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

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

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

@@ -153,3 +153,8 @@ nb.options.categories.tabPanelForeground = @foreground
 nb.options.categories.separatorColor = $Separator.foreground
 nb.options.categories.selectionBorderColor = $nb.options.categories.selectionBackground
 nb.options.categories.highlightBorderColor = $nb.options.categories.highlightBackground
+
+#---- Tree ----
+
+Tree.closedIcon = org.netbeans.swing.laf.flatlaf.ui.FlatTreeClosedIcon
+Tree.openIcon = org.netbeans.swing.laf.flatlaf.ui.FlatTreeOpenIcon

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/ui/FlatTreeClosedIcon.java

@@ -0,0 +1,34 @@
+/*
+ * 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.ui;
+
+import javax.swing.ImageIcon;
+import org.openide.util.ImageUtilities;
+
+/**
+ * "closed" icon for {@link javax.swing.JTree} used by {@link javax.swing.tree.DefaultTreeCellRenderer}.
+ *
+ * @author Karl Tauber
+ */
+public class FlatTreeClosedIcon extends ImageIcon {
+
+    public FlatTreeClosedIcon() {
+        super( ImageUtilities.loadImage( "org/netbeans/swing/plaf/resources/hidpi-folder-closed.png" ) ); // NOI18N
+    }
+}

platform/o.n.swing.laf.flatlaf/src/org/netbeans/swing/laf/flatlaf/ui/FlatTreeOpenIcon.java

@@ -0,0 +1,34 @@
+/*
+ * 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.ui;
+
+import javax.swing.ImageIcon;
+import org.openide.util.ImageUtilities;
+
+/**
+ * "open" icon for {@link javax.swing.JTree} used by {@link javax.swing.tree.DefaultTreeCellRenderer}.
+ *
+ * @author Karl Tauber
+ */
+public class FlatTreeOpenIcon extends ImageIcon {
+
+    public FlatTreeOpenIcon() {
+        super( ImageUtilities.loadImage( "org/netbeans/swing/plaf/resources/hidpi-folder-open.png" ) ); // NOI18N
+    }
+}