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1 <appendix>
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2 <title>The &b09; Graphics Interface Module</title>
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3 <para>
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4 The Graphics Interface module provides a simple and convenient
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5 way to access the color graphics and joystick functions of the
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6 Dragon Computer from &b09; programs. The module is a program
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7 written in assembly language and stored in a file called "GFX". It
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8 can be loaded into memory using the OS-9 "LOAD" command prior to or
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9 after called &b09;, or it will be automatically called by &b09;
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10 the first time it is referenced in a program if the "GFX" file is
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11 located in the execution ("CMDS") directory.
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12 </para>
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13 <para>
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14 "GFX" is called using the &b09; "RUN" statement. The first
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15 parameter passed is the name of the graphics function desired.
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16 Other parameters are used to pass coordinates, color modes, etc.
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17 </para>
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18 <para>
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19 The are two basic graphics modes: 4-color having 128 by 192
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20 pixel resolution, and 2-color having 256 by 192 pixel resolution.
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21 The display is treated as a 256 by 192 point grid with coordinates
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22 0,0 in the lower left-hand corner. X (horizontal) coordinates in
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23 either mode must be in the range of 0 to 255. An X-coordinate
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24 greater than 255 will cause a run-time error. Y coordinates
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25 (vertical) must be in the range of 0 to 191. A number greater than
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26 191 will be replaced by 191. Some of the graphics functions require
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27 or optionally accept a color mode which controls the foreground
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28 color and color set. The mode and color codes are given in the
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29 table on the next page.
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30 </para>
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31 <beginpage/>
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32 <table frame="none">
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33 <title>Color Graphics Modes and Color Codes</title>
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34 <tgroup cols="6">
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35 <colspec colname="c1" colwidth="0.6in"/>
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36 <colspec colname="c2" colwidth="0.4in"/>
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37 <colspec colname="c3" colwidth="1in"/>
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38 <colspec colname="c4" colwidth="1in"/>
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39 <colspec colname="c5" colwidth="1in"/>
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40 <colspec colname="c6" colwidth="1in"/>
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41 <thead>
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42 <row>
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43 <entry morerows="1" namest="c2">Color Code</entry>
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44 <entry align="center" namest="c3" nameend="c4">Two Color Format</entry>
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45 <entry align="center" namest="c5" nameend="c6">Four Color Format</entry>
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46 </row>
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47 <row>
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48 <entry namest="c3">Background</entry>
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49 <entry namest="c4">Foreground</entry>
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50 <entry namest="c5">Background</entry>
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51 <entry namest="c6">Foreground</entry>
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52 </row>
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53 </thead>
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54 <tbody>
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55 <row>
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56 <entry morerows="3" valign="middle">Color Set 1</entry>
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57 <entry align="center">00</entry>
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58 <entry align="left">Black</entry>
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59 <entry align="left">Black</entry>
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60 <entry align="left">Green</entry>
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61 <entry align="left">Green</entry>
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62 </row>
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63 <row>
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64 <entry align="center">01</entry>
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65 <entry align="left">Black</entry>
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66 <entry align="left">Green</entry>
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67 <entry align="left">Green</entry>
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68 <entry align="left">Yellow</entry>
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69 </row>
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70 <row>
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71 <entry align="center">02</entry>
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72 <entry namest="c5" align="left">Green</entry>
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73 <entry align="left">Blue</entry>
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74 </row>
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75 <row rowsep="1">
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76 <entry align="center">03</entry>
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77 <entry namest="c5" align="left">Green</entry>
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78 <entry align="left">Red</entry>
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79 </row>
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80 <row>
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81 <entry morerows="3" valign="middle">Color Set 2</entry>
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82 <entry align="center">04</entry>
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83 <entry align="left">Black</entry>
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84 <entry align="left">Black</entry>
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85 <entry align="left">Buff</entry>
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86 <entry align="left">Buff</entry>
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87 </row>
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88 <row>
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89 <entry align="center" namest="c2">05</entry>
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90 <entry align="left">Black</entry>
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91 <entry align="left">Buff</entry>
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92 <entry align="left">Buff</entry>
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93 <entry align="left">Cyan</entry>
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94 </row>
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95 <row>
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96 <entry align="center" namest="c2">06</entry>
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97 <entry namest="c5" align="left">Buff</entry>
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98 <entry align="left">Magenta</entry>
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99 </row>
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100 <row rowsep="1">
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101 <entry align="center" namest="c2">07</entry>
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102 <entry namest="c5" align="left">Buff</entry>
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103 <entry align="left">Orange</entry>
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104 </row>
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105 <row>
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106 <entry morerows="3" valign="middle">Color Set 3*</entry>
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107 <entry align="center">08</entry>
