Add keyboard handling code and refactor input handlers

Canvas gets the keyboard handler (top level)
CanvasObjects can now be clickable
Buttons refactored to be 'tappable' as the high level API should not care about event types

ui/canvas.go

@@ -10,6 +10,8 @@ type Canvas interface {
 	Size() Size
 	Scale() float32
 	SetScale(float32)
+
+	SetOnKeyDown(func(*KeyEvent))
 }
 
 // GetCanvas returns the canvas containing the passed CanvasObject.

ui/canvasobject.go

@@ -13,3 +13,10 @@ type CanvasObject interface {
 
 	MinSize() Size
 }
+
+// ClickableObject describes any CanvasObject that can also be clicked
+// (i.e. has mouse handlers). This should be implemented by buttons etc that
+// wish to handle pointer interactions.
+type ClickableObject interface {
+	OnMouseDown(*MouseEvent)
+}

ui/event.go

@@ -0,0 +1,19 @@
+package ui
+
+import "github.com/fyne-io/fyne/ui/input"
+
+// KeyEvent describes a keyboard input event.
+type KeyEvent struct {
+	String string
+
+	Name      string
+	Code      input.KeyCode
+	Modifiers input.Modifier
+}
+
+// MouseEvent describes a pointer input event. The position is relative to the top-left
+// of the CanvasObject this is triggered on.
+type MouseEvent struct {
+	Position Position          // The position of the event
+	Button   input.MouseButton // The mouse button which caused the event
+}

ui/input/key.go

@@ -0,0 +1,13 @@
+package input
+
+// KeyCode represents the numeric code of a key pressed without modifiers
+type KeyCode int
+
+// Modifier captures any key modifiers (shift etc) pressed during this key event
+type Modifier int
+
+const (
+	ShiftModifier Modifier = 1 << iota
+	ControlModifier
+	AltModifier
+)

ui/event/mouse.go → ui/input/mouse.go

@@ -1,15 +1,4 @@
-// Package event defines the various types of events that widgets or apps can
-// listen for
-package event
-
-import "github.com/fyne-io/fyne/ui"
-
-// MouseEvent describes an input event. The position is relative to the top-left
-// of the CanvasObject this is triggered on.
-type MouseEvent struct {
-	Position ui.Position // The position of the event
-	Button   MouseButton // The mouse button which caused the event
-}
+package input
 
 // MouseButton represents a single button in a MouseEvent
 type MouseButton int

ui/widget/button.go

@@ -2,7 +2,6 @@ package widget
 
 import "github.com/fyne-io/fyne/ui"
 import "github.com/fyne-io/fyne/ui/canvas"
-import "github.com/fyne-io/fyne/ui/event"
 import "github.com/fyne-io/fyne/ui/layout"
 import "github.com/fyne-io/fyne/ui/theme"
 
@@ -11,7 +10,7 @@ type Button struct {
 	baseWidget
 	Style ButtonStyle
 
-	OnClicked func(*event.MouseEvent)
+	OnTapped func()
 
 	label      *canvas.Text
 	background *canvas.Rectangle
@@ -43,8 +42,14 @@ func (b *Button) Layout(size ui.Size) []ui.CanvasObject {
 	return b.objects
 }
 
-// NewButton creates a new button widget with the set label and click handler
-func NewButton(label string, clicked func(*event.MouseEvent)) *Button {
+func (b *Button) OnMouseDown(*ui.MouseEvent) {
+	if b.OnTapped != nil {
+		b.OnTapped()
+	}
+}
+
+// NewButton creates a new button widget with the set label and tap handler
+func NewButton(label string, tapped func()) *Button {
 	text := canvas.NewText(label)
 	bg := canvas.NewRectangle(theme.ButtonColor())
 
@@ -56,7 +61,7 @@ func NewButton(label string, clicked func(*event.MouseEvent)) *Button {
 			},
 		},
 		DefaultButton,
-		clicked,
+		tapped,
 		text,
 		bg,
 	}