Red Hat Bugzilla – Bug 76978
The Linux console does not display the vt100 graphics characters
Last modified: 2008-08-01 12:22:52 EDT
From Bugzilla Helper: User-Agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows 98; DigExt) Description of problem: if I send to the linux text console the control characters in order to enter the graphics mode (vt100 graphics) , the video remains in text mode and instead of diplaying lines, it displays characters. In red hat 7.2 it works fine. Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1.go to init 3 2.create a file called text containing ESC ( 0 qqqqqqqqqq 3. run the command cat text instead of seeing a continuos line, you see qqqqqqqqqq Actual Results: see above Expected Results: see above Additional info:
I've noticed this too. The Linux console correctly interprets some VT sequences (scroll regions, for example), but does not handle the VT alternate "linedrawing" character set. If it helps, here is some documentation on the codes used to generate these symbols: Description of VT100 codes: http://www.cs.utk.edu/~shuford/terminal/dec_vt100_codes.txt Description of the alternate character set: http://vt100.net/docs/vt100-ug/table3-9.html I am no expert on the subject, but I have an interest in getting this bug resolved so I'll be verbose. The VT codes allow the terminal to switch among several character sets. However, in my experience, the only alternate character set actually commonly used is the one for linedrawing. Switching to any other character set typically just returns you to ISO-8859-15 or UTF-8 or whatever your system's default is (other character sets are rarely implemented. In fact, most of the linedrawing character set is usually also identical to the default character set, it's just the range (decimal) 95-126 that is different (this in in implementation, I have no idea what's "correct"). Here's a list of the decimal codes and my *best guess* as to the matching Unicode value for the glyph they represent. If someone knows better than me, please correct it. Decimal Description Unicode (hex) > 95 blank 00A0 > 96 diamond 2666 > 97 checkerboard 2592 > 98 ht symbol 2409 > 99 ff symbol 240C > 100 cr symbol 240D > 101 lf symbol 240A > 102 degree 00B0 > 103 plus/minus 00B1 > 104 nl symbol 2424 > 105 vt symbol 000B > 106 lower-right corner 2518 > 107 upper-right corner 2510 > 108 upper-left corner 250C > 109 lower-left corner 2514 > 110 crossing lines 253C > 111 horiz line-scan1 23BA > 112 horiz line-scan3 23BB > 113 horiz line-scan5 2500 > 114 horiz line-scan7 23BC > 115 horiz line-scan9 23BD > 116 left "T" 251C > 117 right "T" 2524 > 118 bottom "T" 2534 > 119 top "T" 252C > 120 vert line 2502 > 121 <= 2264 > 122 >= 2265 > 123 pi 03C0 > 124 != 2260 > 125 UK pound 00A3 > 126 centered dot 00B7 Lastly, it's worth noting that this behavior seems to work correctly in an xterm and on the consoles of the RedHat 7.x series. I will attach a linedrawing testcase file that you can cat in an xterm and in the console to see the difference.
Created attachment 89204 [details] VT100 box test Cat this file to test VT100 emulation. If correct, the text "VT100 linedrawing test" should be inside a box of linedrawing characters.
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