After Shock: Routine at 9F28

9F28: Print Room Image

Used by the routine at Handler_Images.

Input
IX	Pointer to room image data

Print_RoomImage 9F28 PUSH IX Copy the room-image pointer from IX into HL.

9F2A POP HL

Step over the 0200 mask bytes and aim at the display file.

9F2B LD DE,$0200 The pixel data follows the mask.

9F2E ADD HL,DE

9F2F LD DE,$4000

Expand each mask byte. Each bit stands for one screen byte (08 pixels).

9F32 LD BC,$0200 0200 mask bytes cover the screen, eight screen bytes at a time.

PixelControl_Loop 9F35 PUSH BC Take the next mask byte.

9F36 LD B,$08

9F38 LD C,(IX+$00)

A set bit copies the next pixel byte onto the screen. When the bit is clear, DE still advances but nothing is written, so those 08 pixels stay blank.

PixelBit_Loop 9F3B SLA C Jump to Print_RoomImage_0 if the mask bit is clear (skip that screen byte).

9F3D JR NC,Print_RoomImage_0

9F3F LD A,(HL) Copy the next pixel byte onto the screen.

9F40 LD (DE),A

9F41 INC HL

Print_RoomImage_0 9F42 INC DE Move along the screen.

9F43 DJNZ PixelBit_Loop This mask byte's eight screen bytes are done.

9F45 INC IX

9F47 POP BC Restore the mask-byte counter from the stack and decrease it.

9F48 DEC BC

9F49 LD A,B Another mask byte remains.

9F4A OR C

9F4B JR NZ,PixelControl_Loop

The bytes that follow are the attribute stream.

9F4D PUSH HL Copy the attribute-stream pointer from HL into IX.

9F4E POP IX

Paint attributes from 5800 until the display ends at 5A00.

9F50 LD HL,$5800 Start at the attribute file.

Attribute_Loop 9F53 LD A,(IX+$00) The colour, and how many cells it covers (00 means 0100).

9F56 LD B,(IX+$01)

9F59 INC IX

9F5B INC IX

Print_RoomImage_1 9F5D LD (HL),A Paint that many cells (B=00 runs the DJNZ loop 0100 times).

9F5E INC HL

9F5F DJNZ Print_RoomImage_1

9F61 LD A,H Continue until the attribute file is full.

9F62 CP $5A

9F64 JR NZ,Attribute_Loop

The picture is on screen.

9F66 RET Return.

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