Routines
Prev: 47012 Up: Map Next: 47325
47054: Update Extra Record
Used by the routine at UpdateExtraRecords.
Builds the extra record for an entity, and fills the temporary entity at TemporaryEntity so that SetEntitySize can measure its sprite. Field 31 chooses the size class: below 23 is class 0, below 37 is class 1, and any higher value is class 2. A size index of zero or 255 leaves the record unset.
Bit 6 of the flags in field 30 selects the higher frame. The frame written for the temporary entity is the class when the bit is clear, and the class plus three when it is set. The same bit is copied into bit 7 of byte 12 of the extra record. Purpose of the flag beyond that choice is not yet known. The instructions at UpdateExtraRecord_Unused would step the shape bits of the height and then start a burst, but they are not reached: the class is only 0, 1 or 2, so the jump at UpdateExtraRecord_HigherFrame is always taken. The saved zero flag then makes the height adjustment subtract field 31 rather than add the z extent.
The adjusted x coordinate is the entity's x plus half of field 11 its x extent, and the adjusted y coordinate is the entity's y plus half of field 12 its y extent. Both are reduced by a margin taken from the class. The z coordinate is the entity's z less field 31 or 256 when that would leave the high byte zero. Bytes 2 and 3 of the extra record receive the adjusted x, bytes 4 and 5 the adjusted y, and bytes 6 and 7 the adjusted z. Byte 11 holds the width in bits 0-3 and the frame in bits 4-7. Byte 12 holds the height in bits 0-5.
Input
IX The entity
IY The extra record
Output
A Zero if the record was set up, otherwise non-zero
Leave the record unset when the size index is zero or 255.
UpdateExtraRecord 47054 LD A,(IX+31) Fetch the size index.
47057 AND A Jump to UpdateExtraRecord_Start if the size index is not zero.
47058 JR NZ,UpdateExtraRecord_Start
UpdateExtraRecord_Return 47060 OR %00000001 Report that the record was not set up.
47062 RET Return.
UpdateExtraRecord_Start 47063 INC A Advance the size index.
47064 JR Z,UpdateExtraRecord_Return Leave the record unset if the size index was 255.
47066 LD D,0 Take class 0.
47068 CP 24 Use class 0 when the size index is below 23.
47070 JR C,UpdateExtraRecord_Class
47072 INC D Take the next class.
47073 CP 38 Use class 1 when the size index is below 37.
47075 JR C,UpdateExtraRecord_Class
47077 INC D Take class 2.
Remember a clear zero flag, so the height adjustment later subtracts the size index. Then choose the higher frame when bit 6 of the flags is set.
UpdateExtraRecord_Class 47078 XOR A Clear the alternate flags.
47079 EX AF,AF' Save the alternate flags.
47080 LD A,D Take the class as the frame.
47081 BIT 6,(IX+30) Jump to UpdateExtraRecord_Position to keep this frame if bit 6 is clear.
47085 JR Z,UpdateExtraRecord_Position
47087 LD A,(IX+31) Fetch the size index again.
47090 CP 5 Compare the size index with 5. The result is not used.
47092 LD A,D Take the class again.
47093 INC A Advance to the higher frame.
UpdateExtraRecord_HigherFrame 47094 JR NC,UpdateExtraRecord_Size Use the higher frame. This jump is always taken.
These instructions are not reached. They would cycle bits 6-7 of the height, play the medium buzz the first time, and start a burst when the cycle wraps, clearing bit 6 of the flags.
UpdateExtraRecord_Unused 47096 EX AF,AF' Restore the alternate flags.
47097 LD A,(IX+23) Fetch the height byte.
47100 AND %11000000 Keep the shape bits of the height.
47102 JR NZ,UpdateExtraRecord_Frame Step the shape if it has already started.
47104 SET 6,(IX+23) Set the first shape bit of the height.
47108 CALL PlayMediumBuzz Play the medium buzz.
47111 JR UpdateExtraRecord_Shape Join the shape calculation.
UpdateExtraRecord_Frame 47113 LD A,(41693) Fetch the frame counter.
47116 AND %00000011 Act on every fourth frame.
47118 JR NZ,UpdateExtraRecord_Shape Leave the shape as it is on the other frames.
47120 LD A,(IX+23) Fetch the height byte.
47123 ADD A,64 Step the shape bits.
47125 JR NC,UpdateExtraRecord_Store Store the new shape if it has not wrapped.
47127 CALL StartBurst Start a burst.
47130 RES 6,(IX+30) Clear bit 6 of the flags.
47134 RES 7,(IX+23) Clear the upper shape bit of the height.
47138 RES 6,(IX+23) Clear the lower shape bit of the height.
47142 JR UpdateExtraRecord_Return Leave the record unset.
UpdateExtraRecord_Store 47144 LD (IX+23),A Store the stepped height byte.
UpdateExtraRecord_Shape 47147 LD A,(IX+23) Fetch the height byte.
47150 RLCA Move the shape bits down.
47151 RLCA
47152 NEG Make the shape number negative.
47154 AND %00000011 Keep the two shape bits.
UpdateExtraRecord_Size 47156 ADD A,2 Move up by two frames from the shape, or from the higher frame.
47158 LD D,2 Use a fixed margin for the higher frame.
Write the frame, then the x extent of the temporary entity, which is four times the complement of the class margin.