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108 <entry namest="c5" align="left">Black</entry>
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109 <entry align="left">Black</entry>
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110 </row>
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111 <row>
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112 <entry align="center" namest="c2">09</entry>
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113 <entry namest="c5" align="left">Black</entry>
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114 <entry align="left">Dark Green</entry>
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115 </row>
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116 <row>
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117 <entry align="center" namest="c2">10</entry>
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118 <entry namest="c5" align="left">Black</entry>
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119 <entry align="left">Med. Green</entry>
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120 </row>
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121 <row rowsep="1">
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122 <entry align="center" namest="c2">11</entry>
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123 <entry namest="c5" align="left">Black</entry>
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124 <entry align="left">Light Green</entry>
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125 </row>
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126 <row>
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127 <entry morerows="3" valign="middle">Color Set 4*</entry>
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128 <entry align="center">12</entry>
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129 <entry namest="c5" align="left">Black</entry>
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130 <entry align="left">Black</entry>
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131 </row>
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132 <row>
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133 <entry align="center" namest="c2">13</entry>
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134 <entry namest="c5" align="left">Black</entry>
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135 <entry align="left">Green</entry>
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136 </row>
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137 <row>
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138 <entry align="center" namest="c2">14</entry>
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139 <entry namest="c5" align="left">Black</entry>
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140 <entry align="left">Red</entry>
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141 </row>
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142 <row>
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143 <entry align="center" namest="c2">15</entry>
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144 <entry namest="c5" align="left">Black</entry>
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145 <entry align="left">Buff</entry>
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146 </row>
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147 </tbody>
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148 </tgroup>
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149 </table>
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150 <note>
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151 <para>
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152 Color Sets 3 and 4 are not available on PAL video system
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153 (U.K. and European) models.
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154 </para>
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155 </note>
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156 <bridgehead renderas="sect2">MODE</bridgehead>
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157 <cmdsynopsis>
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158 <command>RUN GFX("Mode",<replaceable>format,color</replaceable>)</command>
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159 </cmdsynopsis>
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160 <para>
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161 MODE switches the screen from alphanumeric to graphics display mode,
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162 and selects the screen mode and color mode. "Format" determines
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163 between two-color (Format = 0), or four-color (Format = 1)
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164 graphics modes. "Color" is the initial color code that specifies
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165 the foreground color and color set.
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166 </para>
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167 <para>
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168 This command must be given before aby other graphics command is
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169 used. The first time MODE is called, it requests 6K bytres of memory
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170 from OS-9 for use as the graphics display memory. MODE will return
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171 an error if sufficient free memory is not available.
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172 </para>
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173 <para>
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174 An example:
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175 <programlisting>
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176 RUN GFX("Mode",1,3)
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177 </programlisting>
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178 selects four-color mode graphics is used, and the initial
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179 foreground color is red.
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180 </para>
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181 <bridgehead renderas="sect2">MOVE</bridgehead>
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182 <cmdsynopsis>
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183 <command>RUN GFX("Move",<replaceable>x,y</replaceable>)</command>
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184 </cmdsynopsis>
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185 <para>
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186 MOVE positions the (invisible) graphics cursor to the specified
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187 location without changing the display. X and Y are the coordinates
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188 of the new position.
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189 </para>
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190 <para>
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191 Example:
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192 <programlisting>
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193 RUN GFX("Move",0,0)
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194 </programlisting>
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195 This example positions the cursor in the lower left-hand corner.
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196 </para>
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197 <bridgehead renderas="sect2">COLOR</bridgehead>
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198 <cmdsynopsis>
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199 <command>RUN GFX("Color",<replaceable>color</replaceable>)</command>
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200 </cmdsynopsis>
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201 <para>
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202 COLOR changes the current foreground color (and possibly the color
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203 set). The current graphics mode and cursor position are not
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204 changed. For example:
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205 <programlisting>
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206 RUN GFX("Color",0)
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207 </programlisting>
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208 changes the foreground color to green in four-color format (or
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209 black in two-color format).
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210 </para>
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211 <bridgehead renderas="sect2">POINT</bridgehead>
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212 <cmdsynopsis>
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213 <command>RUN GFX("Point",<replaceable>x,y</replaceable>) or</command><sbr/>
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214 <command>RUN GFX("Point",<replaceable>x,y,color</replaceable>)</command>
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215 </cmdsynopsis>
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216 <para>
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217 POINT moves the graphics cursor to the specified X.Y coordinate and
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218 sets the pixel at that coordinate to the current foreground color.
