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Routines |
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Used by the routine at BuildShapeTables.
Merges a description of a shape into the buffers, once for each of the three shifts, using the first of the two formats. The description starts with the number of rows and the number of bytes in a row; the rows follow. Each row is merged into the buffer, with the byte that is left over at the end of the row from the shifted bytes, and the buffer moves on 30 bytes after each shift.
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| BuildShiftedShapeA | F8E2 | CALL ReadShapeHeader_Rows | Call ReadShapeHeader_Rows. | |||||||
| BuildShiftedShapeA_Shift | F8E5 | PUSH HL | Stash HL on the stack. | |||||||
| BuildShiftedShapeA_Row | F8E6 | LD B,C | B=C. | |||||||
| F8E7 | INC B | Advance B. | ||||||||
| BuildShiftedShapeA_Merge | F8E8 | CALL MergeShiftedByte | Call MergeShiftedByte. | |||||||
| F8EB | INC HL | Advance HL. | ||||||||
| F8EC | DJNZ BuildShiftedShapeA_Merge | Decrease B and jump to BuildShiftedShapeA_Merge until none remain. | ||||||||
| F8EE | EXX | Switch to the alternate registers. | ||||||||
| F8EF | LD (HL),$00 | Store 00 at the address in HL. | ||||||||
| F8F1 | DEC HL | Step HL back. | ||||||||
| F8F2 | DEC HL | Step HL back. | ||||||||
| F8F3 | DEC HL | Step HL back. | ||||||||
| F8F4 | OR (HL) | Set the bits of A that are set in the byte at HL. | ||||||||
| F8F5 | LD (HL),A | Write A where HL points. | ||||||||
| F8F6 | INC HL | Advance HL. | ||||||||
| F8F7 | INC HL | Advance HL. | ||||||||
| F8F8 | INC HL | Advance HL. | ||||||||
| F8F9 | EXX | Switch to the alternate registers. | ||||||||
| F8FA | CALL FetchShiftedByte_Count | Call FetchShiftedByte_Count. | ||||||||
| F8FD | LD ($5C20),A | Update the segments still to draw. | ||||||||
| BuildShiftedShapeA_Next | F900 | INC B | Advance B. | |||||||
| BuildShiftedShapeA_Loop | F901 | CALL MergeNextShiftedByte | Call MergeNextShiftedByte. | |||||||
| F904 | CALL FetchShiftedByte_Byte | Call FetchShiftedByte_Byte. | ||||||||
| F907 | CALL MergeBackgroundByte_Merge | Call MergeBackgroundByte_Merge. | ||||||||
| F90A | DJNZ BuildShiftedShapeA_Loop | Decrease B and jump to BuildShiftedShapeA_Loop until none remain. | ||||||||
| F90C | INC D | Advance D. | ||||||||
| F90D | LD A,(DE) | Read DE. | ||||||||
| F90E | DEC D | Step D back. | ||||||||
| F90F | EXX | Switch to the alternate registers. | ||||||||
| F910 | DEC HL | Step HL back. | ||||||||
| F911 | XOR (HL) | Flip the bits of A that are set in the byte at HL. | ||||||||
| F912 | LD (HL),A | Write A where HL points. | ||||||||
| F913 | LD A,($5C20) | The segments still to draw. | ||||||||
| F916 | CALL MergeBackgroundByte_Store | Call MergeBackgroundByte_Store. | ||||||||
| F919 | LD A,($5C1C) | The number of rows. | ||||||||
| F91C | DEC A | Step A back. | ||||||||
| F91D | LD ($5C1C),A | One fewer row of the shifted shape. | ||||||||
| F920 | JR NZ,BuildShiftedShapeA_Row | Jump to BuildShiftedShapeA_Row if the zero flag is clear. | ||||||||
| F922 | CALL NextShift_Rows | Call NextShift_Rows. | ||||||||
| F925 | EXX | Switch to the alternate registers. | ||||||||
| F926 | LD DE,$0030 | DE=30. | ||||||||
| F929 | ADD HL,DE | HL gains DE. | ||||||||
| F92A | EXX | Switch to the alternate registers. | ||||||||
| F92B | POP HL | Bring HL back off the stack. | ||||||||
| F92C | JR NZ,BuildShiftedShapeA_Shift | Jump to BuildShiftedShapeA_Shift if the zero flag is clear. | ||||||||
| F92E | LD A,$5C | A=5C. | ||||||||
| F930 | LD ($EB34),A | Purpose not yet known. | ||||||||
| F933 | LD A,$40 | A=40. | ||||||||
| F935 | LD ($EC30),A | Purpose not yet known. | ||||||||
| F938 | RET | Return. | ||||||||
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