UpdateExtraRecord_Position 47160 LD (47013),A Store the frame in the temporary entity.
47163 LD A,D Take the class, or the fixed margin of the higher frame.
47164 ADD A,252 Subtract four.
47166 CPL Complement the margin.
47167 ADD A,A Double the margin.
47168 LD D,A Keep the doubled margin.
47169 ADD A,A Double it again.
47170 LD (47023),A Store the x extent of the temporary entity.
Move the x coordinate by half of the x extent, less the margin.
47173 LD H,(IX+2) Fetch the high byte of the x coordinate.
47176 LD L,(IX+3) Fetch the low byte of the x coordinate.
47179 LD A,(IX+11) Fetch the x extent.
47182 SRL A Halve the x extent.
47184 DEC A Reduce it by one.
47185 SUB D Subtract the margin.
47186 LD C,A Keep the adjustment.
47187 LD B,0 Take a positive adjustment.
47189 JR NC,UpdateExtraRecord_AddX Keep the positive adjustment.
47191 LD B,255 Take a negative adjustment.
UpdateExtraRecord_AddX 47193 ADD HL,BC Add the adjustment to the x coordinate.
47194 LD A,L Swap the bytes of the x coordinate.
47195 LD L,H
47196 LD H,A
47197 LD (47014),HL Store the adjusted x coordinate in the temporary entity.
47200 LD (IY+2),L Store the high byte of the adjusted x coordinate in the extra record.
47203 LD (IY+3),H Store the low byte of the adjusted x coordinate in the extra record.
Move the y coordinate by half of the y extent, less the same margin.
47206 LD H,(IX+5) Fetch the high byte of the y coordinate.
47209 LD L,(IX+6) Fetch the low byte of the y coordinate.
47212 LD A,(IX+12) Fetch the y extent.
47215 SRL A Halve the y extent.
47217 DEC A Reduce it by one.
47218 SUB D Subtract the margin.
47219 LD B,0 Take a positive adjustment.
47221 JR NC,UpdateExtraRecord_AddY Keep the positive adjustment.
47223 LD B,255 Take a negative adjustment.
UpdateExtraRecord_AddY 47225 ADD HL,BC Add the adjustment to the y coordinate.
47226 LD A,L Swap the bytes of the y coordinate.
47227 LD L,H
47228 LD H,A
47229 LD (47017),HL Store the adjusted y coordinate in the temporary entity.
47232 LD (IY+4),L Store the high byte of the adjusted y coordinate in the extra record.
47235 LD (IY+5),H Store the low byte of the adjusted y coordinate in the extra record.
Lower the z coordinate by the size index. The saved zero flag makes this the path that is taken. The other path would add the z extent.
47238 LD H,(IX+8) Fetch the top byte of the z coordinate.
47241 LD L,(IX+9) Fetch the middle byte of the z coordinate.
47244 LD D,0 Clear the high byte of the subtraction.
47246 EX AF,AF' Restore the saved zero flag.
47247 JR Z,UpdateExtraRecord_Height Subtract the size index. This jump is always taken.
47249 LD E,(IX+13) Fetch the z extent.
47252 ADD HL,DE Add the z extent. This path is not taken.
47253 JR UpdateExtraRecord_Finish Join the stored height.
UpdateExtraRecord_Height 47255 LD E,(IX+31) Fetch the size index.
47258 XOR A Clear the carry.
47259 SBC HL,DE Subtract the size index from the z coordinate.
47261 OR H Test the high byte of the result.
47262 JR NZ,UpdateExtraRecord_Finish Keep the result when the high byte is not zero.
47264 LD HL,256 Use a height of 256 when the result is zero.
UpdateExtraRecord_Finish 47267 LD (IY+6),H Store the high byte of the adjusted z coordinate in the extra record.
47270 LD (IY+7),L Store the low byte of the adjusted z coordinate in the extra record.
47273 LD A,L Swap the bytes of the z coordinate.
47274 LD L,H
47275 LD H,A
47276 LD (47020),HL Store the adjusted z coordinate in the temporary entity.
47279 LD IX,47012 Use the temporary entity.
47283 LD (IX+23),0 Clear the height byte of the temporary entity.
47287 CALL SetEntitySize Measure the sprite.
47290 LD A,(IX+1) Fetch the frame of the temporary entity.
47293 ADD A,A Move the frame into the high nibble.
47294 ADD A,A
47295 ADD A,A
47296 ADD A,A
47297 LD B,A
47298 LD A,(IX+22) Fetch the width of the temporary entity.
47301 AND %00001111 Keep the width.
47303 OR B Combine the frame with the width.
47304 LD (IY+11),A Store the frame and the width in the extra record.
47307 LD A,(IX+23) Fetch the height of the temporary entity.
47310 AND %00111111 Keep the height.
47312 LD B,A Keep the height aside.
47313 LD A,(IX+30) Fetch the flags.
47316 ADD A,A Move bit 6 of the flags up to bit 7.
47317 AND %10000000 Keep that bit.
47319 OR B Combine it with the height.
47320 LD (IY+12),A Store the height in the extra record.
47323 XOR A Report that the record was set up.
47324 RET Return.
Prev: 47012 Up: Map Next: 47325