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  1. JDK
  2. JDK-4063897

AWT's scrollbar locks program for Windows NT version JDK 1.1.1 and 1.1.2


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    • OS:
      windows_95, windows_nt
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        JDK 1.1.1, 1.1.2 and 1.1.3 for Window NT version.

        From Customer's email:

        Under 1.1.1 and 1.1.2, you can lock the program by grabbing the
        scrollbar tab and moving the cursor inside and outside of the scrollbar
        region vigerously, eventually the setValues call will lock up the

        Under 1.1.3, it doesn't lock, but in _all cases I never get the
        mouseReleased event_. Furthermore (not crucial, but annoying) I now
        have to explicitly call setValue in response to an adjustment event to
        make sure the thumb 'sticks' in the proper spot.

        <<Scroll 'lag' issue:>>

        Under 1.1.1, 1.1.2 and 1.1.3 if I spend too much time in the adjustment
        event a huge cache of events starts stacking up underneath me.
        Specifically, I repaint on a scroll and sometimes it can take on the
        order of 100 ms to redraw. If the user grabs the thumb and moves it a
        lot, quite a few messages get queued up and he spends a long time
        sitting around watching data scroll by. Is there any other than
        starting a second thread to solve this problem? Like dumping all but
        the last event?

        Under 1.1.1, 1.1.2 and 1.1.3 if I move the scroll bar thumb around a
        _lot_ the arrow icons turn black and the thumb starts jumping around

        <<Blinking focus issue:>>

        Under 1.1.1, 1.1.2 and 1.1.3 when I issue a setValues call the blinking
        'focus indicator' does not follow along with the new values and remains
        too large. To clarify, the focus indicator is a block just smaller than
        the thumb tab which blinks inside of the tab -- when the tab shrinks or
        grows, this indicator does not.

        The primary problem _was_ the locking, which until yesterday's
        acquisition of 1.1.3 was killing me -- I'd like to note that somehow
        Sun's HotJava browser got around this problem under 1.1.1/1.1.2 by
        (seemingly) disallowing any modifications of scrollbar parameters while
        the user is moving the thumb around. This works but has an annoying
        side-affect of 'freezing' the scrollbar from background updates while a
        user moves it. Again, this part has been fixed in 1.1.3 but I thought
        it was interesting, and for over a week I was trying (unsuccessfully) to
        duplicate this HotJava behavior.

        The primary problem now lies in the lack of released events, the
        strange erratic behavior with the black icons/jumping thumb tab, and the
        lagging focus indicator. Through 1.1.3 we can ship customers a working
        product, but it still looks unprofessional -- I want to remedy this.

        And the sample test case is as following:

        --- BugMain.java

         * $History: $
        import java.awt.*;
        import java.awt.event.*;

        class BugMain
                public static void main(String argv[])
                        Frame frame = new TestFrame();



        class TestFrame extends Frame implements MouseListener, AdjustmentListener, Ru
                Scrollbar scrollbar = new Scrollbar();
                int maxval = 100;

                        setLayout(new BorderLayout());

                        add(scrollbar, "East");

                        scrollbar.setValues(0, 10, 0, maxval);
                        setBounds(0, 0, 300, 300);


                        new Thread(this).start();

                public void run()
                                        } catch(InterruptedException io)

                                        maxval += 10;
                                scrollbar.setValues(scrollbar.getValue(), 10, 0, maxval)

                public void mouseEntered(MouseEvent evt)

                public void mouseExited(MouseEvent evt)
                        scrollbar.setValues(scrollbar.getValue(), 10, 0, maxval);

                public void mousePressed(MouseEvent evt)

                public void mouseReleased(MouseEvent evt)

                public void mouseClicked(MouseEvent evt)

                public void adjustmentValueChanged(AdjustmentEvent evt)
                        System.err.println("adjust: " + evt.getValue());
                                } catch(InterruptedException io)

        Please note that:
        The reason I increment maxval in my second thread is for
        three reasons: to decrease the thumb buffer size to demonstrate the
        thumb focus bug, for visible feedback that the thread is updating the
        scrollbar, and to avoid any possible caching of variables that would
        throw out a setValues() request on the basis of variables being
        identical to the last set that were passed in.

        Specifically, grab the thumb with your mouse, without releasing
        the mouse button move the cursor _outside_ of the scrollbar but not so
        far that you can't still move the scrollbar. Now, move the scroll bar
        up and down and sooner or later your thread will lock.


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                • Assignee:
                  tdv Dmitri Trembovetski (Inactive)
                  duke J. Duke (Inactive)
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