v0.1.6 tui clipped box, scrollbar, and keyvalue improvements, single column document widget added

tui/border.go

@@ -38,7 +38,14 @@ const (
 
 // Box draws border around region edge
 func (r Region) Box(line LineType, fg color.RGB) {
-	if r.W < 2 || r.H < 2 {
+	r.BoxClipped(line, fg, r.H, 0)
+}
+
+// BoxClipped draws the visible slice of a box whose logical height is totalH,
+// with off rows scrolled past its top edge. Rows outside the box are skipped,
+// so a partially visible box keeps its sides and grows no false edges.
+func (r Region) BoxClipped(line LineType, fg color.RGB, totalH, off int) {
+	if r.W < 2 || r.H < 1 || totalH < 2 {
 		return
 	}
 	if line >= LineType(len(boxChars)) {
@@ -48,22 +55,28 @@ func (r Region) Box(line LineType, fg color.RGB) {
 	chars := boxChars[line]
 	bg := color.RGB{} // Transparent (use existing bg)
 
-	// Corners
+	for y := range r.H {
-	r.Cell(0, 0, chars[boxTL], fg, bg, terminal.AttrNone)
+		c := off + y
-	r.Cell(r.W-1, 0, chars[boxTR], fg, bg, terminal.AttrNone)
+		if c < 0 || c >= totalH {
-	r.Cell(0, r.H-1, chars[boxBL], fg, bg, terminal.AttrNone)
+			continue
-	r.Cell(r.W-1, r.H-1, chars[boxBR], fg, bg, terminal.AttrNone)
+		}
-
+		switch c {
-	// Horizontal edges
+		case 0:
-	for x := 1; x < r.W-1; x++ {
+			r.Cell(0, y, chars[boxTL], fg, bg, terminal.AttrNone)
-		r.Cell(x, 0, chars[boxH], fg, bg, terminal.AttrNone)
+			r.Cell(r.W-1, y, chars[boxTR], fg, bg, terminal.AttrNone)
-		r.Cell(x, r.H-1, chars[boxH], fg, bg, terminal.AttrNone)
+			for x := 1; x < r.W-1; x++ {
-	}
+				r.Cell(x, y, chars[boxH], fg, bg, terminal.AttrNone)
-
+			}
-	// Vertical edges
+		case totalH - 1:
-	for y := 1; y < r.H-1; y++ {
+			r.Cell(0, y, chars[boxBL], fg, bg, terminal.AttrNone)
-		r.Cell(0, y, chars[boxV], fg, bg, terminal.AttrNone)
+			r.Cell(r.W-1, y, chars[boxBR], fg, bg, terminal.AttrNone)
-		r.Cell(r.W-1, y, chars[boxV], fg, bg, terminal.AttrNone)
+			for x := 1; x < r.W-1; x++ {
+				r.Cell(x, y, chars[boxH], fg, bg, terminal.AttrNone)
+			}
+		default:
+			r.Cell(0, y, chars[boxV], fg, bg, terminal.AttrNone)
+			r.Cell(r.W-1, y, chars[boxV], fg, bg, terminal.AttrNone)
+		}
 	}
 }
 
@@ -158,4 +171,3 @@ func (r Region) Card(title string, line LineType, fg color.RGB) Region {
 
