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List: openjdk-openjfx-dev
Subject: Re: Node.lookupAll behaves differently before Scene is shown
From: Scott Palmer <swpalmer () gmail ! com>
Date: 2022-12-25 17:51:21
Message-ID: 24068185-D7DE-47F8-B2F1-5DD66DFB6636 () gmail ! com
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<html><head><meta http-equiv="content-type" content="text/html; \
charset=utf-8"></head><body dir="auto">Items added to a control like ListView, \
TableView, TreeView, are of an arbitrary type and are rendered via a CellFactory, not \
added as Nodes. (And in fact, as recent clarifications to the Javadoc mention, \
Nodes as items in the lists are strongly discouraged.). The items of a SplitPane are \
explicitly Nodes. So it isn't quite the same, but I get your \
point.<div><br></div><div>I think if anything a clarification in the Javadoc would \
help. I suspect changing the behaviour of lookup/lookupAll might be more \
problem than it is worth.</div><div><br></div><div>In my application, I've worked \
around the issue by deferring the call until the CSS has been applied through the \
usual flow, but I can confirm that explicitly calling applyCss() is also a valid \
workaround.</div><div><br><div dir="ltr">Scott</div><div dir="ltr"><br><blockquote \
type="cite">On Dec 24, 2022, at 7:05 PM, John Hendrikx \
<john.hendrikx@gmail.com> wrote:<br><br></blockquote></div><blockquote \
type="cite"><div dir="ltr">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<p>One thing you could try still, whether acceptable or not, is to
call `applyCss` on the border pane before calling the count
function.</p>
<p>As for the "and any children", I'm not sure how you should
interpret that. For a SplitPane, the nodes that are part of it
are in the items list (you don't add them as actual children).
The example in split pane also does something like
`splitPane.getItems().addAll(x, y, z)`. <br>
</p>
<p>Same may apply to items in a List / Table / TreeView -- are they
children?<br>
</p>
<p>--John<br>
</p>
<div class="moz-cite-prefix">On 24/12/2022 19:09, Scott Palmer
wrote:<br>
</div>
<blockquote type="cite" \
cite="mid:3BF24C3E-D6C0-4610-972F-C7CFC7EEBECB@gmail.com"> <meta \
http-equiv="content-type" content="text/html; charset=UTF-8"> That's interesting. \
It leads me to wonder what is the expected
result from a call to lookupAll in various scenarios. If, after
the window was showing, the SplitPane divider is pushed all the
way to one size such that the skin can potentially choose to leave
the hidden child out of the scene graph, presumable the current
lookupAll implementation would then fail to find it again.
<div><br>
</div>
<div>I think that either that's a bug, or it needs to be made
clearer in the documentation that non-rendered child nodes may
not be found. I personally lean toward "bug", as I think any
Node reachable through a parent Node's public API to access
child nodes should be found via Node.lookupAll. I suppose you
could argue that Scene.lookup is searching the scene graph in a
more literal sense and wouldn't find some Nodes.</div>
<div><br>
</div>
<div>The docs for Scene.lookup say:</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>"Looks
for any node within the scene graph based on the specified CSS
selector."</div>
<div><span style="caret-color: rgb(71, 71, 71); color: rgb(71, 71,
71); font-family: "DejaVu Serif", Georgia,
"Times New Roman", Times, serif; font-size: 14px;
background-color: rgb(255, 255, 255);"><br>
</span></div>
<div>The docs for Node.lookup say:</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>"Finds
this Node, or the first sub-node, based on the given CSS
selector"</div>
<div><br>
</div>
<div>The docs for Node.lookupAll say:</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>"Finds
all Nodes, including this one <b>and any children</b>, which
match the given CSS selector."</div>
<div><br>
<div>It doesn't mention the scene graph or if the node is
currently being rendered in a visible portion of the scene.
It explicitly states "any children".</div>
<div><br>
</div>
<div>So I'm saying it's a bug.</div>
<div><br>
</div>
<div><br>
</div>
<div>Scott</div>
<div><br>
<blockquote type="cite">
<div>On Dec 24, 2022, at 3:34 AM, John Hendrikx
<a class="moz-txt-link-rfc2396E" \
href="mailto:john.hendrikx@gmail.com"><john.hendrikx@gmail.com></a> \
wrote:</div> <br class="Apple-interchange-newline">
<div>
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<div>
<p>Hi,<br>
</p>
<p>In this case, this is because SplitPane doesn't
actually add its split items as children -- only its
Skin does this. Skins are AFAIK installed after a CSS
pass.</p>
<p>In the split pane case, I guess a Skin could choose
to completely leave out a child if its splitter
completely hides it (ie, dragged all the way to the
left or right if allowed).</p>
<p>This may be another case where it may make sense to
have both a document graph (logical graph) and a scene
graph as Michael Strauss mentioned here: <a \
class="moz-txt-link-freetext" \
href="https://mail.openjdk.org/pipermail/openjfx-dev/2022-June/034417.html" \
moz-do-not-send="true">https://mail.openjdk.org/pipermail/openjfx-dev/2022-June/034417.html</a></p>
<p>I doubt this is documented anywhere at all, it's one
of those things that doesn't work quite right in
JavaFX before a Scene is displayed.<br>
</p>
<p>--John<br>
</p>
<div class="moz-cite-prefix">On 23/12/2022 23:49, Scott
Palmer wrote:<br>
</div>
<blockquote type="cite" \
cite="mid:2C7CB4BB-5FC3-4185-9CA3-1202F804E407@gmail.com"> <meta \
http-equiv="content-type" content="text/html; charset=UTF-8">
I just want to make sure this is not expected
behaviour. I don't think so, the documentation for
lookupAll doesn't mention anything related, but maybe
I missed something somewhere else.
