1 files changed, 253 insertions, 0 deletions
diff --git a/examples/histogram.go b/examples/histogram.go
new file mode 100644
index 0000000..610d65a
--- /dev/null
+++ b/examples/histogram.go
@@ -0,0 +1,253 @@
+// 12 august 2018
+
+// +build OMIT
+
+package main
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/andlabs/ui"
+)
+
+var (
+	histogram *ui.Area
+	datapoints [10]*ui.Spinbox
+	colorButton *ui.ColorButton
+
+	currentPoint = -1
+)
+
+// some metrics
+const (
+	xoffLeft = 20		// histogram margins
+	yoffTop = 20
+	xoffRight = 20
+	yoffBottom = 20
+	pointRadius = 5
+)
+
+// helper to quickly set a brush color
+func mkSolidBrush(color uint32, alpha float64) *ui.DrawBrush {
+	brush := new(ui.DrawBrush)
+	brush.Type = ui.DrawBrushTypeSolid
+	component := uint8((color >> 16) & 0xFF)
+	brush.R = float64(component) / 255
+	component = uint8((color >> 8) & 0xFF)
+	brush.G = float64(component) / 255
+	component = uint8(color & 0xFF)
+	brush.B = float64(component) / 255
+	brush.A = alpha
+	return brush
+}
+
+// and some colors
+// names and values from https://msdn.microsoft.com/en-us/library/windows/desktop/dd370907%28v=vs.85%29.aspx
+const (
+	colorWhite = 0xFFFFFF
+	colorBlack = 0x000000
+	colorDodgerBlue = 0x1E90FF
+)
+
+func pointLocations(width, height float64) (xs, ys [10]float64) {
+	xincr := width / 9		// 10 - 1 to make the last point be at the end
+	yincr := height / 100
+	for i := 0; i < 10; i++ {
+		// get the value of the point
+		n := datapoints[i].Value()
+		// because y=0 is the top but n=0 is the bottom, we need to flip
+		n = 100 - n
+		xs[i] = xincr * float64(i)
+		ys[i] = yincr * float64(n)
+	}
+	return xs, ys
+}
+
+func constructGraph(width, height float64, extend bool) *ui.DrawPath {
+	xs, ys := pointLocations(width, height)
+	path := ui.DrawNewPath(ui.DrawFillModeWinding)
+
+	path.NewFigure(xs[0], ys[0])
+	for i := 1; i < 10; i++ {
+		path.LineTo(xs[i], ys[i])
+	}
+
+	if extend {
+		path.LineTo(width, height)
+		path.LineTo(0, height)
+		path.CloseFigure()
+	}
+
+	path.End()
+	return path
+}
+
+func graphSize(clientWidth, clientHeight float64) (graphWidth, graphHeight float64) {
+	return clientWidth - xoffLeft - xoffRight,
+		clientHeight - yoffTop - yoffBottom
+}
+
+type areaHandler struct{}
+
+func (areaHandler) Draw(a *ui.Area, p *ui.AreaDrawParams) {
+	// fill the area with white
+	brush := mkSolidBrush(colorWhite, 1.0)
+	path := ui.DrawNewPath(ui.DrawFillModeWinding)
+	path.AddRectangle(0, 0, p.AreaWidth, p.AreaHeight)
+	path.End()
+	p.Context.Fill(path, brush)
+	path.Free()
+
+	graphWidth, graphHeight := graphSize(p.AreaWidth, p.AreaHeight)
+
+	sp := &ui.DrawStrokeParams{
+		Cap:			ui.DrawLineCapFlat,
+		Join:			ui.DrawLineJoinMiter,
+		Thickness:	2,
+		MiterLimit:	ui.DrawDefaultMiterLimit,
+	}
+
+	// draw the axes
+	brush = mkSolidBrush(colorBlack, 1.0)
+	path = ui.DrawNewPath(ui.DrawFillModeWinding)
+	path.NewFigure(xoffLeft, yoffTop)
+	path.LineTo(xoffLeft, yoffTop + graphHeight)
+	path.LineTo(xoffLeft + graphWidth, yoffTop + graphHeight)
+	path.End()
+	p.Context.Stroke(path, brush, sp)
+	path.Free()
+
+	// now transform the coordinate space so (0, 0) is the top-left corner of the graph
