From ea26ee7898b093fc971a22105e2ea3076f7e151f Mon Sep 17 00:00:00 2001
From: Bill Foote <billf@jovial.com>
Date: Sat, 14 Sep 2024 12:09:26 -0700
Subject: [PATCH] Clean up gradient stop style API:  #117

---
 lib/dom.dart            |  1 +
 lib/src/svg_graph.dart  | 45 +++++++++++++++++++++++++++++++++++++----
 lib/src/svg_parser.dart |  4 +++-
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/lib/dom.dart b/lib/dom.dart
index f8362ed..0cb3255 100644
--- a/lib/dom.dart
+++ b/lib/dom.dart
@@ -92,6 +92,7 @@ export 'src/svg_graph.dart'
         SvgValueColor,
         SvgColorReference,
         SvgGradientStop,
+        SvgGradientStopStyle,
         SvgGradientColor,
         SvgCoordinate,
         SvgLinearGradientColor,
diff --git a/lib/src/svg_graph.dart b/lib/src/svg_graph.dart
index 5fc44e1..0d565bb 100644
--- a/lib/src/svg_graph.dart
+++ b/lib/src/svg_graph.dart
@@ -373,7 +373,7 @@ class Style extends SvgInheritableAttributes {
   ///
   /// The gradient stop attributes for this style.
   ///
-  SvgGradientStop? gradientStop;
+  SvgGradientStopStyle? gradientStop;
 
   // We inherit an applyStyle implementation that's unreachable, so we need to
   // stub this out.
@@ -2700,6 +2700,20 @@ class SvgColorReference extends SvgColor {
       throw StateError('Internal error: color inheritance');
 }
 
+///
+/// The style attributes for an SVG gradient stop.  See
+/// https://www.w3.org/TR/2008/REC-SVGTiny12-20081222/painting.html#Gradients .
+///
+/// {@category SVG DOM}
+///
+class SvgGradientStopStyle {
+  double? offset;
+  SvgColor? color;
+  int? alpha;
+
+  SvgGradientStopStyle(this.offset, this.color, this.alpha);
+}
+
 ///
 /// An SVG gradient stop.  See
 /// https://www.w3.org/TR/2008/REC-SVGTiny12-20081222/painting.html#Gradients .
@@ -2710,10 +2724,22 @@ class SvgGradientStop extends _HasStylesheet {
   double? _offset;
   SvgColor? _color; // But not a gradient!
   int? _alpha;
+
+  /// The offset, or 0 if it is not set.  See [offsetIsSet].  offset cannot
+  /// return null due to backwards compatibility constraints.
   double get offset => _offset ?? 0.0;
+  bool get offsetIsSet => _offset != null;
+
+  /// The offset, or black if it is not set.  See [colorIsSet].  color
+  /// cannot return null due to backwards compatibility constraints.
   SvgColor get color => _color ?? SvgColor.black; // But not a gradient!
+  bool get colorIsSet => _offset != null;
   //default stop-color is 'black'. Ref https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/stop-color
+
+  /// The alpha, or 0xff if it is not set.  See [alphaIsSet].  alpha
+  /// cannot return null due to backwards compatibility constraints.
   int get alpha => _alpha ?? 0xff;
+  bool get alphaIsSet => _offset != null;
 
   ///
   /// The class of this stop for applying stylesheets
@@ -2739,6 +2765,17 @@ class SvgGradientStop extends _HasStylesheet {
     }
   }
 
+  ///
+  /// Get the style attributes for this stop, or null if none are set
+  ///
+  SvgGradientStopStyle? getStopStyle() {
+    if (alphaIsSet || colorIsSet || offsetIsSet) {
+      return SvgGradientStopStyle(_offset, _color, _alpha);
+    } else {
+      return null;
+    }
+  }
+
   ///
   /// Apply the stylesheet.  If it results in a change, create a new stop
   /// with the changes; otherwise, return null.
@@ -2762,9 +2799,9 @@ class SvgGradientStop extends _HasStylesheet {
 
   @override
   void _takeFrom(Style s, void Function(String) warn) {
-    _alpha ??= s.gradientStop?._alpha;
-    _color ??= s.gradientStop?._color;
-    _offset ??= s.gradientStop?._offset;
+    _alpha ??= s.gradientStop?.alpha;
+    _color ??= s.gradientStop?.color;
+    _offset ??= s.gradientStop?.offset;
   }
 }
 
diff --git a/lib/src/svg_parser.dart b/lib/src/svg_parser.dart
index 3f4f9dd..93ac21f 100644
--- a/lib/src/svg_parser.dart
+++ b/lib/src/svg_parser.dart
@@ -1056,7 +1056,9 @@ abstract class SvgParser extends GenericParser {
           // Unlike a node, our styleClass doesn't come from the
           // parser.  A badly formed CSS entry could try to set an attribute
           // called 'class,' so we set styleClass last.
-          s.gradientStop = _processStop(attrs);
+
+          final stop = _processStop(attrs);
+          s.gradientStop = stop?.getStopStyle();
         }
       }
       assert(lastPos != pos);