Make the map sidebar a resizable island

Long palette names were cut off by the sidebar's fixed width. The
sidebar is now a rounded island set apart from the window edges, and
dragging the gap beside it makes it wider or narrower.

Model used: Claude Opus 5.5

core/src/main/java/com/volmit/iris/core/gui/IslandPanel.java

@@ -0,0 +1,60 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package com.volmit.iris.core.gui;
+
+import javax.swing.JComponent;
+import javax.swing.JPanel;
+import java.awt.BorderLayout;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import java.awt.geom.RoundRectangle2D;
+
+/**
+ * A rounded panel set apart from the window edges, like the tool windows of IntelliJ's islands theme. Its right edge
+ * meets a split pane divider, which provides the gap there.
+ */
+final class IslandPanel extends JPanel {
+    private static final long serialVersionUID = 7313084027614358519L;
+    private static final int GAP = 6;
+    private static final int CORNER_ARC = 12;
+    private static final int INNER_PADDING = 4;
+
+    IslandPanel(JComponent content) {
+        super(new BorderLayout());
+        setOpaque(false);
+        setBorder(StudioTheme.emptyBorder(GAP + INNER_PADDING, GAP + INNER_PADDING, GAP + INNER_PADDING, INNER_PADDING));
+        add(content, BorderLayout.CENTER);
+    }
+
+    @Override
+    protected void paintComponent(Graphics graphics) {
+        Graphics2D canvas = (Graphics2D) graphics.create();
+        try {
+            canvas.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+            canvas.setColor(StudioTheme.PANEL_BACKGROUND);
+            int gap = StudioTheme.scale(GAP);
+            int arc = StudioTheme.scale(CORNER_ARC);
+            canvas.fill(new RoundRectangle2D.Double(gap, gap, getWidth() - gap, getHeight() - gap * 2D, arc, arc));
+        } finally {
+            canvas.dispose();
+        }
+    }
+}

core/src/main/java/com/volmit/iris/core/gui/MapWindow.java

@@ -53,6 +53,9 @@ public final class MapWindow implements MapCanvas.Listener {
     private static final String MAP_CARD = "map";
     private static final String PALETTES_CARD = "palettes";
     private static final int SIDEBAR_WIDTH = 270;
+    private static final int SIDEBAR_MINIMUM_WIDTH = 200;
+    private static final int CONTENT_MINIMUM_WIDTH = 320;
+    private static final int SIDEBAR_DIVIDER_WIDTH = 6;
     private static final double PALETTE_RECENTER_DISTANCE_BLOCKS = 1D;
     private static final double VIEW_LIST_SHARE_WITH_PALETTES = 0.34D;
 
@@ -110,14 +113,11 @@ public final class MapWindow implements MapCanvas.Listener {
     private void buildFrame() {
         content.add(canvas, MAP_CARD);
         statusBars.add(canvas.statusBar(), MAP_CARD);
-        sidebar.setPreferredSize(StudioTheme.scaledSize(SIDEBAR_WIDTH, 0));
-        sidebar.setBorder(BorderFactory.createMatteBorder(0, 0, 0, 1, StudioTheme.SEPARATOR));
         sidebar.add(viewListScroll, BorderLayout.CENTER);
 
         frame.setLayout(new BorderLayout());
         frame.add(buildToolbar(), BorderLayout.NORTH);
-        frame.add(sidebar, BorderLayout.WEST);
+        frame.add(buildSidebarSplit(), BorderLayout.CENTER);
-        frame.add(content, BorderLayout.CENTER);
         frame.add(inspectorSlot, BorderLayout.EAST);
         frame.add(statusBars, BorderLayout.SOUTH);
         installShortcuts(frame.getRootPane());
@@ -226,6 +226,20 @@ public final class MapWindow implements MapCanvas.Listener {
         }
     }
 
+    // Dragging the gap beside the sidebar island makes it wider, so long palette names fit.
+    private JSplitPane buildSidebarSplit() {
+        IslandPanel island = new IslandPanel(sidebar);
+        island.setMinimumSize(StudioTheme.scaledSize(SIDEBAR_MINIMUM_WIDTH, 0));
+        content.setMinimumSize(StudioTheme.scaledSize(CONTENT_MINIMUM_WIDTH, 0));
+        JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, true, island, content);
+        split.setBorder(BorderFactory.createEmptyBorder());
+        split.setBackground(StudioTheme.EDITOR_BACKGROUND);
+        split.setDividerSize(StudioTheme.scale(SIDEBAR_DIVIDER_WIDTH));
+        split.setResizeWeight(0D);
+        split.setDividerLocation(StudioTheme.scale(SIDEBAR_WIDTH));
+        return split;
+    }
+
     // The palettes need the room more than the view list, which scrolls once it is squeezed.
     private int viewListHeightBesidePalettes() {
         int fullHeight = viewList.getPreferredSize().height + 4;