[tests] Add testing of keyboard events in FullscreenRenderer.GetChar()

This contains one test case of each tcell.Key* event type that can be
sent to and subsequently processed in fzf's GetChar(). The test cases
describe status quo, and all of them PASS.

Small function util.ToTty() was added. It is similar to util.IsTty(),
but for stdout (hence the To preposition).

3 files changed, 400 insertions, 4 deletions

diff --git a/src/tui/tcell.go b/src/tui/tcell.go
index 52bb6b68..f6bd05d8 100644
--- a/src/tui/tcell.go
+++ b/src/tui/tcell.go
@@ -233,6 +233,7 @@ func (r *FullscreenRenderer) GetChar() Event {
 			return EventType(CtrlA.Int() - 'a' + int(r)).AsEvent()
 		}
 		switch ev.Key() {
+		// section 1: Ctrl+(Alt)+[a-z]
 		case tcell.KeyCtrlA:
 			return keyfn('a')
 		case tcell.KeyCtrlB:
@@ -285,6 +286,7 @@ func (r *FullscreenRenderer) GetChar() Event {
 			return keyfn('y')
 		case tcell.KeyCtrlZ:
 			return keyfn('z')
+		// section 2: Ctrl+[ \]_]
 		case tcell.KeyCtrlSpace:
 			return Event{CtrlSpace, 0, nil}
 		case tcell.KeyCtrlBackslash:
@@ -293,12 +295,14 @@ func (r *FullscreenRenderer) GetChar() Event {
 			return Event{CtrlRightBracket, 0, nil}
 		case tcell.KeyCtrlUnderscore:
 			return Event{CtrlSlash, 0, nil}
+		// section 3: (Alt)+Backspace2
 		case tcell.KeyBackspace2:
 			if alt {
 				return Event{AltBS, 0, nil}
 			}
 			return Event{BSpace, 0, nil}
 
+		// section 4: (Alt+Shift)+Key(Up|Down|Left|Right)
 		case tcell.KeyUp:
 			if altShift {
 				return Event{AltSUp, 0, nil}
@@ -344,6 +348,7 @@ func (r *FullscreenRenderer) GetChar() Event {
 			}
 			return Event{Right, 0, nil}
 
+		// section 5: (Insert|Home|Delete|End|PgUp|PgDn|BackTab|F1-F12)
 		case tcell.KeyInsert:
 			return Event{Insert, 0, nil}
 		case tcell.KeyHome:
@@ -356,10 +361,8 @@ func (r *FullscreenRenderer) GetChar() Event {
 			return Event{PgUp, 0, nil}
 		case tcell.KeyPgDn:
 			return Event{PgDn, 0, nil}
-
 		case tcell.KeyBacktab:
 			return Event{BTab, 0, nil}
-
 		case tcell.KeyF1:
 			return Event{F1, 0, nil}
 		case tcell.KeyF2:
@@ -385,6 +388,7 @@ func (r *FullscreenRenderer) GetChar() Event {
 		case tcell.KeyF12:
 			return Event{F12, 0, nil}
 
+		// section 6: (Alt)+'rune'
 		case tcell.KeyRune:
 			r := ev.Rune()
 			if alt {
@@ -392,12 +396,13 @@ func (r *FullscreenRenderer) GetChar() Event {
 			}
 			return Event{Rune, r, nil}
 
+		// section 7: Esc
 		case tcell.KeyEsc:
 			return Event{ESC, 0, nil}
-
 		}
 	}
 
+	// section 8: Invalid
 	return Event{Invalid, 0, nil}
 }
 
diff --git a/src/tui/tcell_test.go b/src/tui/tcell_test.go
new file mode 100644
index 00000000..84501b87
--- /dev/null
+++ b/src/tui/tcell_test.go
@@ -0,0 +1,386 @@
+// +build tcell windows
+
+package tui
+
+import (
+	"testing"
+
+	"github.com/gdamore/tcell"
+	"github.com/junegunn/fzf/src/util"
+)
+
+func assert(t *testing.T, context string, got interface{}, want interface{}) bool {
+	if got == want {
+		return true
+	} else {
+		t.Errorf("%s = (%T)%v, want (%T)%v", context, got, got, want, want)
+		return false
+	}
+}
+
+// Test the handling of the tcell keyboard events.
