ui/tooltip.go

package ui

import (
	"fmt"
	"strings"

	"git.kirsle.net/go/render"
	"git.kirsle.net/go/ui/style"
)

func init() {
	precomputeArrows()
}

/*
Tooltip attaches a mouse-over popup to another widget.


*/
type Tooltip struct {
	BaseWidget

	// Configurable attributes.
	Text         string  // Text to show in the tooltip.
	TextVariable *string // String pointer instead of text.
	Edge         Edge    // side to display tooltip on
	supervisor   *Supervisor

	style      *style.Tooltip
	target     Widget
	lineHeight int
	font       render.Text
}

// Constants for tooltips.
const (
	tooltipArrowSize = 5
)

// NewTooltip creates a new tooltip attached to a widget.
func NewTooltip(target Widget, tt Tooltip) *Tooltip {
	w := &Tooltip{
		Text:         tt.Text,
		TextVariable: tt.TextVariable,
		Edge:         tt.Edge,
		target:       target,
	}

	// Default style.
	w.Hide()
	w.SetBackground(render.RGBA(0, 0, 0, 230))
	w.font = render.Text{
		Size:    10,
		Color:   render.White,
		Padding: 4,
	}

	// Add event bindings to the target widget.
	// - Show the tooltip on MouseOver
	// - Hide it on MouseOut
	// - Compute the tooltip when the parent widget Computes
	// - Present the tooltip when the parent widget Presents
	target.Handle(MouseOver, func(ed EventData) error {
		w.Show()
		return nil
	})
	target.Handle(MouseOut, func(ed EventData) error {
		w.Hide()
		return nil
	})
	target.Handle(Compute, func(ed EventData) error {
		w.Compute(ed.Engine)
		return nil
	})
	target.Handle(Present, func(ed EventData) error {
		if w.supervisor == nil {
			w.Present(ed.Engine, w.Point())
		}
		return nil
	})

	w.IDFunc(func() string {
		return fmt.Sprintf(`Tooltip<"%s">`, w.Value())
	})

	w.SetStyle(Theme.Tooltip)

	return w
}

/*
Supervise the tooltip widget. This will put the rendering of this widget under the
Supervisor's care to be drawn "on top" of all other widgets. Your main loop should
call the Supervisor.Present() function lastly so that things managed by it (such as
Windows, Menus and Tooltips) draw on top of everything else.

If you don't call this, the Tooltip by default will present when its attached widget
presents (if moused over and tooltip is to be visible). This alone is fine in many
simple use cases, but in a densely packed UI layout and depending on the Edge the
tooltip draws at, it may get over-drawn by other widgets and not appear "on top."
*/
func (w *Tooltip) Supervise(s *Supervisor) {
	w.supervisor = s

	// Supervisor will manage our presentation and draw us "on top"
	w.supervisor.DrawOnTop(w)
}

// SetStyle sets the tooltip's default style.
func (w *Tooltip) SetStyle(v *style.Tooltip) {
	if v == nil {
		v = &style.DefaultTooltip
	}

	w.style = v
	w.SetBackground(w.style.Background)
	w.font.Color = w.style.Foreground
}

// Value returns the current text displayed in the tooltop, whether from the
// configured Text or the TextVariable pointer.
func (w *Tooltip) Value() string {
	return w.text().Text
}

// text returns the raw render.Text holding the current value to be displayed
// in the tooltip, either from Text or TextVariable.
func (w *Tooltip) text() render.Text {
	if w.TextVariable != nil {
		w.font.Text = *w.TextVariable
	} else {
		w.font.Text = w.Text
	}
	return w.font
}

// Compute the size of the tooltip.
func (w *Tooltip) Compute(e render.Engine) {
	// Compute the size based on the text.
	w.computeText(e)

	// Compute the position based on the Edge and the target widget.
	var (
		size = w.Size()

		target = w.target
		tSize  = target.Size()
		tPoint = AbsolutePosition(target)

		moveTo render.Point
	)

	switch w.Edge {
	case Top:
		moveTo.Y = tPoint.Y - size.H - tooltipArrowSize
		moveTo.X = tPoint.X + (tSize.W / 2) - (size.W / 2)
	case Left:
		moveTo.X = tPoint.X - size.W - tooltipArrowSize
		moveTo.Y = tPoint.Y + (tSize.H / 2) - (size.H / 2)
	case Right:
		moveTo.X = tPoint.X + tSize.W + tooltipArrowSize
		moveTo.Y = tPoint.Y + (tSize.H / 2) - (size.H / 2)
	case Bottom:
		moveTo.Y = tPoint.Y + tSize.H + tooltipArrowSize
		moveTo.X = tPoint.X + (tSize.W / 2) - (size.W / 2)
	}

	// Adjust to keep the tooltip from clipping outside the window boundaries.
	{
		width, height := e.WindowSize()
		if moveTo.X < 0 {
			moveTo.X = 0
		} else if moveTo.X+size.W > width {
			moveTo.X = width - size.W
		}

		if moveTo.Y < 0 {
			moveTo.Y = 0
		} else if moveTo.Y+size.H > height {
			moveTo.Y = height - size.H
		}
	}

	w.MoveTo(moveTo)
}

// computeText handles the text compute, very similar to Label.Compute.
func (w *Tooltip) computeText(e render.Engine) {
	text := w.text()
	lines := strings.Split(text.Text, "\n")

