save app width and height across restarts

src/main/java/com/sparrowwallet/sparrow/MainApp.java

@@ -90,6 +90,11 @@ public class MainApp extends Application {
 
         System.setProperty(Wallet.ALLOW_DERIVATIONS_MATCHING_OTHER_SCRIPT_TYPES_PROPERTY, Boolean.toString(!Config.get().isValidateDerivationPaths()));
 
+        if(Config.get().getAppHeight() != null && Config.get().getAppWidth() != null) {
+            mainStage.setWidth(Config.get().getAppWidth());
+            mainStage.setHeight(Config.get().getAppHeight());
+        }
+
         AppController appController = AppServices.newAppWindow(stage);
 
         if(createNewWallet) {
@@ -119,6 +124,8 @@ public class MainApp extends Application {
     @Override
     public void stop() throws Exception {
         AppServices.get().stop();
+        Config.get().setAppWidth(mainStage.getWidth());
+        Config.get().setAppHeight(mainStage.getHeight());
         mainStage.close();
         if(sparrowInstance != null) {
             sparrowInstance.freeLock();

src/main/java/com/sparrowwallet/sparrow/io/Config.java

@@ -57,6 +57,8 @@ public class Config {
     private File electrumServerCert;
     private boolean useProxy;
     private String proxyServer;
+    private Double appWidth;
+    private Double appHeight;
     private String scode;
 
     private static Config INSTANCE;
@@ -458,6 +460,24 @@ public class Config {
         flush();
     }
 
+    public Double getAppWidth() {
+        return appWidth;
+    }
+
+    public void setAppWidth(Double appWidth) {
+        this.appWidth = appWidth;
+        flush();
+    }
+
+    public Double getAppHeight() {
+        return appHeight;
+    }
+
+    public void setAppHeight(Double appHeight) {
+        this.appHeight = appHeight;
+        flush();
+    }
+
     public String getScode() {
         return scode;
     }