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    <p>Feel free, it is also somewhere on my github.  I'm not entirely
      confident it works for all cases, but it can be tweaked. Here's
      the missing piece you may need:</p>
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      <div
style="color:#000000;background-color:#ffffff;font-family:"Consolas";font-size:11pt;white-space:pre;"><p
      style="margin:0;"><span style="color:#3f5fbf;">/**</span></p><p
      style="margin:0;"><span style="color:#3f5fbf;"> * Tracks time spent (in milliseconds) between calls of </span><span
      style="color:#3f3fbf;">{@link #enterNested()}</span><span
      style="color:#3f5fbf;"> and </span><span style="color:#3f3fbf;">{@link #exitNested()}</span></p><p
      style="margin:0;"><span style="color:#3f5fbf;"> * excluding time spent in deeper nested levels.  This allows to find the time spent at a certain</span></p><p
      style="margin:0;"><span style="color:#3f5fbf;"> * nesting level without including time spent at any deeper </span><span
style="color:#3f5fbf;text-decoration:underline;text-decoration-color:#ff8040;text-decoration-style:wavy;">nestings</span><span
      style="color:#3f5fbf;">.</span></p><p style="margin:0;"><span
      style="color:#3f5fbf;"> */</span></p><p style="margin:0;"><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">public</span><span
      style="color:#000000;background-color:#fff4f4;"> </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">class</span><span
      style="color:#000000;background-color:#fff4f4;"> </span><span
      style="color:#000000;background-color:#d4d4d4;">NestedTimeTracker</span><span
      style="color:#000000;background-color:#fff4f4;"> {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">  </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">private</span><span
      style="color:#000000;background-color:#fff4f4;"> </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">final</span><span
      style="color:#000000;background-color:#fff4f4;"> Deque<Long> </span><span
      style="color:#0000c0;background-color:#fff4f4;">startTimes</span><span
      style="color:#000000;background-color:#fff4f4;"> = </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">new</span><span
      style="color:#000000;background-color:#fff4f4;"> ArrayDeque<>();</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">  </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">private</span><span
      style="color:#000000;background-color:#fff4f4;"> </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">final</span><span
      style="color:#000000;background-color:#fff4f4;"> Deque<Long> </span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;"> = </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">new</span><span
      style="color:#000000;background-color:#fff4f4;"> ArrayDeque<>();</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;">.add(0L);  </span><span
      style="color:#3f7f5f;background-color:#fff4f4;">// Add root level, always present (this is never used, the entry is there to avoid having to check if we're at root level)</span></p><p
      style="margin:0;"><span style="color:#000000;">  }</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  </span><span
      style="color:#0000a0;font-weight:bold;">public</span><span
      style="color:#000000;"> </span><span
      style="color:#0000a0;font-weight:bold;">int</span><span
      style="color:#000000;"> getCurrentLevel() {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#7f0055;background-color:#fff4f4;font-weight:bold;">return</span><span
      style="color:#000000;background-color:#fff4f4;"> </span><span
      style="color:#0000c0;background-color:#fff4f4;">startTimes</span><span
      style="color:#000000;background-color:#fff4f4;">.size();</span></p><p
      style="margin:0;"><span style="color:#000000;">  }</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  </span><span
      style="color:#0000a0;font-weight:bold;">public</span><span
      style="color:#000000;"> </span><span
      style="color:#0000a0;font-weight:bold;">void</span><span
      style="color:#000000;"> enterNested() {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    enterNested(System.</span><span
      style="color:#000000;background-color:#fff4f4;font-style:italic;">currentTimeMillis</span><span
      style="color:#000000;background-color:#fff4f4;">());</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">  }</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  </span><span
      style="color:#0000a0;font-weight:bold;">public</span><span
      style="color:#000000;"> </span><span
      style="color:#0000a0;font-weight:bold;">void</span><span
      style="color:#000000;"> enterNested(</span><span
      style="color:#0000a0;font-weight:bold;">long</span><span
      style="color:#000000;"> currentTimeMillis) {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000c0;background-color:#fff4f4;">startTimes</span><span
      style="color:#000000;background-color:#fff4f4;">.addLast(currentTimeMillis);</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;">.add(0L);</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">  }</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  </span><span
      style="color:#0000a0;font-weight:bold;">public</span><span
      style="color:#000000;"> </span><span
      style="color:#0000a0;font-weight:bold;">void</span><span
