support cursor in TUI layouts

1 files changed, 47 insertions, 15 deletions

diff --git a/tui/layout.go b/tui/layout.go
index 4feda2f..0681e8e 100644
--- a/tui/layout.go
+++ b/tui/layout.go
@@ -16,6 +16,9 @@ type Box struct {
 	Scroll *ScrollState
 	text []textRun
 	computedLines [][]textRun
+	cursorLine int
+	cursorCol int
+	hasCursor bool
 	children []*Box
 	computedPosition int
 	computedSize [2]int
@@ -62,6 +65,7 @@ func (d Direction) reverse() bool {
 type textRun struct {
 	text string
 	style *Style
+	hasCursor bool
 }
 
 type rect struct {
@@ -124,7 +128,11 @@ func Push(id string, box Box) {
 }
 
 func Text(text string, style *Style) {
-	top().text = append(top().text, textRun {text, style})
+	top().text = append(top().text, textRun {text, style, false})
+}
+
+func Cursor() {
+	top().text = append(top().text, textRun {"", nil, true})
 }
 
 func Pop() {
@@ -232,23 +240,36 @@ func (b *Box) computeText(axis int) {
 			line []textRun
 			text, word strings.Builder
 			lineWidth, wordWidth int
+			hasCursor bool
+			cursorAt int
 			run textRun
 		)
-		breakLine := func() {
+		flushText := func() {
 			if text.Len() != 0 {
-				line = append(line, textRun {text.String(), run.style})
+				line = append(line, textRun {text.String(), run.style, false})
 			}
 			text.Reset()
+		}
+		flushLine := func() {
+			flushText()
 			b.computedLines = append(b.computedLines, line)
 			lineWidth = 0
 			line = nil
 		}
-		flushWord := func() {
+		breakWord := func() {
 			if lineWidth + wordWidth > limit {
-				breakLine()
+				flushLine()
 			}
 			g := uniseg.NewGraphemes(word.String())
+			pos := 0
 			for g.Next() {
+				if hasCursor && pos == cursorAt {
+					b.cursorLine = len(b.computedLines)
+					b.cursorCol = lineWidth
+					b.hasCursor = true
+					hasCursor = false
+				}
+
 				if g.Width() > limit {
 					continue
 				}
@@ -257,18 +278,24 @@ func (b *Box) computeText(axis int) {
 				}
 				text.WriteString(g.Str())
 				if g.Width() + lineWidth > limit {
-					breakLine()
+					flushLine()
 				}
 				lineWidth += g.Width()
+
+				pos++
 			}
 			wordWidth = 0
 			word.Reset()
 		}
 		for _, run := range b.text {
+			if run.hasCursor {
+				hasCursor = true
+				cursorAt = wordWidth
+			}
 			g := uniseg.NewGraphemes(run.text)
 			for g.Next() {
 				if g.LineBreak() == uniseg.LineCanBreak {
-					flushWord()
+					breakWord()
 				}
 				if lineWidth != 0 || !unicode.IsSpace(g.Runes()[0]) {
 					word.WriteString(g.Str())
@@ -276,21 +303,18 @@ func (b *Box) computeText(axis int) {
 				}
 				_, end := g.Positions()
 				if end == len(run.text) {
-					flushWord()
+					breakWord()
 					break
 				}
 				if g.LineBreak() == uniseg.LineMustBreak {
-					flushWord()
-					breakLine()
+					breakWord()
+					flushLine()
 				}
 			}
-			if text.Len() != 0 {
-				line = append(line, textRun {text.String(), run.style})
-				text.Reset()
-			}
+			flushText()
 		}
 		if len(line) != 0 || text.Len() != 0 {
-			breakLine()
+			flushLine()
 		}
 		if b.Height == TextSize {
 			b.computedSize[axis] = len(b.computedLines) + b.marginsSize(axis)
@@ -437,6 +461,14 @@ func (b *Box) drawComputed(parentRect rect, parentStyle Style) {
 			x += WriteAt(x, y, t.text, s)
 		}
 	}
+	if b.hasCursor {
+		cx := b.cursorCol + b.computedRect.min[0] + b.Margins[0]
+		cy := b.cursorLine + b.computedRect.min[1] + b.Margins[2]
+		if cx >= viewRect.min[0] && cx < viewRect.max[0] &&
+				cy >= viewRect.min[1] && cy < viewRect.max[1] {
+			ShowCursor(cx, cy)
+		}
+	}
 	for _, c := range b.children {
 		c.drawComputed(viewRect, style)
 	}