Caps the automatic font size at no more than 25% larger than the current scaleFactor. In debug mode, resizing the application frame now updates the scaleFactor (if automatic). This behavior can only be enabled outside of the debug mode when all panels are automatically refreshed when the scalingFactor and/or font size changes.

src/net/sf/freecol/client/gui/Canvas.java

@@ -277,6 +277,8 @@ public final class Canvas extends JDesktopPane {
     // Internals
     
     private void updateSize() {
+        freeColClient.getGUI().refreshScaleFactorIfNecessary();
+        
         Dimension size = getSize();
         if (oldSize.width != size.width || oldSize.height != size.height) {
             logger.info("Canvas resize from " + oldSize + " to " + size);

src/net/sf/freecol/client/gui/GUI.java

@@ -2639,4 +2639,11 @@ public class GUI extends FreeColClientHolder {
     public void emergencyPurge() {
 
     }
+
+    /**
+     * Updates the scaleFactor, if necessary, after the window has been resized. 
+     */
+    public void refreshScaleFactorIfNecessary() {
+
+    }
 }

src/net/sf/freecol/client/gui/SwingGUI.java

@@ -59,7 +59,6 @@ import net.sf.freecol.client.ClientOptions;
 import net.sf.freecol.client.FreeColClient;
 import net.sf.freecol.client.control.MapTransform;
 import net.sf.freecol.client.control.SoundController;
-import net.sf.freecol.client.gui.SwingGUI.PopupPosition;
 import net.sf.freecol.client.gui.animation.Animation;
 import net.sf.freecol.client.gui.animation.Animations;
 // Special dialogs and panels
@@ -73,7 +72,6 @@ import net.sf.freecol.client.gui.mapviewer.MapViewerState;
 import net.sf.freecol.client.gui.mapviewer.TileViewer;
 import net.sf.freecol.client.gui.panel.ColonyPanel;
 import net.sf.freecol.client.gui.panel.CornerMapControls;
-import net.sf.freecol.client.gui.panel.ErrorPanel;
 import net.sf.freecol.client.gui.panel.FreeColImageBorder;
 import net.sf.freecol.client.gui.panel.FreeColPanel;
 import net.sf.freecol.client.gui.panel.InformationPanel;
@@ -93,6 +91,7 @@ import net.sf.freecol.client.gui.plaf.FreeColToolTipUI;
 import net.sf.freecol.common.FreeColException;
 import net.sf.freecol.common.MemoryManager;
 import net.sf.freecol.common.debug.DebugUtils;
+import net.sf.freecol.common.debug.FreeColDebugger;
 import net.sf.freecol.common.i18n.Messages;
 import net.sf.freecol.common.io.FreeColDataFile;
 import net.sf.freecol.common.metaserver.ServerInfo;
@@ -2037,23 +2036,28 @@ public class SwingGUI extends GUI {
         }
         
         final int displayScaling = getClientOptions().getInteger(ClientOptions.DISPLAY_SCALING);
-        if (displayScaling == 0) {
+        final float scaleFactor = determineScaleFactorUsingClientOptions(dpi);
-            int fontSize = (int) ((FontLibrary.DEFAULT_UNSCALED_MAIN_FONT_SIZE * dpi) / DEFAULT_DPI);
+        final int fontSizeUsingScaling = (int) (FontLibrary.DEFAULT_UNSCALED_MAIN_FONT_SIZE * scaleFactor);
-            
+        
-            final int screenHeight = graphicsDevice.getDisplayMode().getHeight();
+        if (displayScaling != 0) {
-            if (screenHeight < 900) {
+            logger.info("Font size based on manual display scaling: " + fontSizeUsingScaling + " (reported DPI: " + dpi + ")");
-                fontSize = Math.min(14, fontSize);
+            return fontSizeUsingScaling;
-            } else if (screenHeight < 1050) {
-                fontSize = Math.min(18, fontSize);
-            }
-                    
-            logger.info("Automatic font size: " + fontSize + " (reported DPI: " + dpi + ", screen height: " + screenHeight + ")");        
-            return fontSize;
         }
         
-        final int fontSize = (int) (FontLibrary.DEFAULT_UNSCALED_MAIN_FONT_SIZE * (displayScaling / 100f));
+        int fontSizeUsingDpi = (int) ((FontLibrary.DEFAULT_UNSCALED_MAIN_FONT_SIZE * dpi) / DEFAULT_DPI);
-        logger.info("Font size based on manual display scaling: " + fontSize + " (reported DPI: " + dpi + ")");        
+        final int screenHeight = graphicsDevice.getDisplayMode().getHeight();
-        return fontSize;
+        if (screenHeight < 900) {
+            fontSizeUsingDpi = Math.min(14, fontSizeUsingDpi);
+        } else if (screenHeight < 1050) {
+            fontSizeUsingDpi = Math.min(18, fontSizeUsingDpi);
+        }
+        
+        if (fontSizeUsingDpi >= fontSizeUsingScaling * 0.25f) {
+            return fontSizeUsingScaling;
+        }
+                
+        logger.info("Automatic font size: " + fontSizeUsingDpi + " (reported DPI: " + dpi + ", screen height: " + screenHeight + ")");        
+        return fontSizeUsingDpi;        
     }
 
     private float determineScaleFactorUsingClientOptions(final int dpi) {
@@ -2073,7 +2077,12 @@ public class SwingGUI extends GUI {
                 scaleFactor = 2F;
             }
             
-            final int screenHeight = graphicsDevice.getDisplayMode().getHeight();
+            final int screenHeight;
+            if (FreeColDebugger.isAutomaticRescalingOnWindowResize()) {
+                screenHeight = (canvas != null && canvas.getParentFrame() != null) ? canvas.getParentFrame().getHeight() : graphicsDevice.getDisplayMode().getHeight();
+            } else {
+                screenHeight = graphicsDevice.getDisplayMode().getHeight();
+            }
             if (screenHeight < 720) {
                 scaleFactor = 0.75F;
             } else if (screenHeight < 900) {
@@ -2872,4 +2881,19 @@ public class SwingGUI extends GUI {
     public boolean canGameChangingModsBeAdded() {
         return getFreeColClient().getGame() == null;
     }
+    
+    @Override
+    public void refreshScaleFactorIfNecessary() {
+        if (!FreeColDebugger.isAutomaticRescalingOnWindowResize()) {
+            return;
+        }
+        
+        final int dpi = Utils.determineDpi(graphicsDevice);
+        final float scaleFactor = determineScaleFactorUsingClientOptions(dpi);
+        if (Math.abs(getFixedImageLibrary().getScaleFactor() - scaleFactor) <= 0.1) {
+            return;
+        }
+        
+        refreshGuiUsingClientOptions();
+    }
 }

src/net/sf/freecol/common/debug/FreeColDebugger.java

@@ -114,6 +114,16 @@ public class FreeColDebugger {
     public static boolean isInDebugMode() {
         return FreeColDebugger.debugMode != 0;
     }
+    
+    /**
+     * Checks if automatic changing of the scaleFactor on window resize
+     * has been enabled.
+     * 
+     * @return {@code true} if any debug mode is enabled.
+     */
+    public static boolean isAutomaticRescalingOnWindowResize() {
+        return FreeColDebugger.debugMode != 0;    
+    }
 
     /**
      * Is a particular debug mode enabled in this game?