1 /* This file is part of the GNU plotutils package. Copyright (C) 1995,
2 1996, 1997, 1998, 1999, 2000, 2005, 2008, Free Software Foundation, Inc.
3
4 The GNU plotutils package is free software. You may redistribute it
5 and/or modify it under the terms of the GNU General Public License as
6 published by the Free Software foundation; either version 2, or (at your
7 option) any later version.
8
9 The GNU plotutils package is distributed in the hope that it will be
10 useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 General Public License for more details.
13
14 You should have received a copy of the GNU General Public License along
15 with the GNU plotutils package; see the file COPYING. If not, write to
16 the Free Software Foundation, Inc., 51 Franklin St., Fifth Floor,
17 Boston, MA 02110-1301, USA. */
18
19 /* This file contains the low-level _pl_t_tek_vector() method, which takes
20 two integer arguments and writes them, in the format used by a Tektronix
21 4014 terminal for addresses while in vector or point-plot mode, to a
22 specified output stream. It is called by several TekPlotter methods.
23
24 Original Tek 4014 resolution was 1024 by 1024, with 1024 by 780
25 displayable, i.e. 0x400 by 0x30c. Extended (EGM) resolution, supported
26 by 4014's with the Enhanced Graphics Module, is four times that: 4096 by
27 3120. This is the resolution of the xterm Tektronix emulator.
28
29 With EGM, have an allowed range of 12 bits (0 <= x,y <=4095). A Tek
30 code for a point address (x,y) consists of a sequence of bytes:
31
32 [Hi_Y] [EGM] [Lo_Y] [Hi_X] Lo_X.
33
34 Since the EGM byte was added later, to improve resolution, it contains
35 the lowest 2 bits of each of the X and Y bytes, packed into the lowest
36 four bits of the byte. The remaining 10 bits are subdivided as follows
37 among the remaining four code bytes. Lo=lowest 5 of the 10 bits,
38 Hi=highest 5 of the 10 bits, all packed into the lowest 5 bits of the
39 byte. Code bytes are distinguished from each other by the pattern of
40 the high three bits. (Hi_Y = ?01, EGM = ?11, Lo_Y = ?11, Hi_X = ?01,
41 Lo_X = ?10, where ? is ignored [or should be].) If EGM is included then
42 Lo_Y must be included to prevent ambiguity. Also if Hi_X is included
43 then Lo_Y must be included.
44
45 If a byte is omitted, then its value defaults to the value of the
46 corresponding byte in the most recently received point. The exception
47 is the EGM byte; if omitted, it defaults to zero.
48
49 Warning: some emulators, the xterm emulator in particular, get this
50 scheme wrong. The xterm emulator will behave unpredicably if Lo_Y is
51 omitted. And if EGM is omitted, its value (as far as the xterm emulator
52 goes) is not zero, but is equal to the value of the EGM byte in the most
53 recently received point. */
54
55 #include "sys-defines.h"
56 #include "extern.h"
57
58 #define FIVEBITS 0x1F
59 #define TWOBITS 0x03 /* a dollar and six bits for a haircut... */
60
61 void
_pl_t_tek_vector(R___ (Plotter * _plotter)int xx,int yy)62 _pl_t_tek_vector (R___(Plotter *_plotter) int xx, int yy)
63 {
64 unsigned char xx_high, yy_high;
65 unsigned char xx_low, yy_low;
66 unsigned char xx_topsig, yy_topsig;
67 unsigned char egm;
68 unsigned char byte_buf[5];
69 int num_bytes = 0;
70
71 #ifdef NO_WRAP /* could completely restrict to box */
72 if (xx < 0)
73 xx = 0;
74 if (yy < 0)
75 yy = 0;
76 #endif
77
78 xx_high = (xx>>7) & FIVEBITS; /* bits 11 through 7 of xx */
79 yy_high = (yy>>7) & FIVEBITS; /* bits 11 through 7 of yy */
80
81 xx_low = (xx>>2) & FIVEBITS; /* bits 6 through 2 of xx */
82 yy_low = (yy>>2) & FIVEBITS; /* bits 6 through 2 of yy */
83
84 xx_topsig = xx & TWOBITS; /* bits 1 through 0 of xx */
85 yy_topsig = yy & TWOBITS; /* bits 1 through 0 of yy */
86 egm = (yy_topsig<<2) + xx_topsig;
87
88 /* The bit patterns 0x20, 0x40, 0x60 are magic */
89
90 byte_buf[num_bytes++] = yy_high | 0x20; /* bits 5 through 9 of yy */
91 #ifdef CAN_OMIT_EGM
92 if (egm)
93 #endif
94 byte_buf[num_bytes++] = egm | 0x60;
95 byte_buf[num_bytes++] = yy_low | 0x60; /* bits 0 through 4 of yy */
96 byte_buf[num_bytes++] = xx_high | 0x20; /* bits 5 through 9 of xx */
97 byte_buf[num_bytes++] = xx_low | 0x40; /* bits 0 through 4 of xx */
98
99 /* invoke low-level output routine */
100 _write_bytes (_plotter->data, num_bytes, byte_buf);
101
102 return;
103 }
104
105 /* This version checks whether the supplied x and y coordinates are similar
106 to the x and y coordinates of another point, presumed to be the most
107 recently output point. If they are, the Tek code is shortened by the
108 omission of optional bytes. Hi_Y, Lo_Y and Hi_X are all held in memory,
109 so need not be transmitted if they did not change. Lo_X must always be
110 transmitted. EGM is not held in memory; if not transmitted, it defaults
111 to zero.
