internal/ui: disable IME and enable it only when necessary

Closes #2918

exp/textinput/api_windows.go

@@ -15,6 +15,7 @@
 package textinput
 
 import (
+	"errors"
 	"fmt"
 	"runtime"
 	"unsafe"
@@ -73,6 +74,7 @@ var (
 	imm32  = windows.NewLazySystemDLL("imm32.dll")
 	user32 = windows.NewLazySystemDLL("user32.dll")
 
+	procImmAssociateContext      = imm32.NewProc("ImmAssociateContext")
 	procImmGetCompositionStringW = imm32.NewProc("ImmGetCompositionStringW")
 	procImmGetContext            = imm32.NewProc("ImmGetContext")
 	procImmReleaseContext        = imm32.NewProc("ImmReleaseContext")
@@ -94,6 +96,14 @@ func _GetActiveWindow() windows.HWND {
 	return windows.HWND(r)
 }
 
+func _ImmAssociateContext(hwnd windows.HWND, hIMC uintptr) (uintptr, error) {
+	r, _, e := procImmAssociateContext.Call(uintptr(hwnd), hIMC)
+	if e != nil && !errors.Is(e, windows.ERROR_SUCCESS) {
+		return 0, fmt.Errorf("textinput: ImmAssociateContext failed: error code: %w", e)
+	}
+	return r, nil
+}
+
 func _ImmGetCompositionStringW(unnamedParam1 _HIMC, unnamedParam2 uint32, lpBuf unsafe.Pointer, dwBufLen uint32) (uint32, error) {
 	r, _, e := procImmGetCompositionStringW.Call(uintptr(unnamedParam1), uintptr(unnamedParam2), uintptr(lpBuf), uintptr(dwBufLen))
 	runtime.KeepAlive(lpBuf)

exp/textinput/textinput_windows.go

@@ -15,6 +15,7 @@
 package textinput
 
 import (
+	"sync"
 	"unsafe"
 
 	"golang.org/x/sys/windows"
@@ -29,8 +30,13 @@ type textInput struct {
 	origWndProc     uintptr
 	wndProcCallback uintptr
 	window          windows.HWND
+	immContext      uintptr
 
 	highSurrogate uint16
+
+	initOnce sync.Once
+
+	err error
 }
 
 var theTextInput textInput
@@ -52,11 +58,29 @@ func (t *textInput) Start(x, y int) (chan State, func()) {
 		session.ch <- State{Error: err}
 		session.end()
 	}
-	return session.ch, session.end
+	return session.ch, func() {
+		ui.Get().RunOnMainThread(func() {
+			// Disable IME again.
+			if t.immContext != 0 {
+				return
+			}
+			c, err := _ImmAssociateContext(t.window, 0)
+			if err != nil {
+				t.err = err
+				return
+			}
+			t.immContext = c
+			t.end()
+		})
+	}
 }
 
 // start must be called from the main thread.
 func (t *textInput) start(x, y int) error {
+	if t.err != nil {
+		return t.err
+	}
+
 	if t.window == 0 {
 		t.window = _GetActiveWindow()
 	}
@@ -72,6 +96,22 @@ func (t *textInput) start(x, y int) error {
 		t.origWndProc = h
 	}
 
+	// By default, IME was disabled by setting 0 as the IMM context.
+	// Restore the context once.
+	var err error
+	t.initOnce.Do(func() {
+		err = ui.Get().RestoreIMMContextOnMainThread()
+	})
+	if err != nil {
+		return err
+	}
+
+	if t.immContext != 0 {
+		if _, err := _ImmAssociateContext(t.window, t.immContext); err != nil {
+			return err
+		}
+		t.immContext = 0
+	}
 	h := _ImmGetContext(t.window)
 	if err := _ImmSetCandidateWindow(h, &_CANDIDATEFORM{
 		dwIndex: 0,
@@ -168,14 +208,20 @@ func (t *textInput) send(text string, startInBytes, endInBytes int, committed bo
 
 // end must be called from the main thread.
 func (t *textInput) end() {
-	if t.session != nil {
-		t.session.end()
-		t.session = nil
+	if t.session == nil {
+		return
 	}
+
+	t.session.end()
+	t.session = nil
 }
 
 // update must be called from the main thread.
 func (t *textInput) update() (ferr error) {
+	if t.err != nil {
+		return t.err
+	}
+
 	hIMC := _ImmGetContext(t.window)
 	defer func() {
 		if err := _ImmReleaseContext(t.window, hIMC); err != nil && ferr != nil {
@@ -236,6 +282,10 @@ func (t *textInput) update() (ferr error) {
 
