Routines
Prev: 32632 Up: Map Next: 33006
32679: Drawing: Start A Picture Command
Used by the routine at Drawing.
Reads picture commands. 0 ends the picture, 8 moves the pen, bit 7 draws a line, and the other bytes fill or paint.
Drawing routines.
DrawingSetup 32679 PUSH IY Save the picture registers and clear the window when the place is dark.
32681 PUSH HL
32682 PUSH HL
32683 POP IY
32685 PUSH DE
32686 PUSH BC
32687 CALL DrawingClear
32690 LD D,127 Start the high coordinate at 127.
32692 LD E,63 Start the low coordinate at 63.
32694 LD B,1 Start the step count at 1.
32696 LD C,1 Start the direction at 1.
32698 LD L,1 Start the length at 1.
Drawing_Loop 32700 LD A,(IY+0) Fetch the next drawing instruction.
32703 AND A If the drawing instruction is zero, jump to Drawing_End.
32704 JP Z,Drawing_End
32707 INC IY Increment the graphics data pointer by one.
32709 CP 8 If the graphics data value which was fetched is not 8 (move to X/Y) jump to DrawingSetup_TestForALine.
32711 JR NZ,DrawingSetup_TestForALine
Moves the "pen" held in DE to a screen location.
32713 LD D,(IY+0) Populate DE with two values from the graphics data and increment the pointer by two.
32716 INC IY
32718 LD E,(IY+0)
32721 INC IY
32723 JR Drawing_Loop Jump back to Drawing_Loop for the next drawing instruction.
DrawingSetup_TestForALine 32725 BIT 7,A If bit 7 is clear, jump to DrawingSetup_TestForAFill. A set bit 7 is a line.
32727 JR Z,DrawingSetup_TestForAFill
32729 LD B,A Keep the line command.
32730 AND %00000111 The low three bits are the direction.
32732 LD C,A Store the direction in C.
32733 LD A,B Bring the line command back.
32734 RRCA
32735 AND 60
32737 LD B,A Store this in B.
32738 LD A,(IY+0) Read the length byte of the line.
32741 AND %00111111 The low six bits are the length.
32743 LD L,A Store that length.
32744 INC L A stored length of zero draws one pixel.
32745 LD A,(IY+0) Read the length byte again for the step spacing.
32748 INC IY Increment the graphics data pointer by one.
32750 RLCA Move bits 6-7 down to bits 0-1.
32751 RLCA
32752 AND 3
32754 OR B Combine the step spacing from both command bytes.
32755 LD B,A Store the step spacing.
32756 INC B A stored spacing of zero steps every pixel.
32757 CALL Drawing_PlotTheSelectedPixel Call Drawing_PlotTheSelectedPixel to plot the line.
32760 JR Drawing_Loop Jump back to Drawing_Loop for the next drawing instruction.
A set bit 6 is a fill.
DrawingSetup_TestForAFill 32762 BIT 6,A Jump to DrawingSetup_RepeatWhileBitFiveIsClear if bit 6 is clear.
32764 JR Z,DrawingSetup_RepeatWhileBitFiveIsClear
32766 AND %00000111 The low three bits are the fill ink.
32768 PUSH DE Read the fill's X coordinate.
32769 LD D,(IY+0)
32772 INC IY Advance the graphics pointer.
32774 LD E,(IY+0) Read the fill's other coordinate.
32777 INC IY Advance the graphics pointer.
Flood-fill from the point in DE.
32779 CALL DrawingSetup_0 Call DrawingSetup_0 to flood-fill from that point.
32782 POP DE Jump back to Drawing_Loop to fetch the next drawing instruction.
32783 JP Drawing_Loop
DrawingSetup_RepeatWhileBitFiveIsClear 32786 BIT 5,A Jump back to Drawing_Loop if bit 5 of this picture command is clear.
32788 JP Z,Drawing_Loop
32791 AND %00000111 The low three bits are the ink to paint.
32793 RLCA Shift the ink towards the paper bits.
32794 RLCA Shift the ink towards the paper bits.
32795 RLCA Shift the ink into the paper bits.
32796 PUSH HL Save HL, DE and BC, and keep the scaled bits in C.
32797 PUSH DE
32798 PUSH BC
32799 LD C,A
32800 LD H,(IY+0) Read the attribute address high byte into H.
32803 INC IY Advance the graphics pointer.
32805 LD L,(IY+0) Read the attribute address low byte into L.
32808 INC IY Advance the graphics pointer.
DrawingSetup_ReadTheNextAttributeByte 32810 LD A,(IY+0) Read the next attribute byte.