      style="color:#000000;"> exitNested() {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    exitNested(System.</span><span
      style="color:#000000;background-color:#fff4f4;font-style:italic;">currentTimeMillis</span><span
      style="color:#000000;background-color:#fff4f4;">());</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">  }</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">  </span><span
      style="color:#0000a0;font-weight:bold;">public</span><span
      style="color:#000000;"> </span><span
      style="color:#0000a0;font-weight:bold;">long</span><span
      style="color:#000000;"> exitNested(</span><span
      style="color:#0000a0;font-weight:bold;">long</span><span
      style="color:#000000;"> currentTimeMillis) {</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">long</span><span
      style="color:#000000;background-color:#fff4f4;"> startTime = </span><span
      style="color:#0000c0;background-color:#fff4f4;">startTimes</span><span
      style="color:#000000;background-color:#fff4f4;">.removeLast();</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">long</span><span
      style="color:#000000;background-color:#fff4f4;"> timeSpentInNested = </span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;">.removeLast();  </span><span
      style="color:#3f7f5f;background-color:#fff4f4;">// nested time, not part of this level</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">long</span><span
      style="color:#000000;background-color:#fff4f4;"> totalTime = currentTimeMillis - startTime;  </span><span
      style="color:#3f7f5f;background-color:#fff4f4;">// total time, including nested levels</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000a0;background-color:#fff4f4;font-weight:bold;">long</span><span
      style="color:#000000;background-color:#fff4f4;"> timeSpentAtThisLevel = totalTime - timeSpentInNested;</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span style="color:#000000;">    </span><span
      style="color:#3f7f5f;">// Consolidate total time spent in next higher level:</span></p><p
      style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;">.addLast(</span><span
      style="color:#0000c0;background-color:#fff4f4;">cumulativeDurations</span><span
      style="color:#000000;background-color:#fff4f4;">.removeLast() + totalTime);</span></p><p
      style="margin:0;">
</p><p style="margin:0;"><span
      style="color:#000000;background-color:#fff4f4;">    </span><span
      style="color:#7f0055;background-color:#fff4f4;font-weight:bold;">return</span><span
      style="color:#000000;background-color:#fff4f4;"> timeSpentAtThisLevel;</span></p><p
      style="margin:0;"><span style="color:#000000;">  }</span></p><p
      style="margin:0;"><span style="color:#000000;">}</span></p><p
      style="margin:0;"><span style="color:#000000;">
</span></p><p style="margin:0;"><span style="color:#000000;">--John
</span></p></div>
    </div>
    <p></p>
    <div class="moz-cite-prefix">On 08/08/2024 12:47, Thiago Milczarek
      Sayão wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAAP_wu=TuDzUCLWKRM83Rr_FQPPxK4U4zmF2wFx-LyZB8YarDQ@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">Nice! I will steal it if you don't mind.</div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">Em qua., 7 de ago. de 2024 às
          15:55, John Hendrikx <<a
            href="mailto:john.hendrikx@gmail.com" moz-do-not-send="true"
            class="moz-txt-link-freetext">john.hendrikx@gmail.com</a>>
          escreveu:<br>
        </div>
        <blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
          <div>
            <p>For detecting long running tasks on the FX thread, there
              are some other options which you can do as a user (but
              perhaps we can support it directly within FX).  I use this
              kind of code to detect long running things on the FX
              thread:</p>
            <div
style="background-color:rgb(255,255,255);padding:0px 0px 0px 2px">
              <div
style="color:rgb(0,0,0);background-color:rgb(255,255,255);font-family:Consolas;font-size:11pt;white-space:pre-wrap"><p
              style="margin:0px"><span style="color:rgb(0,0,0)">    </span><span
              style="color:rgb(63,95,191)">/**</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * Adds a slow event warning whenever an event takes more than 10 </span><span
style="color:rgb(63,95,191);text-decoration:underline wavy rgb(255,128,64)">ms</span><span
              style="color:rgb(63,95,191)"> to process.  Note</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * that time spent in nested event loops cannot be properly taken into account as time</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * spent in nested event loops will be part of the event that triggered it giving false</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * positives.  In order for this time to be accurately reflected, the methods to enter</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * a nested event loop in this class should be used instead of the ones in </span><span
              style="color:rgb(63,63,191)">{@link Platform}</span><span
              style="color:rgb(63,95,191)">.</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     *</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     * </span><span
              style="color:rgb(127,159,191);font-weight:bold">@param</span><span
              style="color:rgb(63,95,191)"> scene a Scene to which to add the slow event warning detection, cannot be null</span></p><p
