docs: Update

docs/examples/_resources/fonts/license.md

@@ -1,5 +1,31 @@
 # License
 
+## arcade_n.ttf
+
+```
+=============================================================
+P.Font Series No.       : 1013
+Type                    : TrueType
+Family Name             : Arcade
+Style Name              : Arcade Normal
+                          Arcade Interlaced
+                          Arcade Rounded
+Author                  : Yuji Adachi
+Description             : Copyright (C)1997-2003 Yuji Adachi
+Support URL             : http://www.9031.com/
+=============================================================
+
+Attention
+
+印刷物、WEBページ等での御使用は自由ですが、このフォントを、
+作者の許可なく販売したり、営利目的の製品に添付することは禁じます。
+また、このフォントのデザインは予告なく変更することがあります。
+
+
+足立　裕司
+yuji@9031.com
+```
+
 ## mplus-1p-regular.ttf
 
 ```

docs/examples/alphablending.html

@@ -60,10 +60,14 @@ func update(screen *ebiten.Image) error {
         case 240 < count:
                 diff = float64(480-count) * 0.2
         }
+
         if ebiten.IsRunningSlowly() {
                 return nil
         }
+
         screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff})
+
+        // Draw 100 Ebitens
         op := &ebiten.DrawImageOptions{}
         op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
         for i := 0; i < 10*10; i++ {

docs/examples/audio.html

@@ -62,6 +62,11 @@ var (
         playerCurrentColor = color.RGBA{0xff, 0xff, 0xff, 0xff}
 )
 
+// Input manages the current input state to detect keys 'just pressed'.
+//
+// Note: 'just pressed' is a very common idiom.
+// There is a plan to create a new package for input utility.
+// See https://github.com/hajimehoshi/ebiten/issues/415.
 type Input struct {
         mouseButtonStates map[ebiten.MouseButton]int
         keyStates         map[ebiten.Key]int
@@ -82,7 +87,7 @@ func (i *Input) update() {
         }
 }
 
-func (i *Input) isKeyTriggered(key ebiten.Key) bool {
+func (i *Input) isKeyJustPressed(key ebiten.Key) bool {
         return i.keyStates[key] == 1
 }
 
@@ -90,25 +95,22 @@ func (i *Input) isKeyPressed(key ebiten.Key) bool {
         return i.keyStates[key] > 0
 }
 
-func (i *Input) isMouseButtonTriggered(mouseButton ebiten.MouseButton) bool {
+func (i *Input) isMouseButtonJustPressed(mouseButton ebiten.MouseButton) bool {
         return i.mouseButtonStates[mouseButton] == 1
 }
 
+// Player represents the current audio state.
 type Player struct {
         input        *Input
         audioContext *audio.Context
         audioPlayer  *audio.Player
         current      time.Duration
         total        time.Duration
-        seBytes      []uint8
-        seCh         chan []uint8
+        seBytes      []byte
+        seCh         chan []byte
         volume128    int
 }
 
-var (
-        musicPlayer *Player
-)
-
 func playerBarRect() (x, y, w, h int) {
         w, h = 300, 4
         x = (screenWidth - w) / 2
@@ -141,9 +143,9 @@ func NewPlayer(audioContext *audio.Context) (*Player, error) {
                 },
                 audioContext: audioContext,
                 audioPlayer:  p,
-                total:        time.Second * time.Duration(s.Size()) / bytesPerSample / sampleRate,
+                total:        time.Second * time.Duration(s.Length()) / bytesPerSample / sampleRate,
                 volume128:    128,
-                seCh:         make(chan []uint8),
+                seCh:         make(chan []byte),
         }
         if player.total == 0 {
                 player.total = 1
@@ -173,32 +175,36 @@ func (p *Player) update() error {
                 p.seCh = nil
         default:
         }
+
         if p.audioPlayer.IsPlaying() {
                 p.current = p.audioPlayer.Current()
         }
-        p.updateBar()
-        p.updatePlayPause()
-        p.updateSE()
-        p.updateVolume()
-        if p.input.isKeyTriggered(ebiten.KeyB) {
+        p.seekBarIfNeeded()
+        p.switchPlayStateIfNeeded()
+        p.playSEIfNeeded()
+        p.updateVolumeIfNeeded()
+
+        if p.input.isKeyJustPressed(ebiten.KeyB) {
                 b := ebiten.IsRunnableInBackground()
                 ebiten.SetRunnableInBackground(!b)
         }
         return nil
 }
 
-func (p *Player) updateSE() {
+func (p *Player) playSEIfNeeded() {
         if p.seBytes == nil {
+                // Bytes for the SE is not loaded yet.
