Fix scaling issues on Linux

src/main/java/com/loomcom/symon/ui/X11ResourceReader.java

@@ -0,0 +1,54 @@
+package com.loomcom.symon.ui;
+
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+import com.sun.jna.Pointer;
+import com.sun.jna.ptr.IntByReference;
+import com.sun.jna.ptr.PointerByReference;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class X11ResourceReader {
+
+    private final static Logger logger = LoggerFactory.getLogger(X11ResourceReader.class.getName());
+
+
+    public interface X11 extends Library {
+        X11 INSTANCE = Native.load("X11", X11.class);
+
+        Pointer XOpenDisplay(String display);
+        Pointer XResourceManagerString(Pointer display);
+        void XCloseDisplay(Pointer display);
+    }
+
+    public static Double readXftDpiScale() {
+        Pointer display = null;
+        try {
+            display = X11.INSTANCE.XOpenDisplay(null);
+            if (display == null) {
+                return null; // não conseguimos ligar ao X server (ex: Wayland puro sem XWayland)
+            }
+
+            Pointer resourceString = X11.INSTANCE.XResourceManagerString(display);
+            if (resourceString == null) {
+                return null;
+            }
+
+            String resources = resourceString.getString(0);
+            for (String line : resources.split("\n")) {
+                if (line.startsWith("Xft.dpi:")) {
+                    int dpi = Integer.parseInt(line.split(":")[1].trim());
+                    return Math.round((dpi / 96.0) * 4) / 4.0;
+                }
+            }
+            return null;
+        } catch (UnsatisfiedLinkError | Exception e) {
+            logger.debug("Could not read X11 resource manager (libX11 unavailable?)", e);
+            return null;
+        } finally {
+            if (display != null) {
+                X11.INSTANCE.XCloseDisplay(display);
+            }
+        }
+    }
+}