              style="margin:0px"><span style="color:rgb(63,95,191)">     */</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">    </span><span
              style="color:rgb(0,0,160);font-weight:bold">public</span><span
              style="color:rgb(0,0,0)"> </span><span
              style="color:rgb(0,0,160);font-weight:bold">static</span><span
              style="color:rgb(0,0,0)"> </span><span
              style="color:rgb(0,0,160);font-weight:bold">void</span><span
              style="color:rgb(0,0,0)"> </span><span
style="text-decoration:underline solid rgb(0,102,204);color:rgb(0,102,204)">addSlowEventWarning</span><span
              style="color:rgb(0,0,0)">(Scene scene) {</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">      </span><span
              style="color:rgb(0,0,160);font-weight:bold">final</span><span
              style="color:rgb(0,0,0)"> EventDispatcher eventDispatcher = scene.getEventDispatcher();</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">      scene.setEventDispatcher(</span><span
              style="color:rgb(0,0,160);font-weight:bold">new</span><span
              style="color:rgb(0,0,0)"> EventDispatcher() {</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">        </span><span
              style="color:rgb(0,0,160);font-weight:bold">private</span><span
              style="color:rgb(0,0,0)"> ScheduledFuture<StackTraceElement[]> </span><span
              style="color:rgb(0,0,192)">future</span><span
              style="color:rgb(0,0,0)">;</span></p><p style="margin:0px"><span
              style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">        </span><span
              style="color:rgb(100,100,100)">@Override</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">        </span><span
              style="color:rgb(0,0,160);font-weight:bold">public</span><span
              style="color:rgb(0,0,0)"> Event dispatchEvent(Event event, EventDispatchChain tail) {</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,160);font-weight:bold">if</span><span
              style="color:rgb(0,0,0)">(</span><span
              style="color:rgb(0,0,192)">future</span><span
              style="color:rgb(0,0,0)"> != </span><span
              style="color:rgb(0,0,160);font-weight:bold">null</span><span
              style="color:rgb(0,0,0)">) {</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">            </span><span
              style="color:rgb(0,0,192)">future</span><span
              style="color:rgb(0,0,0)">.cancel(</span><span
              style="color:rgb(0,0,160);font-weight:bold">false</span><span
              style="color:rgb(0,0,0)">);</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          }</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,160);font-weight:bold">long</span><span
              style="color:rgb(0,0,0)"> startTime = System.</span><span
              style="color:rgb(0,0,0);font-style:italic">currentTimeMillis</span><span
              style="color:rgb(0,0,0)">();</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,192)">TIME_TRACKER</span><span
              style="color:rgb(0,0,0)">.enterNested(startTime);  </span><span
              style="color:rgb(63,127,95)">// nesting can happen in two ways, an event triggering another event, or when a nested event loop is entered</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          Event returnedEvent = eventDispatcher.dispatchEvent(event, tail);</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,160);font-weight:bold">long</span><span
              style="color:rgb(0,0,0)"> endTime = System.</span><span
              style="color:rgb(0,0,0);font-style:italic">currentTimeMillis</span><span
              style="color:rgb(0,0,0)">();</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,160);font-weight:bold">long</span><span
              style="color:rgb(0,0,0)"> timeSpentInNested = </span><span
              style="color:rgb(0,0,192)">TIME_TRACKER</span><span
              style="color:rgb(0,0,0)">.exitNested(endTime);</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(0,0,160);font-weight:bold">if</span><span
              style="color:rgb(0,0,0)">(timeSpentInNested > 10) {</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">            </span><span
              style="color:rgb(0,0,160);font-weight:bold">long</span><span
              style="color:rgb(0,0,0)"> total = endTime - startTime;</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">            </span><span
              style="color:rgb(0,0,192)">LOGGER</span><span
              style="color:rgb(0,0,0)">.warning(</span><span
              style="color:rgb(42,0,255)">"Slow Event (self/total: "</span><span
              style="color:rgb(0,0,0)"> + timeSpentInNested + </span><span
              style="color:rgb(42,0,255)">"/"</span><span
              style="color:rgb(0,0,0)"> + total + </span><span
              style="color:rgb(42,0,255)">" ms @ level "</span><span
              style="color:rgb(0,0,0)"> + </span><span
              style="color:rgb(0,0,192)">TIME_TRACKER</span><span
              style="color:rgb(0,0,0)">.getCurrentLevel() + </span><span
              style="color:rgb(42,0,255)">"): "</span><span
              style="color:rgb(0,0,0)"> + event);</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          }</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">  </span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">          </span><span
