Add default implementation of UIAwareIcon which don't rely on the IconLoader mechanism for external custom icons.

property-loader/src/main/java/com/github/weisj/darklaf/icons/DefaultUIAwareIcon.java

@@ -0,0 +1,108 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020 Jannis Weis
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package com.github.weisj.darklaf.icons;
+
+import java.awt.*;
+
+import javax.swing.*;
+
+/**
+ * Default base implementation for {@link UIAwareIcon}. The specific loading mechanism needs to be
+ * implemented in the subclass.
+ */
+public abstract class DefaultUIAwareIcon implements UIAwareIcon {
+
+    private final UIAwareIcon dual;
+
+    protected Icon light;
+    protected Icon dark;
+
+    public DefaultUIAwareIcon() {
+        this.dual = createDual();
+    }
+
+    protected abstract UIAwareIcon createDual();
+
+    protected DefaultUIAwareIcon(final DefaultUIAwareIcon dual) {
+        this.dark = dual.light;
+        this.light = dual.dark;
+        this.dual = dual;
+    }
+
+
+    @Override
+    public UIAwareIcon getDual() {
+        return dual;
+    }
+
+    private boolean isDark() {
+        return IconLoader.getAwareStyle() == AwareIconStyle.DARK;
+    }
+
+    private Icon getEffectiveIcon() {
+        return isDark() ? getDarkIcon() : getLightIcon();
+    }
+
+    /**
+     * Load the light version of the icon. This method should never return a null value.
+     *
+     * @return the light icon.
+     */
+    protected abstract Icon loadLightIcon();
+
+    /**
+     * Load the dark version of the icon. This method should never return a null value.
+     *
+     * @return the dark icon.
+     */
+    protected abstract Icon loadDarkIcon();
+
+    private Icon getLightIcon() {
+        if (light == null) {
+            light = loadLightIcon();
+        }
+        return light;
+    }
+
+    private Icon getDarkIcon() {
+        if (dark == null) {
+            dark = loadDarkIcon();
+        }
+        return dark;
+    }
+
+    @Override
+    public void paintIcon(final Component c, final Graphics g, final int x, final int y) {
+        getEffectiveIcon().paintIcon(c, g, x, y);
+    }
+
+
+    @Override
+    public int getIconWidth() {
+        return getEffectiveIcon().getIconWidth();
+    }
+
+    @Override
+    public int getIconHeight() {
+        return getEffectiveIcon().getIconHeight();
+    }
+}

property-loader/src/main/java/com/github/weisj/darklaf/icons/IconLoader.java

@@ -158,6 +158,29 @@ public final class IconLoader {
         return getUIAwareIcon(path, getDefaultWidth(path), getDefaultHeight(path));
     }
 
+    /**
+     * Creates a new {@link UIAwareIcon} which is loaded lazily through the given supplier.
+     *
+     * @param lightIconSupplier the supplier for the light icon.
+     * @param darkIconSupplier the supplier for the dark icon.
+     * @return the {@link UIAwareIcon}
+     */
+    public UIAwareIcon createUIAwareIcon(final IconSupplier<Icon> lightIconSupplier,
+            final IconSupplier<Icon> darkIconSupplier) {
+        return new LazyUIAwareIcon(lightIconSupplier, darkIconSupplier);
+    }
+
+    /**
+     * Creates a new {@link UIAwareIcon} from the given icon.
+     *
+     * @param light the light version of the icon.
+     * @param dark the dark version of the icon.
+     * @return the {@link UIAwareIcon}.
+     */
+    public UIAwareIcon createUIAwareIcon(final Icon light, final Icon dark) {
+        return new SimpleUIAwareIcon(light, dark);
+    }
+
     /**
      * Get an aware icon. If [path] is the search root of the current icon loader then the icon resource
      * will be resolved to [path]/dark/[icon_path] and [path]/light/[icon_path]

property-loader/src/main/java/com/github/weisj/darklaf/icons/LazyUIAwareIcon.java

@@ -0,0 +1,70 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020 Jannis Weis
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package com.github.weisj.darklaf.icons;
+
+import javax.swing.*;
+
+public class LazyUIAwareIcon extends DefaultUIAwareIcon {
+
+    private IconSupplier<Icon> lightSupplier;
+    private IconSupplier<Icon> darkSupplier;
+
+    public LazyUIAwareIcon(final IconSupplier<Icon> lightSupplier, final IconSupplier<Icon> darkSupplier) {
+        this.lightSupplier = lightSupplier;
+        this.darkSupplier = darkSupplier;
+    }
+
+    protected LazyUIAwareIcon(final LazyUIAwareIcon dual) {
+        super(dual);
+        this.lightSupplier = dual.darkSupplier;
+        this.darkSupplier = dual.lightSupplier;
+    }
+
+    @Override
+    protected UIAwareIcon createDual() {
+        return new LazyUIAwareIcon(this);
+    }
+
+    protected Icon loadLightIcon() {
+        Icon icon;
+        if (lightSupplier != null) {
+            icon = lightSupplier.getIcon();
+            lightSupplier = null;
+        } else {
+            // Should never happen.
+            icon = EmptyIcon.create(0);
+        }
+        return icon;
+    }
+
+    protected Icon loadDarkIcon() {
+        Icon icon;
+        if (darkSupplier != null) {
+            icon = darkSupplier.getIcon();
+            darkSupplier = null;
+        } else {
+            // Should never happen.
+            icon = EmptyIcon.create(0);
+        }
+        return icon;
+    }
+}

property-loader/src/main/java/com/github/weisj/darklaf/icons/SimpleUIAwareIcon.java

@@ -0,0 +1,56 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020 Jannis Weis
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package com.github.weisj.darklaf.icons;
+
+import javax.swing.*;
+
+/**
+ * Implementation of {@link UIAwareIcon} which delegates to preloaded icons.
+ */
+public class SimpleUIAwareIcon extends DefaultUIAwareIcon {
+
+    public SimpleUIAwareIcon(final Icon light, final Icon dark) {
+        this.light = light;
+        this.dark = dark;
+    }
+
+    protected SimpleUIAwareIcon(final SimpleUIAwareIcon dual) {
+        super(dual);
+        this.light = dual.dark;
+        this.dark = dual.light;
+    }
+
+    @Override
+    protected UIAwareIcon createDual() {
+        return new SimpleUIAwareIcon(this);
+    }
+
+    @Override
+    protected Icon loadLightIcon() {
+        return null;
+    }
+
+    @Override
+    protected Icon loadDarkIcon() {
+        return null;
+    }
+}

property-loader/src/main/java/com/github/weisj/darklaf/icons/UIAwareIcon.java

@@ -21,10 +21,20 @@
  */
 package com.github.weisj.darklaf.icons;
 
-import javax.swing.*;
-
-/** @author Jannis Weis */
+/**
+ * Icon which dynamically adapts to whether the UI is currently {@link AwareIconStyle#LIGHT light}
+ * or {@link AwareIconStyle#DARK dark}.
+ */
 public interface UIAwareIcon extends DynamicIcon {
 
+    /**
+     * Return the dual version of the icon. i.e. if the current icon is light then the dual version will
+     * be dark and vice versa.
+     *
+     * Implementations of this method should respect that the appearance of the icon after invoking this
+     * method twice should be the same.
+     *
+     * @return the dual icon.
+     */
     UIAwareIcon getDual();
 }