Routines
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58186: Centre And Draw Message Row
Used by the routine at Paint_MessageBuffer.
Count characters in the current message row (until $ + or ]), centre that run within 32 columns, then draw it via Draw_MessageCharacter.
Input
HL Attribute-file address for the row
IX Pointer into the decoded message buffer
Count characters until a row or message end, then centre and draw the run.
Centre_AndDrawMessageRow 58186 PUSH HL Stash HL and IX on the stack.
58187 PUSH IX
58189 LD C,255 Start the character count at 255 (pre-increment).
Count characters until $ + or ] to measure the current message row.
Centre_AndDrawMessageRow_Count 58191 INC C Advance the character count.
58192 LD A,(IX+0) Fetch the next buffer byte through IX.
58195 CP 36 Is it $ + or ] (row/message end)?, then if $ stop counting at Centre_AndDrawMessageRow_Centre.
58197 JR Z,Centre_AndDrawMessageRow_Centre
58199 CP 43 Is it a new-row marker (+)? If so, stop counting at Centre_AndDrawMessageRow_Centre.
58201 JR Z,Centre_AndDrawMessageRow_Centre
58203 CP 93 Is it the message terminator (])? If so, stop counting at Centre_AndDrawMessageRow_Centre.
58205 JR Z,Centre_AndDrawMessageRow_Centre
58207 INC IX Advance IX to the next buffer byte.
58209 JR Centre_AndDrawMessageRow_Count Jump to Centre_AndDrawMessageRow_Count to keep counting.
Centre the counted run within 32 columns and draw it via Draw_MessageCharacter.
Centre_AndDrawMessageRow_Centre 58211 POP IX Restore IX from the stack.
58213 LD (56737),A Remember the terminator byte in 56737.
58216 LD A,32 Compute (32−length)/2 as a left-indent.
58218 SUB C Subtract the row width from 32 to get the left pad.
58219 SRL A Halve that pad so the row is centred.
58221 LD B,0 Clear B.
58223 LD C,A Keep the indent in BC.
58224 ADD HL,BC Add it to the row's attribute address.
58225 CALL Draw_MessageCharacter Call Draw_MessageCharacter to draw the centred row.
58228 POP HL Restore HL from the stack.
58229 RET Return.
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