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219 If the optional "Color" is specified, the current foreground color
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220 is set to the given "Color". For example:
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221 <programlisting>
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222 RUN GFX("Point",0,192,1)
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223 </programlisting>
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224 Point moves the cursor to the upper left-hand corner and changes
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225 the foreground color to green in two-color format, or it changes
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226 the color to yellow in the four-color format.
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227 </para>
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228 <bridgehead renderas="sect2">CLEAR</bridgehead>
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229 <cmdsynopsis>
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230 <command>RUN GFX("Clear") or</command><sbr/>
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231 <command>RUN GFX("Clear",<replaceable>color</replaceable>)</command>
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232 </cmdsynopsis>
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233 <para>
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234 CLEAR resets all points on the screen to the background color, or
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235 if the optional color is given presets the screen to that color.
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236 The current graphics cursor is reset to (0,0).
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237 </para>
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238 <bridgehead renderas="sect2">LINE</bridgehead>
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239 <cmdsynopsis>
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240 <command>RUN GFX("Line",<replaceable>x2,y2</replaceable>)</command><sbr/>
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241 <command>RUN GFX("Line",<replaceable>x2,y2,color</replaceable>)</command><sbr/>
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242 <command>RUN GFX("Line",<replaceable>x1,y1,x2,y2</replaceable>)</command><sbr/>
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243 <command>RUN GFX("Line",<replaceable>x1,y1,x2,y2,color</replaceable>)</command>
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244 </cmdsynopsis>
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245 <para>
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246 LINE draw lines in various ways. If one coordinate is given, the
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247 line will be drawn from the current graphics cursor position to the
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248 coordinates specified. If two sets of coordinates are given, they
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249 are used as the start and end points of the line. The line will be
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250 drawn in the current foreground color unless a new color is given
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251 as a parameter. After the line is drawn the graphics cursor will be
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252 positioned at x2,y2. For example
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253 <programlisting>
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254 RUN GFX("Line",0,0,0,192)
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255 </programlisting>
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256 draws a line from (0,0) to (0,192).
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257 <programlisting>
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258 RUN GFX("line",24,65,2)
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259 </programlisting>
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260 draws a blue line (4-color mode) to point 24,65.
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261 </para>
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262 <bridgehead renderas="sect2">CIRCLE</bridgehead>
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263 <cmdsynopsis>
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264 <command>RUN GFX("Circle",<replaceable>radius</replaceable>)</command><sbr/>
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265 <command>RUN GFX("Circle",<replaceable>radius,color</replaceable>)</command><sbr/>
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266 <command>RUN GFX("Circle",<replaceable>x,y,radius</replaceable>)</command><sbr/>
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267 <command>RUN GFX("Circle",<replaceable>x,y,radius,color</replaceable>)</command>
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268 </cmdsynopsis>
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269 <para>
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270 CIRCLE draws a circle of the given radius. The current graphics
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271 cursor position is assumed if no X,Y value is given. The current
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272 foreground color is assumed if the Color parameter is not used.
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273 The center of the circle must be on the screen.
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274 </para>
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275 <bridgehead renderas="sect2">ALPHA</bridgehead>
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276 <cmdsynopsis>
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277 <command>RUN GFX("Alpha")</command>
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278 </cmdsynopsis>
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279 <para>
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280 Alpha is a quick convenient way of getting the screen back to
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281 alphanumeric mode. When graphics mode is entered again, the screen
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282 will show the previous unchanged graphics display.
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283 </para>
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284 <bridgehead renderas="sect2">QUIT</bridgehead>
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285 <cmdsynopsis>
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286 <command>RUN GFX("Quit")</command>
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287 </cmdsynopsis>
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288 <para>
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289 QUIT switches the screen back to alpha mode and returns the 6K byte
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290 graphics display memory to OS-9.
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291 </para>
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292 <bridgehead renderas="sect2">GLOC</bridgehead>
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293 <cmdsynopsis>
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294 <command>RUN GFX("Gloc",<replaceable>vdisp</replaceable>)</command>
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295 </cmdsynopsis>
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296 <para>
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297 GLOC returns the address of the video display RAM as an integer number.
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298 This address may be used in subsequent PEEK and POKE
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299 operations to access the video display directly. GLOC can be used
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300 to create special functions that are not available in the Graphics
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301 Module.