 	return r.Inset(1)
 }
-

tui/document.go

@@ -0,0 +1,224 @@
+package tui
+
+// DocKind classifies a document block
+type DocKind uint8
+
+const (
+	DocSection DocKind = iota // Section header with an inline rule
+	DocEntry                  // Key + description in aligned columns
+	DocPara                   // Wrapped paragraph across the document width
+	DocGap                    // One blank row
+)
+
+// DocBlock is one logical unit of a document
+type DocBlock struct {
+	Kind DocKind
+	Key  string // DocEntry only
+	Text string
+}
+
+// DocOpts configures document layout and rendering
+// Layout-affecting fields must not change between Layout and Doc
+type DocOpts struct {
+	HeaderStyle Style
+	KeyStyle    Style
+	TextStyle   Style
+	RuleStyle   Style
+	Rule        LineType // Header rule; LineNone draws the header alone
+	KeyWidth    int      // Fixed key column, 0 = measured from the entries
+	KeyMaxW     int      // Cap for the measured key column, 0 = 40% of width
+	MinTextW    int      // Text column narrower than this stacks every entry
+	Gap         int      // Columns between key and text, minimum 1
+	Indent      int      // Left indent of section content
+	StackIndent int      // Indent of a stacked description
+	SectionGap  int      // Blank rows before a section header
+	MaxWidth    int      // Document width cap, 0 = region width
+	Center      bool     // Center the document when the cap applies
+}
+
+// Row kinds in the flattened document
+const (
+	docRowBlank uint8 = iota
+	docRowSection
+	docRowKey   // Stacked entry key, left-aligned
+	docRowEntry // Key column plus the first description line
+	docRowText  // Continuation or stacked description line
+)
+
+type docRow struct {
+	key  string
+	text string
+	x    int
+	kind uint8
+}
+
+// DocState holds a laid-out document and its scroll position
+type DocState struct {
+	Viewport *ViewportScroll
+	rows     []docRow
+	width    int // Document width used by the layout
+	xOff     int // Document offset within the render region
+	keyW     int
+	gap      int
+}
+
+// NewDocState creates document state
+func NewDocState() *DocState {
+	return &DocState{Viewport: NewViewportScroll()}
+}
+
+// SetViewport updates viewport height
+func (d *DocState) SetViewport(h int) {
+	d.Viewport.ViewportH = h
+	d.Viewport.ScrollTo(d.Viewport.Offset)
+}
+
+// Layout flattens blocks into rows for the given width; the row count becomes
+// the viewport content height. Entries stack when the text column is too
+// narrow, and an over-long key stacks on its own rather than truncating.
+func (d *DocState) Layout(blocks []DocBlock, width int, opts DocOpts) {
+	d.rows = d.rows[:0]
+	if width < 1 {
+		d.width, d.Viewport.ContentH = 0, 0
+		return
+	}
+
+	docW := width
+	if opts.MaxWidth > 0 && docW > opts.MaxWidth {
+		docW = opts.MaxWidth
+	}
+	d.width = docW
+	d.xOff = 0
+	if opts.Center {
+		d.xOff = (width - docW) / 2
+	}
+
+	d.gap = max(opts.Gap, 1)
+	indent := min(max(opts.Indent, 0), docW-1)
+
+	keyMax := opts.KeyMaxW
+	if keyMax <= 0 {
+		keyMax = docW * 2 / 5
+	}
+	keyMax = min(keyMax, max(docW/2, 1))
+
+	keyW := opts.KeyWidth
+	if keyW <= 0 {
+		for i := range blocks {
+			if blocks[i].Kind != DocEntry {
+				continue
+			}
+			if n := RuneLen(blocks[i].Key); n > keyW && n <= keyMax {
+				keyW = n
+			}
+		}
+	}
+	d.keyW = min(max(keyW, 1), keyMax)
+
+	textX := indent + d.keyW + d.gap
+	textW := docW - textX
+	stackX := min(indent+max(opts.StackIndent, 0), docW-1)
+	stackW := max(docW-stackX, 1)
+	stacked := textW < opts.MinTextW || textW < 1
+
+	for i := range blocks {
+		b := &blocks[i]
+		switch b.Kind {
+		case DocGap:
+			d.rows = append(d.rows, docRow{kind: docRowBlank})
+
+		case DocSection:
+			for range opts.SectionGap {
+				if len(d.rows) > 0 {
+					d.rows = append(d.rows, docRow{kind: docRowBlank})
+				}
+			}
+			d.rows = append(d.rows, docRow{kind: docRowSection, text: b.Text})
+
+		case DocPara:
+			for _, line := range WrapText(b.Text, max(docW-indent, 1)) {
+				d.rows = append(d.rows, docRow{kind: docRowText, x: indent, text: line})
+			}
+
+		case DocEntry:
+			// Narrow document: every entry stacks at the stack indent
+			if stacked {
+				d.rows = append(d.rows, docRow{kind: docRowKey, x: indent, key: b.Key})
+				for _, line := range WrapText(b.Text, stackW) {
+					d.rows = append(d.rows, docRow{kind: docRowText, x: stackX, text: line})
+				}
+				continue
+			}
+			// Over-long key stacks alone but keeps the shared text column
+			if RuneLen(b.Key) > d.keyW {
+				d.rows = append(d.rows, docRow{kind: docRowKey, x: indent, key: b.Key})
+				for _, line := range WrapText(b.Text, textW) {
+					d.rows = append(d.rows, docRow{kind: docRowText, x: textX, text: line})
+				}
+				continue
+			}
+			lines := WrapText(b.Text, textW)
+			d.rows = append(d.rows, docRow{kind: docRowEntry, x: indent, key: b.Key, text: lines[0]})
+			for _, line := range lines[1:] {
+				d.rows = append(d.rows, docRow{kind: docRowText, x: textX, text: line})
+			}
+		}
+	}
+
+	d.Viewport.ContentH = len(d.rows)
+}
+
+// Doc renders the visible window of a laid-out document
+func (r Region) Doc(d *DocState, opts DocOpts) {
+	if d == nil || r.H < 1 || r.W < 1 {
+		return
+	}
+	d.Viewport.SetDimensions(len(d.rows), r.H)
+
+	for y := range r.H {
+		i := d.Viewport.Offset + y
+		if i >= len(d.rows) {
+			break
+		}
+		row := &d.rows[i]
+		x := d.xOff + row.x
+
+		switch row.kind {
+		case docRowSection:
+			r.docSection(y, d.xOff, d.width, row.text, opts)
+		case docRowKey:
+			r.TextStyled(x, y, row.key, opts.KeyStyle)
+		case docRowEntry:
+			r.TextStyled(x+d.keyW-RuneLen(row.key), y, row.key, opts.KeyStyle)
+			r.TextStyled(x+d.keyW+d.gap, y, row.text, opts.TextStyle)
+		case docRowText:
+			r.TextStyled(x, y, row.text, opts.TextStyle)
+		}
+	}
+}
+
+// docSection draws a full-width rule with the label inset from the left
+func (r Region) docSection(y, x, w int, label string, opts DocOpts) {
+	if opts.Rule == LineNone {
+		r.TextStyled(x, y, label, opts.HeaderStyle)
+		return
+	}
+	line := opts.Rule
+	if line >= LineType(len(boxChars)) {
+		line = LineSingle
+	}
+	ch := boxChars[line][boxH]
+	for i := range w {
+		r.Cell(x+i, y, ch, opts.RuleStyle.Fg, opts.RuleStyle.Bg, opts.RuleStyle.Attr)
+	}
+	if label == "" {
+		return
+	}
+
+	const lead = 2
+	text := " " + label + " "
+	if RuneLen(text)+lead > w {
+		text = Truncate(text, max(w-lead, 1))
+	}
+	r.TextStyled(x+lead, y, text, opts.HeaderStyle)
+}

