1 | * ------------------------------------------------------------------------------
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2 | * vcputsv.s -- output characters to a 4-bit / pixel graphics window
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3 | * with variable vertical pitch
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4 | * Version 2 -- 1987-08-03 -- D.N. Lynx Crowe
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5 | * (c) Copyright 1987 -- D.N. Lynx Crowe
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6 | * ------------------------------------------------------------------------------
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7 | *
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8 | * vcputsv(obase, nw, fg, bg, row, col, str. pitch)
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9 | * int *obase, nw, fg, bg, row, col, pitch;
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10 | * char *str;
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11 | *
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12 | * Outputs characters from the string at 'str' to an 'nw'
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13 | * character wide 4-bit per pixel graphics window at 'obase'
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14 | * at ('row','col'), using 'fg' as the foreground color, and
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15 | * 'bg' as the background color. Uses cgtable[][256] as the
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16 | * VSDD formatted character generator table. Assumes 12 bit
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17 | * high characters in the cgtable. Uses 'pitch' as the vertical
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18 | * spacing between character rows. No error checks are done.
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19 | * The string must fit the output area (no overlaps, single line).
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20 | *
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21 | * ------------------------------------------------------------------------------
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22 | .text
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23 | *
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24 | .xdef _vcputsv
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25 | *
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26 | .xref _cgtable
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27 | *
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28 | * Argument offsets from a6:
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29 | *
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30 | OBASE .equ 8 * LONG - Output area base address
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31 | NW .equ 12 * WORD - Character width of output area
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32 | FG .equ 14 * WORD - Foreground color
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33 | BG .equ 16 * WORD - Background color
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34 | ROW .equ 18 * WORD - Row
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35 | COL .equ 20 * WORD - Column
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36 | STR .equ 22 * LONG - String base address
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37 | PITCH .equ 26 * WORD - Vertical spacing between rows
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38 | *
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39 | * Program constant definitions:
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40 | *
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41 | HPIX .equ 8 * Character width in pixels
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42 | VPIX .equ 12 * Character height in pixels
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43 | HCW .equ 4 * Horizontal character width (bytes)
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44 | PSHIFT .equ 12 * Pixel shift into MS bits
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45 | HSHIFT .equ 4 * Pixel right shift
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46 | *
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47 | .page
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48 | *
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49 | * Register usage:
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50 | *
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51 | * d0 output word and scratch
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52 | * d1 CG word and scratch
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53 | * d2 pixel counter
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54 | *
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55 | * d3 foreground color (in the 4 ms bits)
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56 | * d4 background color (in the 4 ms bits)
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57 | * d5 width of the area in bytes
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58 | * d6 scan line counter
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59 | *
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60 | * a0 CG table pointer
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61 | * a1 output area scan line pointer
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62 | * a2 input string character pointer
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63 | *
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64 | * a3 output area character base pointer
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65 | *
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66 | * a6 frame pointer
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67 | * a7 stack pointer
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68 | *
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69 | .page
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70 | *
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71 | _vcputsv: link a6,#0 * Link stack frames
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72 | movem.l d3-d6/a3,-(a7) * Save registers we use
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73 | move.w #PSHIFT,d1 * Set shift constant
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74 | move.w FG(a6),d3 * Setup foreground color
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75 | lsl.w d1,d3 * ... in ms 4 bits of d3.W
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76 | move.w BG(a6),d4 * Setup background color
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77 | lsl.w d1,d4 * ... in ms 4 bits of d4.W
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78 | move.w NW(a6),d5 * Get line width in d5.W
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79 | lsl.w #2,d5 * Multiply width by 4 for offset
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80 | move.w ROW(a6),d0 * Calculate output address
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81 | move.w PITCH(a6),d1 * ... PITCH
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82 | mulu d1,d0 * ... * ROW
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83 | add.w #VPIX-1,d0 * ... + VPIX-1
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84 | mulu d5,d0 * ... * NW
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85 | clr.l d1 * ...
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86 | move.w COL(a6),d1 * ... +
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87 | lsl.w #2,d1 * ... COL * 4
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88 | add.l d1,d0 * ...
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89 | add.l OBASE(a6),d0 * ... + OBASE
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90 | movea.l d0,a3 * Leave output address in a3
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91 | movea.l STR(a6),a2 * Put string address in a2
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92 | *
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93 | cgl0: clr.l d0 * Clear out upper bits of d0
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94 | move.b (a2)+,d0 * Get next character
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95 | beq cgl5 * Done if character EQ 0
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96 | *
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97 | movea.l a3,a1 * Establish output pointer in a1
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98 | adda.l #HCW,a3 * Update output pointer for next char.
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99 | lea _cgtable,a0 * Establish CG pointer in a0
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100 | lsl.w #1,d0 * ... 2 * character
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101 | adda.w d0,a0 * ... + _cgtable address
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102 | move.w #VPIX-1,d6 * Set scan line counter in d6
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103 | *
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104 | .page
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105 | cgl1: move.w (a0),d1 * Get character generator word in d1
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106 | move.w #(HPIX/2)-1,d2 * Set pixel counter in d2
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107 | *
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108 | cgl2: lsr.w #HSHIFT,d0 * Shift output word right 1 pixel
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109 | btst.l #0,d1 * Check CG word ls bit
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110 | beq cgl3 * Set background color if bit EQ 0
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111 | *
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112 | or.w d3,d0 * OR foreground color into output word
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113 | bra cgl4 * Go update CG word
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114 | *
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115 | cgl3: or.w d4,d0 * OR background color into output word
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116 | *
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117 | cgl4: lsr.w #1,d1 * Shift CG word right 1 pixel
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118 | dbf d2,cgl2 * Loop for first 4 pixels
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119 | *
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120 | move.w d0,(a1)+ * Store first output word in scan line
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121 | move.w #(HPIX/2)-1,d2 * Set pixel counter in d2
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122 | *
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123 | cgl2a: lsr.w #HSHIFT,d0 * Shift output word right 1 pixel
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124 | btst.l #0,d1 * Check CG word ls bit
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125 | beq cgl3a * Set background color if bit EQ 0
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126 | *
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127 | or.w d3,d0 * OR foreground color into output word
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128 | bra cgl4a * Go update CG word
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129 | *
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130 | cgl3a: or.w d4,d0 * OR background color into output word
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131 | *
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132 | cgl4a: lsr.w #1,d1 * Shift CG word right 1 pixel
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133 | dbf d2,cgl2a * Loop for last 4 pixels
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134 | *
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135 | move.w d0,(a1) * Store second output word in scan line
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136 | suba.w d5,a1 * Update output pointer
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137 | suba.w #2,a1 * ...
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138 | adda.l #512,a0 * Update CG pointer for next scan line
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139 | dbf d6,cgl1 * Loop for all scan lines
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140 | *
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141 | bra cgl0 * Loop for next character
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142 | *
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143 | cgl5: movem.l (a7)+,d3-d6/a3 * Restore registers
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144 | unlk a6 * Unlink stack frames
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145 | rts * Return to caller
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146 | *
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147 | .end
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