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302 </para>
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303 <bridgehead renderas="sect2">GCOLR</bridgehead>
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304 <cmdsynopsis>
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305 <command>RUN GFX("Gcolr",<replaceable>color</replaceable>)</command><sbr/>
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306 <command>RUN GFX("Gcolr",<replaceable>x,y,color</replaceable>)</command>
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307 </cmdsynopsis>
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308 <para>
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309 GCOLR is used to read the color of the pixel at the current
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310 graphics cursor position, or from the coordinates X,Y. The
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311 parameter "Color" may be an integer or a byte variable in which the
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312 color code is returned.
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313 </para>
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314 <bridgehead renderas="sect2">JOYSTK</bridgehead>
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315 <cmdsynopsis>
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316 <command>RUN GFX("Joystk",<replaceable>stick,fire,x,y</replaceable>)</command>
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317 </cmdsynopsis>
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318 <para>
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319 JOYSTK returns the status of the specified joystick's Fire button,
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320 and returns the X,Y position of the joystick. The Fire button may
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321 be read as a BYTE, INTEGER, or a BOOLEAN value. Non-zero (TRUE)
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322 means the button was pressed. The X,Y values returned may be BYTE
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323 or INTEGER variables, and they will be in the range 0 to 63. The
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324 Stick parameter may be BYTE or INTEGER, and should be 0 for
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325 RIGHT, or 1 for LEFT, depending on whether the RIGHT or the LEFT
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326 joystick is to be tested.
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327 </para>
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328 <para>
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329 Example:
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330 <programlisting>
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331 RUN GRX("Joystk",1,leftfire,leftx,lefty)
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332 </programlisting>
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333 </para>
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334 <bridgehead renderas="sect1">A Sample Graphics Program</bridgehead>
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335 <para>
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336 The program on the next page illustrates how the GFX module is
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337 called and used. It creates an analog clock on the graphics
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338 display.
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339 </para>
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340 <para>
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341 <programlisting>
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342 PROCEDURE clk
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343 0000 (* Simple Clock Simulator *)
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344 001C DIM time(4),last(4),xx(3),yy(3):INTEGER
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345 0043 DIM x0,y0,radius,bkg:INTEGER
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346 0056 DIM i,j,x1,y1,x2,y2:INTEGER
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347 0071 DEG
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348 0073 bkg=0
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349 007A x0=128
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350 0081 y0=96
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351 0088 radius=95
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352 008F RUN GFX("MODE",1,bkg+1)
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353 00A5 RUN GFX("CLEAR")
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354 00B2 RUN GFX("CIRCLE",x0,y0,radius)
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355 00CF FOR i=0 to 89 STEP 6
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356 00E4 x2=SIN(i)*radius
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357 00F4 y2=COS(i)*radius
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358 0104 x1=x2*.9
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359 0115 y1=y2*.9
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360 0126 j=MOD(i/30,3)+bkg+1
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361 013B RUN GFX("LINE",x0+x1,y0+y1,x0+x2,y0+y2,j)
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362 016C RUN GFX("LINE",x0-x1,y0-y1,x0-x2,y0-y2,j)
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363 019D RUN GFX("LINE",x0+y1,y0-x1,x0+y2,y0-x2,j)
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364 01CE RUN GFX("LINE",x0-y1,y0+x1,x0-y2,y0+x2,j)
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365 01FF NEXT i
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366 020A FOR i=1 TO 3
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367 021A time(i)=0
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368 0225 xx(i)=x0
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369 0231 yy(i)=y0
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370 023D NEXT i
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371 0248 LOOP
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372 024A time$=DATE$
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373 0250 last=time
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374 0258 time(3)=VAL(MID$(time$,16,2))*6
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375 026E time(2)=VAL(MID$(time$(13,2))*6
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376 0284 time(1)=MOD(VAL(MID$(time$,10,2))*30+time/2)/12,360)
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377 02A9 j=last(3)
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378 02B3 FOR i=3 TO 1 STEP -1
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379 02C9 IF i=3 OR j=0 OR ABS(time(i)-last(i+1))<6 OR
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380 ABS(time(i)-j)<6 THEN
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381 0300 RUN GFX("LINE",x0,y0,xx(i),yy(i),bkg)
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382 032B xx(i)=x0+SIN(time(i))*radius*(.3+i*.2)
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383 035A yy(i)=y0+COS(time(i))*radius*(.3+i*.2)
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384 0389 RUN GFX("LINE",x0,y0,xx(i),yy(i),bkg+i)
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385 03B7 ENDIF
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386 03B9 NEXT i
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387 03C4 WHILE time$=DATE$ DO
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388 03CF ENDWHILE
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389 03D3 ENDLOOP
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390 </programlisting>
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391 </para>
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392
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393 </appendix>
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