windows: add GetKeyboardLayout & ToUnicodeEx

These are used along with GetForegroundWindow and GetWindowThreadProcessId to determine the current user layout and translate the base key the user has pressed.

Change-Id: Ib833ba7ab54213d83e889ff74c5bc0ace5edbe95
GitHub-Last-Rev: 2afe997
GitHub-Pull-Request: #188
Reviewed-on: https://go-review.googlesource.com/c/sys/+/574755
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Ayman Bagabas <ayman.bagabas@gmail.com>

windows/syscall_windows.go

@@ -17,8 +17,10 @@ import (
 	"unsafe"
 )
 
-type Handle uintptr
-type HWND uintptr
+type (
+	Handle uintptr
+	HWND   uintptr
+)
 
 const (
 	InvalidHandle = ^Handle(0)
@@ -211,6 +213,10 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	OpenProcess(desiredAccess uint32, inheritHandle bool, processId uint32) (handle Handle, err error)
 //sys	ShellExecute(hwnd Handle, verb *uint16, file *uint16, args *uint16, cwd *uint16, showCmd int32) (err error) [failretval<=32] = shell32.ShellExecuteW
 //sys	GetWindowThreadProcessId(hwnd HWND, pid *uint32) (tid uint32, err error) = user32.GetWindowThreadProcessId
+//sys	LoadKeyboardLayout(name *uint16, flags uint32) (hkl Handle, err error) [failretval==0] = user32.LoadKeyboardLayoutW
+//sys	UnloadKeyboardLayout(hkl Handle) (err error) = user32.UnloadKeyboardLayout
+//sys	GetKeyboardLayout(tid uint32) (hkl Handle) = user32.GetKeyboardLayout
+//sys	ToUnicodeEx(vkey uint32, scancode uint32, keystate *byte, pwszBuff *uint16, cchBuff int32, flags uint32, hkl Handle) (ret int32) = user32.ToUnicodeEx
 //sys	GetShellWindow() (shellWindow HWND) = user32.GetShellWindow
 //sys	MessageBox(hwnd HWND, text *uint16, caption *uint16, boxtype uint32) (ret int32, err error) [failretval==0] = user32.MessageBoxW
 //sys	ExitWindowsEx(flags uint32, reason uint32) (err error) = user32.ExitWindowsEx
@@ -1368,9 +1374,11 @@ func SetsockoptLinger(fd Handle, level, opt int, l *Linger) (err error) {
 func SetsockoptInet4Addr(fd Handle, level, opt int, value [4]byte) (err error) {
 	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(&value[0])), 4)
 }
+
 func SetsockoptIPMreq(fd Handle, level, opt int, mreq *IPMreq) (err error) {
 	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
 }
+
 func SetsockoptIPv6Mreq(fd Handle, level, opt int, mreq *IPv6Mreq) (err error) {
 	return syscall.EWINDOWS
 }

windows/syscall_windows_test.go

@@ -1437,3 +1437,50 @@ uintptr_t beep(void) {
 		t.Fatal("LoadLibraryEx unexpectedly found beep.dll")
 	}
 }
+
+func TestGetKeyboardLayout(t *testing.T) {
+	fg := windows.GetForegroundWindow()
+	tid, err := windows.GetWindowThreadProcessId(fg, nil)
+	if err != nil {
+		t.Fatalf("GetWindowThreadProcessId failed: %v", err)
+	}
+
+	// We don't care about the result, just that it doesn't crash.
+	_ = windows.GetKeyboardLayout(tid)
+}
+
+func TestToUnicodeEx(t *testing.T) {
+	var utf16Buf [16]uint16
+
+	// Arabic (101) Keyboard Identifier
+	// See https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/windows-language-pack-default-values
+	ara, err := windows.UTF16PtrFromString("00000401")
+	if err != nil {
+		t.Fatalf("UTF16PtrFromString failed: %v", err)
+	}
+	araLayout, err := windows.LoadKeyboardLayout(ara, windows.KLF_ACTIVATE)
+	if err != nil {
+		t.Fatalf("LoadKeyboardLayout failed: %v", err)
+	}
+
+	var keyState [256]byte
+	ret := windows.ToUnicodeEx(
+		0x41, // 'A' vkCode
+		0x1e, // 'A' scanCode
+		&keyState[0],
+		&utf16Buf[0],
+		int32(len(utf16Buf)),
+		0x4, // don't change keyboard state
+		araLayout,
+	)
+
+	if ret != 1 {
+		t.Errorf("ToUnicodeEx failed, wanted 1, got %d", ret)
+	}
+	if utf16Buf[0] != 'ش' {
+		t.Errorf("ToUnicodeEx failed, wanted 'ش', got %q", utf16Buf[0])
+	}
+	if err := windows.UnloadKeyboardLayout(araLayout); err != nil {
+		t.Errorf("UnloadKeyboardLayout failed: %v", err)
+	}
+}

windows/types_windows.go

@@ -3418,3 +3418,14 @@ type DCB struct {
 	EvtChar    byte
 	wReserved1 uint16
 }
+
+// Keyboard Layout Flags.
+// See https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-loadkeyboardlayoutw
+const (
+	KLF_ACTIVATE      = 0x00000001
+	KLF_SUBSTITUTE_OK = 0x00000002
+	KLF_REORDER       = 0x00000008
+	KLF_REPLACELANG   = 0x00000010
+	KLF_NOTELLSHELL   = 0x00000080
+	KLF_SETFORPROCESS = 0x00000100
+)