8195738: scroll poistion in ScrollPane is reset after calling validate()

Reviewed-by: serb, ssadetsky

src/java.desktop/windows/native/libawt/windows/awt_ScrollPane.cpp

@@ -196,15 +196,7 @@ void AwtScrollPane::SetScrollInfo(int orient, int max, int page,
     // and the page size changes
     posAfter = GetScrollPos(orient);
     if (posBefore != posAfter) {
-        if(max==0 && posAfter==0) {
-            // Caller used nMin==nMax idiom to hide scrollbar.
-            // On the new themes (Windows XP, Vista) this would reset
-            // scroll position to zero ("just inside the range") (6404832).
-            //
-            PostScrollEvent(orient, SB_THUMBPOSITION, posBefore);
-        }else{
-            PostScrollEvent(orient, SB_THUMBPOSITION, posAfter);
-        }
+        PostScrollEvent(orient, SB_THUMBPOSITION, posAfter);
     }
 }
 
@@ -263,8 +255,11 @@ void AwtScrollPane::RecalcSizes(int parentWidth, int parentHeight,
                       (policy == java_awt_ScrollPane_SCROLLBARS_ALWAYS));
         env->DeleteLocalRef(hAdj);
     } else {
-        SetScrollInfo(SB_HORZ, 0, 0,
+        /* Set scroll info to imitate the behaviour and since we don't
+            need to display it, explicitly don't show the bar */
+        SetScrollInfo(SB_HORZ, childWidth - 1, parentWidth,
                       (policy == java_awt_ScrollPane_SCROLLBARS_ALWAYS));
+        ::ShowScrollBar(GetHWnd(), SB_HORZ, false);
     }
 
     if (needsVert) {
@@ -275,8 +270,11 @@ void AwtScrollPane::RecalcSizes(int parentWidth, int parentHeight,
                       (policy == java_awt_ScrollPane_SCROLLBARS_ALWAYS));
         env->DeleteLocalRef(vAdj);
     } else {
-        SetScrollInfo(SB_VERT, 0, 0,
+        /* Set scroll info to imitate the behaviour and since we don't
+            need to display it, explicitly don't show the bar */
+        SetScrollInfo(SB_VERT, childHeight - 1, parentHeight,
                       (policy == java_awt_ScrollPane_SCROLLBARS_ALWAYS));
+        ::ShowScrollBar(GetHWnd(), SB_VERT, false);
     }
 
     env->DeleteLocalRef(target);

test/jdk/java/awt/ScrollPane/ScrollPaneValidateTest.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @key headful
+ * @bug 8195738
+ * @summary scroll position in ScrollPane is reset after calling validate()
+ * @run main ScrollPaneValidateTest
+ */
+
+import java.awt.ScrollPane;
+import java.awt.BorderLayout;
+import java.awt.GridLayout;
+import java.awt.Button;
+import java.awt.Dimension;
+import java.awt.Frame;
+import java.awt.Panel;
+import java.awt.Point;
+import java.awt.Robot;
+import java.awt.AWTException;
+
+public class ScrollPaneValidateTest extends Frame {
+  ScrollPane pane;
+
+  public ScrollPaneValidateTest() {
+    setBounds(300, 300, 300, 300);
+    pane = new ScrollPane(ScrollPane.SCROLLBARS_NEVER);
+    add(pane, BorderLayout.NORTH);
+    pane.add(new InnerPanel());
+  }
+
+  public static void main(String[] args) throws AWTException {
+    Robot robot = new Robot();
+    final ScrollPaneValidateTest obj = new ScrollPaneValidateTest();
+    obj.setVisible(true);
+
+    // set to some scroll position
+    obj.pane.setScrollPosition(600, 200);
+
+    // get the newly set position
+    Point scrollPosition = obj.pane.getScrollPosition();
+
+    // call validate multiple times
+    obj.pane.validate();
+    robot.delay(1000);
+    obj.pane.validate();
+    robot.delay(1000);
+
+    // compare position after calling the validate function
+    if(!scrollPosition.equals(obj.pane.getScrollPosition())) {
+      obj.dispose();
+      throw new RuntimeException("Scrolling position is changed in ScrollPane");
+    }
+
+    obj.dispose();
+    return;
+  }
+
+  class InnerPanel extends Panel {
+    public InnerPanel() {
+      this.setLayout(new GridLayout(2, 4));
+      for (int i = 1; i <= 8; i++) {
+        this.add(new Button("Button" + i));
+      }
+    }
+
+    public Dimension getPreferredSize() {
+      return new Dimension(980, 200);
+    }
+  }
+}