Added property to enable scrollbar highlighting when scrolling (disabled by default).

Added property to hide scrollbar if it isn't currently used (macOS only, disabled by default).

core/src/main/java/com/github/weisj/darklaf/graphics/Animator.java

@@ -145,7 +145,7 @@ public abstract class Animator {
     }
 
     public void resume(final int startFrame, final JComponent target) {
-        if (!target.isVisible() || !target.isShowing()) {
+        if (target != null && (!target.isVisible() || !target.isShowing())) {
             stopAnimation();
             return;
         }

core/src/main/java/com/github/weisj/darklaf/ui/scrollpane/DarkMacScrollBarUI.java

@@ -27,16 +27,23 @@ import java.awt.geom.RoundRectangle2D;
 import javax.swing.*;
 import javax.swing.plaf.ComponentUI;
 
-import com.github.weisj.darklaf.graphics.Animator;
 import com.github.weisj.darklaf.graphics.GraphicsContext;
 import com.github.weisj.darklaf.graphics.GraphicsUtil;
 
 public class DarkMacScrollBarUI extends DarkScrollBarUI {
 
+    private boolean hideScrollBar;
+
     public static ComponentUI createUI(final JComponent c) {
         return new DarkMacScrollBarUI();
     }
 
+    @Override
+    protected void installDefaults() {
+        super.installDefaults();
+        hideScrollBar = UIManager.getBoolean("ScrollBar.macos.hideScrollBar");
+    }
+
     @Override
     protected void paintTrack(final Graphics g, final JComponent c, final Rectangle bounds) {}
 
@@ -46,9 +53,26 @@ public class DarkMacScrollBarUI extends DarkScrollBarUI {
         g.setComposite(COMPOSITE.derive(thumbAlpha));
         boolean horizontal = scrollbar.getOrientation() == JScrollBar.HORIZONTAL;
         int ins = 2;
-        int arc = horizontal ? (rect.height - 2 * ins) : (rect.width - 2 * ins);
         RoundRectangle2D roundRect = new RoundRectangle2D.Float();
-        roundRect.setRoundRect(rect.x + ins, rect.y + ins, rect.width - 2 * ins, rect.height - 2 * ins, arc, arc);
+        int width = rect.width - 2 * ins;
+        int height = rect.height - 2 * ins;
+        int x = rect.x + ins;
+        int y = rect.y + ins;
+        if (hideScrollBar) {
+            if (horizontal) {
+                int newHeight = (int) (height * scrollBarListener.getTrackState());
+                y += (height - newHeight);
+                height = newHeight;
+            } else {
+                int newWidth = (int) (width * scrollBarListener.getTrackState());
+                if (scrollbar.getComponentOrientation().isLeftToRight()) {
+                    x += (width - newWidth);
+                }
+                width = newWidth;
+            }
+        }
+        int arc = horizontal ? height : width;
+        roundRect.setRoundRect(x, y, width, height, arc, arc);
         g.setColor(getThumbColor());
         g.fill(roundRect);
         g.setColor(getThumbBorderColor());
@@ -68,14 +92,14 @@ public class DarkMacScrollBarUI extends DarkScrollBarUI {
             super(scrollbar, ui);
         }
 
-        @Override
+        // @Override
-        protected Animator createTrackFadeinAnimator() {
+        // protected Animator createTrackFadeinAnimator() {
-            return null;
+        // return null;
-        }
+        // }
-
+        //
-        @Override
+        // @Override
-        protected Animator createTrackFadeoutAnimator() {
+        // protected Animator createTrackFadeoutAnimator() {
-            return null;
+        // return null;
-        }
+        // }
     }
 }

core/src/main/java/com/github/weisj/darklaf/ui/scrollpane/DarkScrollBarListener.java

@@ -50,6 +50,8 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
 
     protected boolean mouseOverThumb = false;
     protected boolean mouseOverTrack = false;
+    protected float trackState;
+    protected float thumbState;
     protected float trackAlpha;
     protected float thumbAlpha;
 
@@ -82,6 +84,14 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         return trackAlpha;
     }
 
+    public float getTrackState() {
+        return trackState;
+    }
+
+    public float getThumbState() {
+        return thumbState;
+    }
+
     public float getThumbAlpha() {
         return thumbAlpha;
     }
@@ -164,19 +174,22 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         if (!e.getValueIsAdjusting()) return;
 
         JScrollBar scrollBar = (JScrollBar) e.getAdjustable();
+
+        if (PropertyUtil.getBooleanProperty(scrollBar, KEY_HIGHLIGHT_ON_SCROLL)) {
             int extent = scrollBar.getModel().getExtent();
             int value = scrollBar.getValue() + extent;
             if (value == extent || value == scrollBar.getMaximum()) return;
 
             Point p = MouseInfo.getPointerInfo().getLocation();
             SwingUtilities.convertPointFromScreen(p, scrollbar);
-        if (!ui.getThumbBounds().contains(p) && !e.getValueIsAdjusting()) {
+            if (!ui.getThumbBounds().contains(p)) {
                 if (!thumbFadeinAnimator.isRunning()) {
                     mouseOverThumb = true;
                     resetThumbAnimator();
                 }
             }
         }
+    }
 
     protected boolean isOverThumb(final Point p) {
         final Rectangle bounds = ui.getThumbBounds();
@@ -234,8 +247,9 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         }
 
