textinput: support every environment even without IME

Closes #3072

exp/textinput/textinput_noime.go

@@ -0,0 +1,58 @@
+// Copyright 2023 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 (!darwin && !js && !windows) || ios
+
+package textinput
+
+import (
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/internal/ui"
+)
+
+type textInput struct {
+	rs       []rune
+	lastTick uint64
+}
+
+var theTextInput textInput
+
+func (t *textInput) Start(x, y int) (chan State, func()) {
+	// AppendInputChars is updated only when the tick is updated.
+	// If the tick is not updated, return nil immediately.
+	tick := ui.Get().Tick()
+	if t.lastTick == tick {
+		return nil, nil
+	}
+	defer func() {
+		t.lastTick = tick
+	}()
+
+	s := newSession()
+
+	// This is a pseudo implementation with AppendInputChars without IME.
+	// This is tentative and should be replaced with IME in the future.
+	t.rs = ebiten.AppendInputChars(t.rs[:0])
+	if len(t.rs) == 0 {
+		return nil, nil
+	}
+	s.ch <- State{
+		Text:      string(t.rs),
+		Committed: true,
+	}
+	// Keep the channel as end() resets s.ch.
+	ch := s.ch
+	s.end()
+	return ch, nil
+}

exp/textinput/textinput_null.go

@@ -1,25 +0,0 @@
-// Copyright 2023 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 (!darwin && !js && !windows) || ios
-
-package textinput
-
-type textInput struct{}
-
-var theTextInput textInput
-
-func (t *textInput) Start(x, y int) (chan State, func()) {
-	return nil, nil
-}

internal/ui/context.go

@@ -153,6 +153,8 @@ func (c *context) updateFrameImpl(graphicsDriver graphicsdriver.Graphics, update
 		if err := ui.error(); err != nil {
 			return err
 		}
+
+		ui.tick.Add(1)
 	}
 
 	// Update window icons during a frame, since an icon might be *ebiten.Image and

internal/ui/ui.go

@@ -79,6 +79,7 @@ type UserInterface struct {
 	graphicsLibrary           atomic.Int32
 	running                   atomic.Bool
 	terminated                atomic.Bool
+	tick                      atomic.Uint64
 
 	whiteImage *Image
 
@@ -230,3 +231,7 @@ func (u *UserInterface) isTerminated() bool {
 func (u *UserInterface) setTerminated() {
 	u.terminated.Store(true)
 }
+
+func (u *UserInterface) Tick() uint64 {
+	return u.tick.Load()
+}