debugui: integrate IsCapturingInput and Update

Closes #28

Author: hajimehoshi

context.go

@@ -65,9 +65,9 @@ func (c *Context) wrapError(f func() error) {
 	c.err = f()
 }
 
-func (c *Context) update(f func(ctx *Context) error) (err error) {
+func (c *Context) update(f func(ctx *Context) error) (captured bool, err error) {
 	if c.err != nil {
-		return c.err
+		return false, c.err
 	}
 
 	c.pointing.update()
@@ -80,12 +80,12 @@ func (c *Context) update(f func(ctx *Context) error) (err error) {
 	}()
 
 	if err := f(c); err != nil {
-		return err
+		return false, err
 	}
 	if c.err != nil {
-		return c.err
+		return false, c.err
 	}
-	return nil
+	return c.isCapturingInput(), nil
 }
 
 func (c *Context) beginUpdate() {

debugui.go

@@ -14,9 +14,16 @@ type DebugUI struct {
 
 // Update updates the debug UI.
 //
+// Update returns true if the debug UI is capturing input, e.g. when a widget has focus.
+// Otherwise, Update returns false.
+//
 // Update should be called once in the game's Update function.
-func (d *DebugUI) Update(f func(ctx *Context) error) error {
-	return d.ctx.update(f)
+func (d *DebugUI) Update(f func(ctx *Context) error) (bool, error) {
+	captured, err := d.ctx.update(f)
+	if err != nil {
+		return false, err
+	}
+	return captured, nil
 }
 
 // Draw draws the debug UI.
@@ -26,8 +33,3 @@ func (d *DebugUI) Draw(screen *ebiten.Image) {
 	d.ctx.draw(screen)
 	d.ctx.screenWidth, d.ctx.screenHeight = screen.Bounds().Dx(), screen.Bounds().Dy()
 }
-
-// IsCapturingInput reports whether the debug UI is capturing input, e.g. when a widget has focus.
-func (d *DebugUI) IsCapturingInput() bool {
-	return d.ctx.isCapturingInput()
-}