+func TestGetCharEventKey(t *testing.T) {
+	if util.ToTty() {
+		// This test is skipped when output goes to terminal, because it causes
+		// some glitches:
+		// - output lines may not start at the beginning of a row which makes
+		//   the output unreadable
+		// - terminal may get cleared which prevents you from seeing results of
+		//   previous tests
+		// Good ways to prevent the glitches are piping the output to a pager
+		// or redirecting to a file. I've found `less +G` to be trouble-free.
+		t.Skip("Skipped because this test misbehaves in terminal, pipe to a pager or redirect output to a file to run it safely.")
+	} else if testing.Verbose() {
+		// I have observed a behaviour when this test outputted more than 8192
+		// bytes (32*256) into the 'less' pager, both the go's test executable
+		// and the pager hanged. The go's executable was blocking on printing.
+		// I was able to create minimal working example of that behaviour, but
+		// that example hanged after 12256 bytes (32*(256+127)).
+		t.Log("If you are piping this test to a pager and it hangs, make the pager greedy for input, e.g. 'less +G'.")
+	}
+
+	if !HasFullscreenRenderer() {
+		t.Skip("Can't test FullscreenRenderer.")
+	}
+
+	// construct test cases
+	type giveKey struct {
+		Type tcell.Key
+		Char rune
+		Mods tcell.ModMask
+	}
+	type wantKey = Event
+	type testCase struct {
+		giveKey
+		wantKey
+	}
+	/*
+		Some test cases are marked "fabricated". It means that giveKey value
+		is valid, but it is not what you get when you press the keys. For
+		example Ctrl+C will NOT give you tcell.KeyCtrlC, but tcell.KeyETX
+		(End-Of-Text character, causing SIGINT).
+		I was trying to accompany the fabricated test cases with real ones.
+
+		Some test cases are marked "unhandled". It means that giveKey.Type
+		is not present in tcell.go source code. It can still be handled via
+		implicit or explicit alias.
+
+		If not said otherwise, test cases are for US keyboard.
+
+		(tabstop=44)
+	*/
+	tests := []testCase{
+
+		// section 1: Ctrl+(Alt)+[a-z]
+		{giveKey{tcell.KeyCtrlA, rune(tcell.KeyCtrlA), tcell.ModCtrl}, wantKey{CtrlA, 0, nil}},
+		{giveKey{tcell.KeyCtrlC, rune(tcell.KeyCtrlC), tcell.ModCtrl}, wantKey{CtrlC, 0, nil}}, // fabricated
+		{giveKey{tcell.KeyETX, rune(tcell.KeyETX), tcell.ModCtrl}, wantKey{CtrlC, 0, nil}},     // this is SIGINT (Ctrl+C)
+		{giveKey{tcell.KeyCtrlZ, rune(tcell.KeyCtrlZ), tcell.ModCtrl}, wantKey{CtrlZ, 0, nil}}, // fabricated
+		// KeyTab is alias for KeyTAB
+		{giveKey{tcell.KeyCtrlI, rune(tcell.KeyCtrlI), tcell.ModCtrl}, wantKey{Tab, 0, nil}}, // fabricated
+		{giveKey{tcell.KeyTab, rune(tcell.KeyTab), tcell.ModNone}, wantKey{Tab, 0, nil}},     // unhandled, actual "Tab" keystroke
+		{giveKey{tcell.KeyTAB, rune(tcell.KeyTAB), tcell.ModNone}, wantKey{Tab, 0, nil}},     // fabricated, unhandled
+		// KeyEnter is alias for KeyCR
+		{giveKey{tcell.KeyCtrlM, rune(tcell.KeyCtrlM), tcell.ModNone}, wantKey{CtrlM, 0, nil}}, // actual "Enter" keystroke