tui/keyvalue.go

@@ -4,82 +4,57 @@ import (
 	"github.com/lixenwraith/terminal"
 )
 
-// KeyValue renders right-aligned key, separator, left-aligned value on row
+// keyValueSplit divides a row between the key and value columns, excluding the
-// Key width auto-sizes based on content, capped at 40% of region width
+// separator. Each column takes the width it needs and yields only when that
-// Value gets remainder, minimum 30% of region width
+// would push the other below a third of the row.
+func keyValueSplit(width, keyLen, valLen int) (keyW, valW int) {
+	avail := width - 1 // Separator column
+	if avail < 2 {
+		return 1, 1
+	}
+	third := max(avail/3, 1)
+
+	keyW = max(keyLen, 1)
+	if valFloor := min(valLen, third); avail-keyW < valFloor {
+		keyW = avail - valFloor
+	}
+	keyW = min(max(keyW, min(keyLen, third)), avail-1)
+	return keyW, avail - keyW
+}
+
+// KeyValue renders right-aligned key, separator and left-aligned value on row y,
+// sizing the key column to this row alone
 func (r Region) KeyValue(y int, key, value string, keyStyle, valStyle Style, sep rune) {
+	r.KeyValueColumn(y, 0, key, value, keyStyle, valStyle, sep)
+}
+
+// KeyValueColumn renders a key-value row against an explicit key column, so a
+// set of rows aligns on the separator; keyW <= 0 sizes the column to this row
+func (r Region) KeyValueColumn(y, keyW int, key, value string, keyStyle, valStyle Style, sep rune) {
 	if y < 0 || y >= r.H || r.W < 3 {
 		return
 	}
 