32813 INC IY Advance the graphics pointer.
32815 CP 255 Jump to DrawingSetup_FetchTheNextDrawingInstruction at the 255 terminator.
32817 JR Z,DrawingSetup_FetchTheNextDrawingInstruction
32819 LD B,A Copy the result into B.
32820 AND %00000011 The low two bits choose which way this attribute run steps.
32822 LD E,A Store that step.
32823 LD A,B Shift the length down two bits.
32824 RRCA
32825 RRCA
32826 AND 63
32828 INC A A stored length of zero paints one cell.
32829 LD B,A Copy the result into B.
DrawingSetup_Loop 32830 LD A,(HL) Read the next byte.
32831 AND %00000111 Jump to DrawingSetup_StoreTheAttribute when this cell's ink is not the ink being replaced.
32833 RLCA
32834 RLCA
32835 RLCA
32836 CP C
32837 JR NZ,DrawingSetup_StoreTheAttribute
32839 XOR 56 Flip the bits selected by 56.
DrawingSetup_StoreTheAttribute 32841 RRCA Shift the ink back into bits 0-2, merge it with C and store the attribute; then call Drawing_StepUpOneRow if the direction in E is 0.
32842 RRCA
32843 RRCA
32844 OR C
32845 LD (HL),A
32846 LD A,E
32847 AND A
32848 CALL Z,Drawing_StepUpOneRow
32851 DEC A Call Drawing_StepRightOnePixel if the direction is 1.
32852 CALL Z,Drawing_StepRightOnePixel
32855 DEC A Call Drawing_StepDownOneRow if the direction is 2.
32856 CALL Z,Drawing_StepDownOneRow
32859 DEC A Call Drawing_StepLeftOnePixel if the direction is 3.
32860 CALL Z,Drawing_StepLeftOnePixel
32863 DJNZ DrawingSetup_Loop Loop back to DrawingSetup_Loop until the count runs out.
32865 JR DrawingSetup_ReadTheNextAttributeByte Jump back to DrawingSetup_ReadTheNextAttributeByte for the next attribute byte.
Restore the registers saved for this shape.
DrawingSetup_FetchTheNextDrawingInstruction 32867 POP BC Restore BC, DE and HL from the stack, then jump to Drawing_Loop for the next drawing instruction.
32868 POP DE
32869 POP HL
32870 JP Drawing_Loop
This entry point is used by the routine at DrawingClear.
Drawing_End 32873 POP BC Restore BC, DE, HL and IY from the stack.
32874 POP DE
32875 POP HL
32876 POP IY
32878 RET Return.
32879 DEFB 0,0
DrawingSetup_0 32881 LD (33358),A Store the result at 33358.
32884 PUSH DE Allow 128 steps of this flood fill.
32885 PUSH HL
32886 LD HL,128
32889 PUSH HL
DrawingSetup_MaskOneScreenByte 32890 CALL Drawing_MaskOneScreenByte Call Drawing_MaskOneScreenByte to mask one screen byte.
32893 JR NZ,DrawingSetup_AddressThePixel Jump to DrawingSetup_AddressThePixel if Drawing_MaskOneScreenByte found the masked screen byte set.
32895 CALL Drawing_RetreatTheHighCoordinate Call Drawing_RetreatTheHighCoordinate to retreat the high coordinate.
32898 JR NZ,DrawingSetup_MaskOneScreenByte Jump back to DrawingSetup_MaskOneScreenByte if Drawing_RetreatTheHighCoordinate did not wrap the high coordinate.
32900 JR DrawingSetup_ClearTheFloodFillCount Jump to DrawingSetup_ClearTheFloodFillCount to clear the saved coordinate, because the high coordinate wrapped.
DrawingSetup_AddressThePixel 32902 CALL Drawing_AddressThePixel Call Drawing_AddressThePixel to address the pixel.
32905 CALL Drawing_AdvanceTheHighCoordinate Call Drawing_AdvanceTheHighCoordinate to advance the high coordinate.
DrawingSetup_ClearTheFloodFillCount 32908 LD HL,0 Store 0000 in *32879.
