Reduce issue of non-available subpixel AA on windows for plain tooltips.

core/src/main/java/com/github/weisj/darklaf/ui/tooltip/DarkToolTipUI.java

@@ -178,8 +178,19 @@ public class DarkToolTipUI extends BasicToolTipUI implements PropertyChangeListe
             startAnimation();
         } else {
             Window window = DarkUIUtil.getWindow(c);
-            if (window != null && window.getOpacity() != 1 && !transparencySupported(window)) {
-                window.setOpacity(1);
+            if (window != null) {
+                if (window.getOpacity() != 1 && !transparencySupported(window)) {
+                    window.setOpacity(1);
+                }
+                /*
+                 * In non opaque windows on Windows subpixel AA doesn't work. The translucent background isn't needed
+                 * for the plain tooltip style, so we set it here.
+                 *
+                 * See https://bugs.openjdk.java.net/browse/JDK-8215980?attachmentOrder=desc
+                 */
+                if (style == ToolTipStyle.PLAIN) {
+                    window.setBackground(c.getBackground());
+                }
             }
         }
         GraphicsContext context = GraphicsUtil.setupAntialiasing(g);