Add scroll bar to List, DropDown, Table and TreeView

dropdown.go

@@ -374,7 +374,6 @@ func (d *DropDown) Draw(screen tcell.Screen) {
 		// We prefer to drop down but if there is no space, maybe drop up?
 		lx := x
 		ly := y + 1
-		lwidth := maxWidth
 		lheight := len(d.options)
 		_, sheight := screen.Size()
 		if ly+lheight >= sheight && ly-2 > lheight-ly {
@@ -386,6 +385,10 @@ func (d *DropDown) Draw(screen tcell.Screen) {
 		if ly+lheight >= sheight {
 			lheight = sheight - ly
 		}
+		lwidth := maxWidth
+		if d.list.scrollBarVisibility == ScrollBarAlways || (d.list.scrollBarVisibility == ScrollBarAuto && len(d.options) > lheight) {
+			lwidth++ // Add space for scroll bar
+		}
 		d.list.SetRect(lx, ly, lwidth, lheight)
 		d.list.Draw(screen)
 	}

inputfield.go

@@ -422,6 +422,9 @@ func (i *InputField) Draw(screen tcell.Screen) {
 		if ly+lheight >= sheight {
 			lheight = sheight - ly
 		}
+		if i.autocompleteList.scrollBarVisibility == ScrollBarAlways || (i.autocompleteList.scrollBarVisibility == ScrollBarAuto && i.autocompleteList.GetItemCount() > lheight) {
+			lwidth++ // Add space for scroll bar
+		}
 		i.autocompleteList.SetRect(lx, ly, lwidth, lheight)
 		i.autocompleteList.Draw(screen)
 	}

list.go

@@ -42,6 +42,12 @@ type List struct {
 	// The text color for selected items.
 	selectedTextColor tcell.Color
 
+	// Visibility of the scroll bar.
+	scrollBarVisibility ScrollBarVisibility
+
+	// The scroll bar color.
+	scrollBarColor tcell.Color
+
 	// The background color for selected items.
 	selectedBackgroundColor tcell.Color
 
@@ -75,10 +81,12 @@ func NewList() *List {
 		Box:                     NewBox(),
 		showSecondaryText:       true,
 		wrapAround:              true,
+		scrollBarVisibility:     ScrollBarAuto,
 		mainTextColor:           Styles.PrimaryTextColor,
 		secondaryTextColor:      Styles.TertiaryTextColor,
 		shortcutColor:           Styles.SecondaryTextColor,
 		selectedTextColor:       Styles.PrimitiveBackgroundColor,
+		scrollBarColor:          Styles.ScrollBarColor,
 		selectedBackgroundColor: Styles.PrimaryTextColor,
 	}
 }
@@ -216,6 +224,18 @@ func (l *List) ShowSecondaryText(show bool) *List {
 	return l
 }
 
+// SetScrollBarVisibility specifies the display of the scroll bar.
+func (l *List) SetScrollBarVisibility(visibility ScrollBarVisibility) *List {
+	l.scrollBarVisibility = visibility
+	return l
+}
+
+// SetScrollBarColor sets the color of the scroll bar.
+func (l *List) SetScrollBarColor(color tcell.Color) *List {
+	l.scrollBarColor = color
+	return l
+}
+
 // SetWrapAround sets the flag that determines whether navigating the list will
 // wrap around. That is, navigating downwards on the last item will move the
 // selection to the first item (similarly in the other direction). If set to
@@ -395,6 +415,18 @@ func (l *List) Draw(screen tcell.Screen) {
 	x, y, width, height := l.GetInnerRect()
 	bottomLimit := y + height
 
+	screenWidth, _ := screen.Size()
+	scrollBarHeight := height
+	scrollBarX := x + (width - 1)
+	if scrollBarX > screenWidth-1 {
+		scrollBarX = screenWidth - 1
+	}
+
+	// Halve scroll bar height when drawing two lines per list item.
+	if l.showSecondaryText {
+		scrollBarHeight /= 2
+	}
+
 	// Do we show any shortcuts?
 	var showShortcuts bool
 	for _, item := range l.items {
@@ -457,6 +489,10 @@ func (l *List) Draw(screen tcell.Screen) {
 			}
 		}
 
+		if l.scrollBarVisibility == ScrollBarAlways || (l.scrollBarVisibility == ScrollBarAuto && len(l.items) > scrollBarHeight) {
+			RenderScrollBar(screen, scrollBarX, y, scrollBarHeight, len(l.items), l.currentItem, index-l.offset, l.hasFocus, l.scrollBarColor)
+		}
+
 		y++
 
 		if y >= bottomLimit {
@@ -466,6 +502,11 @@ func (l *List) Draw(screen tcell.Screen) {
 		// Secondary text.
 		if l.showSecondaryText {
 			Print(screen, item.SecondaryText, x, y, width, AlignLeft, l.secondaryTextColor)
+
+			if l.scrollBarVisibility == ScrollBarAlways || (l.scrollBarVisibility == ScrollBarAuto && len(l.items) > scrollBarHeight) {
+				RenderScrollBar(screen, scrollBarX, y, scrollBarHeight, len(l.items), l.currentItem, index-l.offset, l.hasFocus, l.scrollBarColor)
+			}
+
 			y++
 		}
 	}

