fix(mobile): restore canvas offset after hidding the soft keyboard (#14506)

* fix(mobile): restore canvas offset after hidding the soft keyboard

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(mobile): ingore mobileFocusCanvasCursor in didChangeMetrics

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(mobile): remove unused code

Signed-off-by: fufesou <linlong1266@gmail.com>

* refact(mobile): simple refactor

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(mobile): restore canvas, cancel focus timer

Signed-off-by: fufesou <linlong1266@gmail.com>

---------

Signed-off-by: fufesou <linlong1266@gmail.com>

flutter/lib/mobile/pages/remote_page.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:ui' as ui;
 
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
@@ -65,9 +64,7 @@ class _RemotePageState extends State<RemotePage> with WidgetsBindingObserver {
   bool _showGestureHelp = false;
   String _value = '';
   Orientation? _currentOrientation;
-  double _viewInsetsBottom = 0;
   final _uniqueKey = UniqueKey();
-  Timer? _timerDidChangeMetrics;
   Timer? _iosKeyboardWorkaroundTimer;
 
   final _blockableOverlayState = BlockableOverlayState();
@@ -140,7 +137,6 @@ class _RemotePageState extends State<RemotePage> with WidgetsBindingObserver {
     _physicalFocusNode.dispose();
     await gFFI.close();
     _timer?.cancel();
-    _timerDidChangeMetrics?.cancel();
     _iosKeyboardWorkaroundTimer?.cancel();
     gFFI.dialogManager.dismissAll();
     await SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual,
@@ -167,26 +163,6 @@ class _RemotePageState extends State<RemotePage> with WidgetsBindingObserver {
     gFFI.invokeMethod("try_sync_clipboard");
   }
 
-  @override
-  void didChangeMetrics() {
-    // If the soft keyboard is visible and the canvas has been changed(panned or scaled)
-    // Don't try reset the view style and focus the cursor.
-    if (gFFI.cursorModel.lastKeyboardIsVisible &&
-        gFFI.canvasModel.isMobileCanvasChanged) {
-      return;
-    }
-
-    final newBottom = MediaQueryData.fromView(ui.window).viewInsets.bottom;
-    _timerDidChangeMetrics?.cancel();
-    _timerDidChangeMetrics = Timer(Duration(milliseconds: 100), () async {
-      // We need this comparation because poping up the floating action will also trigger `didChangeMetrics()`.
-      if (newBottom != _viewInsetsBottom) {
-        gFFI.canvasModel.mobileFocusCanvasCursor();
-        _viewInsetsBottom = newBottom;
-      }
-    });
-  }
-
   // to-do: It should be better to use transparent color instead of the bgColor.
   // But for now, the transparent color will cause the canvas to be white.
   // I'm sure that the white color is caused by the Overlay widget in BlockableOverlay.

flutter/lib/models/model.dart

@@ -2152,6 +2152,9 @@ class CanvasModel with ChangeNotifier {
   ViewStyle _lastViewStyle = ViewStyle.defaultViewStyle();
 
   Timer? _timerMobileFocusCanvasCursor;
+  Timer? _timerMobileRestoreCanvasOffset;
+  Offset? _offsetBeforeMobileSoftKeyboard;
+  double? _scaleBeforeMobileSoftKeyboard;
 
   // `isMobileCanvasChanged` is used to avoid canvas reset when changing the input method
   // after showing the soft keyboard.
@@ -2639,6 +2642,9 @@ class CanvasModel with ChangeNotifier {
     _scale = 1.0;
     _lastViewStyle = ViewStyle.defaultViewStyle();
     _timerMobileFocusCanvasCursor?.cancel();
+    _timerMobileRestoreCanvasOffset?.cancel();
+    _offsetBeforeMobileSoftKeyboard = null;
+    _scaleBeforeMobileSoftKeyboard = null;
   }
 
   updateScrollPercent() {
@@ -2667,6 +2673,31 @@ class CanvasModel with ChangeNotifier {
     });
   }
 
+  void saveMobileOffsetBeforeSoftKeyboard() {
+    _timerMobileRestoreCanvasOffset?.cancel();
+    _offsetBeforeMobileSoftKeyboard = Offset(_x, _y);
+    _scaleBeforeMobileSoftKeyboard = _scale;
+  }
+
+  void restoreMobileOffsetAfterSoftKeyboard() {
+    _timerMobileRestoreCanvasOffset?.cancel();
+    _timerMobileFocusCanvasCursor?.cancel();
+    final targetOffset = _offsetBeforeMobileSoftKeyboard;
+    final targetScale = _scaleBeforeMobileSoftKeyboard;
+    if (targetOffset == null || targetScale == null) {
+      return;
+    }
+    _timerMobileRestoreCanvasOffset = Timer(Duration(milliseconds: 100), () {
+      updateSize();
+      _x = targetOffset.dx;
+      _y = targetOffset.dy;
+      _scale = targetScale;
+      _offsetBeforeMobileSoftKeyboard = null;
+      _scaleBeforeMobileSoftKeyboard = null;
+      notifyListeners();
+    });
+  }
+
   // mobile only
   // Move the canvas to make the cursor visible(center) on the screen.
   void _moveToCenterCursor() {
@@ -2919,8 +2950,13 @@ class CursorModel with ChangeNotifier {
       _lastIsBlocked = true;
     }
     if (isMobile && _lastKeyboardIsVisible != keyboardIsVisible) {
-      parent.target?.canvasModel.mobileFocusCanvasCursor();
+      if (keyboardIsVisible) {
-      parent.target?.canvasModel.isMobileCanvasChanged = false;
+        parent.target?.canvasModel.saveMobileOffsetBeforeSoftKeyboard();
+        parent.target?.canvasModel.mobileFocusCanvasCursor();
+        parent.target?.canvasModel.isMobileCanvasChanged = false;
+      } else {
+        parent.target?.canvasModel.restoreMobileOffsetAfterSoftKeyboard();
+      }
     }
     _lastKeyboardIsVisible = keyboardIsVisible;
   }