From 3a18d3adf92b83b81756c1b61d4a79ada941b64e Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Fri, 15 May 2020 16:39:53 +0200
Subject: [PATCH] Added support for tooltips.

---
 ui/context.go                 | 24 +++++++++++--
 ui/controlbase.go             |  6 ++++
 ui/examples/01_basic/basic.go |  1 +
 ui/style.go                   |  2 ++
 ui/tooltip.go                 | 64 +++++++++++++++++++++++++++++++++++
 ui/ui.go                      |  2 ++
 6 files changed, 97 insertions(+), 2 deletions(-)
 create mode 100644 ui/tooltip.go

diff --git a/ui/context.go b/ui/context.go
index a4a41ee..9e50161 100644
--- a/ui/context.go
+++ b/ui/context.go
@@ -1,12 +1,18 @@
 package ui
 
+import (
+	"opslag.de/schobers/geom"
+)
+
 type Context interface {
 	Animate()
 	Fonts() *Fonts
 	HasQuit() bool
+	MousePosition() geom.PointF32
 	Overlays() *Overlays
 	Quit()
 	Renderer() Renderer
+	ShowTooltip(t string)
 	Style() *Style
 	Textures() *Textures
 }
@@ -19,6 +25,8 @@ type context struct {
 	quit     chan struct{}
 	renderer Renderer
 	view     Control
+	mouse    geom.PointF32
+	tooltip  *Tooltip
 	overlays *Overlays
 	fonts    *Fonts
 	textures *Textures
@@ -26,14 +34,17 @@ type context struct {
 }
 
 func newContext(r Renderer, s *Style, view Control) *context {
-	return &context{
+	ctx := &context{
 		quit:     make(chan struct{}),
 		renderer: r,
 		style:    s,
 		view:     view,
+		tooltip:  &Tooltip{},
 		overlays: NewOverlays(view),
 		fonts:    NewFonts(r),
 		textures: NewTextures(r)}
+	ctx.overlays.AddOnTop(uiDefaultTooltipOverlay, ctx.tooltip, false)
+	return ctx
 }
 
 func (c *context) Animate() { c.animate = true }
@@ -54,10 +65,17 @@ func (c *context) HasQuit() bool {
 	}
 }
 
+func (c *context) MousePosition() geom.PointF32 { return c.mouse }
+
 func (c *context) Overlays() *Overlays { return c.overlays }
 
 func (c *context) Renderer() Renderer { return c.renderer }
 
+func (c *context) ShowTooltip(t string) {
+	c.overlays.Show(uiDefaultTooltipOverlay)
+	c.tooltip.Text = t
+}
+
 func (c *context) Style() *Style { return c.style }
 
 func (c *context) Quit() {
@@ -71,10 +89,12 @@ func (c *context) Textures() *Textures { return c.textures }
 // Handle implement EventTarget
 
 func (c *context) Handle(e Event) {
-	switch e.(type) {
+	switch e := e.(type) {
 	case *DisplayCloseEvent:
 		c.Quit()
 		return
+	case *MouseMoveEvent:
+		c.mouse = e.Pos()
 	}
 	c.overlays.Handle(c, e)
 }
diff --git a/ui/controlbase.go b/ui/controlbase.go
index 7df85ce..64ea79b 100644
--- a/ui/controlbase.go
+++ b/ui/controlbase.go
@@ -31,6 +31,8 @@ type ControlBase struct {
 	Background    color.Color
 	Font          FontStyle
 	TextAlignment HorizontalAlignment
+
+	Tooltip string
 }
 
 func (c *ControlBase) Arrange(ctx Context, bounds geom.RectangleF32, offset geom.PointF32, parent Control) {
@@ -100,6 +102,10 @@ func (c *ControlBase) Handle(ctx Context, e Event) {
 			c.pressed = false
 		}
 	}
+
+	if c.Tooltip != "" && c.over {
+		ctx.ShowTooltip(c.Tooltip)
+	}
 }
 