styles.go

@@ -15,6 +15,7 @@ type Theme struct {
 	TertiaryTextColor           tcell.Color // Tertiary text (e.g. subtitles, notes).
 	InverseTextColor            tcell.Color // Text on primary-colored backgrounds.
 	ContrastSecondaryTextColor  tcell.Color // Secondary text on ContrastBackgroundColor-colored backgrounds.
+	ScrollBarColor              tcell.Color // Scroll bar.
 }
 
 // Styles defines the theme for applications. The default is for a black
@@ -32,4 +33,5 @@ var Styles = Theme{
 	TertiaryTextColor:           tcell.ColorGreen,
 	InverseTextColor:            tcell.ColorBlue,
 	ContrastSecondaryTextColor:  tcell.ColorDarkCyan,
+	ScrollBarColor:              tcell.ColorWhite,
 }

table.go

@@ -251,6 +251,12 @@ type Table struct {
 	// The number of visible rows the last time the table was drawn.
 	visibleRows int
 
+	// Visibility of the scroll bar.
+	scrollBarVisibility ScrollBarVisibility
+
+	// The scroll bar color.
+	scrollBarColor tcell.Color
+
 	// The style of the selected rows. If this value is 0, selected rows are
 	// simply inverted.
 	selectedStyle tcell.Style
@@ -273,10 +279,12 @@ type Table struct {
 // NewTable returns a new table.
 func NewTable() *Table {
 	return &Table{
-		Box:          NewBox(),
-		bordersColor: Styles.GraphicsColor,
-		separator:    ' ',
-		lastColumn:   -1,
+		Box:                 NewBox(),
+		scrollBarVisibility: ScrollBarAuto,
+		scrollBarColor:      Styles.ScrollBarColor,
+		bordersColor:        Styles.GraphicsColor,
+		separator:           ' ',
+		lastColumn:          -1,
 	}
 }
 
@@ -300,6 +308,18 @@ func (t *Table) SetBordersColor(color tcell.Color) *Table {
 	return t
 }
 
+// SetScrollBarVisibility specifies the display of the scroll bar.
+func (t *Table) SetScrollBarVisibility(visibility ScrollBarVisibility) *Table {
+	t.scrollBarVisibility = visibility
+	return t
+}
+
+// SetScrollBarColor sets the color of the scroll bar.
+func (t *Table) SetScrollBarColor(color tcell.Color) *Table {
+	t.scrollBarColor = color
+	return t
+}
+
 // SetSelectedStyle sets a specific style for selected cells. If no such style
 // is set, per default, selected cells are inverted (i.e. their foreground and
 // background colors are swapped).
@@ -570,6 +590,11 @@ func (t *Table) Draw(screen tcell.Screen) {
 		t.visibleRows = height
 	}
 
+	showVerticalScrollBar := t.scrollBarVisibility == ScrollBarAlways || (t.scrollBarVisibility == ScrollBarAuto && len(t.cells) > t.visibleRows-t.fixedRows)
+	if showVerticalScrollBar {
+		width-- // Subtract space for scroll bar.
+	}
+
 	// Return the cell at the specified position (nil if it doesn't exist).
 	getCell := func(row, column int) *TableCell {
 		if row < 0 || column < 0 || row >= len(t.cells) || column >= len(t.cells[row]) {
@@ -766,6 +791,7 @@ ColumnLoop:
 			toDistribute -= expWidth
 			expansionTotal -= expansion
 		}
+		tableWidth = width - toDistribute
 	}
 
 	// Helper function which draws border runes.
@@ -861,6 +887,38 @@ ColumnLoop:
 		}
 	}
 
+	if showVerticalScrollBar {
+		// Calculate scroll bar position and dimensions.
+		rows := len(t.cells)
+
+		scrollBarItems := rows - t.fixedRows
+		scrollBarHeight := t.visibleRows - t.fixedRows
+
+		scrollBarX := x + width
+		scrollBarY := y + t.fixedRows
+		if scrollBarX > x+tableWidth {
+			scrollBarX = x + tableWidth
+		}
+
+		padTotalOffset := 1
+		if t.borders {
+			padTotalOffset = 2
+
+			scrollBarItems *= 2
+			scrollBarHeight = (scrollBarHeight * 2) - 1
+
+			scrollBarY += t.fixedRows + 1
+		}
+
+		// Draw scroll bar.
+		cursor := int(float64(scrollBarItems) * (float64(t.rowOffset) / float64(((rows-t.fixedRows)-t.visibleRows)+padTotalOffset)))
+		for printed := 0; printed < scrollBarHeight; printed++ {
+			RenderScrollBar(screen, scrollBarX, scrollBarY+printed, scrollBarHeight, scrollBarItems, cursor, printed, t.hasFocus, t.scrollBarColor)
+		}
+	}
+
+	// TODO Draw horizontal scroll bar
+
 	// Helper function which colors the background of a box.
 	// backgroundColor == tcell.ColorDefault => Don't color the background.
 	// textColor == tcell.ColorDefault => Don't change the text color.

