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showcap plot



showcap -- show and decode graphcap entries






Showcap is an interactive, parameterless task that prints and interprets entries in the IRAF graphics device capability file dev$graphcap. These entries contain device dimensions, character sizes etc. plus information for encoding and decoding the ASCII control sequences sent to or returned by the device. Showcap is thus mainly used by IRAF programmers for debugging new graphcap device entries.

At startup showcap prints the following instructions to STDOUT, then prompts with an asterisk.

	cmd :  `set' device
	    |  `*' (to dump full graphcap entry)
	    |  cc [arg1 [arg2 [arg3]]]
	cc  :   a two chararacter capcode (e.g., 'cm')
	    |   an encoder program (non alpha first char)
The user must first use `set' to tell showcap which graphics device to read from graphcap. After a `set' or `*', the full graphcap entry for the named device will be printed. To view an individual capability, type the two-character capability name.

Some device capability entries take up to three arguments, which may be listed on the same line after `cc', separated by whitespace. Showcap is particularly useful for decoding the binary encoder entries used by the graphics kernels. See the examples below.


1. Examine the graphcap entry for the Retrographics vt640.

	cl> showcap
	  * set vt640		(dumps vt640 entry)

2. Decode the sequence sent to the terminal for setting text height 2.

	  * TH 2
		    program:  ^[(1#47+.
		    encoding: ^[1

3. Decode the sequence sent to the terminal to set line type 3.

	  * LT 3
		    program:  LT=\E/(1$0)1d\E`($1-5)0d\E(1_+.$D)0d\E`($$:\
		    encoding: ^[/0d^[b

4. Set environment variable "graphcap" to your local test graphcap file, set device to vt240 and examine the write-cursor (WC) command for x-coordinate 150, y-coordinate 350, and cursor 1.

	cl> set graphcap = "mytest.graphcap"
	cl> showcap
	  * set vt240		(dumps vt240 entry)
	  * WC 150 350 1
		    program:  P[(1)%d,(2)%d]
		    encoding: P[150,350]

5. Examine the scan-cursor function returned when the user types key `a' from coordinate x=150, y=350 after a read-cursor request.

	  * SC a[150,350]
		    program:  (#0!1#0!2,!3,#0!8,#48-!99$0-91#10*9+!1#1!8
		    X(R1)=150 Y(R2)=350, key = a


Diagnostics are mostly limited to a numeric status return when debugging binary encoder entries that contain bugs.


Graphics I/O Design Document.

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