Work tree rows by their whole line, and outline the hovered one

Swing hit-tests a tree row only as far as its label, so a click past the
end of the name did nothing. Rows are now found by their vertical band
alone, which covers selection, the context menus, double-click join and
middle-click info; the expand handle to the left of a label still works
the row without selecting it.

The hovered row is outlined across that same full width, so what a click
would act on is visible before making it. Spacers, which nothing can be
done with, are skipped, and the outline gives way to the drag-and-drop
indicator while a drag is in progress.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/DropIndicatorTree.java

@@ -6,6 +6,7 @@ import com.ts3client.net.ServerModel;
 
 import javax.swing.Icon;
 import javax.swing.JTree;
+import javax.swing.SwingUtilities;
 import javax.swing.tree.DefaultMutableTreeNode;
 import javax.swing.tree.TreeModel;
 import javax.swing.tree.TreePath;
@@ -14,6 +15,9 @@ import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.Rectangle;
 import java.awt.RenderingHints;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+import java.awt.event.MouseWheelEvent;
 import java.util.List;
 
 /**
@@ -34,11 +38,69 @@ final class DropIndicatorTree extends JTree {
     private final GroupIcons groupIcons;
     /** Set while a drop would move a client into this channel row. */
     private TreePath highlight;
+    /** The row the pointer is over, or -1 when it is over none. */
+    private int hoverRow = -1;
 
     DropIndicatorTree(TreeModel treeModel, ServerModel model, GroupIcons groupIcons) {
         super(treeModel);
         this.model = model;
         this.groupIcons = groupIcons;
+        MouseAdapter hover = new MouseAdapter() {
+            @Override
+            public void mouseMoved(MouseEvent e) {
+                setHoverRow(rowAt(e.getY()));
+            }
+
+            @Override
+            public void mouseDragged(MouseEvent e) {
+                setHoverRow(-1);
+            }
+
+            @Override
+            public void mouseExited(MouseEvent e) {
+                setHoverRow(-1);
+            }
+
+            @Override
+            public void mouseWheelMoved(MouseWheelEvent e) {
+                // The pointer stays put while the rows move under it, so the row it is
+                // over has to be looked up again once the scroll has been applied.
+                SwingUtilities.invokeLater(() -> setHoverRow(rowAt(e.getY())));
+            }
+        };
+        addMouseMotionListener(hover);
+        addMouseListener(hover);
+        addMouseWheelListener(hover);
+    }
+
+    /**
+     * The row a point falls on, going by its vertical band alone: a row reaches
+     * across the whole width, not just as far as its label.
+     */
+    int rowAt(int y) {
+        int row = getClosestRowForLocation(0, y);
+        if (row < 0) return -1;
+        Rectangle bounds = getRowBounds(row);
+        return bounds != null && y >= bounds.y && y < bounds.y + bounds.height ? row : -1;
+    }
+
+    /** The path a point falls on, by the same rule as {@link #rowAt(int)}. */
+    TreePath pathAt(int y) {
+        int row = rowAt(y);
+        return row < 0 ? null : getPathForRow(row);
+    }
+
+    private void setHoverRow(int row) {
+        if (row == hoverRow) return;
+        repaintRow(hoverRow);
+        hoverRow = row;
+        repaintRow(row);
+    }
+
+    private void repaintRow(int row) {
+        if (row < 0) return;
+        Rectangle bounds = getRowBounds(row);
+        if (bounds != null) repaint(0, bounds.y, getWidth(), bounds.height);
     }
 
     /** Keeps the server row permanently open; collapsing it would hide everything. */
@@ -69,6 +131,7 @@ final class DropIndicatorTree extends JTree {
     protected void paintComponent(Graphics g) {
         super.paintComponent(g);
         paintBadges(g);
+        paintHover(g);
         JTree.DropLocation loc = getDropLocation();
         if (loc == null || loc.getPath() == null) return;
 
@@ -91,6 +154,30 @@ final class DropIndicatorTree extends JTree {
         g2.dispose();
     }
 
