inpututil: Add PressedKeys

Closes #770

examples/keyboard/main.go

@@ -27,6 +27,7 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
 	"github.com/hajimehoshi/ebiten/v2/examples/keyboard/keyboard"
 	rkeyboard "github.com/hajimehoshi/ebiten/v2/examples/resources/images/keyboard"
+	"github.com/hajimehoshi/ebiten/v2/inpututil"
 )
 
 const (
@@ -46,16 +47,9 @@ func init() {
 }
 
 type Game struct {
-	pressed []ebiten.Key
 }
 
 func (g *Game) Update() error {
-	g.pressed = nil
-	for k := ebiten.Key(0); k <= ebiten.KeyMax; k++ {
-		if ebiten.IsKeyPressed(k) {
-			g.pressed = append(g.pressed, k)
-		}
-	}
 	return nil
 }
 
@@ -73,7 +67,8 @@ func (g *Game) Draw(screen *ebiten.Image) {
 
 	// Draw the highlighted keys.
 	op = &ebiten.DrawImageOptions{}
-	for _, p := range g.pressed {
+	keys := inpututil.PressedKeys()
+	for _, p := range keys {
 		op.GeoM.Reset()
 		r, ok := keyboard.KeyRect(p)
 		if !ok {
@@ -85,7 +80,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 	}
 
 	keyStrs := []string{}
-	for _, p := range g.pressed {
+	for _, p := range keys {
 		keyStrs = append(keyStrs, p.String())
 	}
 	ebitenutil.DebugPrint(screen, strings.Join(keyStrs, ", "))

inpututil/inpututil.go

@@ -161,6 +161,23 @@ func (i *inputState) update() {
 	}
 }
 
+// PressedKeys returns a set of currently pressed keyboard keys.
+//
+// PressedKeys is concurrent safe.
+func PressedKeys() []ebiten.Key {
+	theInputState.m.RLock()
+	defer theInputState.m.RUnlock()
+
+	keys := make([]ebiten.Key, 0, len(theInputState.keyDurations))
+	for i, d := range theInputState.keyDurations {
+		if d == 0 {
+			continue
+		}
+		keys = append(keys, ebiten.Key(i))
+	}
+	return keys
+}
+
 // IsKeyJustPressed returns a boolean value indicating
 // whether the given key is pressed just in the current frame.
 //