FlatLaf: use NetBeans folder icons in NB Explorer component instead o…

…f FlatLaf outlined folder icons (e.g. Projects or Files views)

patch from https://gist.github.com/eirikbakke/5587bd548a668cb0588c3fdc7d9e9f48

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/FlatLaf.properties

@@ -36,6 +36,12 @@ TabbedPane.tabHeight=30
 TabbedPane.inactiveUnderlineColor = $TabbedContainer.editor.contentBorderColor
 
 
+#---- Tree ----
+
+Tree.closedIcon = org.netbeans.swing.laf.flatlaf.icons.NBFlatTreeClosedIcon
+Tree.openIcon = org.netbeans.swing.laf.flatlaf.icons.NBFlatTreeOpenIcon
+
+
 #---- TabbedContainer ----
 
 TabbedContainer.editor.contentBorderColor=$Component.borderColor

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/icons/NBFlatAdapterIcon.java

@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.netbeans.swing.laf.flatlaf.icons;
+
+import com.formdev.flatlaf.util.UIScale;
+import java.awt.Component;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.Image;
+import javax.swing.Icon;
+import javax.swing.ImageIcon;
+import javax.swing.plaf.UIResource;
+import org.openide.util.ImageUtilities;
+
+/**
+ * Adapter class which allows a NetBeans-loaded PNG or SVG icon to be used as a FlatLAF
+ * configuration setting. Respects FlatLAF's own scaling properties, as in
+ * {@code com.formdev.flatlaf.icons.FlatAbstractIcon}.
+ */
+abstract class NBFlatAdapterIcon implements Icon, UIResource {
+    private final Icon delegate;
+
+    public NBFlatAdapterIcon(String resourcePath) {
+        if (resourcePath == null) {
+            throw new NullPointerException();
+        }
+        Image delegateImg = ImageUtilities.loadImage(resourcePath);
+        this.delegate = delegateImg == null ? new ImageIcon() : ImageUtilities.image2Icon(delegateImg);
+    }
+
+    @Override
+    public void paintIcon(Component c, Graphics g, int x, int y) {
+        Graphics2D g2 = (Graphics2D) g.create();
+        try {
+            g2.translate(x, y);
+            UIScale.scaleGraphics(g2);
+            delegate.paintIcon(c, g2, 0, 0);
+        } finally {
+            g2.dispose();
+        }
+    }
+
+    @Override
+    public int getIconWidth() {
+        return UIScale.scale(delegate.getIconWidth());
+    }
+
+    @Override
+    public int getIconHeight() {
+        return UIScale.scale(delegate.getIconHeight());
+    }
+}

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/icons/NBFlatTreeClosedIcon.java

@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.netbeans.swing.laf.flatlaf.icons;
+
+public class NBFlatTreeClosedIcon extends NBFlatAdapterIcon {
+    public NBFlatTreeClosedIcon() {
+        // Will load the SVG version if available.
+        super("org/netbeans/swing/plaf/resources/hidpi-folder-closed.png");
+    }
+}

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/icons/NBFlatTreeOpenIcon.java

@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.netbeans.swing.laf.flatlaf.icons;
+
+public class NBFlatTreeOpenIcon extends NBFlatAdapterIcon {
+    public NBFlatTreeOpenIcon() {
+        // Will load the SVG version if available.
+        super("org/netbeans/swing/plaf/resources/hidpi-folder-open.png");
+    }
+}