all: add handling of left/middle/right mouse buttons

Author: sbinet

context.go

@@ -91,6 +91,7 @@ func (gctx *gcontext) run(setup, draw Func) error {
 				Event.Mouse.Position.X = float64(e.Position.X)
 				Event.Mouse.Position.Y = float64(e.Position.Y)
 			}
+			Event.Mouse.Buttons = Buttons(e.Buttons)
 
 		case system.FrameEvent:
 			gctx.draw(e, draw)

event.go

@@ -16,5 +16,21 @@ var Event struct {
 			X float64
 			Y float64
 		}
+		Buttons Buttons
 	}
 }
+
+// Buttons is a set of mouse buttons.
+type Buttons uint8
+
+// Contain reports whether the set b contains
+// all of the buttons.
+func (b Buttons) Contain(buttons Buttons) bool {
+	return b&buttons == buttons
+}
+
+const (
+	ButtonLeft Buttons = 1 << iota
+	ButtonRight
+	ButtonMiddle
+)

example/mouse-pressed/main.go

@@ -22,7 +22,9 @@ func setup() {
 func draw() {
 	switch {
 	case p5.Event.Mouse.Pressed:
-		p5.Fill(color.RGBA{R: 255, A: 255})
+		if p5.Event.Mouse.Buttons.Contain(p5.ButtonLeft) {
+			p5.Fill(color.RGBA{R: 255, A: 255})
+		}
 	default:
 		p5.Fill(color.Transparent)
 	}