Linux:

- allow user scaling mode on Linux even if running in Java 9+
- update fonts (and scaling) when user changes text size or scaling in Gnome settings

(#1)

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java

@@ -124,6 +124,11 @@ public abstract class FlatLaf
 			// Windows 10 allows increasing font size independent of scaling:
 			//   Settings > Ease of Access > Display > Make text bigger (100% - 225%)
 			desktopPropertyName = "win.messagebox.font";
+		} else if( SystemInfo.IS_LINUX ) {
+			// Linux/Gnome allows extra scaling and larger text:
+			//   Settings > Devices > Displays > Scale (100% or 200%)
+			//   Settings > Universal access > Large Text (off or on, 125%)
+			desktopPropertyName = "gnome.Xft/DPI";
 		}
 		if( desktopPropertyName != null ) {
 			desktopPropertyListener = e -> {

flatlaf-core/src/main/java/com/formdev/flatlaf/util/UIScale.java

@@ -48,8 +48,7 @@ import javax.swing.plaf.UIResource;
  *
  * 2) user scaling mode
  *
- * This mode is for Java 8 compatibility and can be removed when changing minimum
- * required Java version to 9.
+ * This mode is mainly for Java 8 compatibility, but is also used on Linux.
  * The user scale factor is computed based on the used font.
  * The JRE does not scale anything.
  * So we have to invoke {@link #scale(float)} where necessary.
@@ -166,7 +165,7 @@ public class UIScale
 	}
 
 	private static boolean isUserScalingEnabled() {
-		if( isSystemScalingEnabled() )
+		if( isSystemScalingEnabled() && !SystemInfo.IS_LINUX )
 			return false; // disable user scaling if JRE scales
 
 		// same as in IntelliJ IDEA