         @Override
-        protected void updateValue(final float value) {
+        protected void updateValue(final float state, final float value) {
             trackAlpha = value;
+            trackState = state;
         }
     }
 
@@ -246,8 +260,9 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         }
 
         @Override
-        protected void updateValue(final float value) {
+        protected void updateValue(final float state, final float value) {
             trackAlpha = value;
+            trackState = state;
         }
     }
 
@@ -258,8 +273,9 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         }
 
         @Override
-        protected void updateValue(final float value) {
+        protected void updateValue(final float state, final float value) {
             thumbAlpha = value;
+            thumbState = state;
         }
 
         @Override
@@ -282,8 +298,9 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
         }
 
         @Override
-        protected void updateValue(final float value) {
+        protected void updateValue(final float state, final float value) {
             thumbAlpha = value;
+            thumbState = state;
         }
     }
 
@@ -304,18 +321,18 @@ public class DarkScrollBarListener extends MouseAdapter implements AdjustmentLis
             this.fadeIn = fadeIn;
         }
 
-        protected abstract void updateValue(final float value);
+        protected abstract void updateValue(final float state, final float value);
 
         @Override
         public void paintNow(final float fraction) {
             float fr = fadeIn ? fraction : (1 - fraction);
-            updateValue(minValue + maxValue * fr);
+            updateValue(fr, minValue + maxValue * fr);
             repaint();
         }
 
         @Override
         protected void paintCycleEnd() {
-            updateValue(fadeIn ? maxValue : minValue);
+            updateValue(fadeIn ? 1 : 0, fadeIn ? maxValue : minValue);
             repaint();
         }
 

core/src/main/java/com/github/weisj/darklaf/ui/scrollpane/DarkScrollBarUI.java

@@ -30,6 +30,7 @@ import javax.swing.plaf.basic.BasicScrollBarUI;
 
 import com.github.weisj.darklaf.graphics.PaintUtil;
 import com.github.weisj.darklaf.util.ColorUtil;
+import com.github.weisj.darklaf.util.PropertyUtil;
 
 /** @author Jannis Weis */
 public class DarkScrollBarUI extends BasicScrollBarUI implements ScrollBarConstants {
@@ -66,6 +67,8 @@ public class DarkScrollBarUI extends BasicScrollBarUI implements ScrollBarConsta
             UIManager.put("ScrollBar.incrementButtonGap", incGap);
             UIManager.put("ScrollBar.decrementButtonGap", decGap);
         }
+        PropertyUtil.installProperty(scrollbar, KEY_HIGHLIGHT_ON_SCROLL,
+                UIManager.getBoolean("ScrollBar.highlightOnScroll"));
         thumbBorderColor = UIManager.getColor("ScrollBar.thumbBorderColor");
         thumbFadeStartColor = UIManager.getColor("ScrollBar.fadeStartColor");
         thumbFadeEndColor = UIManager.getColor("ScrollBar.fadeEndColor");

core/src/main/java/com/github/weisj/darklaf/ui/scrollpane/ScrollBarConstants.java

@@ -28,6 +28,7 @@ import com.github.weisj.darklaf.util.PropertyUtil;
 public interface ScrollBarConstants {
     String KEY_SCROLL_PANE_PARENT = "JScrollBar.scrollPaneParent";
     String KEY_FAST_WHEEL_SCROLLING = "JScrollBar.fastWheelScrolling";
+    String KEY_HIGHLIGHT_ON_SCROLL = "JScrollBar.highlightOnScroll";
     String KEY_SMALL = "JComponent.small";
 
     static boolean isSmall(final JScrollBar scrollBar) {

core/src/main/java/com/github/weisj/darklaf/ui/scrollpane/ScrollBarUtil.java

@@ -30,6 +30,12 @@ import com.github.weisj.darklaf.util.PropertyUtil;
 
 public class ScrollBarUtil implements ScrollBarConstants {
 
+    public static JScrollPane getScrollPane(final JScrollBar scrollBar) {
+        Component parent = scrollBar.getParent();
+        if (parent instanceof JScrollPane) return (JScrollPane) parent;
+        return PropertyUtil.getObject(scrollBar, KEY_SCROLL_PANE_PARENT, JScrollPane.class);
+    }
+
     @SuppressWarnings("MagicConstant")
     public static void doScroll(final JScrollBar toScroll, final JViewport vp, final MouseWheelEvent e,
             final boolean leftToRight) {

core/src/main/resources/com/github/weisj/darklaf/properties/platform/mac.properties

@@ -28,6 +28,7 @@ macos.coloredTitleBar                    = true
 ScrollBarUI                              = com.github.weisj.darklaf.ui.scrollpane.DarkMacScrollBarUI
 ScrollBar.smallWidth                     = 10
 ScrollBar.width                          = 12
+ScrollBar.macos.hideScrollBar            = false
 
 TooltipUI                                = com.github.weisj.darklaf.ui.tooltip.DarkMacTooltipUI
 

core/src/main/resources/com/github/weisj/darklaf/properties/ui/scrollBar.properties

@@ -36,3 +36,4 @@ ScrollBar.smallWidth       = 8
 ScrollBar.width             = 10
 ScrollBar.thumbAlpha        = 60
 ScrollBar.animated          = true
+ScrollBar.highlightOnScroll = false