Hand the display server one finished map picture per paint

The map drew every visible tile to the window on its own, hundreds of
scaled images per paint, and since tiles are no longer cached in the
display server each of those was uploaded again on every frame, which
made dragging and zooming lag. The tiles are now put together in memory
once, only when tiles or the view change, and drawn as a single image
like the palette view does.

Model used: Claude Opus 5.5

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

@@ -88,6 +88,8 @@ final class MapCanvas extends JPanel {
     private IrisRenderer renderer;
     private VisionOverlay overlay;
     private VisionRenderController.Frame renderFrame;
+    private BufferedImage tileLayer;
+    private boolean tileLayerStale = true;
     private RenderType currentType = RenderType.BIOME;
     private String viewLabel = MapView.BIOMES.label();
     private List<GuiMarker> players = List.of();
@@ -455,7 +457,32 @@ final class MapCanvas extends JPanel {
         }
     }
 
+    // The display server gets one finished picture per paint: handing it every tile separately made the map lag.
     private void renderTiles(Graphics2D canvas) {
+        canvas.drawImage(currentTileLayer(), 0, 0, null);
+    }
+
+    private BufferedImage currentTileLayer() {
+        int width = Math.max(1, getWidth());
+        int height = Math.max(1, getHeight());
+        if (tileLayer == null || tileLayer.getWidth() != width || tileLayer.getHeight() != height) {
+            tileLayer = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
+            tileLayer.setAccelerationPriority(0F);
+            tileLayerStale = true;
+        }
+        if (tileLayerStale) {
+            Graphics2D layer = tileLayer.createGraphics();
+            try {
+                composeTiles(layer);
+            } finally {
+                layer.dispose();
+            }
+            tileLayerStale = false;
+        }
+        return tileLayer;
+    }
+
+    private void composeTiles(Graphics2D canvas) {
         VisionRenderController.Frame frame = renderFrame;
         canvas.setColor(StudioTheme.EDITOR_BACKGROUND);
         canvas.fillRect(0, 0, getWidth(), getHeight());
@@ -746,11 +773,13 @@ final class MapCanvas extends JPanel {
     }
 
     private void onTilesChanged() {
+        tileLayerStale = true;
         repaint();
         refreshStatus();
     }
 
     private void requestRender() {
+        tileLayerStale = true;
         if (closed || !active || getWidth() < 1 || getHeight() < 1 || !ensureEngine()) {
             repaint();
             return;