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Routines |
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Builds the list of items to be drawn for the current frame, at DrawList. Each item is three bytes: a flag byte followed by the address of the record to draw. The flag is 01 for an entity (see Entities), 02 for one of the 0C extra records at ExtraRecords and 03 for one of the 14-byte records at Records. The list ends with a zero byte, and DrawListPointer holds the address of the next free item.
Every entity that is in use and not hidden is prepared with PrepareEntityItem. The matching extra record is then prepared as well, if it has been flagged as visible.
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Start with an empty list and with no table records, and go through the 0C entities and their extra records.
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| BuildDrawList | AC40 | LD HL,$AFFB | Make the next free item of the draw list the start of the list. | |
| AC43 | LD ($B06C),HL | |||
| AC46 | XOR A | Clear the count of table records that have been prepared. | ||
| AC47 | LD ($F500),A | |||
| AC4A | LD IX,$B540 | Point IX at Entities. | ||
| AC4E | LD IY,$B708 | Point IY at ExtraRecords. | ||
| AC52 | LD HL,$F501 | Point HL at the start of the table of records. | ||
| AC55 | LD B,$0C | Set a counter in B for the 0C entities. | ||
| BuildDrawList_Loop | AC57 | PUSH BC | Stash the counter on the stack. | |
| AC58 | LD A,(IX+$00) | Fetch the type of the entity. | ||
| AC5B | AND A | Test it. | ||
| AC5C | JR Z,BuildDrawList_Next | Jump to BuildDrawList_Next if the entity is not in use. | ||
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Add the entity to the draw list, unless it is hidden.
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| AC5E | BIT 7,(IX+$01) | Test bit 7 of field 01 of the entity, which is set if it is hidden. | ||
| AC62 | CALL Z,PrepareEntityItem | Add the entity to the draw list if it is not hidden. | ||
| AC65 | BIT 7,(IY+$09) | Jump to BuildDrawList_Next if the extra record is not in use. | ||
| AC69 | JR Z,BuildDrawList_Next | |||
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Build the temporary entity from the extra record, so that the extra record can be drawn in the same way as an entity.
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| AC6B | PUSH IX | Stash the entity and the table pointer on the stack. | ||
| AC6D | PUSH HL | Stash the table pointer on the stack. | ||
| AC6E | LD L,(IY+$00) | Copy the screen position of the extra record into the temporary entity. | ||
| AC71 | LD H,(IY+$01) | |||
| AC74 | LD ($B7B2),HL | |||
| AC77 | LD L,(IY+$02) | Copy the x coordinate of the extra record into the temporary entity. | ||
| AC7A | LD H,(IY+$03) | |||
| AC7D | LD ($B7A6),HL | |||
| AC80 | LD L,(IY+$04) | Copy the y coordinate of the extra record into the temporary entity. | ||
| AC83 | LD H,(IY+$05) | |||
| AC86 | LD ($B7A9),HL | |||
| AC89 | LD L,(IY+$06) | Copy the z coordinate of the extra record into the temporary entity. | ||
| AC8C | LD H,(IY+$07) | |||
| AC8F | LD ($B7AC),HL | |||
| AC92 | LD A,(IY+$0B) | Copy the width of the extra record into the temporary entity. | ||
| AC95 | AND $0F | |||
| AC97 | LD ($B7BA),A | |||
| AC9A | LD A,(IY+$0C) | Copy the height of the extra record into the temporary entity. | ||
| AC9D | AND $3F | |||
| AC9F | LD ($B7BB),A | |||
| ACA2 | LD IX,$B7A4 | Point IX at TemporaryEntity. | ||
| ACA6 | LD (IX+$00),$02 | Make it an entity of type 02. | ||
| ACAA | CALL ConvertEntityPosition | Find its address in the screen buffer. | ||
| ACAD | LD (IY+$08),L | Store the address in the extra record. | ||
| ACB0 | LD (IY+$09),H | |||
| ACB3 | POP HL | Restore the table pointer. | ||
| ACB4 | CALL PrepareEntityItem_Table | Add the temporary entity to the draw list. | ||
| ACB7 | POP IX | Restore the entity. | ||
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Move on to the next entity and the next extra record.
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| BuildDrawList_Next | ACB9 | LD DE,$0026 | Move IX on to the next entity. | |
| ACBC | ADD IX,DE | |||
| ACBE | LD E,$0D | Move IY on to the next extra record. | ||
| ACC0 | ADD IY,DE | |||
| ACC2 | POP BC | Restore the counter. | ||
| ACC3 | DJNZ BuildDrawList_Loop | Decrease the counter and loop back to BuildDrawList_Loop until all 0C entities have been done. | ||
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Add the records of the objects of the level that are in view to the draw list.
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| BuildDrawList_Records | ACC5 | LD HL,($B06C) | Fetch the next free item of the draw list. | |
| ACC8 | LD A,($BBF6) | Fetch the number of records. | ||
| ACCB | AND A | Test it. | ||
| ACCC | JR Z,BuildDrawList_End | Jump to BuildDrawList_End if there are none. | ||
| ACCE | LD IY,$BBF7 | Point IY at Records. | ||
| ACD2 | LD BC,$0014 | Set the length of a record, 14. | ||
| BuildDrawList_RecordLoop | ACD5 | BIT 7,(IY+$0A) | Jump to BuildDrawList_RecordNext if the record is not to be drawn. | |
| ACD9 | JR Z,BuildDrawList_RecordNext | |||
| ACDB | RES 7,(IY+$0A) | Reset the bit so that the record is only drawn once. | ||
| ACDF | LD (HL),$03 | Mark the item as a record. | ||
| ACE1 | PUSH IY | Copy the address of the record into DE. | ||
| ACE3 | POP DE | |||
| ACE4 | INC HL | Store the address of the record in the item. | ||
| ACE5 | LD (HL),E | |||
| ACE6 | INC HL | |||
| ACE7 | LD (HL),D | |||
| ACE8 | INC HL | Move on to the next item. | ||
| BuildDrawList_RecordNext | ACE9 | ADD IY,BC | Move IY on to the next record. | |
| ACEB | DEC A | Decrease the number of records by one. | ||
| ACEC | JR NZ,BuildDrawList_RecordLoop | Loop back to BuildDrawList_RecordLoop until all of the records have been done. | ||
| BuildDrawList_End | ACEE | LD (HL),$00 | Mark the end of the draw list. | |
| ACF0 | LD ($B06C),HL | Store the new end of the list. | ||
| ACF3 | RET | Return. | ||
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