Routines
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E3C7: Plot Message Glyph Half
Used by the routine at Draw_MessageCharacter.
Write one 0008-byte half-glyph from the message font into the screen bitmap under attribute address HL. Applies the roll/shift mode in DD9F and the inverse shift count in DDA0.
Input
HL Attribute-file address for this character
DE Glyph half-index (×0008 into Pointer_CurrentCharacterSet)
Paint the attribute and resolve the screen and font addresses.
Plot_MessageGlyphHalf E3C7 PUSH DE Stash DE, HL and BC on the stack.
E3C8 PUSH HL
E3C9 PUSH BC
E3CA LD A,($7307) Fetch the current text attribute (CurrentTextAttribute).
E3CD OR %01000000 Force bright (OR 40).
E3CF LD (HL),A Write it at HL.
E3D0 LD A,H Multiply the attribute high byte by 08.
E3D1 ADD A,A
E3D2 ADD A,A
E3D3 ADD A,A
E3D4 AND %01011011 Keep only the screen-bitmap high bits (mask 5B).
E3D6 LD H,A Write the result back to H.
E3D7 PUSH HL Stash HL on the stack.
E3D8 EX DE,HL Swap so HL holds the glyph index, multiply it by 08, and add the character-set base at Pointer_CurrentCharacterSet.
E3D9 ADD HL,HL
E3DA ADD HL,HL
E3DB ADD HL,HL
E3DC LD DE,($72F9)
E3E0 ADD HL,DE
E3E1 POP DE Restore DE from the stack.
Nudge the font pointer for roll modes 02 / 03.
E3E2 LD A,($DD9F) Fetch the roll mode (DD9F). Is it mode 02? If not, try mode 03 at Plot_MessageGlyphHalf_CheckMode3.
E3E5 CP $02
E3E7 JR NZ,Plot_MessageGlyphHalf_CheckMode3
E3E9 INC HL Advance the font pointer by one (roll left source).
E3EA JR Plot_MessageGlyphHalf_Rows Jump to Plot_MessageGlyphHalf_Rows to plot.
For roll mode 03, step the font pointer back one before plotting the half-glyph.
Plot_MessageGlyphHalf_CheckMode3 E3EC CP $03 Is it mode 03? If not, plot as-is at Plot_MessageGlyphHalf_Rows. Otherwise step the font pointer back by one (roll right source).
E3EE JR NZ,Plot_MessageGlyphHalf_Rows
E3F0 DEC HL
Plot all 08 pixel rows of this half-glyph into the screen bitmap.
Plot_MessageGlyphHalf_Rows E3F1 LD B,$08 There are 08 pixel rows in a character.
Build or roll one glyph row using the inverse shift in DDA0 and the mode in DD9F.
Plot_MessageGlyphHalf_RowLoop E3F3 PUSH BC Stash BC on the stack.
E3F4 LD A,($DDA0) Fetch the inverse shift count (DDA0). Is it zero (no thicken/shift)? If so, take the plain bitmap byte at Plot_MessageGlyphHalf_ShiftBuild.
E3F7 OR A
E3F8 JR NZ,Plot_MessageGlyphHalf_ShiftBuild
E3FA LD A,(HL) Fetch the plain glyph row into A.
E3FB JR Plot_MessageGlyphHalf_Roll Jump to Plot_MessageGlyphHalf_Roll to apply left/right roll.
Thicken the glyph row by OR-shifting left and right by the count in DDA0.
Plot_MessageGlyphHalf_ShiftBuild E3FD LD B,A Keep the shift count in B.
E3FE PUSH HL Stash HL on the stack.
E3FF LD A,(HL) Fetch the glyph row. Copy it into L. Mirror it into H for right-shift thickening.
E400 LD L,A
E401 LD H,A
OR left- and right-shifted copies into the thickened glyph bitmap.
Plot_MessageGlyphHalf_ShiftLoop E402 SLA L Shift left into L and OR.
E404 OR L OR in the left-shifted copy.
E405 DEC B Decrease the shift count.
E406 JR Z,Plot_MessageGlyphHalf_ShiftDone If done, finish at Plot_MessageGlyphHalf_ShiftDone.
E408 SRL H Also shift right into H and OR (thicken both ways).
E40A OR H OR in the right-shifted copy.
E40B DJNZ Plot_MessageGlyphHalf_ShiftLoop Loop at Plot_MessageGlyphHalf_ShiftLoop.
Finish the thicken pass and continue into the roll/write path.
Plot_MessageGlyphHalf_ShiftDone E40D POP HL Restore HL from the stack.
Apply roll mode 00 (left) or 01 (right) before writing the glyph row.
Plot_MessageGlyphHalf_Roll E40E LD C,A Keep the built bitmap in C.
E40F LD A,($DD9F) Fetch the roll mode (DD9F). Is it mode 00? If not, try mode 01 at Plot_MessageGlyphHalf_RollRight.
E412 OR A
E413 JR NZ,Plot_MessageGlyphHalf_RollRight
E415 SLA C Shift the bitmap left one (roll mode 00).
E417 JR Plot_MessageGlyphHalf_WriteRow Jump to Plot_MessageGlyphHalf_WriteRow to store.
Roll the glyph bitmap one bit right for mode 01.
Plot_MessageGlyphHalf_RollRight E419 CP $01 Is it mode 01? If not, store as-is at Plot_MessageGlyphHalf_WriteRow. Shift the bitmap right one.
E41B JR NZ,Plot_MessageGlyphHalf_WriteRow
E41D SRL C
Write the finished glyph row to the screen and advance to the next pixel row.
Plot_MessageGlyphHalf_WriteRow E41F LD A,C Write the bitmap row to the screen.
E420 LD (DE),A Write the thickened glyph row to the screen.
E421 INC D Move one pixel-row down.
E422 INC HL Advance the font pointer.
E423 POP BC Restore BC from the stack.
E424 DJNZ Plot_MessageGlyphHalf_RowLoop Loop until all 08 rows are plotted.
E426 POP BC Restore BC, HL and DE from the stack.
E427 POP HL
E428 POP DE
E429 RET Return.
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