iinternal/gamepad: start implementation for Xbox

Updates #2084

internal/gamepad/api_xbox_windows.go

@@ -0,0 +1,50 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !ebitencbackend
+// +build !ebitencbackend
+
+package gamepad
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var (
+	gameInput = windows.NewLazySystemDLL("GameInput.dll")
+
+	procGameInputCreate = gameInput.NewProc("GameInputCreate")
+)
+
+func _GameInputCreate() (*_IGameInput, error) {
+	var gameInput *_IGameInput
+	r, _, _ := procGameInputCreate.Call(uintptr(unsafe.Pointer(&gameInput)))
+	if uint32(r) != uint32(windows.S_OK) {
+		return nil, fmt.Errorf("gamepad: GameInputCreate failed: HRESULT(%d)", uint32(r))
+	}
+	return gameInput, nil
+}
+
+type _IGameInput struct {
+	vtbl *_IGameInput_Vtbl
+}
+
+type _IGameInput_Vtbl struct {
+	QueryInterface uintptr
+	AddRef         uintptr
+	Release        uintptr
+}

internal/gamepad/gamepad_xbox_windows.go

@@ -17,9 +17,16 @@
 
 package gamepad
 
-type nativeGamepadsXbox struct{}
+type nativeGamepadsXbox struct {
+	gameInput *_IGameInput
+}
 
 func (n *nativeGamepadsXbox) init(gamepads *gamepads) error {
+	g, err := _GameInputCreate()
+	if err != nil {
+		return err
+	}
+	n.gameInput = g
 	return nil
 }