treeview.go

@@ -270,6 +270,12 @@ type TreeView struct {
 	// The color of the lines.
 	graphicsColor tcell.Color
 
+	// Visibility of the scroll bar.
+	scrollBarVisibility ScrollBarVisibility
+
+	// The scroll bar color.
+	scrollBarColor tcell.Color
+
 	// An optional function which is called when the user has navigated to a new
 	// tree node.
 	changed func(node *TreeNode)
@@ -288,9 +294,11 @@ type TreeView struct {
 // NewTreeView returns a new tree view.
 func NewTreeView() *TreeView {
 	return &TreeView{
-		Box:           NewBox(),
-		graphics:      true,
-		graphicsColor: Styles.GraphicsColor,
+		Box:                 NewBox(),
+		scrollBarVisibility: ScrollBarAuto,
+		graphics:            true,
+		graphicsColor:       Styles.GraphicsColor,
+		scrollBarColor:      Styles.ScrollBarColor,
 	}
 }
 
@@ -365,6 +373,18 @@ func (t *TreeView) SetGraphicsColor(color tcell.Color) *TreeView {
 	return t
 }
 
+// SetScrollBarVisibility specifies the display of the scroll bar.
+func (t *TreeView) SetScrollBarVisibility(visibility ScrollBarVisibility) *TreeView {
+	t.scrollBarVisibility = visibility
+	return t
+}
+
+// SetScrollBarColor sets the color of the scroll bar.
+func (t *TreeView) SetScrollBarColor(color tcell.Color) *TreeView {
+	t.scrollBarColor = color
+	return t
+}
+
 // SetChangedFunc sets the function which is called when the user navigates to
 // a new tree node.
 func (t *TreeView) SetChangedFunc(handler func(node *TreeNode)) *TreeView {
@@ -601,12 +621,16 @@ func (t *TreeView) Draw(screen tcell.Screen) {
 		t.offsetY = 0
 	}
 
+	// Calculate scroll bar position.
+	rows := len(t.nodes)
+	cursor := int(float64(rows) * (float64(t.offsetY) / float64(rows-height)))
+
 	// Draw the tree.
 	posY := y
 	lineStyle := tcell.StyleDefault.Background(t.backgroundColor).Foreground(t.graphicsColor)
 	for index, node := range t.nodes {
 		// Skip invisible parts.
-		if posY >= y+height+1 {
+		if posY >= y+height {
 			break
 		}
 		if index < t.offsetY {
@@ -668,6 +692,11 @@ func (t *TreeView) Draw(screen tcell.Screen) {
 			}
 		}
 
+		// Draw scroll bar.
+		if t.scrollBarVisibility == ScrollBarAlways || (t.scrollBarVisibility == ScrollBarAuto && rows > height) {
+			RenderScrollBar(screen, x+(width-1), posY, height, rows, cursor, posY-y, t.hasFocus, tcell.ColorWhite)
+		}
+
 		// Advance.
 		posY++
 	}

util.go

@@ -628,3 +628,50 @@ func iterateStringReverse(text string, callback func(main rune, comb []rune, tex
 
 	return false
 }
+
+// ScrollBarVisibility specifies the display of a scroll bar.
+type ScrollBarVisibility int
+
+const (
+	// ScrollBarNever never shows a scroll bar.
+	ScrollBarNever ScrollBarVisibility = iota
+
+	// ScrollBarAuto shows a scroll bar when there are items offscreen.
+	ScrollBarAuto
+
+	// ScrollBarAlways always shows a scroll bar.
+	ScrollBarAlways
+)
+
+// RenderScrollBar renders a scroll bar character at the specified position.
+func RenderScrollBar(screen tcell.Screen, x int, y int, height int, items int, cursor int, printed int, focused bool, color tcell.Color) {
+	// Do not render a scroll bar when all items are visible.
+	if items <= height {
+		return
+	}
+
+	// Handle negative cursor.
+	if cursor < 0 {
+		cursor = 0
+	}
+
+	// Calculate handle position.
+	handlePosition := int(float64(height-1) * (float64(cursor) / float64(items-1)))
+
+	// Print character.
+	var scrollBar string
+	if printed == handlePosition {
+		if focused {
+			scrollBar = "[::r] [-:-:-]"
+		} else {
+			scrollBar = "▓"
+		}
+	} else {
+		if focused {
+			scrollBar = "▒"
+		} else {
+			scrollBar = "░"
+		}
+	}
+	Print(screen, scrollBar, x, y, 1, AlignLeft, color)
+}