github.com/markusbkk/elvish@v0.0.0-20231204143114-91dc52438621/pkg/cli/term/setup.go (about) 1 package term 2 3 import ( 4 "fmt" 5 "os" 6 7 "github.com/markusbkk/elvish/pkg/sys" 8 "github.com/markusbkk/elvish/pkg/wcwidth" 9 ) 10 11 // Setup sets up the terminal so that it is suitable for the Reader and 12 // Writer to use. It returns a function that can be used to restore the 13 // original terminal config. 14 func Setup(in, out *os.File) (func() error, error) { 15 return setup(in, out) 16 } 17 18 // SetupGlobal sets up the terminal for the entire Elvish session. 19 func SetupGlobal() func() { 20 return setupGlobal() 21 } 22 23 // Sanitize sanitizes the terminal after an external command has executed. 24 func Sanitize(in, out *os.File) { 25 sanitize(in, out) 26 } 27 28 const ( 29 lackEOLRune = '\u23ce' 30 lackEOL = "\033[7m" + string(lackEOLRune) + "\033[m" 31 enableSGRMouse = false 32 ) 33 34 // setupVT performs setup for VT-like terminals. 35 func setupVT(out *os.File) error { 36 _, width := sys.WinSize(out) 37 38 s := "" 39 /* 40 Write a lackEOLRune if the cursor is not in the leftmost column. This is 41 done as follows: 42 43 1. Turn on autowrap; 44 45 2. Write lackEOL along with enough padding, so that the total width is 46 equal to the width of the screen. 47 48 If the cursor was in the first column, we are still in the same line, 49 just off the line boundary. Otherwise, we are now in the next line. 50 51 3. Rewind to the first column, write one space and rewind again. If the 52 cursor was in the first column to start with, we have just erased the 53 LackEOL character. Otherwise, we are now in the next line and this is 54 a no-op. The LackEOL character remains. 55 */ 56 s += fmt.Sprintf("\033[?7h%s%*s\r \r", lackEOL, width-wcwidth.OfRune(lackEOLRune), "") 57 58 /* 59 Turn off autowrap. 60 61 The terminals sometimes has different opinions about how wide some 62 characters are (notably emojis and some dingbats) with elvish. When that 63 happens, elvish becomes wrong about where the cursor is when it writes 64 its output, and the effect can be disastrous. 65 66 If we turn off autowrap, the terminal won't insert any newlines behind 67 the scene, so elvish is always right about which line the cursor is. 68 With a bit more caution, this can restrict the consequence of the 69 mismatch within one line. 70 */ 71 s += "\033[?7l" 72 73 // Turn on SGR-style mouse tracking. 74 if enableSGRMouse { 75 s += "\033[?1000;1006h" 76 } 77 78 // Enable bracketed paste. 79 s += "\033[?2004h" 80 81 _, err := out.WriteString(s) 82 return err 83 } 84 85 // restoreVT performs restore for VT-like terminals. 86 func restoreVT(out *os.File) error { 87 s := "" 88 // Turn on autowrap. 89 s += "\033[?7h" 90 // Turn off mouse tracking. 91 if enableSGRMouse { 92 s += "\033[?1000;1006l" 93 } 94 // Disable bracketed paste. 95 s += "\033[?2004l" 96 // Move the cursor to the first row, even if we haven't written anything 97 // visible. This is because the terminal driver might not be smart enough to 98 // recognize some escape sequences as invisible and wrongly assume that we 99 // are not in the first column, which can mess up with tabs. See 100 // https://github.com/markusbkk/elvish/pkg/issues/629 for an example. 101 s += "\r" 102 _, err := out.WriteString(s) 103 return err 104 }