don't draw clipped tabs on the bottom when vertical layout is used

platform/platform-api/src/com/intellij/ui/tabs/impl/singleRow/ScrollableSingleRowLayout.java

@@ -104,7 +104,8 @@ public class ScrollableSingleRowLayout extends SingleRowLayout {
       length = getStrategy().getLengthIncrement(label.getPreferredSize());
       final int moreRectSize = getStrategy().getMoreRectAxisSize();
       if (data.position + length > data.toFitLength - moreRectSize) {
-        super.applyTabLayout(data, label, data.toFitLength - data.position - moreRectSize - 4, deltaToFit);
+        final int clippedLength = getStrategy().drawPartialOverflowTabs() ? data.toFitLength - data.position - moreRectSize - 4 : 0;
+        super.applyTabLayout(data, label, clippedLength, deltaToFit);
         label.setAlignmentToCenter(false);
         label.setActionPanelVisible(false);
         return false;

platform/platform-api/src/com/intellij/ui/tabs/impl/singleRow/SingleRowLayoutStrategy.java

@@ -73,6 +73,13 @@ public abstract class SingleRowLayoutStrategy {
 
   public abstract boolean isDragOut(TabLabel tabLabel, int deltaX, int deltaY);
 
+  /**
+   * Whether a tab that didn't fit completely on the right/bottom side in scrollable layout should be clipped or hidden altogether.
+   *
+   * @return true if the tab should be clipped, false if hidden.
+   */
+  public abstract boolean drawPartialOverflowTabs();
+
   abstract static class Horizontal extends SingleRowLayoutStrategy {
     protected Horizontal(final SingleRowLayout layout) {
       super(layout);
@@ -129,6 +136,10 @@ public abstract class SingleRowLayoutStrategy {
       return data.insets.left;
     }
 
+    @Override
+    public boolean drawPartialOverflowTabs() {
+      return true;
+    }
   }
 
   static class Top extends Horizontal {
@@ -287,6 +298,10 @@ public abstract class SingleRowLayoutStrategy {
       return myTabs.myHeaderFitSize.width;
     }
 
+    @Override
+    public boolean drawPartialOverflowTabs() {
+      return false;
+    }
   }
 
   static class Left extends Vertical {