| 🛟 Updated. 28d5985 k33g 20h ago | 1 | package terminal |
| 2 | |
| 3 | import ( |
| 4 | "errors" |
| 5 | "os" |
| 6 | "runtime" |
| 7 | ) |
| 8 | |
| 9 | // ErrUnsupported is returned by Start on a platform where this editor cannot |
| 10 | // open a pseudo-terminal. |
| 11 | // |
| 12 | // It is not a failure of the editor: everything else goes on working, and only |
| 13 | // terminal windows are unavailable. Linux, macOS and Windows all have one; |
| 14 | // anything else does not, yet. |
| 15 | var ErrUnsupported = errors.New("terminal: not supported on " + runtime.GOOS + " yet") |
| 16 | |
| 17 | // Session is a shell running in its own pseudo-terminal. |
| 18 | // |
| 19 | // Reading from it gives whatever the shell has written; writing to it is what |
| 20 | // the shell reads as its input. Both are safe to use from separate goroutines, |
| 21 | // which is how a terminal window is driven: one goroutine reads, the main one |
| 22 | // writes. |
| 23 | // |
| 24 | // session, err := terminal.Start(terminal.Options{Dir: ".", Width: 80, Height: 24}) |
| 25 | // if err != nil { |
| 26 | // return err |
| 27 | // } |
| 28 | // defer session.Close() |
| 29 | // go io.Copy(parser, session) |
| 30 | type Session struct { |
| 31 | child child |
| 32 | } |
| 33 | |
| 34 | // child is the platform's half of a session: the process on the far side of |
| 35 | // the pseudo-terminal, and the two ends of it this side holds. |
| 36 | // |
| 37 | // Unix has one implementation over /dev/ptmx and an exec.Cmd; Windows has one |
| 38 | // over a pseudo-console and a process created by hand, because Go's exec |
| 39 | // cannot attach a process to a pseudo-console. The Session above is the same |
| 40 | // on both, which is what lets the emulator and the view know nothing about |
| 41 | // which one they are talking to. |
| 42 | type child interface { |
| 43 | // Read returns what the shell has written; io.EOF once it has gone. |
| 44 | Read(b []byte) (int, error) |
| 45 | // Write sends input to the shell. |
| 46 | Write(b []byte) (int, error) |
| 47 | // Resize tells the shell its terminal has changed size. |
| 48 | Resize(width, height int) error |
| 49 | // Close ends the shell and releases everything held for it. |
| 50 | Close() error |
| 51 | // Command returns the name of the program that was started. |
| 52 | Command() string |
| 53 | } |
| 54 | |
| 55 | // Options say what shell to run and how big its terminal is. |
| 56 | type Options struct { |
| 57 | // Shell is the program to run. Empty means the user's own shell: $SHELL on |
| 58 | // Unix, %COMSPEC% on Windows. |
| 59 | Shell string |
| 60 | // Args are the arguments to give it. Empty means none, which is how an |
| 61 | // interactive shell is started; ["-c", "go test ./..."] is how one command |
| 62 | // is run instead — or ["/S", "/C", "go test ./..."] for cmd.exe. |
| 63 | Args []string |
| 64 | // Dir is the directory to start in. Empty means the current one. |
| 65 | Dir string |
| 66 | // Width and Height are the size of the terminal, in cells. |
| 67 | Width int |
| 68 | Height int |
| 69 | // Env is the environment for the shell. Empty means the editor's own, |
| 70 | // with TERM set to what this emulator implements. |
| 71 | Env []string |
| 72 | } |
| 73 | |
| 74 | // TermName is what the shell is told its terminal is. |
| 75 | // |
| 76 | // It has to be a terminal the emulator can live up to: promising xterm-256color |
| 77 | // and then not understanding what a program sends back is worse than promising |
| 78 | // less. |
| 79 | const TermName = "xterm-256color" |
| 80 | |
| 81 | // Start runs a shell in a new pseudo-terminal. |
| 82 | // |
| 83 | // On a platform without support it returns ErrUnsupported, which callers are |
| 84 | // expected to report rather than treat as a failure. |
| 85 | func Start(options Options) (*Session, error) { |
| 86 | c, err := startChild(options) |
| 87 | if err != nil { |
| 88 | return nil, err |
| 89 | } |
| 90 | return &Session{child: c}, nil |
| 91 | } |
| 92 | |
| 93 | // shellOrDefault returns the shell to run: the one asked for, or the user's |
| 94 | // own, which each platform names in its own way. |
| 95 | func shellOrDefault(shell string) string { |
| 96 | if shell != "" { |
| 97 | return shell |
| 98 | } |
| 99 | return defaultShell() |
| 100 | } |
| 101 | |
| 102 | // environment returns the environment for the shell, with TERM set to the |
| 103 | // terminal this emulator actually implements. |
| 104 | // |
| 105 | // Inheriting the editor's own TERM would tell the shell about the *outer* |
| 106 | // terminal, which may promise capabilities this window does not have. |
| 107 | func environment(env []string) []string { |
| 108 | if env == nil { |
| 109 | env = os.Environ() |
| 110 | } |
| 111 | |
| 112 | out := make([]string, 0, len(env)+1) |
| 113 | for _, entry := range env { |
| 114 | if !hasPrefix(entry, "TERM=") { |
| 115 | out = append(out, entry) |
| 116 | } |
| 117 | } |
| 118 | return append(out, "TERM="+TermName) |
| 119 | } |
| 120 | |
| 121 | // hasPrefix reports whether a string starts with a prefix. |
| 122 | func hasPrefix(s, prefix string) bool { |
| 123 | return len(s) >= len(prefix) && s[:len(prefix)] == prefix |
| 124 | } |
| 125 | |
| 126 | // Read returns what the shell has written. It blocks until there is something, |
| 127 | // and returns io.EOF once the shell has gone. |
| 128 | func (s *Session) Read(b []byte) (int, error) { return s.child.Read(b) } |
| 129 | |
| 130 | // Write sends input to the shell, as typing at it would. |
| 131 | func (s *Session) Write(b []byte) (int, error) { return s.child.Write(b) } |
| 132 | |
| 133 | // Resize tells the shell its terminal has changed size, which is what makes a |
| 134 | // full-screen program repaint at the new one. |
| 135 | func (s *Session) Resize(width, height int) error { |
| 136 | return s.child.Resize(max(width, 1), max(height, 1)) |
| 137 | } |
| 138 | |
| 139 | // Close ends the session: the pseudo-terminal is closed, which the shell sees |
| 140 | // as its input ending, and the process is waited for so that it leaves nothing |
| 141 | // behind. |
| 142 | // |
| 143 | // A shell that does not take the hint is killed. Closing must not be able to |
| 144 | // hang the editor. |
| 145 | func (s *Session) Close() error { return s.child.Close() } |
| 146 | |
| 147 | // Command returns the name of the shell that was started, without its path, |
| 148 | // which is what a window title wants. |
| 149 | func (s *Session) Command() string { return s.child.Command() } |