<div><br>
<div>I was just coding something to query the Scene
for all SplitPanes and save/restore the divider
positions for when my application is exiting and
launching and came across this issue.</div>
<div>My UI is fully constructed (at least in terms
of all the SplitPanes in the scene graph) before
it is shown.</div>
<div><br>
</div>
<div>This code:</div>
<div><br>
</div>
<div><span class="Apple-tab-span" \
style="white-space:pre"> </span><font face="Courier \
New">window.getScene().getRoot().lookupAll(".split-pane")</font><br> <div><br>
</div>
</div>
<div>returns a different number of Nodes if I call
it before showing the window versus after showing
the window. Specifically, if I call it before
showing the window it appears to only return the
first SplitPane found in the scene graph, but
calling it in an event handler for the window
shown event I get all three.</div>
<div><br>
</div>
<div>This can be demonstrated with the following
program:</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div>
<div><font face="Courier New">import
javafx.application.Application;</font></div>
<div><font face="Courier New">import
javafx.scene.Scene;</font></div>
<div><font face="Courier New">import
javafx.scene.control.SplitPane;</font></div>
<div><font face="Courier New">import
javafx.scene.control.TextArea;</font></div>
<div><font face="Courier New">import
javafx.scene.layout.BorderPane;</font></div>
<div><font face="Courier New">import
javafx.stage.Stage;</font></div>
<div><font face="Courier New">import
javafx.stage.Window;</font></div>
<div><font face="Courier New"><br>
</font></div>
<div><font face="Courier New">public class LookupAll
extends Application {</font></div>
<div><font face="Courier New"> Window \
mainWindow;</font></div>
<div><font face="Courier New"> </font></div>
<div><font face="Courier New"> public static void
main(String[] args) {</font></div>
<div><font face="Courier New"> \
launch(args);</font></div>
<div><font face="Courier New"> }</font></div>
<div><font face="Courier New"> </font></div>
<div><font face="Courier New"> \
@Override</font></div>
<div><font face="Courier New"> public void
start(Stage primaryStage) throws Exception {</font></div>
<div><font face="Courier New"> var bp \
= new BorderPane(new SplitPane(new TextArea(),new
SplitPane(new TextArea(),new SplitPane(new
TextArea()))));</font></div>
<div><font face="Courier New"> var \
scene = new Scene(bp);</font></div>
<div><font face="Courier New">
primaryStage.setScene(scene);</font></div>
<div><font face="Courier New"> \
mainWindow = primaryStage;</font></div>
<div><font face="Courier New">
System.out.println("Before showing:");</font></div>
<div><font face="Courier New">
countSplitPanes();</font></div>
<div><font face="Courier New">
primaryStage.setOnShown(we -> {</font></div>
<div><font face="Courier New"> \
System.out.println("After showing:");</font></div>
<div><font face="Courier New"> \
countSplitPanes();</font></div>
<div><font face="Courier New"> \
});</font></div>
<div><font face="Courier New">
primaryStage.show();</font></div>
<div><font face="Courier New"> }</font></div>
<div><font face="Courier New"> </font></div>
<div><font face="Courier New"> private void
countSplitPanes() {</font></div>
<div><font face="Courier New"> var \
splitPanes =
\
mainWindow.getScene().getRoot().lookupAll(".split-pane");</font></div>
<div><font face="Courier New">
System.out.printf("Found %d SpitPanes:
%s\n",splitPanes.size(), splitPanes);</font></div>
<div><font face="Courier New"> }</font></div>
<div><font face="Courier New">}</font></div>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>
<div>Before showing:</div>
<div>Found 1 SpitPanes:
[SplitPane@16bca2d9[styleClass=split-pane]]</div>
<div>After showing:</div>
<div>Found 3 SpitPanes:
[SplitPane@16bca2d9[styleClass=split-pane],
SplitPane@7078ef3c[styleClass=split-pane],
SplitPane@56a29626[styleClass=split-pane]]</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Scott</div>
<div><br>
</div>
</blockquote>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
</div></blockquote></div></body></html>
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