              style="color:rgb(127,0,85);font-weight:bold">return</span><span
              style="color:rgb(0,0,0)"> returnedEvent;</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">        }</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">      });</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">    }</span></p><p
              style="margin:0px"><span style="color:rgb(0,0,0)">
</span></p><p style="margin:0px"><span style="color:rgb(0,0,0)">--John
</span></p></div>
            </div>
            <div>On 05/08/2024 17:17, Thiago Milczarek Sayão wrote:<br>
            </div>
            <blockquote type="cite">
              <div dir="ltr">
                <div dir="ltr">Hi,
                  <div><br>
                  </div>
                  <div>Interesting idea. We have this problem specially
                    when Junior developers touch the code.</div>
                  <div><br>
                  </div>
                  <div>The other way around would be nice too - if some
                    I/O task executes on the FX thread.</div>
                  <div><br>
                  </div>
                  <div>This can make the OS think the application hanged
                    and offer to kill it, since it won't respond to
                    "pings". And I/O tasks processing time may vary
                    between installations. Also causes "white screens"
                    since it blocks painting.</div>
                  <div><br>
                  </div>
                  <div>-- Thiago.</div>
                </div>
                <br>
                <div class="gmail_quote">
                  <div dir="ltr" class="gmail_attr">Em seg., 5 de ago.
                    de 2024 às 11:59, Kevin Rushforth <<a
                      href="mailto:kevin.rushforth@oracle.com"
                      target="_blank" moz-do-not-send="true"
                      class="moz-txt-link-freetext">kevin.rushforth@oracle.com</a>>
                    escreveu:<br>
                  </div>
                  <blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
                    <div>
                      <blockquote type="cite">Wouldn't it be better to
                        implement this check in assert to avoid any
                        impact in production?</blockquote>
                      <br>
                      No. Using an assert in a case like this is an
                      anti-pattern. A call to assert in a library such
                      as JavaFX is only appropriate for checking an
                      invariant in internal logic. If we are going to go
                      down this route of doing a thread check when
                      mutating properties of "live" nodes, we will throw
                      the same IllegalStateException that is currently
                      thrown by some methods on Stage and Scene.<br>
                      <br>
                      As for the proposal itself, adding this check is
                      an interesting idea. We considered doing this back
                      in the JDK 7 (JavaFX 2) time frame, but decided
                      not to pursue it then. I think the idea is worth
                      further discussion. I would limit any thread
                      checking to setting the property. It would be too
                      restrictive (and largely unnecessary) to prevent
                      reading a property from the application thread.<br>
                      <br>
                      The things to consider would be:<br>
                      <br>
                      1. What is the performance hit of doing this check
                      on the setting of every property?<br>
                      2. What is the effect on bound properties?<br>
                      3. How intrusive is it in the code?<br>
                      4. Should we add a property to enable / disable
                      the thread check, possibly a three- or four-valued
                      property (allow|warn|debug?|deny), as was recently
                      done in JEP 471 for sun.misc.Unsafe memory access
                      methods. If so, what should the default be?<br>
                      <br>
                      My quick take is that if this can be done in a
                      minimally intrusive manner with low overhead, we
                      should consider pursing this. As for 4, my
                      preference would be to add a three- or four-valued
                      system property to control the check, with "warn"
                      as the default initially, changing the default to
                      "disallow" in a subsequent version. This would, of
                      course, require a lot of testing.<br>
                      <br>
                      -- Kevin<br>
                      <br>
                      <br>
                      <div>On 8/4/2024 8:40 PM, quizynox wrote:<br>
                      </div>
                      <blockquote type="cite">
                        <div dir="ltr">Hello,<br>
                          <br>
                          Wouldn't it be better to implement this check
                          in assert to avoid any impact in production?</div>
                        <br>
                        <div class="gmail_quote">
                          <div dir="ltr" class="gmail_attr">пн, 5 авг.
