Name: nt126004 Date: 08/22/2001


java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, mixed mode)

Background:

I am using a JTable within a JScrollPane. I am providing a custom table model
for the JTable which extends AbstractDataModel. The application has a
simulation modelling thread that rapidly changes the values in the table model,
and fires many table rows updated events. Each of the update events is for a
single row (the first and last rows updated is always the same value). The
table has 40,000 rows, and about 5,000 update events are generated per second.

Symptom:

When the JTable is not being scrolled the performance is as expected.

When the JTable is being scrolled horizontally *sometimes* the viewport update
routines seem to get confused and attempt to update (repaint) every row in the
table, even rows that are not currently visible in the viewport. This results
in the application 'freezing' temporarily while all 40,000 rows are painted.

I am sure that it is the table disply routines that are causing a problem
because I have added the following lines to BasicTableUI.java at around lines
835:
        int rMin = table.rowAtPoint(minLocation);
        int rMax = table.rowAtPoint(maxLocation);
        // This should never happen.
        if (rMin == -1) {
+ System.err.println("rMin="+rMin+" rMax="+rMax);
+ System.err.println("minLocation x="+minLocation.x+"
y="+minLocation.y);
+ System.err.println("maxLocation x="+maxLocation.x+"
y="+maxLocation.y);
rMin = 0;
        }

The resulting value that is printed out is:
rMin=-1 rMax=-1
minLocation x=365 y=-23
maxLocation x=366 y=-24

As a consequence of rMin and rMax being == -1, all rows in the table are then
painted, resulting in poor performance.

This problem cannot be triggered while the simulation model is quiescent, or
while the table is not being scrolled. It only seems to occur while many table
row update events occur while the JTable is being scrolled.

Source Code:

The actual source code that triggers this event is complex, and the datasets are
large. I am not able to submit source code and data at this time. However, I
would be able to work on developing a sample app that can be used to exhibit
this bug. Please contact me and I will respond right away.

Impact:

This bug cause the application to stall unexplainably. The user interface
appears unresponsive and it appears as though the application has failed.
(Review ID: 130274)
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