Initial patterm project

internal/app/viewport_renderer.go

@@ -0,0 +1,294 @@
+package app
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// viewportRenderer rewrites child PTY output so it lands inside the
+// main viewport instead of controlling patterm's full host terminal.
+type viewportRenderer struct {
+	mu      sync.Mutex
+	shifter *cursorShifter
+	layout  terminalLayout
+	row     int
+	col     int
+
+	state   viewportState
+	buf     []byte
+	pending strings.Builder
+}
+
+type viewportState int
+
+const (
+	vpNormal viewportState = iota
+	vpEsc
+	vpCSI
+	vpOSC
+	vpOSCEsc
+	vpDCS
+	vpDCSEsc
+	vpSOSPMAPC
+	vpSOSPMAPCEsc
+)
+
+func newViewportRenderer(l terminalLayout) *viewportRenderer {
+	return &viewportRenderer{
+		shifter: newCursorShifter(int(l.mainTop) - 1),
+		layout:  l,
+		row:     1,
+		col:     1,
+	}
+}
+
+func (vr *viewportRenderer) SetLayout(l terminalLayout) {
+	vr.mu.Lock()
+	defer vr.mu.Unlock()
+	vr.layout = l
+	vr.shifter.SetRowOffset(int(l.mainTop) - 1)
+}
+
+func (vr *viewportRenderer) Render(in []byte) []byte {
+	vr.mu.Lock()
+	defer vr.mu.Unlock()
+	vr.pending.Reset()
+	for _, b := range in {
+		vr.feed(b)
+	}
+	return []byte(vr.pending.String())
+}
+
+func (vr *viewportRenderer) feed(b byte) {
+	switch vr.state {
+	case vpNormal:
+		if b == 0x1b {
+			vr.state = vpEsc
+			vr.buf = vr.buf[:0]
+			vr.buf = append(vr.buf, b)
+			return
+		}
+		vr.pending.WriteByte(b)
+		vr.advancePrintable(b)
+	case vpEsc:
+		vr.buf = append(vr.buf, b)
+		switch b {
+		case '[':
+			vr.state = vpCSI
+		case ']':
+			vr.state = vpOSC
+		case 'P':
+			vr.state = vpDCS
+		case 'X', '^', '_':
+			vr.state = vpSOSPMAPC
+		default:
+			vr.pending.Write(vr.buf)
+			vr.state = vpNormal
+			vr.buf = vr.buf[:0]
+		}
+	case vpCSI:
+		vr.buf = append(vr.buf, b)
+		if isCSIFinal(b) {
+			vr.emitCSI()
+			vr.state = vpNormal
+			vr.buf = vr.buf[:0]
+		}
+	case vpOSC:
+		vr.buf = append(vr.buf, b)
+		switch b {
+		case 0x07:
+			vr.pending.Write(vr.buf)
+			vr.state = vpNormal
+			vr.buf = vr.buf[:0]
+		case 0x1b:
+			vr.state = vpOSCEsc
+		}
+	case vpOSCEsc:
+		vr.buf = append(vr.buf, b)
+		vr.pending.Write(vr.buf)
+		vr.state = vpNormal
+		vr.buf = vr.buf[:0]
+	case vpDCS:
+		vr.buf = append(vr.buf, b)
+		if b == 0x1b {
+			vr.state = vpDCSEsc
+		}
+	case vpDCSEsc:
+		vr.buf = append(vr.buf, b)
+		vr.pending.Write(vr.buf)
+		vr.state = vpNormal
+		vr.buf = vr.buf[:0]
+	case vpSOSPMAPC:
+		vr.buf = append(vr.buf, b)
+		if b == 0x1b {
+			vr.state = vpSOSPMAPCEsc
+		}
+	case vpSOSPMAPCEsc:
+		vr.buf = append(vr.buf, b)
+		vr.pending.Write(vr.buf)
+		vr.state = vpNormal
+		vr.buf = vr.buf[:0]
+	}
+}
+
+func (vr *viewportRenderer) emitCSI() {
+	if len(vr.buf) < 3 {
+		vr.pending.Write(vr.buf)
+		return
+	}
+	final := vr.buf[len(vr.buf)-1]
+	params := vr.buf[2 : len(vr.buf)-1]
+
+	if final == 'h' || final == 'l' {
+		if isAltScreenMode(params) {
+			return
+		}
+	}
+