+    /**
+     * Outlines the row under the pointer, across the full width the row occupies —
+     * the same area a click on it acts on. Spacers, which nothing can be done with,
+     * are left alone.
+     */
+    private void paintHover(Graphics g) {
+        if (hoverRow < 0 || getDropLocation() != null) return;
+        Rectangle bounds = getRowBounds(hoverRow);
+        TreePath path = getPathForRow(hoverRow);
+        if (bounds == null || path == null || isSpacer(path)) return;
+
+        Rectangle visible = getVisibleRect();
+        Graphics2D g2 = (Graphics2D) g.create();
+        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+        g2.setColor(Theme.TREE_HOVER);
+        g2.drawRoundRect(visible.x, bounds.y, visible.width - 1, bounds.height - 1, 4, 4);
+        g2.dispose();
+    }
+
+    private boolean isSpacer(TreePath path) {
+        Object obj = ((DefaultMutableTreeNode) path.getLastPathComponent()).getUserObject();
+        return obj instanceof ChannelNode && Spacers.isSpacer(((ChannelNode) obj).name);
+    }
+
     /** The 1px-tall strip where the insertion line goes, in tree coordinates. */
     private Rectangle insertLine(JTree.DropLocation loc) {
         DefaultMutableTreeNode parent = (DefaultMutableTreeNode) loc.getPath().getLastPathComponent();

ts3-client/swing/src/main/java/com/ts3client/ui/ServerTreePanel.java

@@ -14,6 +14,7 @@ import javax.swing.plaf.basic.BasicTreeUI;
 import javax.swing.tree.DefaultMutableTreeNode;
 import javax.swing.tree.DefaultTreeModel;
 import javax.swing.tree.TreePath;
+import java.awt.Rectangle;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.util.List;
@@ -159,6 +160,7 @@ public final class ServerTreePanel extends JScrollPane {
         tree.addMouseListener(new MouseAdapter() {
             @Override
             public void mousePressed(MouseEvent e) {
+                selectRowUnder(e);
                 maybePopup(e);
             }
 
@@ -183,6 +185,21 @@ public final class ServerTreePanel extends JScrollPane {
         });
     }
 
+    /**
+     * Selects the row a press landed on. A row acts on its whole line, but Swing's own
+     * hit testing stops at the end of the label, so a press further right would leave
+     * the selection where it was.
+     */
+    private void selectRowUnder(MouseEvent e) {
+        if (!SwingUtilities.isLeftMouseButton(e) && !e.isPopupTrigger()) return;
+        TreePath path = tree.pathAt(e.getY());
+        if (path == null || path.equals(tree.getSelectionPath())) return;
+        Rectangle bounds = tree.getPathBounds(path);
+        // Left of the label is the expand handle, which Swing works the row without selecting it.
+        if (bounds != null && e.getX() < bounds.x) return;
+        tree.setSelectionPath(path);
+    }
+
     public void setSelfClientId(int id) {
         this.selfClientId = id;
     }
@@ -198,7 +215,7 @@ public final class ServerTreePanel extends JScrollPane {
     }
 
     private Object nodeAt(MouseEvent e) {
-        TreePath path = tree.getPathForLocation(e.getX(), e.getY());
+        TreePath path = tree.pathAt(e.getY());
         if (path == null) return null;
         DefaultMutableTreeNode n = (DefaultMutableTreeNode) path.getLastPathComponent();
         return n.getUserObject();
@@ -206,7 +223,7 @@ public final class ServerTreePanel extends JScrollPane {
 
     private void maybePopup(MouseEvent e) {
         if (!e.isPopupTrigger()) return;
-        TreePath path = tree.getPathForLocation(e.getX(), e.getY());
+        TreePath path = tree.pathAt(e.getY());
         if (path == null) return;
         tree.setSelectionPath(path);
         Object obj = ((DefaultMutableTreeNode) path.getLastPathComponent()).getUserObject();

ts3-client/swing/src/main/java/com/ts3client/ui/Theme.java

@@ -9,6 +9,8 @@ public final class Theme {
     public static final Color WINDOW_BG = new Color(0xF0F0F0);
     public static final Color TREE_BG = new Color(0xFFFFFF);
     public static final Color TREE_SELECTION = new Color(0xCFE3FB);
+    /** Outline drawn around the row the pointer is over. */
+    public static final Color TREE_HOVER = new Color(0x9CC4EE);
     public static final Color TREE_TEXT = new Color(0x1E1E1E);
     public static final Color CHANNEL_TEXT = new Color(0x21486B);
     public static final Color SERVER_TEXT = new Color(0x123456);