference pointer on the stack.
59527 PUSH HL
59528 LD BC,10 Copy 0010 bytes from HL to DE.
59531 LDIR
59533 LD HL,22 DE+=0022.
59536 ADD HL,DE
59537 EX DE,HL
59538 POP HL Restore the attribute reference pointer and the block counter from the stack.
59539 POP BC
59540 DJNZ PreviewGrid_BlockCounter_Loop Decrease block counter by one and loop back to PreviewGrid_BlockCounter_Loop until the block counter is zero.
59542 POP BC Restore the row counter from the stack.
This is how it becomes checkered, we move the pointer forward by two (each block is two character blocks wide) and then it can alternate between the two attribute values. Although we copy 10 bytes - the data is actually 16 bytes long, to cope with this reference movement.
59543 INC HL Increment the attribute reference pointer by two.
59544 INC HL
59545 DJNZ PreviewGrid_RowCounter_Loop Decrease the row counter by one and loop back to PreviewGrid_RowCounter_Loop until all the rows have been coloured in.
59547 RET Return.
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