From f2573c3765c5e2d436c4d2871f3a450ee3ada1ed Mon Sep 17 00:00:00 2001
From: Niki Roo <niki@nikiroo.be>
Date: Sat, 25 Apr 2020 20:01:12 +0200
Subject: [PATCH] ListSnapshot (used on ListModel)

---
 ui/ListModel.java    | 34 ++++++++++++++++++++++++
 ui/ListSnapshot.java | 62 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 ui/ListSnapshot.java

diff --git a/ui/ListModel.java b/ui/ListModel.java
index 06e7914..52fa816 100644
--- a/ui/ListModel.java
+++ b/ui/ListModel.java
@@ -81,6 +81,7 @@ public class ListModel<T> extends DefaultListModel6<T> {
 	private int hoveredIndex;
 	private List<T> items = new ArrayList<T>();
 	private JList6<T> list;
+	private boolean keepSelection = true;
 
 	/**
 	 * Create a new {@link ListModel}.
@@ -185,6 +186,31 @@ public class ListModel<T> extends DefaultListModel6<T> {
 		});
 	}
 
+	/**
+	 * (Try and) keep the elements that were selected when filtering.
+	 * <p>
+	 * This will use toString on the elements to identify them, and can be a bit
+	 * resource intensive.
+	 * 
+	 * @return TRUE if we do
+	 */
+	public boolean isKeepSelection() {
+		return keepSelection;
+	}
+
+	/**
+	 * (Try and) keep the elements that were selected when filtering.
+	 * <p>
+	 * This will use toString on the elements to identify them, and can be a bit
+	 * resource intensive.
+	 * 
+	 * @param keepSelection
+	 *            TRUE to try and keep them selected
+	 */
+	public void setKeepSelection(boolean keepSelection) {
+		this.keepSelection = keepSelection;
+	}
+
 	/**
 	 * Check if this element is currently under the mouse.
 	 * 
@@ -289,6 +315,11 @@ public class ListModel<T> extends DefaultListModel6<T> {
 	 */
 	@SuppressWarnings("unchecked") // ListModel<T> and JList<T> are not java 1.6
 	public void filter(Predicate<T> filter) {
+		ListSnapshot snapshot = null;
+
+		if (keepSelection)
+			snapshot = new ListSnapshot(list);
+
 		clear();
 		for (T item : items) {
 			if (filter == null || filter.test(item)) {
@@ -296,6 +327,9 @@ public class ListModel<T> extends DefaultListModel6<T> {
 			}
 		}
 
+		if (keepSelection)
+			snapshot.apply();
+
 		list.repaint();
 	}
 
diff --git a/ui/ListSnapshot.java b/ui/ListSnapshot.java
new file mode 100644
index 0000000..d2e89c8
--- /dev/null
+++ b/ui/ListSnapshot.java
@@ -0,0 +1,62 @@
+package be.nikiroo.utils.ui;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.swing.JList;
+
+public class ListSnapshot {
+	private JList list;
+	private List<Object> elements = new ArrayList<Object>();
+
+	public ListSnapshot(JList list) {
+		this.list = list;
+
+		for (int index : list.getSelectedIndices()) {
+			elements.add(list.getModel().getElementAt(index));
+		}
+	}
+
+	public void apply() {
+		applyTo(list);
+	}
+
+	public void applyTo(JList list) {
+		List<Integer> indices = new ArrayList<Integer>();
+		for (int i = 0; i < list.getModel().getSize(); i++) {
+			Object newObject = list.getModel().getElementAt(i);
+			for (Object oldObject : elements) {
+				if (isSameElement(oldObject, newObject)) {
+					indices.add(i);
+					break;
+				}
+			}
+		}
+
+		int a[] = new int[indices.size()];
+		for (int i = 0; i < indices.size(); i++) {
+			a[i] = indices.get(i);
+		}
+		list.setSelectedIndices(a);
+	}
+
+	// You can override this
+	protected boolean isSameElement(Object oldElement, Object newElement) {
+		if (oldElement == null || newElement == null)
+			return oldElement == null && newElement == null;
+
+		return oldElement.toString().equals(newElement.toString());
+	}
+
+	@Override
+	public String toString() {
+		StringBuilder builder = new StringBuilder();
+		builder.append("List Snapshot of: ").append(list).append("\n");
+		builder.append("Selected elements:\n");
+		for (Object element : elements) {
+			builder.append("\t").append(element).append("\n");
+		}
+
+		return builder.toString();
+	}
+}
-- 
2.27.0