Support polymorphic values

modules/javafx.graphics/src/main/java/com/sun/glass/ui/Application.java

@@ -789,6 +789,8 @@ public Map<String, String> getPlatformKeyMappings() {
 
     /**
      * Returns a mapping of platform-specific keys to the types of their values.
+     * Polymorphic types are supported by specifying the common base type; for example, a key can
+     * be mapped to {@code Paint.class} to support any type of paint.
      * <p>
      * Implementors must keep this map in sync with the mappings reported by the native Glass toolkit.
      * If a native toolkit reports mappings for keys that are not contained in this map, the typed getters

modules/javafx.graphics/src/main/java/com/sun/javafx/application/preferences/PlatformPreferences.java

@@ -147,7 +147,7 @@ public <T> Optional<T> getValue(String key, Class<T> type) {
             return Optional.empty();
         }
 
-        if (!type.isAssignableFrom(platformType)) {
+        if (!platformType.isAssignableFrom(type)) {
             throw new IllegalArgumentException(
                 "Incompatible types: requested = " + type.getName() +
                 ", actual = " + platformType.getName());
@@ -157,9 +157,15 @@ public <T> Optional<T> getValue(String key, Class<T> type) {
             return Optional.empty();
         }
 
-        @SuppressWarnings("unchecked")
-        T v = (T)value;
-        return Optional.of(v);
+        if (type.isInstance(value)) {
+            @SuppressWarnings("unchecked")
+            T v = (T)value;
+            return Optional.of(v);
+        }
+
+        throw new IllegalArgumentException(
+            "Incompatible types: requested = " + type.getName() +
+            ", actual = " + value.getClass().getName());
     }
 
     @Override

modules/javafx.graphics/src/test/java/test/com/sun/javafx/application/preferences/PlatformPreferencesTest.java

@@ -26,6 +26,8 @@
 package test.com.sun.javafx.application.preferences;
 
 import com.sun.javafx.application.preferences.PlatformPreferences;
+import javafx.scene.paint.CycleMethod;
+import javafx.scene.paint.LinearGradient;
 import javafx.scene.paint.Paint;
 import test.javafx.collections.MockMapObserver;
 import javafx.beans.InvalidationListener;
@@ -85,6 +87,21 @@ void testWellKnownKeyReturnsEmptyValueWhenMappingNotPresent() {
         assertEquals(Optional.empty(), prefs.getColor("test.aColor"));
         assertEquals(Optional.empty(), prefs.getValue("test.aColor", Color.class));
         assertEquals(Optional.empty(), prefs.getValue("test.aPaint", Paint.class));
+        assertEquals(Optional.empty(), prefs.getValue("test.aPaint", Color.class));
+    }
+
+    @Test
+    void testPolymorphicValues() {
+        prefs.update(Map.of("test.aPaint", Color.RED));
+        assertEquals(Color.RED, prefs.getColor("test.aPaint").orElseThrow());
+        assertEquals(Color.RED, prefs.getValue("test.aPaint", Paint.class).orElseThrow());
+        assertThrows(IllegalArgumentException.class, () -> prefs.getValue("test.aPaint", LinearGradient.class));
+
+        var gradient = new LinearGradient(0, 0, 1, 1, true, CycleMethod.NO_CYCLE);
+        prefs.update(Map.of("test.aPaint", gradient));
+        assertEquals(gradient, prefs.getValue("test.aPaint", Paint.class).orElseThrow());
+        assertEquals(gradient, prefs.getValue("test.aPaint", LinearGradient.class).orElseThrow());
+        assertThrows(IllegalArgumentException.class, () -> prefs.getColor("test.aPaint").orElseThrow());
     }
 
     @Test