Routines
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49257: Check Object Close To Player
Used by the routines at SpawnGhost, UpdateGhost, UpdateCreature, HitOutcome_Split, ColourInventoryItems, UpdateSpore, UpdateSpeedBonus, UpdateHealthBonus and SpawnBonus.
Checks whether the object at IX is within a given number of cells of the player, along both axes. The ghosts, creatures and bonuses use it to find out whether they are near enough to matter.
Input
IX Object
C Distance in cells
Output
F The carry flag is set if the object is closer than the distance
Compare the columns.
CheckPlayerClose 49257 LD A,(48272) Fetch the player's column from 48272.
49260 SUB (IX+2) Work out how many columns the object is from the player.
49263 JP P,CheckPlayerClose_Columns Jump to CheckPlayerClose_Columns if the difference is not negative.
49266 NEG Otherwise turn the distance round, so that it is positive.
CheckPlayerClose_Columns 49268 CP C Compare the distance in columns with the limit.
49269 RET NC Return with the carry flag clear if the object is too far away.
Compare the rows.
49270 LD A,(48274) Fetch the player's row from 48274.
49273 SUB (IX+4) Work out how many rows the object is from the player.
49276 JP P,CheckPlayerClose_Rows Jump to CheckPlayerClose_Rows if the difference is not negative.
49279 NEG Otherwise turn the distance round, so that it is positive.
CheckPlayerClose_Rows 49281 CP C Compare the distance in rows with the limit.
49282 RET Return with the carry flag set only if the object is close enough.
View the equivalent code in;
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