+		{giveKey{tcell.KeyCR, rune(tcell.KeyCR), tcell.ModNone}, wantKey{CtrlM, 0, nil}},       // fabricated, unhandled
+		{giveKey{tcell.KeyEnter, rune(tcell.KeyEnter), tcell.ModNone}, wantKey{CtrlM, 0, nil}}, // fabricated, unhandled
+		// Ctrl+Alt keys
+		{giveKey{tcell.KeyCtrlA, rune(tcell.KeyCtrlA), tcell.ModCtrl | tcell.ModAlt}, wantKey{CtrlAlt, 'a', nil}},                  // fabricated
+		{giveKey{tcell.KeyCtrlA, rune(tcell.KeyCtrlA), tcell.ModCtrl | tcell.ModAlt | tcell.ModShift}, wantKey{CtrlAlt, 'a', nil}}, // fabricated
+
+		/*
+		   "Input method" in Windows Language options:
+		   US: "US Keyboard" does not generate any characters (and thus any events) in Ctrl+Alt+[a-z] range
+		   CS: "Czech keyboard"
+		   DE: "German keyboard"
+
+		   Note that right Alt is not just `tcell.ModAlt` on foreign language keyboards, but it is the AltGr `tcell.ModCtrl|tcell.ModAlt`.
+		*/
+		{giveKey{tcell.KeyRune, '{', tcell.ModCtrl | tcell.ModAlt}, wantKey{Alt, '{', nil}}, // CS: Ctrl+Alt+b = "{"
+		{giveKey{tcell.KeyRune, '{', tcell.ModCtrl | tcell.ModAlt}, wantKey{Alt, '{', nil}}, // DE: Ctrl+Alt+7 = "{"
+		{giveKey{tcell.KeyRune, '@', tcell.ModCtrl | tcell.ModAlt}, wantKey{Alt, '@', nil}}, // DE: Ctrl+Alt+q = "@"
+		{giveKey{tcell.KeyRune, 'µ', tcell.ModCtrl | tcell.ModAlt}, wantKey{Alt, 'µ', nil}}, // DE: Ctrl+Alt+m = "µ"
+
+		// section 2: Ctrl+[ \]_]
+		{giveKey{tcell.KeyCtrlSpace, rune(tcell.KeyCtrlSpace), tcell.ModCtrl}, wantKey{CtrlSpace, 0, nil}}, // fabricated
+		{giveKey{tcell.KeyNUL, rune(tcell.KeyNUL), tcell.ModNone}, wantKey{CtrlSpace, 0, nil}},             // fabricated, unhandled
+		{giveKey{tcell.KeyRune, ' ', tcell.ModCtrl}, wantKey{Rune, ' ', nil}},                              // actual Ctrl+' '
+		{giveKey{tcell.KeyCtrlBackslash, rune(tcell.KeyCtrlBackslash), tcell.ModCtrl}, wantKey{CtrlBackSlash, 0, nil}},
+		{giveKey{tcell.KeyCtrlRightSq, rune(tcell.KeyCtrlRightSq), tcell.ModCtrl}, wantKey{CtrlRightBracket, 0, nil}},
+		{giveKey{tcell.KeyCtrlUnderscore, rune(tcell.KeyCtrlUnderscore), tcell.ModShift | tcell.ModCtrl}, wantKey{CtrlSlash, 0, nil}},
+
+		// section 3: (Alt)+Backspace2
+		// KeyBackspace2 is alias for KeyDEL = 0x7F (ASCII) (allegedly unused by Windows)
+		// KeyDelete = 0x2E (VK_DELETE constant in Windows)
+		// KeyBackspace is alias for KeyBS = 0x08 (ASCII) (implicit alias with KeyCtrlH)
+		{giveKey{tcell.KeyBackspace2, 0, tcell.ModNone}, wantKey{BSpace, 0, nil}}, // fabricated
+		{giveKey{tcell.KeyBackspace2, 0, tcell.ModAlt}, wantKey{AltBS, 0, nil}},   // fabricated
+		{giveKey{tcell.KeyDEL, 0, tcell.ModNone}, wantKey{BSpace, 0, nil}},        // fabricated, unhandled
+		{giveKey{tcell.KeyDelete, 0, tcell.ModNone}, wantKey{Del, 0, nil}},
+		{giveKey{tcell.KeyDelete, 0, tcell.ModAlt}, wantKey{Del, 0, nil}},
+		{giveKey{tcell.KeyBackspace, 0, tcell.ModNone}, wantKey{CtrlH, 0, nil}},                                                    // fabricated, unhandled