 func (c *ControlBase) FontColor(ctx Context) color.Color {
diff --git a/ui/examples/01_basic/basic.go b/ui/examples/01_basic/basic.go
index a7cc762..712376a 100644
--- a/ui/examples/01_basic/basic.go
+++ b/ui/examples/01_basic/basic.go
@@ -62,6 +62,7 @@ func (b *basic) Init(ctx ui.Context) error {
 			b.OnClick(func(geom.PointF32, ui.MouseButton) {
 				ctx.Quit()
 			})
+			b.Tooltip = "Will quit the application"
 		}), 8),
 		ui.BuildLabel("Status...", func(l *ui.Label) {
 			l.Background = style.Palette.PrimaryDark
diff --git a/ui/style.go b/ui/style.go
index f10ef63..7147ebe 100644
--- a/ui/style.go
+++ b/ui/style.go
@@ -19,6 +19,7 @@ type Dimensions struct {
 
 type FontNames struct {
 	Default string
+	Tooltip string
 }
 
 type Palette struct {
@@ -63,6 +64,7 @@ func DefaultDimensions() *Dimensions {
 func DefaultFontNames() *FontNames {
 	return &FontNames{
 		Default: "default",
+		Tooltip: "default",
 	}
 }
 
diff --git a/ui/tooltip.go b/ui/tooltip.go
new file mode 100644
index 0000000..8417a4a
--- /dev/null
+++ b/ui/tooltip.go
@@ -0,0 +1,64 @@
+package ui
+
+import (
+	"image/color"
+
+	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg"
+)
+
+const tooltipBorderThickness = 1
+const tooltipHorizontalPadding = 6
+const tooltipVerticalPadding = 2
+const tooltipMouseDistance = 12
+const uiDefaultTooltipOverlay = "ui-default-tooltip"
+
+type Tooltip struct {
+	ControlBase
+
+	Text string
+}
+
+func (t *Tooltip) FontName(ctx Context) string {
+	var name = t.Font.Name
+	if len(name) == 0 {
+		name = ctx.Style().Fonts.Tooltip
+	}
+	return name
+}
+
+func (t *Tooltip) Handle(Context, Event) {}
+
+func (t *Tooltip) Render(ctx Context) {
+	if len(t.Text) == 0 {
+		return
+	}
+
+	fontName := t.FontName(ctx)
+	size := ctx.Fonts().Font(fontName).Measure(t.Text)
+
+	offset := t.Offset()
+	mouse := ctx.MousePosition().Sub(offset)
+	width := size.Dx() + 2*tooltipBorderThickness + 2*tooltipHorizontalPadding
+	height := size.Dy() + 2*tooltipBorderThickness + 2*tooltipVerticalPadding
+
+	left := mouse.X + tooltipMouseDistance
+	top := mouse.Y + tooltipMouseDistance
+	if left+width > t.bounds.Max.X {
+		left = mouse.X - tooltipMouseDistance - width
+	}
+	if top+height > t.bounds.Max.Y {
+		top = mouse.Y - tooltipMouseDistance - height
+	}
+
+	bounds := geom.RectRelF32(left, top, width, height)
+
+	almostBlack := zntg.MustHexColor("#000000bf")
+	almostWhite := zntg.MustHexColor("ffffffbf")
+
+	ctx.Renderer().FillRectangle(bounds, almostBlack)
+	ctx.Renderer().Rectangle(bounds, almostWhite, 1)
+
+	bottomLeft := bounds.Min.Add2D(tooltipBorderThickness+tooltipHorizontalPadding, tooltipBorderThickness+tooltipVerticalPadding)
+	ctx.Fonts().Text(fontName, bottomLeft, color.White, t.Text)
+}
diff --git a/ui/ui.go b/ui/ui.go
index 6a8a103..ac710f4 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -49,6 +49,8 @@ func RunWait(r Renderer, s *Style, view Control, wait bool) error {
 		if ctx.HasQuit() {
 			return nil
 		}
+
+		ctx.overlays.Hide("ui-default-tooltip")
 		r.PushEvents(ctx, wait)
 	}
 	return nil