+	switch final {
+	case 'J':
+		n, ok := parseOneParam(params, 0)
+		if !ok {
+			vr.pending.Write(vr.shifter.Shift(vr.buf))
+			return
+		}
+		switch n {
+		case 2, 3:
+			vr.pending.WriteString(vr.clearViewport())
+		default:
+			vr.pending.Write(vr.shifter.Shift(vr.buf))
+		}
+	case 'K':
+		n, ok := parseOneParam(params, 0)
+		if !ok {
+			vr.pending.Write(vr.shifter.Shift(vr.buf))
+			return
+		}
+		vr.pending.WriteString(vr.clearLine(n))
+	default:
+		vr.pending.Write(vr.shifter.Shift(vr.buf))
+	}
+	vr.trackCSI(final, params)
+}
+
+func isAltScreenMode(params []byte) bool {
+	s := string(params)
+	if !strings.HasPrefix(s, "?") {
+		return false
+	}
+	for _, p := range strings.Split(strings.TrimPrefix(s, "?"), ";") {
+		switch p {
+		case "47", "1047", "1049":
+			return true
+		}
+	}
+	return false
+}
+
+func (vr *viewportRenderer) clearViewport() string {
+	var b strings.Builder
+	b.WriteString("\x1b7")
+	for r := uint16(0); r < vr.layout.childRows(); r++ {
+		fmt.Fprintf(&b, "\x1b[%d;%dH%s", int(vr.layout.mainTop+r), int(vr.layout.mainLeft), strings.Repeat(" ", int(vr.layout.childCols())))
+	}
+	b.WriteString("\x1b8")
+	return b.String()
+}
+
+func (vr *viewportRenderer) clearLine(n int) string {
+	right := int(vr.layout.childCols())
+	if vr.col < 1 {
+		vr.col = 1
+	}
+	if vr.col > right {
+		vr.col = right
+	}
+	switch n {
+	case 0:
+		return "\x1b[" + strconv.Itoa(right-vr.col+1) + "X"
+	case 1:
+		return "\x1b7\r\x1b[" + strconv.Itoa(vr.col) + "X\x1b8"
+	case 2:
+		return "\x1b7\r\x1b[" + strconv.Itoa(right) + "X\x1b8"
+	default:
+		return "\x1b[" + strconv.Itoa(right-vr.col+1) + "X"
+	}
+}
+
+func (vr *viewportRenderer) advancePrintable(b byte) {
+	switch b {
+	case '\r':
+		vr.col = 1
+	case '\n':
+		vr.row++
+	case '\b':
+		if vr.col > 1 {
+			vr.col--
+		}
+	case '\t':
+		vr.col += 8 - ((vr.col - 1) % 8)
+	default:
+		if b >= 0x20 && b != 0x7f {
+			vr.col++
+		}
+	}
+	vr.clampCursor()
+}
+
+func (vr *viewportRenderer) trackCSI(final byte, params []byte) {
+	switch final {
+	case 'H', 'f':
+		r, c, ok := parseTwoParams(params)
+		if ok {
+			vr.row, vr.col = r, c
+		}
+	case 'G', '`':
+		c, ok := parseOneParam(params, 1)
+		if ok {
+			vr.col = c
+		}
+	case 'd':
+		r, ok := parseOneParam(params, 1)
+		if ok {
+			vr.row = r
+		}
+	case 'A':
+		n, ok := parseOneParam(params, 1)
+		if ok {
+			vr.row -= n
+		}
+	case 'B', 'e':
+		n, ok := parseOneParam(params, 1)
+		if ok {
+			vr.row += n
+		}
+	case 'C', 'a':
+		n, ok := parseOneParam(params, 1)
+		if ok {
+			vr.col += n
+		}
+	case 'D':
+		n, ok := parseOneParam(params, 1)
+		if ok {
+			vr.col -= n
+		}
+	}
+	vr.clampCursor()
+}
+
+func (vr *viewportRenderer) clampCursor() {
+	if vr.row < 1 {
+		vr.row = 1
+	}
+	if vr.col < 1 {
+		vr.col = 1
+	}
+	if max := int(vr.layout.childRows()); vr.row > max {
+		vr.row = max
+	}
+	if max := int(vr.layout.childCols()); vr.col > max {
+		vr.col = max
+	}
+}