Make material slider respect textScaleFactor (#12511)

Make material slider respect textScaleFactor

Fixes #5938

packages/flutter/lib/src/material/slider.dart

@@ -170,11 +170,28 @@ class Slider extends StatefulWidget {
 }
 
 class _SliderState extends State<Slider> with TickerProviderStateMixin {
+  _SliderState() {
+    _reactionController = new AnimationController(
+      duration: kRadialReactionDuration,
+      vsync: this,
+    );
+  }
+
   void _handleChanged(double value) {
     assert(widget.onChanged != null);
     widget.onChanged(value * (widget.max - widget.min) + widget.min);
   }
 
+  @override
+  void dispose() {
+    _reactionController?.dispose();
+    super.dispose();
+  }
+
+  // Have to keep the reaction controller here so that we may dispose of it
+  // properly.
+  AnimationController _reactionController;
+
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
@@ -187,8 +204,10 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
       inactiveColor: widget.inactiveColor ?? theme.unselectedWidgetColor,
       thumbOpenAtMin: widget.thumbOpenAtMin,
       textTheme: theme.accentTextTheme,
+      textScaleFactor: MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0,
       onChanged: (widget.onChanged != null) && (widget.max > widget.min) ? _handleChanged : null,
       vsync: this,
+      reactionController: _reactionController,
     );
   }
 }
@@ -203,8 +222,10 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
     this.inactiveColor,
     this.thumbOpenAtMin,
     this.textTheme,
+    this.textScaleFactor,
     this.onChanged,
     this.vsync,
+    this.reactionController,
   }) : super(key: key);
 
   final double value;
@@ -214,8 +235,10 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
   final Color inactiveColor;
   final bool thumbOpenAtMin;
   final TextTheme textTheme;
+  final double textScaleFactor;
   final ValueChanged<double> onChanged;
   final TickerProvider vsync;
+  final AnimationController reactionController;
 
   @override
   _RenderSlider createRenderObject(BuildContext context) {
@@ -227,8 +250,10 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
       inactiveColor: inactiveColor,
       thumbOpenAtMin: thumbOpenAtMin,
       textTheme: textTheme,
+      textScaleFactor: textScaleFactor,
       onChanged: onChanged,
       vsync: vsync,
+      reactionController: reactionController,
       textDirection: Directionality.of(context),
     );
   }
@@ -243,6 +268,7 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
       ..inactiveColor = inactiveColor
       ..thumbOpenAtMin = thumbOpenAtMin
       ..textTheme = textTheme
+      ..textScaleFactor = textScaleFactor
       ..onChanged = onChanged
       ..textDirection = Directionality.of(context);
       // Ticker provider cannot change since there's a 1:1 relationship between
@@ -290,9 +316,11 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
     Color inactiveColor,
     bool thumbOpenAtMin,
     TextTheme textTheme,
+    double textScaleFactor,
     ValueChanged<double> onChanged,
     TickerProvider vsync,
     @required TextDirection textDirection,
+    @required AnimationController reactionController,
   }) : assert(value != null && value >= 0.0 && value <= 1.0),
        assert(textDirection != null),
        _label = label,
@@ -302,6 +330,7 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
        _inactiveColor = inactiveColor,
        _thumbOpenAtMin = thumbOpenAtMin,
        _textTheme = textTheme,
+       _textScaleFactor = textScaleFactor,
        _onChanged = onChanged,
        _textDirection = textDirection {
     _updateLabelPainter();
@@ -314,10 +343,7 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
     _tap = new TapGestureRecognizer()
       ..team = team
       ..onTapUp = _handleTapUp;
-    _reactionController = new AnimationController(
-      duration: kRadialReactionDuration,
-      vsync: vsync,
-    );
+    _reactionController = reactionController;
     _reaction = new CurvedAnimation(
       parent: _reactionController,
       curve: Curves.fastOutSlowIn
@@ -396,6 +422,16 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
     markNeedsPaint();
   }
 
