Reduced code duplication in ink_splash.dart, ink_ripple.dart (#49480)

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

@@ -237,28 +237,16 @@ class InkRipple extends InteractiveInkFeature {
       referenceBox.size.center(Offset.zero),
       Curves.ease.transform(_radiusController.value),
     );
-    final Offset originOffset = MatrixUtils.getAsTranslation(transform);
-    canvas.save();
-    if (originOffset == null) {
-      canvas.transform(transform.storage);
-    } else {
-      canvas.translate(originOffset.dx, originOffset.dy);
-    }
-    if (_clipCallback != null) {
-      final Rect rect = _clipCallback();
-      if (_customBorder != null) {
-        canvas.clipPath(_customBorder.getOuterPath(rect, textDirection: _textDirection));
-      } else if (_borderRadius != BorderRadius.zero) {
-        canvas.clipRRect(RRect.fromRectAndCorners(
-          rect,
-          topLeft: _borderRadius.topLeft, topRight: _borderRadius.topRight,
-          bottomLeft: _borderRadius.bottomLeft, bottomRight: _borderRadius.bottomRight,
-        ));
-      } else {
-        canvas.clipRect(rect);
-      }
-    }
-    canvas.drawCircle(center, _radius.value, paint);
-    canvas.restore();
+    paintInkCircle(
+      canvas: canvas,
+      transform: transform,
+      paint: paint,
+      center: center,
+      textDirection: _textDirection,
+      radius: _radius.value,
+      customBorder: _customBorder,
+      borderRadius: _borderRadius,
+      clipCallback: _clipCallback,
+    );
   }
 }

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

@@ -202,28 +202,16 @@ class InkSplash extends InteractiveInkFeature {
     Offset center = _position;
     if (_repositionToReferenceBox)
       center = Offset.lerp(center, referenceBox.size.center(Offset.zero), _radiusController.value);
-    final Offset originOffset = MatrixUtils.getAsTranslation(transform);
-    canvas.save();
-    if (originOffset == null) {
-      canvas.transform(transform.storage);
-    } else {
-      canvas.translate(originOffset.dx, originOffset.dy);
-    }
-    if (_clipCallback != null) {
-      final Rect rect = _clipCallback();
-      if (_customBorder != null) {
-        canvas.clipPath(_customBorder.getOuterPath(rect, textDirection: _textDirection));
-      } else if (_borderRadius != BorderRadius.zero) {
-        canvas.clipRRect(RRect.fromRectAndCorners(
-          rect,
-          topLeft: _borderRadius.topLeft, topRight: _borderRadius.topRight,
-          bottomLeft: _borderRadius.bottomLeft, bottomRight: _borderRadius.bottomRight,
-        ));
-      } else {
-        canvas.clipRect(rect);
-      }
-    }
-    canvas.drawCircle(center, _radius.value, paint);
-    canvas.restore();
+    paintInkCircle(
+      canvas: canvas,
+      transform: transform,
+      paint: paint,
+      center: center,
+      textDirection: _textDirection,
+      radius: _radius.value,
+      customBorder: _customBorder,
+      borderRadius: _borderRadius,
+      clipCallback: _clipCallback,
+    );
   }
 }

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

@@ -64,6 +64,80 @@ abstract class InteractiveInkFeature extends InkFeature {
     _color = value;
     controller.markNeedsPaint();
   }
+
+  /// Draws an ink splash or ink ripple on the passed in [Canvas].
+  ///
+  /// The [transform] argument is the [Matrix4] transform that typically
+  /// shifts the coordinate space of the canvas to the space in which
+  /// the ink circle is to be painted.
+  ///
+  /// [center] is the [Offset] from origin of the canvas where the center
+  /// of the circle is drawn.
+  ///
+  /// [paint] takes a [Paint] object that describes the styles used to draw the ink circle.
+  /// For example, [paint] can specify properties like color, strokewidth, colorFilter.
+  ///
+  /// [radius] is the radius of ink circle to be drawn on canvas.
+  ///
+  /// [clipCallback] is the callback used to obtain the [Rect] used for clipping the ink effect.
+  /// If [clipCallback] is null, no clipping is performed on the ink circle.
+  ///
+  /// Clipping can happen in 3 different ways -
+  ///  1. If [customBorder] is provided, it is used to determine the path
+  ///     for clipping.
+  ///  2. If [customBorder] is null, and [borderRadius] is provided, the canvas
+  ///     is clipped by an [RRect] created from [clipCallback] and [borderRadius].
+  ///  3. If [borderRadius] is the default [BorderRadius.zero], then the [Rect] provided
+  ///      by [clipCallback] is used for clipping.
+  ///
+  /// [textDirection] is used by [customBorder] if it is non-null. This allows the [customBorder]'s path
+  /// to be properly defined if it was the path was expressed in terms of "start" and "end" instead of
+  /// "left" and "right".
+  ///
+  /// For examples on how the function is used, see [InkSplash] and [InkRipple].
+  @protected
+  void paintInkCircle({
+    @required Canvas canvas,
+    @required Matrix4 transform,
+    @required Paint paint,
+    @required Offset center,
+    @required double radius,
+    TextDirection textDirection,
+    ShapeBorder customBorder,
+    BorderRadius borderRadius = BorderRadius.zero,
+    RectCallback clipCallback,
+    }) {
+    assert(canvas != null);
+    assert(transform != null);
+    assert(paint != null);
+    assert(center != null);
+    assert(radius != null);
+    assert(borderRadius != null);
+
+    final Offset originOffset = MatrixUtils.getAsTranslation(transform);
+    canvas.save();
+    if (originOffset == null) {
+      canvas.transform(transform.storage);
+    } else {
+      canvas.translate(originOffset.dx, originOffset.dy);
+    }
+    if (clipCallback != null) {
+      final Rect rect = clipCallback();
+      if (customBorder != null) {
+        canvas.clipPath(customBorder.getOuterPath(rect, textDirection: textDirection));
+      } else if (borderRadius != BorderRadius.zero) {
+        canvas.clipRRect(RRect.fromRectAndCorners(
+          rect,
+          topLeft: borderRadius.topLeft, topRight: borderRadius.topRight,
+          bottomLeft: borderRadius.bottomLeft, bottomRight: borderRadius.bottomRight,
+        ));
+      } else {
+        canvas.clipRect(rect);
+      }
+    }
+    canvas.drawCircle(center, radius, paint);
+    canvas.restore();
+  }
 }
 
 /// An encapsulation of an [InteractiveInkFeature] constructor used by