-	keyLen := RuneLen(key)
+	var valW int
-
+	if keyW <= 0 {
-	// Dynamic allocation: key gets what it needs up to 40%
+		keyW, valW = keyValueSplit(r.W, RuneLen(key), RuneLen(value))
-	maxKeyW := (r.W * 2) / 5  // 40%
+	} else {
-	minValW := (r.W * 3) / 10 // 30%
+		keyW = min(max(keyW, 1), r.W-2)
-
+		valW = r.W - keyW - 1
-	keyW := keyLen
-	if keyW > maxKeyW {
-		keyW = maxKeyW
-	}
-	if keyW < 1 {
-		keyW = 1
 	}
 
-	valW := r.W - keyW - 1 // -1 for separator
+	key = Truncate(key, keyW)
-	if valW < minValW && r.W > minValW+2 {
+	value = Truncate(value, valW)
-		// Reclaim from key to meet minimum value width
-		valW = minValW
-		keyW = r.W - valW - 1
-		if keyW < 1 {
-			keyW = 1
-			valW = r.W - 2
-		}
-	}
-	if valW < 1 {
-		valW = 1
-	}
 
-	// Truncate key if needed
+	// Key is right-aligned within its column, so the separators line up when
-	keyRunes := []rune(key)
+	// callers share a column width
-	if len(keyRunes) > keyW {
+	r.TextStyled(keyW-RuneLen(key), y, key, keyStyle)
-		if keyW > 1 {
-			keyRunes = keyRunes[:keyW-1]
-			keyRunes = append(keyRunes, '…')
-		} else {
-			keyRunes = keyRunes[:1]
-		}
-	}
-
-	// Truncate value if needed
-	valRunes := []rune(value)
-	if len(valRunes) > valW {
-		if valW > 1 {
-			valRunes = valRunes[:valW-1]
-			valRunes = append(valRunes, '…')
-		} else {
-			valRunes = valRunes[:1]
-		}
-	}
-
-	// Right-align key within allocated width
-	keyX := keyW - len(keyRunes)
-	for i, ch := range keyRunes {
-		r.Cell(keyX+i, y, ch, keyStyle.Fg, keyStyle.Bg, keyStyle.Attr)
-	}
-
-	// Separator
 	r.Cell(keyW, y, sep, keyStyle.Fg, keyStyle.Bg, terminal.AttrDim)
-
+	r.TextStyled(keyW+1, y, value, valStyle)
-	// Left-align value
-	for i, ch := range valRunes {
-		r.Cell(keyW+1+i, y, ch, valStyle.Fg, valStyle.Bg, valStyle.Attr)
-	}
 }
 
-// KeyValueWrap renders key-value with value wrapping to subsequent lines
+// KeyValueWrap renders a key with its value wrapped into the value column,
-// Returns number of lines used
+// returning the number of lines used
-// Layout:
 //
 //	key: value text that is
 //	     long and wraps to
@@ -89,111 +64,30 @@ func (r Region) KeyValueWrap(y int, key, value string, keyStyle, valStyle Style,
 		return 0
 	}
 
-	keyLen := RuneLen(key)
+	keyW, valW := keyValueSplit(r.W, RuneLen(key), RuneLen(value))
+	k := Truncate(key, keyW)
 
-	// Dynamic allocation same as KeyValue
+	r.TextStyled(keyW-RuneLen(k), y, k, keyStyle)
-	maxKeyW := (r.W * 2) / 5  // 40%
-	minValW := (r.W * 3) / 10 // 30%
-
-	keyW := keyLen
-	if keyW > maxKeyW {
-		keyW = maxKeyW
-	}
-	if keyW < 1 {
-		keyW = 1
-	}
-
-	valW := r.W - keyW - 1 // -1 for separator
-	if valW < minValW && r.W > minValW+2 {
-		valW = minValW
-		keyW = r.W - valW - 1
-		if keyW < 1 {
-			keyW = 1
-			valW = r.W - 2
-		}
-	}
-	if valW < 1 {
-		valW = 1
-	}
-
-	// Truncate key if needed
-	keyRunes := []rune(key)
-	if len(keyRunes) > keyW {
-		if keyW > 1 {
-			keyRunes = keyRunes[:keyW-1]
-			keyRunes = append(keyRunes, '…')
-		} else {
-			keyRunes = keyRunes[:1]
-		}
-	}
-
-	// Right-align key within allocated width
-	keyX := keyW - len(keyRunes)
-	for i, ch := range keyRunes {
-		r.Cell(keyX+i, y, ch, keyStyle.Fg, keyStyle.Bg, keyStyle.Attr)
-	}
-
-	// Separator
 	r.Cell(keyW, y, sep, keyStyle.Fg, keyStyle.Bg, terminal.AttrDim)
 