112
113 The `force' argument will force output even if the vector has zero
114 length. */
115
116 void
_pl_t_tek_vector_compressed(R___ (Plotter * _plotter)int xx,int yy,int oldxx,int oldyy,bool force)117 _pl_t_tek_vector_compressed (R___(Plotter *_plotter) int xx, int yy, int oldxx, int oldyy, bool force)
118 {
119 unsigned char xx_high, yy_high, oldxx_high, oldyy_high;
120 unsigned char xx_low, yy_low, oldyy_low;
121 unsigned char xx_top, yy_top;
122 unsigned char egm;
123 unsigned char byte_buf[5];
124 int num_bytes = 0;
125
126 #ifdef NO_WRAP /* could completely restrict to box */
127 if (xx < 0)
128 xx = 0;
129 if (yy < 0)
130 yy = 0;
131 #endif
132
133 /* if line segment has zero length, do nothing unless forcing an output */
134 if (!force && (xx == oldxx) && (yy == oldyy))
135 return;
136
137 xx_high = (xx>>7) & FIVEBITS; /* bits 11 through 7 of xx */
138 yy_high = (yy>>7) & FIVEBITS; /* bits 11 through 7 of yy */
139 oldxx_high = (oldxx>>7) & FIVEBITS; /* bits 11 through 7 of oldxx */
140 oldyy_high = (oldyy>>7) & FIVEBITS; /* bits 11 through 7 of oldyy */
141
142 xx_low = (xx>>2) & FIVEBITS; /* bits 6 through 2 of xx */
143 yy_low = (yy>>2) & FIVEBITS; /* bits 6 through 2 of yy */
144 oldyy_low = (oldyy>>2) & FIVEBITS; /* bits 4 through 0 of oldyy */
145
146 xx_top = xx & TWOBITS; /* bits 1 through 0 of xx */
147 yy_top = yy & TWOBITS; /* bits 1 through 0 of yy */
148
149 egm = (yy_top<<2) + xx_top;
150
151 /* The bit patterns 0x20, 0x40, 0x60 are magic */
152
153 if (yy_high != oldyy_high)
154 byte_buf[num_bytes++] = yy_high | 0x20; /* bits 11 through 7 of yy: Hi_Y */
155
156 #ifdef CAN_OMIT_EGM
157 if (egm)
158 #endif
159 byte_buf[num_bytes++] = egm | 0x60; /* bits 1 through 0 of xx and yy */
160 #ifdef CAN_OMIT_LO_Y
161 if ((yy_low != oldyy_low) || (xx_high != oldxx_high) || egm)
162 #endif
163 byte_buf[num_bytes++] = yy_low | 0x60; /* bits 6 through 2 of yy: Lo_Y */
164 if (xx_high != oldxx_high)
165 byte_buf[num_bytes++] = xx_high | 0x20; /* bits 11 through 7 of xx: Hi_X */
166 byte_buf[num_bytes++] = xx_low | 0x40; /* bits 6 through 2 of xx: Lo_X */
167
168 /* invoke low-level output routine */
169 _write_bytes (_plotter->data, num_bytes, byte_buf);
170
171 return;
172 }
173