                 return
         }
-        if !p.input.isKeyTriggered(ebiten.KeyP) {
+
+        if !p.input.isKeyJustPressed(ebiten.KeyP) {
                 return
         }
         sePlayer, _ := audio.NewPlayerFromBytes(p.audioContext, p.seBytes)
         sePlayer.Play()
 }
 
-func (p *Player) updateVolume() {
+func (p *Player) updateVolumeIfNeeded() {
         if p.input.isKeyPressed(ebiten.KeyZ) {
                 p.volume128--
         }
@@ -214,8 +220,8 @@ func (p *Player) updateVolume() {
         p.audioPlayer.SetVolume(float64(p.volume128) / 128)
 }
 
-func (p *Player) updatePlayPause() {
-        if !p.input.isKeyTriggered(ebiten.KeyS) {
+func (p *Player) switchPlayStateIfNeeded() {
+        if !p.input.isKeyJustPressed(ebiten.KeyS) {
                 return
         }
         if p.audioPlayer.IsPlaying() {
@@ -225,11 +231,12 @@ func (p *Player) updatePlayPause() {
         p.audioPlayer.Play()
 }
 
-func (p *Player) updateBar() {
-        if !p.input.isMouseButtonTriggered(ebiten.MouseButtonLeft) {
+func (p *Player) seekBarIfNeeded() {
+        if !p.input.isMouseButtonJustPressed(ebiten.MouseButtonLeft) {
                 return
         }
-        // Start seeking.
+
+        // Calculate the next seeking position from the current cursor position.
         x, y := ebiten.CursorPosition()
         bx, by, bw, bh := playerBarRect()
         const padding = 4
@@ -249,40 +256,45 @@ func (p *Player) close() error {
 }
 
 func (p *Player) draw(screen *ebiten.Image) {
-        // Bar
+        // Draw the bar.
         x, y, w, h := playerBarRect()
         ebitenutil.DrawRect(screen, float64(x), float64(y), float64(w), float64(h), playerBarColor)
 
-        currentTimeStr := "00:00"
-
-        // Current Time
+        // Draw the cursor on the bar.
         c := p.current
-        m := (c / time.Minute) % 100
-        s := (c / time.Second) % 60
-        currentTimeStr = fmt.Sprintf("%02d:%02d", m, s)
-
-        // Cursor
         cw, ch := 4, 10
         cx := int(time.Duration(w)*c/p.total) + x - cw/2
         cy := y - (ch-h)/2
         ebitenutil.DrawRect(screen, float64(cx), float64(cy), float64(cw), float64(ch), playerCurrentColor)
 
+        // Compose the curren time text.
+        m := (c / time.Minute) % 100
+        s := (c / time.Second) % 60
+        currentTimeStr := fmt.Sprintf("%02d:%02d", m, s)
+
+        // Draw the debug message.
