Align painted cursors with Linux texture origins

Use the truncated Linux texture origin while preserving fractional cursor positions and hotspots. Compare painted cursor geometry with the actual video widget in the existing regression tests.

flutter/lib/desktop/pages/remote_page.dart

@@ -1469,7 +1469,10 @@ class CursorPaint extends StatelessWidget {
     final ffi = canvas.parent.target!;
     final peer = ffi.ffiModel;
     if (ffi.imageModel.useTextureRender || peer.pi.forceTextureRender) {
-      return null;
+      // Match Linux's texture origin without rounding the cursor or hotspot.
+      return isLinux
+          ? Offset(canvas.x.toInt().toDouble(), canvas.y.toInt().toDouble())
+          : null;
     }
     var scale = canvas.scale;
     final displays = peer.pi.getCurDisplays();

flutter/test/cursor_paint_scale_test.dart

@@ -4,6 +4,7 @@ import 'dart:ui' as ui;
 import 'package:flutter/widgets.dart';
 import 'package:flutter_hbb/consts.dart';
 import 'package:flutter_hbb/desktop/pages/remote_page.dart';
+import 'package:flutter_hbb/models/desktop_render_texture.dart';
 import 'package:flutter_hbb/models/model.dart';
 import 'package:flutter_hbb/utils/image.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -12,7 +13,7 @@ import 'package:provider/provider.dart';
 
 const _hotspot = Offset(4, 9);
 const _remotePosition = Offset(100.25, 80.75);
-const _canvasOffset = Offset(15.125, 10.25);
+const _canvasOffset = Offset(15.125, -10.25);
 const _viewport = Size(200, 160);
 
 class _CursorModel extends ChangeNotifier implements CursorModel {
@@ -44,11 +45,18 @@ class _Density extends Fake implements CursorData {
   final double pixelRatio;
 }
 
-class _ImageModel extends Fake implements ImageModel {
+class _ImageModel extends ChangeNotifier implements ImageModel {
   _ImageModel(this.useTextureRender);
 
   @override
   final bool useTextureRender;
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+class _TextureModel extends Fake implements TextureModel {
+  @override
+  RxInt getTextureId(int display) => 0.obs;
 }
 
 class _Display extends Display {
@@ -64,7 +72,10 @@ class _Display extends Display {
 
 class _Peer extends Fake implements FfiModel {
   @override
-  final pi = PeerInfo();
+  final pi = PeerInfo()
+    ..displays.add(Display()
+      ..width = _viewport.width.toInt()
+      ..height = _viewport.height.toInt());
   @override
   bool isPeerLinux = false;
   @override
@@ -79,6 +90,8 @@ class _FFI extends Fake implements FFI {
   @override
   final _Peer ffiModel = _Peer();
   @override
+  final textureModel = _TextureModel();
+  @override
   late CanvasModel canvasModel;
 }
 
@@ -151,16 +164,29 @@ Future<ImagePainter> _paintCursor(WidgetTester tester, CanvasModel canvas,
   final image = (await tester
       .runAsync(() => createTestImage(width: source.$1, height: source.$2)))!;
   addTearDown(image.dispose);
-  await tester.pumpWidget(MediaQuery(
+  tester.view.devicePixelRatio = dpr;
+  tester.view.physicalSize = _viewport * dpr;
+  addTearDown(tester.view.reset);
+  await tester.pumpWidget(Directionality(textDirection: TextDirection.ltr,
+    child: MediaQuery(
     data: MediaQueryData(devicePixelRatio: dpr),
     child: MultiProvider(
       providers: [
+        ChangeNotifierProvider<ImageModel>.value(value: canvas.parent.target!.imageModel),
         ChangeNotifierProvider<CursorModel>(create: (_) => _CursorModel(image, position, density)),
         ChangeNotifierProvider<CanvasModel>(create: (_) => canvas),
       ],
-      child: CursorPaint(id: 'cursor-test', zoomCursor: zoom.obs),
+      child: Stack(fit: StackFit.expand, children: [
+        // Measure the video's origin instead of copying its rounding policy.
+        if (canvas.parent.target!.imageModel.useTextureRender &&
+            canvas.scrollStyle == ScrollStyle.scrollauto)
+          ImagePaint(ffi: canvas.parent.target!, id: 'cursor-test',
+              zoomCursor: zoom.obs, cursorOverImage: false.obs,
+              keyboardEnabled: true.obs, remoteCursorMoved: false.obs),
+        CursorPaint(id: 'cursor-test', zoomCursor: zoom.obs),
+      ]),
     ),
-  ));
+  )));
   final painter = tester.widget<CustomPaint>(find.byType(CustomPaint)).painter!
       as ImagePainter;
   expect(painter.image, same(image));
@@ -191,7 +217,7 @@ void _linuxDisplayTests() {
               : _remotePosition);
       final pixelScale = 2 / displayScale;
       expect(painter.scale, pixelScale);
-      final origin = texture ? _canvasOffset
+      final origin = texture ? tester.getTopLeft(find.byType(Texture).first)
           : Offset((_canvasOffset.dx / pixelScale).toInt() * pixelScale,
               (_canvasOffset.dy / pixelScale).toInt() * pixelScale);
       final position = allDisplays
@@ -228,7 +254,8 @@ void main() {
           tester, _CanvasModel(style, canvasScale, texture),
           dpr: dpr, zoom: zoom, source: source, density: density);
       expect(painter.scale, scale);
-      var imageOrigin = _canvasOffset;
+      var imageOrigin = texture
+          ? tester.getTopLeft(find.byType(Texture).first) : _canvasOffset;
       if (!texture) {
         final background = _Canvas();
         ImagePainter(