Why is this error???????

cmd/piss/main.go

@@ -1,6 +1,8 @@
 package main
 
+import "os/exec"
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/popups"
 // import "git.tebibyte.media/sashakoshka/tomo/elements"
 import pissElements "git.tebibyte.media/sashakoshka/piss/elements"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/all"
@@ -18,4 +20,18 @@ func run () {
 	window.Adopt(terminal)
 	window.OnClose(tomo.Stop)
 	window.Show()
+
+	shell := "ls"
+
+	command := exec.Command(shell)
+	err := terminal.Start(command)
+	if err != nil {
+		popups.NewDialog (
+			popups.DialogKindError,
+			window,
+			"Couldn't start shell",
+			"Could not start " + command.String() + ":\n" +
+			err.Error(),
+		).OnClose(tomo.Stop)
+	}
 }

elements/terminal.go

@@ -1,35 +1,111 @@
 package elements
 
+import "io"
+import "os"
 import "image"
+import "os/exec"
+import "github.com/creack/pty"
 import "git.tebibyte.media/sashakoshka/tomo"
 import "git.tebibyte.media/sashakoshka/piss/ansi"
 
 type Terminal struct {
 	*Grid
-	decoder ansi.Decoder
+
+	stdin  io.WriteCloser
+	stdout io.ReadCloser
+	stderr io.ReadCloser
+	pty    *os.File
+	bufferSize int
+	
+	decoder    ansi.Decoder
+	cursor     image.Point 
+	foreground tomo.Color
+	background tomo.Color
 }
 
 func NewTerminal () (element *Terminal) {
-	element = &Terminal { Grid: NewGrid() }
+	element = &Terminal {
+		Grid: NewGrid(),
+		foreground: tomo.ColorForeground,
+		background: tomo.ColorBackground,
+		bufferSize: 256,
+	}
 	element.Grid.OnResize(element.handleResize)
+
+	element.decoder.OnText = element.handleText
 	return
 }
 
-func (element *Terminal) Write (buffer []byte) (wrote int, err error) {
+func (element *Terminal) Start (command *exec.Cmd) (err error) {
+	winsize := element.winsize()
+	worked  := false
+
+	defer func () { if !worked { element.Close() } } ()
+	
+	element.stdin, err = command.StdinPipe()
+	if err != nil { return }
+	element.stdout, err = command.StdoutPipe()
+	if err != nil { return }
+	element.stderr, err = command.StderrPipe()
+	if err != nil { return }
+
+	element.pty, err = pty.StartWithSize(command, &winsize)
+	if err != nil { return }
+
+	worked = true
+	go element.run()
+	return
+}
+
+func (element *Terminal) Close () {
+	if element.pty    != nil { element.pty.Close()    }
+	if element.stdin  != nil { element.stdin.Close()  }
+	if element.stdout != nil { element.stdout.Close() }
+	if element.stderr != nil { element.stderr.Close() }
+}
+
+func (element *Terminal) run () {
+	buffer := make([]byte, element.bufferSize)
+	for {
+		amount, err := element.stdout.Read(buffer)
+		if err != nil { break }
+		
+		got := buffer[:amount]
+		for len(got) > 0 {
+			wrote, err := element.writeFromProcess(got)
+			got = got[wrote:]
+			if err != nil { break }
+		}
+	}
+}
+
+func (element *Terminal) handleText (text string) {
+	for _, char := range text {
+		element.Set(element.cursor, Cell {
+			Rune:       char,
+			Foreground: element.foreground,
+			Background: element.background,
+		})
+	}
+}
+
+func (element *Terminal) writeFromProcess (buffer []byte) (wrote int, err error) {
 	wrote, err = element.decoder.Write(buffer)
 	element.Push()
 	return
 }
 
 func (element *Terminal) handleResize () {
-	element.Set(image.Pt(0, 0), Cell {
-		Rune: 'X',
-		Background: tomo.ColorRed,
-		Foreground: tomo.ColorBrightWhite,
-	})
-	element.Set(image.Pt(15, 10), Cell {
-		Rune: 'Y',
-		Background: tomo.ColorBrightYellow,
-		Foreground: tomo.ColorBlack,
-	})
+	
+}
+
+func (element *Terminal) winsize () pty.Winsize {
+	columns, rows := element.Size()
+	bounds := element.Bounds()
+	return pty.Winsize {
+		Rows: uint16(rows),
+		Cols: uint16(columns),
+		X:    uint16(bounds.Dx()),
+		Y:    uint16(bounds.Dy()),
+	}
 }

go.mod

@@ -4,6 +4,7 @@ go 1.20
 
 require (
 	git.tebibyte.media/sashakoshka/tomo v0.0.0-20230408034005-dc077a02abe8
+	github.com/creack/pty v1.1.18
 	golang.org/x/image v0.7.0
 )
 

go.sum

@@ -1,11 +1,11 @@
-git.tebibyte.media/sashakoshka/tomo v0.0.0-20230408030342-43a664009c03 h1:muzaW520ATZPL8Nq/ROBqbxZbBkPLTEPS2lcrKmuv2Q=
-git.tebibyte.media/sashakoshka/tomo v0.0.0-20230408030342-43a664009c03/go.mod h1:A0HUbWbA5NgaPVN2ASSn2Y0DxWfaxSV2c0OCSDkYh4c=
 git.tebibyte.media/sashakoshka/tomo v0.0.0-20230408034005-dc077a02abe8 h1:H4VTKYHpZTM+HyCtfIhw1QDcvY6iJvLUyinPJnalCNU=
 git.tebibyte.media/sashakoshka/tomo v0.0.0-20230408034005-dc077a02abe8/go.mod h1:A0HUbWbA5NgaPVN2ASSn2Y0DxWfaxSV2c0OCSDkYh4c=
 github.com/BurntSushi/freetype-go v0.0.0-20160129220410-b763ddbfe298 h1:1qlsVAQJXZHsaM8b6OLVo6muQUQd4CwkH/D3fnnbHXA=
 github.com/BurntSushi/freetype-go v0.0.0-20160129220410-b763ddbfe298/go.mod h1:D+QujdIlUNfa0igpNMk6UIvlb6C252URs4yupRUV4lQ=
 github.com/BurntSushi/graphics-go v0.0.0-20160129215708-b43f31a4a966 h1:lTG4HQym5oPKjL7nGs+csTgiDna685ZXjxijkne828g=
 github.com/BurntSushi/graphics-go v0.0.0-20160129215708-b43f31a4a966/go.mod h1:Mid70uvE93zn9wgF92A/r5ixgnvX8Lh68fxp9KQBaI0=
+github.com/creack/pty v1.1.18 h1:n56/Zwd5o6whRC5PMGretI4IdRLlmBXYNjScPaBgsbY=
+github.com/creack/pty v1.1.18/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
 github.com/jezek/xgb v1.1.0 h1:wnpxJzP1+rkbGclEkmwpVFQWpuE2PUGNUzP8SbfFobk=
 github.com/jezek/xgb v1.1.0/go.mod h1:nrhwO0FX/enq75I7Y7G8iN1ubpSGZEiA3v9e9GyRFlk=
 github.com/jezek/xgbutil v0.0.0-20230403164920-e2f86723ca07 h1:Fr2Oaa4N2oo30/PGecdDkkrth26nD2/yfQFAoddzXmU=