-	// Wrap value text
-	valueX := keyW + 1
-	lines := WrapText(value, valW)
-	if len(lines) == 0 {
-		return 1
-	}
-
 	rendered := 0
-	for i, line := range lines {
+	for i, line := range WrapText(value, valW) {
-		lineY := y + i
+		if y+i >= r.H {
-		if lineY >= r.H {
 			break
 		}
-		r.Text(valueX, lineY, line, valStyle.Fg, valStyle.Bg, valStyle.Attr)
+		r.TextStyled(keyW+1, y+i, line, valStyle)
 		rendered++
 	}
-
+	return max(rendered, 1)
-	if rendered < 1 {
-		rendered = 1
-	}
-	return rendered
 }
 
-// MeasureKeyValueWrap calculates lines needed for KeyValueWrap without rendering
+// MeasureKeyValueWrap returns the line count KeyValueWrap needs, for layout
-// Useful for layout pre-calculation
+// pre-calculation. Shares the column split with the renderer, so the two agree.
 func (r Region) MeasureKeyValueWrap(key, value string) int {
 	if r.W < 3 {
 		return 1
 	}
-
+	_, valW := keyValueSplit(r.W, RuneLen(key), RuneLen(value))
-	keyLen := RuneLen(key)
+	return max(len(WrapText(value, valW)), 1)
-	maxKeyW := (r.W * 2) / 5
-	minValW := (r.W * 3) / 10
-
-	keyW := keyLen
-	if keyW > maxKeyW {
-		keyW = maxKeyW
-	}
-	if keyW < 1 {
-		keyW = 1
-	}
-
-	valW := r.W - keyW - 1
-	if valW < minValW && r.W > minValW+2 {
-		valW = minValW
-		keyW = r.W - valW - 1
-		if keyW < 1 {
-			keyW = 1
-			valW = r.W - 2
-		}
-	}
-	if valW < 1 {
-		valW = 1
-	}
-
-	lines := WrapText(value, valW)
-	if len(lines) == 0 {
-		return 1
-	}
-	return len(lines)
 }
+

tui/masonry.go

@@ -16,7 +16,8 @@ type MasonryLayout struct {
 // MasonryOpts configures masonry layout
 type MasonryOpts struct {
 	Columns     int
-	Gap         int
+	GapX        int // Columns between masonry columns
+	GapY        int // Rows between stacked items
 	MinColW     int
 	Breakpoints map[int]int
 }
@@ -24,7 +25,8 @@ type MasonryOpts struct {
 // DefaultMasonryOpts returns sensible defaults
 func DefaultMasonryOpts() MasonryOpts {
 	return MasonryOpts{
-		Gap:     1,
+		GapX:    2,
+		GapY:    1,
 		MinColW: 30,
 		Breakpoints: map[int]int{
 			140: 4,
@@ -54,15 +56,10 @@ func (m *MasonryState) CalculateLayout(items []MasonryItem, width int, opts Maso
 		cols = m.autoColumns(width, opts)
 	}
 
-	gap := opts.Gap
+	gapX := max(opts.GapX, 0)
-	if gap < 0 {
+	gapY := max(opts.GapY, 0)
-		gap = 1
-	}
 
-	colW := (width - (cols-1)*gap) / cols
+	colW := max((width-(cols-1)*gapX)/cols, 1)
-	if colW < 1 {
-		colW = 1
-	}
 
 	m.Layouts = make([]MasonryLayout, 0, len(items))
 	colHeights := make([]int, cols)
@@ -77,7 +74,7 @@ func (m *MasonryState) CalculateLayout(items []MasonryItem, width int, opts Maso
 			}
 		}
 
-		x := minCol * (colW + gap)
+		x := minCol * (colW + gapX)
 		y := colHeights[minCol]
 
 		m.Layouts = append(m.Layouts, MasonryLayout{
@@ -85,7 +82,7 @@ func (m *MasonryState) CalculateLayout(items []MasonryItem, width int, opts Maso
 			Item: item,
 		})
 