+		{giveKey{tcell.KeyBS, 0, tcell.ModNone}, wantKey{CtrlH, 0, nil}},                                                           // fabricated, unhandled
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModNone}, wantKey{CtrlH, 0, nil}},                                     // actual "Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModAlt}, wantKey{CtrlAlt, 'h', nil}},                                  // actual "Alt+Backspace" keystroke
+		{giveKey{tcell.KeyDEL, rune(tcell.KeyDEL), tcell.ModCtrl}, wantKey{BSpace, 0, nil}},                                        // actual "Ctrl+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModShift}, wantKey{CtrlH, 0, nil}},                                    // actual "Shift+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, 0, tcell.ModCtrl | tcell.ModAlt}, wantKey{CtrlAlt, 'h', nil}},                                     // actual "Ctrl+Alt+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, 0, tcell.ModCtrl | tcell.ModShift}, wantKey{CtrlH, 0, nil}},                                       // actual "Ctrl+Shift+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModShift | tcell.ModAlt}, wantKey{CtrlAlt, 'h', nil}},                 // actual "Shift+Alt+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, 0, tcell.ModCtrl | tcell.ModAlt | tcell.ModShift}, wantKey{CtrlAlt, 'h', nil}},                    // actual "Ctrl+Shift+Alt+Backspace" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl}, wantKey{CtrlH, 0, nil}},                                     // actual "Ctrl+H" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl | tcell.ModAlt}, wantKey{CtrlAlt, 'h', nil}},                  // fabricated "Ctrl+Alt+H" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl | tcell.ModShift}, wantKey{CtrlH, 0, nil}},                    // actual "Ctrl+Shift+H" keystroke
+		{giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl | tcell.ModAlt | tcell.ModShift}, wantKey{CtrlAlt, 'h', nil}}, // fabricated "Ctrl+Shift+Alt+H" keystroke
+
+		// section 4: (Alt+Shift)+Key(Up|Down|Left|Right)
+		{giveKey{tcell.KeyUp, 0, tcell.ModNone}, wantKey{Up, 0, nil}},
+		{giveKey{tcell.KeyDown, 0, tcell.ModAlt}, wantKey{AltDown, 0, nil}},
+		{giveKey{tcell.KeyLeft, 0, tcell.ModShift}, wantKey{SLeft, 0, nil}},
+		{giveKey{tcell.KeyRight, 0, tcell.ModShift | tcell.ModAlt}, wantKey{AltSRight, 0, nil}},
+		{giveKey{tcell.KeyUpLeft, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},    // fabricated, unhandled
+		{giveKey{tcell.KeyUpRight, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},   // fabricated, unhandled
+		{giveKey{tcell.KeyDownLeft, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},  // fabricated, unhandled
+		{giveKey{tcell.KeyDownRight, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}}, // fabricated, unhandled
+		{giveKey{tcell.KeyCenter, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},    // fabricated, unhandled