	// Max rect to encompass all lines of text.
	var maxRect = render.Rect{}
	for _, line := range lines {
		if line == "" {
			line = "<empty>"
		}

		text.Text = line // only this line at this time.
		rect, err := e.ComputeTextRect(text)
		if err != nil {
			panic(fmt.Sprintf("%s: failed to compute text rect: %s", w, err)) // TODO return an error
		}

		if rect.W > maxRect.W {
			maxRect.W = rect.W
		}
		maxRect.H += rect.H
		w.lineHeight = int(rect.H)
	}

	var (
		padX = w.font.Padding + w.font.PadX
		padY = w.font.Padding + w.font.PadY
	)

	w.Resize(render.Rect{
		W: maxRect.W + (padX * 2),
		H: maxRect.H + (padY * 2),
	})
}

// Present the tooltip.
func (w *Tooltip) Present(e render.Engine, P render.Point) {
	if w.Hidden() {
		return
	}

	// Draw the text.
	w.presentText(e, P)

	// Draw the arrow.
	w.presentArrow(e, P)
}

// presentText draws the text similar to Label.
func (w *Tooltip) presentText(e render.Engine, P render.Point) {
	var (
		text = w.text()
		padX = w.font.Padding + w.font.PadX
		padY = w.font.Padding + w.font.PadY
	)

	w.DrawBox(e, P)
	for i, line := range strings.Split(text.Text, "\n") {
		text.Text = line
		e.DrawText(text, render.Point{
			X: P.X + padX,
			Y: P.Y + padY + (i * w.lineHeight),
		})
	}
}

// presentArrow draws the arrow between the tooltip and its target widget.
func (w *Tooltip) presentArrow(e render.Engine, P render.Point) {
	var (
		// size = w.Size()

		target = w.target
		tSize  = target.Size()
		tPoint = AbsolutePosition(target)

		drawAt render.Point
		arrow  [][]render.Point
	)

	switch w.Edge {
	case Top:
		arrow = arrowDown
		drawAt = render.Point{
			X: tPoint.X + (tSize.W / 2) - tooltipArrowSize,
			Y: tPoint.Y - tooltipArrowSize,
		}
	case Bottom:
		arrow = arrowUp
		drawAt = render.Point{
			X: tPoint.X + (tSize.W / 2) - tooltipArrowSize,
			Y: tPoint.Y + tSize.H,
		}
	case Left:
		arrow = arrowRight
		drawAt = render.Point{
			X: tPoint.X - tooltipArrowSize,
			Y: tPoint.Y + (tSize.H / 2) - tooltipArrowSize,
		}
	case Right:
		arrow = arrowLeft
		drawAt = render.Point{
			X: tPoint.X + tSize.W,
			Y: tPoint.Y + (tSize.H / 2) - tooltipArrowSize,
		}
	}
	drawArrow(e, w.Background(), drawAt, arrow)
}

// Draw an arrow at a given top/left coordinate.
func drawArrow(e render.Engine, color render.Color, p render.Point, arrow [][]render.Point) {
	for _, row := range arrow {
		if len(row) == 1 {
			point := render.NewPoint(row[0].X, row[0].Y)
			point.Add(p)
			e.DrawPoint(color, point)
		} else {
			start := render.NewPoint(row[0].X, row[0].Y)
			end := render.NewPoint(row[1].X, row[1].Y)
			start.Add(p)
			end.Add(p)
			e.DrawLine(color, start, end)
		}
	}
}

// Arrows for the tooltip widget.
var (
	arrowDown  [][]render.Point
	arrowUp    [][]render.Point
	arrowLeft  [][]render.Point
	arrowRight [][]render.Point
)

func precomputeArrows() {
	arrowDown = [][]render.Point{
		{render.NewPoint(0, 0), render.NewPoint(10, 0)},
		{render.NewPoint(1, 1), render.NewPoint(9, 1)},
		{render.NewPoint(2, 2), render.NewPoint(8, 2)},
		{render.NewPoint(3, 3), render.NewPoint(7, 3)},
		{render.NewPoint(4, 4), render.NewPoint(6, 4)},
		{render.NewPoint(5, 5)},
	}
	arrowUp = [][]render.Point{
		{render.NewPoint(5, 0)},
		{render.NewPoint(4, 1), render.NewPoint(6, 1)},
		{render.NewPoint(3, 2), render.NewPoint(7, 2)},
		{render.NewPoint(2, 3), render.NewPoint(8, 3)},
		{render.NewPoint(1, 4), render.NewPoint(9, 4)},
		// {render.NewPoint(0, 5), render.NewPoint(10, 5)},
	}
	arrowLeft = [][]render.Point{
		{render.NewPoint(0, 5)},
		{render.NewPoint(1, 4), render.NewPoint(1, 6)},
		{render.NewPoint(2, 3), render.NewPoint(2, 7)},
		{render.NewPoint(3, 2), render.NewPoint(3, 8)},
		{render.NewPoint(4, 1), render.NewPoint(4, 9)},
		// {render.NewPoint(5, 0), render.NewPoint(5, 10)},
	}
	arrowRight = [][]render.Point{
		{render.NewPoint(0, 0), render.NewPoint(0, 10)},
		{render.NewPoint(1, 1), render.NewPoint(1, 9)},
		{render.NewPoint(2, 2), render.NewPoint(2, 8)},
		{render.NewPoint(3, 3), render.NewPoint(3, 7)},
		{render.NewPoint(4, 4), render.NewPoint(4, 6)},
		{render.NewPoint(5, 5)},
	}
}