-		colHeights[minCol] += item.Height + gap
+		colHeights[minCol] += item.Height + gapY
 	}
 
 	totalH := 0
@@ -95,7 +92,7 @@ func (m *MasonryState) CalculateLayout(items []MasonryItem, width int, opts Maso
 		}
 	}
 	if totalH > 0 {
-		totalH -= gap
+		totalH -= gapY
 	}
 
 	m.Viewport.ContentH = totalH
@@ -114,10 +111,7 @@ func (m *MasonryState) autoColumns(width int, opts MasonryOpts) int {
 		return best
 	}
 
-	cols := width / opts.MinColW
+	cols := max(width/opts.MinColW, 1)
-	if cols < 1 {
-		cols = 1
-	}
 	return cols
 }
 

tui/scrollbar.go

@@ -5,45 +5,61 @@ import (
 	"github.com/lixenwraith/terminal"
 )
 
-// ScrollBar draws vertical scrollbar track with thumb
+// ScrollBarOpts configures scrollbar rendering
+type ScrollBarOpts struct {
+	ThumbFg  color.RGB
+	TrackFg  color.RGB
+	Bg       color.RGB // Zero inherits the existing cell background
+	Thumb    rune      // 0 = '█'
+	Track    rune      // 0 = '░'
+	HideIdle bool      // Draw nothing when content fits the viewport
+}
+
+// ScrollBar draws a vertical scrollbar track with thumb in a single color
 func (r Region) ScrollBar(x int, offset, visible, total int, fg color.RGB) {
+	r.ScrollBarStyled(x, offset, visible, total, ScrollBarOpts{ThumbFg: fg, TrackFg: fg})
+}
+
+// ScrollBarStyled draws a vertical scrollbar at column x with explicit styling
+func (r Region) ScrollBarStyled(x int, offset, visible, total int, opts ScrollBarOpts) {
 	if x < 0 || x >= r.W || r.H < 1 {
 		return
 	}
 
+	thumbCh, trackCh := opts.Thumb, opts.Track
+	if thumbCh == 0 {
+		thumbCh = '█'
+	}
+	if trackCh == 0 {
+		trackCh = '░'
+	}
+
 	trackH := r.H
 	if total <= visible || trackH < 3 {
 		// No scrolling needed or track too small
+		if opts.HideIdle {
+			return
+		}
 		for y := range trackH {
-			r.Cell(x, y, '│', fg, color.RGB{}, terminal.AttrDim)
+			r.Cell(x, y, '│', opts.TrackFg, opts.Bg, terminal.AttrDim)
 		}
 		return
 	}
 
-	// Calculate thumb size and position
 	thumbH := min(max((visible*trackH)/total, 1), trackH)
-
 	maxScroll := total - visible
 	thumbY := 0
 	if maxScroll > 0 {
 		thumbY = (offset * (trackH - thumbH)) / maxScroll
 	}
-	if thumbY < 0 {
+	thumbY = min(max(thumbY, 0), trackH-thumbH)
-		thumbY = 0
-	}
-	if thumbY+thumbH > trackH {
-		thumbY = trackH - thumbH
-	}
 
-	// Draw track and thumb
 	for y := range trackH {
-		var ch rune
 		if y >= thumbY && y < thumbY+thumbH {
-			ch = '█'
+			r.Cell(x, y, thumbCh, opts.ThumbFg, opts.Bg, terminal.AttrNone)
 		} else {
-			ch = '░'
+			r.Cell(x, y, trackCh, opts.TrackFg, opts.Bg, terminal.AttrDim)
 		}
-		r.Cell(x, y, ch, fg, color.RGB{}, terminal.AttrNone)
 	}
 }
 

tui/viewport.go

@@ -105,3 +105,15 @@ func (v *ViewportScroll) ClipToViewport(y, h int) (viewY, viewH, contentOffset i
 
 	return viewY, viewH, contentOffset, viewH > 0
 }
+
+// EnsureRange scrolls the least distance that brings a content row range into
+// view; a range taller than the viewport is top-aligned
+func (v *ViewportScroll) EnsureRange(y, h int) {
+	switch {
+	case h >= v.ViewportH || y < v.Offset:
+		v.Offset = y
+	case y+h > v.Offset+v.ViewportH:
+		v.Offset = y + h - v.ViewportH
+	}
+	v.clamp()
+}