+		// section 5: (Insert|Home|Delete|End|PgUp|PgDn|BackTab|F1-F12)
+		{giveKey{tcell.KeyInsert, 0, tcell.ModNone}, wantKey{Insert, 0, nil}},
+		{giveKey{tcell.KeyF1, 0, tcell.ModNone}, wantKey{F1, 0, nil}},
+		// section 6: (Alt)+'rune'
+		{giveKey{tcell.KeyRune, 'a', tcell.ModNone}, wantKey{Rune, 'a', nil}},
+		{giveKey{tcell.KeyRune, 'a', tcell.ModAlt}, wantKey{Alt, 'a', nil}},
+		{giveKey{tcell.KeyRune, 'A', tcell.ModAlt}, wantKey{Alt, 'A', nil}},
+		{giveKey{tcell.KeyRune, '`', tcell.ModAlt}, wantKey{Alt, '`', nil}},
+		// section 7: Esc
+		// KeyEsc and KeyEscape are aliases for KeyESC
+		{giveKey{tcell.KeyEsc, rune(tcell.KeyEsc), tcell.ModNone}, wantKey{ESC, 0, nil}},               // fabricated
+		{giveKey{tcell.KeyESC, rune(tcell.KeyESC), tcell.ModNone}, wantKey{ESC, 0, nil}},               // unhandled
+		{giveKey{tcell.KeyEscape, rune(tcell.KeyEscape), tcell.ModNone}, wantKey{ESC, 0, nil}},         // fabricated, unhandled
+		{giveKey{tcell.KeyESC, rune(tcell.KeyESC), tcell.ModCtrl}, wantKey{ESC, 0, nil}},               // actual Ctrl+[ keystroke
+		{giveKey{tcell.KeyCtrlLeftSq, rune(tcell.KeyCtrlLeftSq), tcell.ModCtrl}, wantKey{ESC, 0, nil}}, // fabricated, unhandled
+
+		// section 8: Invalid
+		{giveKey{tcell.KeyRune, 'a', tcell.ModMeta}, wantKey{Rune, 'a', nil}}, // fabricated
+		{giveKey{tcell.KeyF24, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},
+		{giveKey{tcell.KeyCtrlCarat, rune(tcell.KeyCtrlCarat), tcell.ModShift | tcell.ModCtrl}, wantKey{Invalid, 0, nil}}, // fabricated, unhandled
+		{giveKey{tcell.KeyRS, rune(tcell.KeyRS), tcell.ModShift | tcell.ModCtrl}, wantKey{Invalid, 0, nil}},               // actual Ctrl+Shift+6 (i.e. Ctrl+^) keystroke
+		{giveKey{tcell.KeyHelp, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                              // fabricated, unhandled
+		{giveKey{tcell.KeyExit, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                              // fabricated, unhandled
+		{giveKey{tcell.KeyClear, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                             // unhandled, actual keystroke Numpad_5 with Numlock OFF
+		{giveKey{tcell.KeyCancel, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                            // fabricated, unhandled
+		{giveKey{tcell.KeyPrint, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                             // fabricated, unhandled
+		{giveKey{tcell.KeyPause, 0, tcell.ModNone}, wantKey{Invalid, 0, nil}},                                             // unhandled
+
+	}
+	r := NewFullscreenRenderer(&ColorTheme{}, false, false)
+	r.Init()
+
+	// run and evaluate the tests
+	for _, test := range tests {
+		// generate key event
+		giveEvent := tcell.NewEventKey(test.giveKey.Type, test.giveKey.Char, test.giveKey.Mods)
+		_screen.PostEventWait(giveEvent)
+		t.Logf("giveEvent = %T{key: %v, ch: %q (%[3]v), mod: %#04b}\n", giveEvent, giveEvent.Key(), giveEvent.Rune(), giveEvent.Modifiers())
