1 # amused-monitor
2 
3 This is a small interface for the amused music player
4 
5 => https://projects.omarpolo.com/amused.html amused
6 
7 	#!/usr/bin/env rc
8 
9 It's written in rc because I found easier to manage subprocesses in it
10 rather than in sh.
11 
12 There are two main processes involved: input and ui.  The input
13 process handles the keybindings and controls amused, the ui input
14 waits for some events and redraws the interface.
15 
16 	fn input {
17 		ifs=()
18 
19 $ifs needs to be set to the empty list (or empty string), otherwise
20 we're not able to read spaces as keybindings.
21 
22 		run=1
23 		while (~ $run 1) {
24 
25 rc lacks a break statement, so I'm using a flag variable to quit
26 looping.
27 
28 			stty raw
29 			t=`{dd bs=1 count=1 status=none}
30 			stty cooked
31 
32 This is just a trick to read without echoing back the characters.
33 
34 			switch ($"t) {
35 			case n
36 				amused next
37 			case p
38 				amused prev
39 			case ' '
40 				amused toggle
41 			case s
42 				amused stop
43 			case q
44 				run=0
45 			case *
46 				printf ' unknown keybinding >'$t'<\r'
47 			}
48 		}
49 	}
50 
51 The ui functions render the interface.  I'd like to keep a small xterm
52 open, that's why I'm narrowing (with grep -A -B) only to the songs
53 around the currently played one.
54 
55 	fn ui {
56 		clear
57 		amused show -p | grep -A3 -B3 '^>' | awk '{printf "%s\r\n", $0}'
58 
59 The awk trick deserves an explanation.  Since the input function is
60 very likely running, the terminal is in "raw" mode: we need \r to
61 reposition the character at the start of the line.
62 
63 	}
64 
65 The uiloop function is the driver for the ui process: it listens to
66 interesting events and redraws the ui when they happen
67 
68 	fn uiloop {
69 		amused monitor next,prev,jump | {
70 			while (read) {
71 				ui
72 			}
73 
74 A small note of merit: unlike other shells read is not a built in in
75 rc bur rather an external command (/usr/local/plan9/bin/read here.)
76 
77 		}
78 	}
79 
80 And that's all.  I only need to launch the functions in the correct
81 order and do one render at the start and amused-monitor is done!
82 
83 	ui
84 	uiloop &
85 	uipid=$apid
86 	input
87 	kill -INT -$uipid
88 
89 
90 
91