                            2024 г. в 03:30, John Hendrikx <<a
                              href="mailto:john.hendrikx@gmail.com"
                              target="_blank" moz-do-not-send="true"
                              class="moz-txt-link-freetext">john.hendrikx@gmail.com</a>>:<br>
                          </div>
                          <blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi
                            list,<br>
                            <br>
                            I know of quite some bugs and users that
                            have been bitten by the <br>
                            threading model used by JavaFX.  Basically,
                            anything directly or <br>
                            indirectly linked to an active Scene must be
                            accessed on the FX thread.  <br>
                            However, as FX also allows manipulating
                            nodes and properties before <br>
                            they're displayed, there can be no "hard"
                            check everywhere to ensure we <br>
                            are on the FX thread (specifically, in
                            properties).<br>
                            <br>
                            Now, I think this situation is annoying, as
                            a simple mistake where a <br>
                            Platform.runLater wrapper was forgotten
                            usually results in programs <br>
                            operating mostly flawlessly, but then fail
                            in mysterious and random and <br>
                            hard to reproduce ways.  The blame is often
                            put on FX as the resulting <br>
                            exceptions will almost never show the user
                            code which was the actual <br>
                            culprit.  It can result in FX being
                            perceived as unstable or buggy.<br>
                            <br>
                            So I've been thinking if there isn't
                            something we can do to detect these <br>
                            bugs originating from user code much
                            earlier, similar to the <br>
                            `ConcurrentModificationException` the
                            collection classes do when <br>
                            accessed in nested or concurrent contexts.<br>
                            <br>
                            I think it may be possible to have
                            properties check whether they're part <br>
                            of an active scene without too much of an
                            performance impact, possibly <br>
                            even behind a switch. It would work like
                            this:<br>
                            <br>
                            Properties involved with Nodes will have an
                            associated bean instance <br>
                            (`getBean`).  This is an object, but we
                            could check here if this <br>
                            instance implements an interface:<br>
                            <br>
                                  if (getBean() instanceof
                            MayBePartOfSceneGraph x) {<br>
                                        if (x.isPartOfActiveScene()
                            && !isOnFxThread()) {<br>
                                             throw new
                            IllegalStateException("Property must only be
                            <br>
                            used from the FX Application Thread");<br>
                                        }<br>
                                  }<br>
                            <br>
                            This check could be done on every set of the
                            property, and potentially <br>
                            on every get as well.  It should be
                            relatively cheap, but will expose <br>
                            problematic code patterns at a much earlier
                            stage.  There's a chance <br>
                            that this will "break" some programs that
                            seemed to be behaving <br>
                            correctly as well, so we may want to put it
                            behind a switch until such <br>
                            programs (or libraries) can be fixed.<br>
                            <br>
                            What do you all think?<br>
                            <br>
                            --John<br>
                            <br>
                            (*) Names of methods/interfaces are only
                            used for illustration purposes, <br>
                            we can think of good names if this moves
                            forward.<br>
                            <br>
                          </blockquote>
                        </div>
                      </blockquote>
                      <br>
                    </div>
                  </blockquote>
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              </div>
            </blockquote>
          </div>
        </blockquote>
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