When generating .app bundle using JavaFX ANT tools I noticed when I run my app that there's an -Xmx1024 added (I see that using jvisualvm) and I have no idea where this is coming from.
My app ID is bloom
In ~/Library/Preferences and /Library/Preferences, I don't have any bloom.plist file, I also checked any starting with ca.antaki*
Here's fx:deploy params:
<fx:deploy verbose="true" width="800" height="600" outdir="distfx" outfile="Bloom" nativeBundles="all"><!--all -->
<fx:info title="Bloom" />
<fx:application id="Bloom" toolkit="swing" name="Bloom" mainClass="ca.antaki.www.bloom.app.Bloom" />
<fx:platform javafx="8.0+" ><!--basedir="" -->
<fx:jvmuserarg name="-Xmx" value="512m" />
<fx:jvmuserarg name="-Xms" value="512m" />
<fx:jvmarg value="-Xmx2048m" />
<fx:jvmarg value="-client" />
<fx:jvmarg value="-Dfile.encoding=UTF-8"/>

</fx:platform>
<fx:resources>
<fx:fileset dir="distfx" includes="*.jar" excludes="jfxrt.jar" />
<fx:fileset dir="lib" includes="*.jar" excludes="jfxrt.jar" />
</fx:resources>
</fx:callbacks>
</fx:deploy>

This ANT generates the following plist:

<?xml version="1.0" ?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
 <dict>
  <key>LSMinimumSystemVersion</key>
  <string>10.7.4</string>
  <key>CFBundleDevelopmentRegion</key>
  <string>English</string>
  <key>CFBundleAllowMixedLocalizations</key>
  <true/>
  <key>CFBundleExecutable</key>
  <string>Bloom</string>
  <key>CFBundleIconFile</key>
  <string>Bloom.icns</string>
  <key>CFBundleIdentifier</key>
  <string>bloom</string>
  <key>CFBundleInfoDictionaryVersion</key>
  <string>6.0</string>
  <key>CFBundleName</key>
  <string>Bloom</string>
  <key>CFBundlePackageType</key>
  <string>APPL</string>
  <key>CFBundleShortVersionString</key>
  <string>1.0.0</string>
  <key>CFBundleSignature</key>
  <string>????</string>
  <!-- See http://developer.apple.com/library/mac/#releasenotes/General/SubmittingToMacAppStore/_index.html
       for list of AppStore categories -->
  <key>LSApplicationCategoryType</key>
  <string>unknown</string>
  <key>CFBundleVersion</key>
  <string>100</string>
  <key>NSHumanReadableCopyright</key>
  <string>Unknown</string>
  <key>JVMRuntime</key>
  <string>jdk1.8.0_05.jdk</string>
  <key>JVMMainClassName</key>
  <string>ca.antaki.www.bloom.app.Bloom&lt;/string>
  <key>JVMAppClasspath</key>
  <string>EmailAddress.jar bcprov-jdk16-145.jar commons-codec-1.6.jar commons-httpclient-3.1.jar commons-lang-2.5.jar commons-logging-1.1.1.jar eventbus-1.4.jar glazedlists_java15-1.9.0.jar jai_imageio.jar jgoodies-binding-2.10.0.jar jgoodies-common-1.8.0.jar jgoodies-forms-1.8.0.jar jgoodies-validation-2.5.0.jar jhbasic.jar json_simple.jar log4j-1.2.17.jar metadata-extractor-2.6.4.jar restfb-1.6.11.jar scribe-1.3.5.jar slf4j-api-1.7.5.jar slf4j-simple-1.7.5.jar swingx-all-1.6.4.jar xmpcore.jar</string>
  <key>JVMMainJarName</key>
  <string>BloomFX.jar</string>
  <key>JVMPreferencesID</key>
  <string>bloom</string>
  <key>JVMOptions</key>
  <array>
    <string>-Xmx2048m</string>
    <string>-client</string>
    <string>-Dfile.encoding=UTF-8</string>
  </array>
  <key>JVMUserOptions</key>
    <dict>
      <key>-Xms</key>
      <string>512m</string>
      <key>-Xmx</key>
      <string>512m</string>
    </dict>
  <key>NSHighResolutionCapable</key>
  <string>true</string>
 </dict>
</plist>


When I run my app, I see the following in jvisualvm:
-Djava.library.path=/Users/carl/Java/progs/Bloom/distfx/bundles/Bloom.app/Contents/Java
-Djvm.preferences.id=bloom
-Xmx2048m
-Dfile.encoding=UTF-8
-Xms512m
-Xmx1024m

Basically the Xmx2048m value that I provided is overwritten with Xmx1024m. If I try to put -Xms2048m the VM won't start.
If I double click on my main executable JAR Xmx=1.8G

When I run my app through eclipse and provide -Xmx2048m this work fine.

I looked at the objective C launcher https://bitbucket.org/openjfxmirrors/openjfx-8-master-rt/src/b8d829dbef439f3ca2c307d6dbcced263e3f4193/deploy/packager/native/macosx/main.m?at=default but couldn't find anything useful.

Can you please tell me why I'm getting -Xmx1024m or point me to the code responsible for that.
Thanks for your help.