Add docs for gamepad API (I checked it worked on Chrome)

_docs/index.tmpl.html

@@ -76,6 +76,14 @@ pre {
 <p>NOTE: <code>file://</code> URL may not work with Ebiten. Execute your game on a HTTP server.</p>
 
 <h2>Change Log</h2>
+<h3>2015-??-??</h3>
+<ul>
+  <li>v1.2.0-rc1 released.
+    <ul>
+      <li>Support for gamepads</li>
+    </ul>
+  </li>
+</ul>
 <h3>2015-01-10</h3>
 <ul>
   <li>v1.1.0-rc1 released.

gamecontext.go

@@ -36,20 +36,34 @@ func IsMouseButtonPressed(mouseButton MouseButton) bool {
 	return ui.IsMouseButtonPressed(ui.MouseButton(mouseButton))
 }
 
-// TODO: docs
+// GamepadAxisNum returns the number of axes of the gamepad.
-
+//
+// NOTE: Gamepad API is available only on desktops, Chrome and Firefox.
+// To use this API, browsers might require rebooting the browser.
 func GamepadAxisNum(id int) int {
 	return ui.GamepadAxisNum(id)
 }
 
+// GamepadAxis returns the float value [-1.0 - 1.0] of the axis.
+//
+// NOTE: Gamepad API is available only on desktops, Chrome and Firefox.
+// To use this API, browsers might require rebooting the browser.
 func GamepadAxis(id int, axis int) float64 {
 	return ui.GamepadAxis(id, axis)
 }
 
+// GamepadButtonNum returns the number of the buttons of the gamepad.
+//
+// NOTE: Gamepad API is available only on desktops, Chrome and Firefox.
+// To use this API, browsers might require rebooting the browser.
 func GamepadButtonNum(id int) int {
 	return ui.GamepadButtonNum(id)
 }
 
+// IsGamepadButtonPressed returns the boolean indicating the buttons is pressed or not.
+//
+// NOTE: Gamepad API is available only on desktops, Chrome and Firefox.
+// To use this API, browsers might require rebooting the browser.
 func IsGamepadButtonPressed(id int, button GamepadButton) bool {
 	return ui.IsGamepadButtonPressed(id, ui.GamepadButton(button))
 }

internal/ui/input_js.go

@@ -65,7 +65,11 @@ func (i *input) mouseMove(x, y int) {
 }
 
 func (i *input) updateGamepads() {
-	gamepads := js.Global.Get("navigator").Call("getGamepads")
+	nav := js.Global.Get("navigator")
+	if nav.Get("getGamepads") == js.Undefined {
+		return
+	}
+	gamepads := nav.Call("getGamepads")
 	l := gamepads.Get("length").Int()
 	for id := 0; id < l; id++ {
 		gamepad := gamepads.Index(id)

internal/ui/ui_js.go

@@ -158,10 +158,6 @@ func init() {
 
 	// Gamepad
 	window.Call("addEventListener", "gamepadconnected", func(e js.Object) {
-		print(e)
-	})
-	window.Call("addEventListener", "gamepaddisconnected", func(e js.Object) {
-		print(e)
 	})
 }