From ff2ece7d0618555a63d45addd6a0a914d62caa77 Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Tue, 5 Mar 2019 22:42:57 +0100
Subject: [PATCH] Added mouse wheel implementation (scrollbar & overflow).
 Fixed bug in length of scrollbar handle.

---
 ui/allg5ui/renderer.go |  2 +-
 ui/control.go          |  1 +
 ui/controlbase.go      |  2 ++
 ui/event.go            |  1 +
 ui/overflow.go         | 16 ++++++++++++++++
 ui/proxy.go            |  2 ++
 ui/scrollbar.go        | 11 ++++++++++-
 7 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/ui/allg5ui/renderer.go b/ui/allg5ui/renderer.go
index 12d48ca..3ae5738 100644
--- a/ui/allg5ui/renderer.go
+++ b/ui/allg5ui/renderer.go
@@ -57,7 +57,7 @@ func (r *Renderer) PushEvents(t ui.EventTarget, wait bool) {
 		case *allg5.MouseButtonUpEvent:
 			t.Handle(&ui.MouseButtonUpEvent{MouseEvent: mouseEvent(e.MouseEvent), Button: ui.MouseButton(e.Button)})
 		case *allg5.MouseMoveEvent:
-			t.Handle(&ui.MouseMoveEvent{MouseEvent: mouseEvent(e.MouseEvent)})
+			t.Handle(&ui.MouseMoveEvent{MouseEvent: mouseEvent(e.MouseEvent), MouseWheel: float32(e.DeltaZ)})
 		}
 		ev = r.eq.Get()
 	}
diff --git a/ui/control.go b/ui/control.go
index f03fb03..ae93029 100644
--- a/ui/control.go
+++ b/ui/control.go
@@ -11,6 +11,7 @@ type Control interface {
 	Render(Context)
 
 	Bounds() geom.RectangleF32
+	Offset() geom.PointF32
 	OnClick(ClickFn)
 	OnDragStart(DragStartFn)
 	OnDragMove(DragMoveFn)
diff --git a/ui/controlbase.go b/ui/controlbase.go
index 6e11420..dc7d2f7 100644
--- a/ui/controlbase.go
+++ b/ui/controlbase.go
@@ -97,6 +97,8 @@ func (c *ControlBase) IsOver() bool { return c.over }
 
 func (c *ControlBase) IsPressed() bool { return c.pressed }
 
+func (c *ControlBase) Offset() geom.PointF32 { return c.offset }
+
 func (c *ControlBase) OnClick(fn ClickFn) {
 	c.onClick = fn
 }
diff --git a/ui/event.go b/ui/event.go
index 4783075..79ca566 100644
--- a/ui/event.go
+++ b/ui/event.go
@@ -47,4 +47,5 @@ func (e *MouseEvent) Pos() geom.PointF32 {
 
 type MouseMoveEvent struct {
 	MouseEvent
+	MouseWheel float32
 }
diff --git a/ui/overflow.go b/ui/overflow.go
index 76715e7..4565ccb 100644
--- a/ui/overflow.go
+++ b/ui/overflow.go
@@ -14,6 +14,7 @@ type overflow struct {
 	barWidth float32
 	desired  geom.PointF32
 	bounds   geom.RectangleF32
+	offset   geom.PointF32
 	buffer   Image
 
 	hor *Scrollbar
@@ -61,6 +62,7 @@ func (o *overflow) Arrange(ctx Context, bounds geom.RectangleF32, offset geom.Po
 	o.barWidth = ctx.Style().Dimensions.ScrollbarWidth
 	o.desired = o.Content.DesiredSize(ctx)
 	o.bounds = bounds
+	o.offset = offset
 
 	var hor, ver = o.shouldScroll(bounds)
 	var contentX, contentY float32 = 0, 0
@@ -92,9 +94,23 @@ func (o *overflow) Handle(ctx Context, e Event) {
 	if ver {
 		o.ver.Handle(ctx, e)
 	}
+	switch e := e.(type) {
+	case *MouseMoveEvent:
+		if ver {
+			var contentO = o.Content.Offset()
+			var content = o.Content.Bounds()
+			content.Min = contentO
+			content.Max = content.Max.Add(contentO)
+			if e.MouseWheel != 0 && e.Pos().In(content) {
+				o.ver.Offset = geom.Max32(0, geom.Min32(o.ver.Content-content.Dy(), o.ver.Offset-36*e.MouseWheel))
+			}
+		}
+	}
 	o.Content.Handle(ctx, e)
 }
 
+func (o *overflow) Offset() geom.PointF32 { return o.offset }
+
 func (o *overflow) Render(ctx Context) {
 	var renderer = ctx.Renderer()
 
diff --git a/ui/proxy.go b/ui/proxy.go
index 1ad365b..669fff5 100644
--- a/ui/proxy.go
+++ b/ui/proxy.go
@@ -28,6 +28,8 @@ func (p *Proxy) Bounds() geom.RectangleF32 {
 	return p.Content.Bounds()
 }
 
+func (p *Proxy) Offset() geom.PointF32 { return p.Content.Offset() }
+
 func (p *Proxy) OnClick(fn ClickFn) {
 	p.Content.OnClick(fn)
 }
diff --git a/ui/scrollbar.go b/ui/scrollbar.go
index 28bcb7c..c7ca03b 100644
--- a/ui/scrollbar.go
+++ b/ui/scrollbar.go
@@ -43,6 +43,12 @@ func (s *Scrollbar) DesiredSize(ctx Context) geom.PointF32 {
 
 func (s *Scrollbar) Handle(ctx Context, e Event) {
 	s.handle.Handle(ctx, e)
+	switch e := e.(type) {
+	case *MouseMoveEvent:
+		if e.MouseWheel != 0 && e.Pos().Sub(s.offset).In(s.bounds) {
+			s.Offset = geom.Max32(0, geom.Min32(s.Content-s.Orientation.SizeParallel(s.bounds), s.Offset-36*e.MouseWheel))
+		}
+	}
 	s.ControlBase.Handle(ctx, e)
 }
 
@@ -56,8 +62,11 @@ func (s *Scrollbar) updateBar(ctx Context) {
 	var handleLength = length
 	var handleOffset = s.Orientation.LengthParallel(s.bounds.Min)
 	if s.Content > length {
-		handleLength = geom.Max32(2*width, length/s.Content)
+		handleLength = geom.Max32(2*width, length*length/s.Content)
 		var hidden = s.Content - length
+		if s.Offset > hidden {
+			s.Offset = hidden
+		}
 		var offset = geom.Min32(1, s.Offset/hidden)
 		handleOffset = handleOffset + offset*(length-handleLength)
 	}