+
+		// process the event in fzf and evaluate the test
+		gotEvent := r.GetChar()
+		// skip Resize events, those are sometimes put in the buffer outside of this test
+		for gotEvent.Type == Resize {
+			t.Logf("Resize swallowed")
+			gotEvent = r.GetChar()
+		}
+		t.Logf("wantEvent = %T{Type: %v, Char: %q (%[3]v)}\n", test.wantKey, test.wantKey.Type, test.wantKey.Char)
+		t.Logf("gotEvent = %T{Type: %v, Char: %q (%[3]v)}\n", gotEvent, gotEvent.Type, gotEvent.Char)
+
+		assert(t, "r.GetChar().Type", gotEvent.Type, test.wantKey.Type)
+		assert(t, "r.GetChar().Char", gotEvent.Char, test.wantKey.Char)
+	}
+
+	r.Close()
+}
+
+/*
+Quick reference
+---------------
+
+(tabstop=18)
+(this is not mapping table, it merely puts multiple constants ranges in one table)
+
+¹) the two columns are each other implicit alias
+²) explicit aliases here
+
+%v	section #	tcell ctrl key¹	tcell ctrl char¹	tcell alias²	tui constants	tcell named keys	tcell mods
+--	---------	--------------	---------------	-----------	-------------	----------------	----------
+0	2	KeyCtrlSpace	KeyNUL = ^@ 		Rune		ModNone
+1	1	KeyCtrlA	KeySOH = ^A		CtrlA		ModShift
+2	1	KeyCtrlB	KeySTX = ^B		CtrlB		ModCtrl
+3	1	KeyCtrlC	KeyETX = ^C		CtrlC
+4	1	KeyCtrlD	KeyEOT = ^D		CtrlD		ModAlt
+5	1	KeyCtrlE	KeyENQ = ^E		CtrlE
+6	1	KeyCtrlF	KeyACK = ^F		CtrlF
+7	1	KeyCtrlG	KeyBEL = ^G		CtrlG
+8	1	KeyCtrlH	KeyBS = ^H	KeyBackspace	CtrlH		ModMeta
+9	1	KeyCtrlI	KeyTAB = ^I	KeyTab	Tab
+10	1	KeyCtrlJ	KeyLF = ^J		CtrlJ
+11	1	KeyCtrlK	KeyVT = ^K		CtrlK
+12	1	KeyCtrlL	KeyFF = ^L		CtrlL
+13	1	KeyCtrlM	KeyCR = ^M	KeyEnter	CtrlM
+14	1	KeyCtrlN	KeySO = ^N		CtrlN
+15	1	KeyCtrlO	KeySI = ^O		CtrlO
+16	1	KeyCtrlP	KeyDLE = ^P		CtrlP
+17	1	KeyCtrlQ	KeyDC1 = ^Q		CtrlQ
+18	1	KeyCtrlR	KeyDC2 = ^R		CtrlR
+19	1	KeyCtrlS	KeyDC3 = ^S		CtrlS
+20	1	KeyCtrlT	KeyDC4 = ^T		CtrlT
+21	1	KeyCtrlU	KeyNAK = ^U		CtrlU
+22	1	KeyCtrlV	KeySYN = ^V		CtrlV
+23	1	KeyCtrlW	KeyETB = ^W		CtrlW
+24	1	KeyCtrlX	KeyCAN = ^X		CtrlX
+25	1	KeyCtrlY	KeyEM = ^Y		CtrlY
+26	1	KeyCtrlZ	KeySUB = ^Z		CtrlZ
+27	7	KeyCtrlLeftSq	KeyESC = ^[	KeyEsc, KeyEscape	ESC
+28	2	KeyCtrlBackslash	KeyFS = ^\		CtrlSpace
+29	2	KeyCtrlRightSq	KeyGS = ^]		CtrlBackSlash
+30	8	KeyCtrlCarat	KeyRS = ^^		CtrlRightBracket
+31	2	KeyCtrlUnderscore	KeyUS = ^_		CtrlCaret
+32					CtrlSlash
+33					Invalid
+34					Resize
+35					Mouse
+36					DoubleClick
+37					LeftClick
+38					RightClick
+39					BTab
+40					BSpace
+41					Del
+42					PgUp
+43					PgDn
+44					Up
+45					Down
+46					Left
+47					Right
+48					Home
+49					End
+50					Insert
+51					SUp
+52					SDown
+53					SLeft
+54					SRight
+55					F1
+56					F2
+57					F3
+58					F4
+59					F5
+60					F6
+61					F7
+62					F8
+63					F9
+64					F10
+65					F11
+66					F12
+67					Change
+68					BackwardEOF
+69					AltBS
+70					AltUp
+71					AltDown
+72					AltLeft
+73					AltRight
+74					AltSUp
+75					AltSDown
+76					AltSLeft
+77					AltSRight
+78					Alt
+79					CtrlAlt
+..
