YaruTitleBarTheme: fix border side lerp (#688)

ubuntu · Mar 30, 2023 · e8f99e5 · e8f99e5
1 parent ff2cc86
commit e8f99e5
Showing 1 changed file with 23 additions and 5 deletions.
diff --git a/lib/src/widgets/yaru_title_bar_theme.dart b/lib/src/widgets/yaru_title_bar_theme.dart
@@ -100,15 +100,33 @@ class YaruTitleBarThemeData extends ThemeExtension<YaruTitleBarThemeData>
       ),
       titleTextStyle: TextStyle.lerp(titleTextStyle, o?.titleTextStyle, t),
       shape: ShapeBorder.lerp(shape, o?.shape, t),
-      border: BorderSide.lerp(
-        border ?? BorderSide.none,
-        o?.border ?? BorderSide.none,
-        t,
-      ),
+      border: _lerpBorderSide(border, o?.border, t),
       style: t < 0.5 ? style : o?.style,
     );
   }
 
+  // Special case because BorderSide.lerp() doesn't support null arguments.
+  static BorderSide? _lerpBorderSide(BorderSide? a, BorderSide? b, double t) {
+    if (a == null && b == null) {
+      return null;
+    }
+    if (a == null) {
+      return BorderSide.lerp(
+        BorderSide(width: 0, color: b!.color.withAlpha(0)),
+        b,
+        t,
+      );
+    }
+    if (b == null) {
+      return BorderSide.lerp(
+        BorderSide(width: 0, color: a.color.withAlpha(0)),
+        a,
+        t,
+      );
+    }
+    return BorderSide.lerp(a, b, t);
+  }
+
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);