         msg := fmt.Sprintf(`FPS: %0.2f
 Press S to toggle Play/Pause
 Press P to play SE
 Press Z or X to change volume of the music
 Press B to switch the run-in-background state
-%s`, ebiten.CurrentFPS(), currentTimeStr)
+Current Time: %s`, ebiten.CurrentFPS(), currentTimeStr)
         ebitenutil.DebugPrint(screen, msg)
 }
 
+var (
+        musicPlayer *Player
+)
+
 func update(screen *ebiten.Image) error {
         if err := musicPlayer.update(); err != nil {
                 return err
         }
+
         if ebiten.IsRunningSlowly() {
                 return nil
         }
+
         musicPlayer.draw(screen)
         return nil
 }
@@ -300,10 +312,8 @@ func main() {
         if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Audio (Ebiten Demo)"); err != nil {
                 log.Fatal(err)
         }
-        if musicPlayer != nil {
-                if err := musicPlayer.close(); err != nil {
-                        log.Fatal(err)
-                }
+        if err := musicPlayer.close(); err != nil {
+                log.Fatal(err)
         }
 }
 </code></pre></div>

docs/examples/piano.html

@@ -34,15 +34,52 @@ package main
 import (
         "fmt"
         "image/color"
+        "io/ioutil"
         "log"
         "math"
 
+        "github.com/golang/freetype/truetype"
+        "golang.org/x/image/font"
+
         "github.com/hajimehoshi/ebiten"
         "github.com/hajimehoshi/ebiten/audio"
         "github.com/hajimehoshi/ebiten/ebitenutil"
-        "github.com/hajimehoshi/ebiten/examples/common"
+        "github.com/hajimehoshi/ebiten/text"
 )
 
+const (
+        arcadeFontSize = 8
+)
+
+var (
+        arcadeFont font.Face
+)
+
+func init() {
+        f, err := ebitenutil.OpenFile(ebitenutil.JoinStringsIntoFilePath("_resources", "fonts", "arcade_n.ttf"))
+        if err != nil {
+                log.Fatal(err)
+        }
+        defer f.Close()
+
+        b, err := ioutil.ReadAll(f)
+        if err != nil {
+                log.Fatal(err)
+        }
+
+        tt, err := truetype.Parse(b)
+        if err != nil {
+                log.Fatal(err)
+        }
+
+        const dpi = 72
+        arcadeFont = truetype.NewFace(tt, &truetype.Options{
+                Size:    arcadeFontSize,
+                DPI:     dpi,
+                Hinting: font.HintingFull,
+        })
+}
+
 const (
         screenWidth  = 320
         screenHeight = 240
@@ -64,15 +101,13 @@ var pcm = make([]float64, 4*sampleRate)
 const baseFreq = 220
 
 func init() {
-        s := float64(sampleRate)
         amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
         x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
         for i := 0; i < len(pcm); i++ {
                 v := 0.0
-                twoPiF := 2.0 * math.Pi * baseFreq
                 for j := 0; j < len(amp); j++ {
-                        a := amp[j] * math.Exp(-5*float64(i)/(x[j]*s))
-                        v += a * math.Sin(float64(i)*twoPiF*float64(j+1)/s)
+                        a := amp[j] * math.Exp(-5*float64(i)/(x[j]*sampleRate))
+                        v += a * math.Sin(2.0*math.Pi*float64(i)*baseFreq*float64(j+1)/sampleRate)
                 }
                 pcm[i] = v / 5.0
         }
@@ -175,7 +210,7 @@ func init() {
                 x := i*width + 36
                 height := 112
                 ebitenutil.DrawRect(imagePiano, float64(x), float64(y), float64(width-1), float64(height), color.White)
-                common.ArcadeFont.DrawText(imagePiano, k, x+8, y+height-16, 1, color.Black)
+                text.Draw(imagePiano, k, arcadeFont, x+8, y+height-8, color.Black)
         }
 
         blackKeys := []string{"Q", "W", "", "R", "T", "", "U", "I", "O"}
@@ -186,7 +221,7 @@ func init() {
                 x := i*width + 24
                 height := 64
                 ebitenutil.DrawRect(imagePiano, float64(x), float64(y), float64(width-1), float64(height), color.Black)
-                common.ArcadeFont.DrawText(imagePiano, k, x+8, y+height-16, 1, color.White)
+                text.Draw(imagePiano, k, arcadeFont, x+8, y+height-8, color.White)
         }
 }