+127	3		  KeyDEL	KeyBackspace2
+..
+256	6					KeyRune
+257	4					KeyUp
+258	4					KeyDown
+259	4					KeyRight
+260	4					KeyLeft
+261	8					KeyUpLeft
+262	8					KeyUpRight
+263	8					KeyDownLeft
+264	8					KeyDownRight
+265	8					KeyCenter
+266	5					KeyPgUp
+267	5					KeyPgDn
+268	5					KeyHome
+269	5					KeyEnd
+270	5					KeyInsert
+271	5					KeyDelete
+272	8					KeyHelp
+273	8					KeyExit
+274	8					KeyClear
+275	8		  			KeyCancel
+276	8				  	KeyPrint
+277	8					KeyPause
+278	5					KeyBacktab
+279	5					KeyF1
+280	5					KeyF2
+281	5					KeyF3
+282	5					KeyF4
+283	5					KeyF5
+284	5					KeyF6
+285	5					KeyF7
+286	5					KeyF8
+287	5					KeyF9
+288	5					KeyF10
+289	5					KeyF11
+290	5					KeyF12
+291	8					KeyF13
+292	8					KeyF14
+293	8					KeyF15
+294	8					KeyF16
+295	8					KeyF17
+296	8					KeyF18
+297	8					KeyF19
+298	8					KeyF20
+299	8					KeyF21
+300	8					KeyF22
+301	8					KeyF23
+302	8					KeyF24
+303	8					KeyF25
+304	8					KeyF26
+305	8					KeyF27
+306	8					KeyF28
+307	8					KeyF29
+308	8					KeyF30
+309	8					KeyF31
+310	8					KeyF32
+311	8					KeyF33
+312	8					KeyF34
+313	8					KeyF35
+314	8					KeyF36
+315	8					KeyF37
+316	8					KeyF38
+317	8					KeyF39
+318	8					KeyF40
+319	8					KeyF41
+320	8					KeyF42
+321	8					KeyF43
+322	8					KeyF44
+323	8					KeyF45
+324	8					KeyF46
+325	8					KeyF47
+326	8					KeyF48
+327	8					KeyF49
+328	8					KeyF50
+329	8					KeyF51
+330	8					KeyF52
+331	8					KeyF53
+332	8					KeyF54
+333	8					KeyF55
+334	8					KeyF56
+335	8					KeyF57
+336	8					KeyF58
+337	8					KeyF59
+338	8					KeyF60
+339	8					KeyF61
+340	8					KeyF62
+341	8					KeyF63
+342	8					KeyF64
+--	---------	--------------	---------------	-----------	-------------	----------------	----------
+%v	section #	tcell ctrl key	tcell ctrl char	tcell alias	tui constants	tcell named keys	tcell mods
+*/
diff --git a/src/util/util.go b/src/util/util.go
index b3c32970..c16f1af0 100644
--- a/src/util/util.go
+++ b/src/util/util.go
@@ -117,11 +117,16 @@ func DurWithin(
 	return val
 }
 
-// IsTty returns true is stdin is a terminal
+// IsTty returns true if stdin is a terminal
 func IsTty() bool {
 	return isatty.IsTerminal(os.Stdin.Fd())
 }
 
+// ToTty returns true if stdout is a terminal
+func ToTty() bool {
+	return isatty.IsTerminal(os.Stdout.Fd())
+}
+
 // Once returns a function that returns the specified boolean value only once
 func Once(nextResponse bool) func() bool {
 	state := nextResponse