32911 LD (32879),HL
DrawingSetup_AdvanceTheLowCoordinate 32914 CALL Drawing_AdvanceTheLowCoordinate Call Drawing_AdvanceTheLowCoordinate to advance the low coordinate.
32917 LD A,0 Take zero and jump to DrawingSetup_StoreTheResultAtFloodFillCount if Drawing_AdvanceTheLowCoordinate wrapped the low coordinate.
32919 JR Z,DrawingSetup_StoreTheResultAtFloodFillCount
32921 CALL Drawing_MaskOneScreenByte Call Drawing_MaskOneScreenByte to mask one screen byte.
32924 LD A,0 Take zero and jump to DrawingSetup_RetreatTheLowCoordinate if Drawing_MaskOneScreenByte found the masked screen byte set.
32926 JR NZ,DrawingSetup_RetreatTheLowCoordinate
Test this flag.
32928 LD A,(32879) Jump to DrawingSetup_RetreatTheLowCoordinate if *32879 is not zero.
32931 AND A
32932 JR NZ,DrawingSetup_RetreatTheLowCoordinate
32934 PUSH DE Use 1 when the coordinate was zero.
32935 LD A,1
DrawingSetup_RetreatTheLowCoordinate 32937 PUSH AF Call Drawing_RetreatTheLowCoordinate to retreat the low coordinate, then restore AF from the stack.
32938 CALL Drawing_RetreatTheLowCoordinate
32941 POP AF
DrawingSetup_StoreTheResultAtFloodFillCount 32942 LD (32879),A Store the result at 32879.
32945 CALL Drawing_RetreatTheLowCoordinate Call Drawing_RetreatTheLowCoordinate to retreat the low coordinate.
32948 LD A,0 Take zero, and jump to DrawingSetup_StoreTheHighCoordinate if Drawing_RetreatTheLowCoordinate returned with the zero flag set.
32950 JR Z,DrawingSetup_StoreTheHighCoordinate
32952 CALL Drawing_MaskOneScreenByte Call Drawing_MaskOneScreenByte to mask one screen byte.
32955 LD A,0 Take zero, and jump to DrawingSetup_AdvanceAndRestore if Drawing_MaskOneScreenByte found the masked screen byte set.
32957 JR NZ,DrawingSetup_AdvanceAndRestore
Test this flag.
32959 LD A,(32880) Jump to DrawingSetup_AdvanceAndRestore if the drawing scratch is not zero.
32962 AND A
32963 JR NZ,DrawingSetup_AdvanceAndRestore
32965 PUSH DE Use 1 when the coordinate was zero.
32966 LD A,1
DrawingSetup_AdvanceAndRestore 32968 PUSH AF Call Drawing_AdvanceTheLowCoordinate to advance the low coordinate, then restore AF from the stack.
32969 CALL Drawing_AdvanceTheLowCoordinate
32972 POP AF
DrawingSetup_StoreTheHighCoordinate 32973 LD (32880),A Store the result at 32880.
32976 CALL Drawing_AddressThePixel Call Drawing_AddressThePixel to address the pixel.
32979 CALL Drawing_AdvanceTheHighCoordinate Call Drawing_AdvanceTheHighCoordinate to advance the high coordinate.
32982 JR Z,DrawingSetup_TestTheFloodFillCount Jump to DrawingSetup_TestTheFloodFillCount if Drawing_AdvanceTheHighCoordinate wrapped the high coordinate.
32984 CALL Drawing_MaskOneScreenByte Call Drawing_MaskOneScreenByte to mask one screen byte.
32987 JR Z,DrawingSetup_AdvanceTheLowCoordinate Jump back to DrawingSetup_AdvanceTheLowCoordinate if Drawing_MaskOneScreenByte found the masked screen byte clear.
32989 CALL Drawing_AddressThePixel Call Drawing_AddressThePixel to address the pixel.
DrawingSetup_TestTheFloodFillCount 32992 POP DE Jump back to DrawingSetup_MaskOneScreenByte unless the flood-fill count is 128.
32993 LD A,E
32994 CP 128
32996 JR NZ,DrawingSetup_MaskOneScreenByte
32998 LD A,0 Write 0 to *33358.
33000 LD (33358),A
33003 POP HL Restore HL and DE from the stack.
33004 POP DE
33005 RET Return.
View the equivalent code in;
Prev: 32632 Up: Map Next: 33006