+	m := ui.DrawNewMatrix()
+	m.Translate(xoffLeft, yoffTop)
+	p.Context.Transform(m)
+
+	// now get the color for the graph itself and set up the brush
+	graphR, graphG, graphB, graphA := colorButton.Color()
+	brush.Type = ui.DrawBrushTypeSolid
+	brush.R = graphR
+	brush.G = graphG
+	brush.B = graphB
+	// we set brush.A below to different values for the fill and stroke
+
+	// now create the fill for the graph below the graph line
+	path = constructGraph(graphWidth, graphHeight, true)
+	brush.A = graphA / 2
+	p.Context.Fill(path, brush)
+	path.Free()
+
+	// now draw the histogram line
+	path = constructGraph(graphWidth, graphHeight, false)
+	brush.A = graphA
+	p.Context.Stroke(path, brush, sp)
+	path.Free()
+
+	// now draw the point being hovered over
+	if currentPoint != -1 {
+		xs, ys := pointLocations(graphWidth, graphHeight)
+		path = ui.DrawNewPath(ui.DrawFillModeWinding)
+		path.NewFigureWithArc(
+			xs[currentPoint], ys[currentPoint],
+			pointRadius,
+			0, 6.23,		// TODO pi
+			false)
+		path.End()
+		// use the same brush as for the histogram lines
+		p.Context.Fill(path, brush)
+		path.Free()
+	}
+}
+
+func inPoint(x, y float64, xtest, ytest float64) bool {
+	// TODO switch to using a matrix
+	x -= xoffLeft
+	y -= yoffTop
+	return (x >= xtest - pointRadius) &&
+		(x <= xtest + pointRadius) &&
+		(y >= ytest - pointRadius) &&
+		(y <= ytest + pointRadius)
+}
+
+func (areaHandler) MouseEvent(a *ui.Area, me *ui.AreaMouseEvent) {
+	graphWidth, graphHeight := graphSize(me.AreaWidth, me.AreaHeight)
+	xs, ys := pointLocations(graphWidth, graphHeight)
+
+	currentPoint = -1
+	for i := 0; i < 10; i++ {
+		if inPoint(me.X, me.Y, xs[i], ys[i]) {
+			currentPoint = i
+			break
+		}
+	}
+
+	// TODO only redraw the relevant area
+	histogram.QueueRedrawAll()
+}
+
+func (areaHandler) MouseCrossed(a *ui.Area, left bool) {
+	// do nothing
+}
+
+func (areaHandler) DragBroken(a *ui.Area) {
+	// do nothing
+}
+
+func (areaHandler) KeyEvent(a *ui.Area, ke *ui.AreaKeyEvent) (handled bool) {
+	// reject all keys
+	return false
+}
+
+func setupUI() {
+	mainwin := ui.NewWindow("libui Histogram Example", 640, 480, true)
+	mainwin.SetMargined(true)
+	mainwin.OnClosing(func(*ui.Window) bool {
+		mainwin.Destroy()
+		ui.Quit()
+		return false
+	})
+	ui.OnShouldQuit(func() bool {
+		mainwin.Destroy()
+		return true
+	})
+
+	hbox := ui.NewHorizontalBox()
+	hbox.SetPadded(true)
+	mainwin.SetChild(hbox)
+
+	vbox := ui.NewVerticalBox()
+	vbox.SetPadded(true)
+	hbox.Append(vbox, false)
+
+	histogram = ui.NewArea(areaHandler{})
+
+	rand.Seed(time.Now().Unix())
+	for i := 0; i < 10; i++ {
+		datapoints[i] = ui.NewSpinbox(0, 100)
+		datapoints[i].SetValue(rand.Intn(101))
+		datapoints[i].OnChanged(func(*ui.Spinbox) {
+			histogram.QueueRedrawAll()
+		})
+		vbox.Append(datapoints[i], false)
+	}
+
+	colorButton = ui.NewColorButton()
+	// TODO inline these
+	brush := mkSolidBrush(colorDodgerBlue, 1.0)
+	colorButton.SetColor(brush.R,
+		brush.G,
+		brush.B,
+		brush.A)
+	colorButton.OnChanged(func(*ui.ColorButton) {
+		histogram.QueueRedrawAll()
+	})
+	vbox.Append(colorButton, false)
+
+	hbox.Append(histogram, true)
+
+	mainwin.Show()
+}
+
+func main() {
+	ui.Main(setupUI)
+}