 // commit must be called from the main thread.
 func (t *textInput) commit() (ferr error) {
+	if t.err != nil {
+		return t.err
+	}
+
 	hIMC := _ImmGetContext(t.window)
 	defer func() {
 		if err := _ImmReleaseContext(t.window, hIMC); err != nil && ferr != nil {

internal/ui/api_windows.go

@@ -68,9 +68,12 @@ type _POINT struct {
 }
 
 var (
+	imm32  = windows.NewLazySystemDLL("imm32.dll")
 	ole32  = windows.NewLazySystemDLL("ole32.dll")
 	user32 = windows.NewLazySystemDLL("user32.dll")
 
+	procImmAssociateContext = imm32.NewProc("ImmAssociateContext")
+
 	procCoCreateInstance = ole32.NewProc("CoCreateInstance")
 
 	procGetSystemMetrics  = user32.NewProc("GetSystemMetrics")
@@ -79,6 +82,14 @@ var (
 	procGetCursorPos      = user32.NewProc("GetCursorPos")
 )
 
+func _ImmAssociateContext(hwnd windows.HWND, hIMC uintptr) (uintptr, error) {
+	r, _, e := procImmAssociateContext.Call(uintptr(hwnd), hIMC)
+	if e != nil && !errors.Is(e, windows.ERROR_SUCCESS) {
+		return 0, fmt.Errorf("ui: ImmAssociateContext failed: error code: %w", e)
+	}
+	return r, nil
+}
+
 func _CoCreateInstance(rclsid *windows.GUID, pUnkOuter unsafe.Pointer, dwClsContext uint32, riid *windows.GUID) (unsafe.Pointer, error) {
 	var ptr unsafe.Pointer
 	r, _, _ := procCoCreateInstance.Call(uintptr(unsafe.Pointer(rclsid)), uintptr(pUnkOuter), uintptr(dwClsContext), uintptr(unsafe.Pointer(riid)), uintptr(unsafe.Pointer(&ptr)))

internal/ui/ui_darwin.go

@@ -444,3 +444,7 @@ func (u *UserInterface) setDocumentEdited(edited bool) error {
 	objc.ID(w).Send(sel_setDocumentEdited, edited)
 	return nil
 }
+
+func (u *UserInterface) afterWindowCreation() error {
+	return nil
+}

internal/ui/ui_glfw.go

@@ -106,6 +106,9 @@ type userInterfaceImpl struct {
 	showWindowOnce        sync.Once
 	bufferOnceSwappedOnce sync.Once
 
+	// immContext is used only in Windows.
+	immContext uintptr
+
 	m sync.RWMutex
 }
 
@@ -897,6 +900,10 @@ func (u *UserInterface) createWindow() error {
 		return err
 	}
 
+	if err := u.afterWindowCreation(); err != nil {
+		return err
+	}
+
 	return nil
 }
 

internal/ui/ui_linbsd.go

@@ -204,3 +204,7 @@ func (u *UserInterface) skipTaskbar() error {
 func (u *UserInterface) setDocumentEdited(edited bool) error {
 	return nil
 }
+
+func (u *UserInterface) afterWindowCreation() error {
+	return nil
+}

internal/ui/ui_windows.go

@@ -246,6 +246,38 @@ func (u *UserInterface) setDocumentEdited(edited bool) error {
 	return nil
 }
 
+func (u *UserInterface) afterWindowCreation() error {
+	if microsoftgdk.IsXbox() {
+		return nil
+	}
+
+	// By default, IME should be disabled (#2918).
+	w, err := u.window.GetWin32Window()
+	if err != nil {
+		return err
+	}
+	c, err := _ImmAssociateContext(w, 0)
+	if err != nil {
+		return err
+	}
+	u.immContext = c
+	return nil
+}
+
+// RestoreIMMContextOnMainThread is called from the main thread.
+// The textinput package invokes RestoreIMMContextOnMainThread to enable IME inputting.
+func (u *UserInterface) RestoreIMMContextOnMainThread() error {
+	w, err := u.window.GetWin32Window()
+	if err != nil {
+		return err
+	}
+	if _, err := _ImmAssociateContext(w, u.immContext); err != nil {
+		return err
+	}
+	u.immContext = 0
+	return nil
+}
+
 func init() {
 	if microsoftgdk.IsXbox() {
 		// TimeBeginPeriod might not be defined in Xbox.