+  double get textScaleFactor => _textScaleFactor;
+  double _textScaleFactor;
+  set textScaleFactor(double value) {
+    if (value == _textScaleFactor)
+      return;
+    _textScaleFactor = value;
+    _updateLabelPainter();
+    markNeedsPaint();
+  }
+
   ValueChanged<double> get onChanged => _onChanged;
   ValueChanged<double> _onChanged;
   set onChanged(ValueChanged<double> value) {
@@ -421,10 +457,9 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
 
   void _updateLabelPainter() {
     if (label != null) {
-      // TODO(abarth): Handle textScaleFactor. https://github.com/flutter/flutter/issues/5938
       _labelPainter
         ..text = new TextSpan(
-          style: _textTheme.body1.copyWith(fontSize: 10.0),
+          style: _textTheme.body1.copyWith(fontSize: 10.0 * _textScaleFactor),
           text: label,
         )
         ..textDirection = textDirection
@@ -628,9 +663,15 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
       }
 
       if (label != null) {
-        final Offset center = new Offset(trackActive, _kLabelBalloonCenterTween.evaluate(_reaction) + trackCenter);
-        final double radius = _kLabelBalloonRadiusTween.evaluate(_reaction);
-        final Offset tip = new Offset(trackActive, _kLabelBalloonTipTween.evaluate(_reaction) + trackCenter);
+        final Offset center = new Offset(
+          trackActive,
+          _kLabelBalloonCenterTween.evaluate(_reaction) * textScaleFactor + trackCenter
+        );
+        final double radius = _kLabelBalloonRadiusTween.evaluate(_reaction) * textScaleFactor;
+        final Offset tip = new Offset(
+          trackActive,
+          _kLabelBalloonTipTween.evaluate(_reaction) * textScaleFactor + trackCenter
+        );
         final double tipAttachment = _kLabelBalloonTipAttachmentRatio * radius;
 
         canvas.drawCircle(center, radius, primaryPaint);

packages/flutter/test/material/slider_test.dart

@@ -445,6 +445,71 @@ void main() {
     expect(tester.renderObject<RenderBox>(find.byType(Slider)).size, const Size(144.0 + 2.0 * 16.0, 32.0));
   });
 
+  testWidgets('discrete Slider respects textScaleFactor', (WidgetTester tester) async {
+    final Key sliderKey = new UniqueKey();
+    double value = 0.0;
+
+    Widget buildSlider({ double textScaleFactor }) {
+      return new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new StatefulBuilder(
+          builder: (BuildContext context, StateSetter setState) {
+            return new MediaQuery(
+              data: new MediaQueryData(textScaleFactor: textScaleFactor),
+              child: new Material(
+                child: new Center(
+                  child: new OverflowBox(
+                    maxWidth: double.INFINITY,
+                    maxHeight: double.INFINITY,
+                    child: new Slider(
+                      key: sliderKey,
+                      min: 0.0,
+                      max: 100.0,
+                      divisions: 10,
+                      label: '${value.round()}',
+                      value: value,
+                      onChanged: (double newValue) {
+                        setState(() {
+                          value = newValue;
+                        });
+                      },
+                    ),
+                  ),
+                ),
+              ),
+            );
+          },
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildSlider(textScaleFactor: 1.0));
+    Offset center = tester.getCenter(find.byType(Slider));
+    TestGesture gesture = await tester.startGesture(center);
+    await gesture.moveBy(const Offset(10.0, 0.0));
+
+    expect(
+      tester.renderObject(find.byType(Slider)),
+      paints..circle(radius: 6.0, x: 16.0, y: 44.0)
+    );
+
+    await gesture.up();
+    await tester.pump(const Duration(seconds: 1));
+
+    await tester.pumpWidget(buildSlider(textScaleFactor: 2.0));
+    center = tester.getCenter(find.byType(Slider));
+    gesture = await tester.startGesture(center);
+    await gesture.moveBy(const Offset(10.0, 0.0));
+
+    expect(
+      tester.renderObject(find.byType(Slider)),
+      paints..circle(radius: 12.0, x: 16.0, y: 44.0)
+    );
+
+    await gesture.up();
+    await tester.pump(const Duration(seconds: 1));
+  });
+
   testWidgets('Slider Semantics', (WidgetTester tester) async {
     final SemanticsTester semantics = new SemanticsTester(tester);