ReleaseNotes.md

$>   geoPluginRun -volmgr -destroy -plugin DD4hep_AlignmentExample_nominal \
         -input file:${DD4hep_DIR}/examples/AlignDet/compact/Telescope.xml
DDCore/include/DD4hep/AlignmentsPrinter.h
DDCore/include/DD4hep/AlignmentsProcessor.h
DDCore/include/DD4hep/ConditionsPrinter.h
DDCore/include/DD4hep/ConditionsProcessor.h
DDCore/include/DD4hep/DetectorProcessor.h
   union {
     int64 key;
     struct {
       int32 item_key;
       int32 det_key;     // Needs to be the high word to have a properly ordered map
     } values;
   };
   det_key  = hash32(DetElement.path())
   item_key = hash32(condition-name)
   geoPluginRun -plugin DD4hepDetectorTypes -input <compact-file>
       <plugin name="DD4hep_SurfaceExamplePlugin">
          <argument value="SiTrackerBarrel"/>
          <argument value="aa=1*mm"/>
          <argument value="bb=2*cm"/>
          <argument value="cc=3*m"/>
       </plugin>
- output:
    SurfaceExamplePlugin: argument[0] = SiTrackerBarrel value = -1
    SurfaceExamplePlugin: argument[1] = aa=1*mm value = 0.1
    SurfaceExamplePlugin: argument[2] = bb=2*cm value = 2
    SurfaceExamplePlugin: argument[3] = cc=3*m value = 300
      context()->event().addExtension(pointer_to_object, typeid(TYPE), 0);
      or
      context()->event().addExtension<TYPE>(pointer_to_object);
      In the first case the object is NOT DELETED at the end of the event.
      In the second case the object is deleted.
- Accessing the context:
          TYPE* ctx = context()->event().extension<TYPE>(false);
      The boolean argument indicates if an exception should be thrown
      if the extension is not present ie. here no exception.
        <include ref="file-name"/>
    for the top level <lccdd> tags
       Parent tag    Included root tag  Data content
    -- <lccdd>       <define>           See below.
                     <detectors>
		     <detector>
		     <display>
		     <lccdd>            Nested includes (with DTD validation for Xerces-C)
    -- <define>      <define>           Set of constants
    -- <detectors>   <detector>         Single XML subdetector description
    -- <detectors>   <detectors>        Multiple XML subdetector descriptions
    -- <display>     <display>          Set ov visualization attributes

    DTD validation is only performed using Xerces-C for root tags <lccdd>.
    Example: tgeo::mm -> 0.1 (Geant3: cm, sec,  GeV, degree)
                 ::mm -> 1.0 (Geant4: mm, nsec, MeV, radian)
    I hope I got all translations right.
    Geant4                                   Geant3
    ----------------------------------------------------------------
    millimeter         mm=1,cm=10            centimeter  mm=0.1,cm=1
    nanosecond         s=1e9                 second      ns=1e-9,s=1
    Mega electron Volt GeV=1e3               GeV         GeV=1
    radian             rad=1                 degree      rad=180/pi

    Unclear to me was if in Geant3 steradian is also 2*2*pi or 2*2*180 degree.
     +----------------------------------------------------------------+
     |   I n s t a n c e   c o u n t e r s   b y    T Y P E I N F O   |
     +----------+---------+-------------------------------------------+
     |   Total  | Leaking |      Type identifier                      |
     +----------+---------+-------------------------------------------+
     |        13|        0|dd4hep::DetElement::Object
     |         3|        0|dd4hep::SensitiveDetector::Object
     |         3|        0|dd4hep::Readout::Object
     |         1|        0|dd4hep::OverlayedField::Object
     |         1|        0|dd4hep::CartesianField::Object
     ....
     Ideally the second column only has "0"s. Instances of 1 may be OK (singletons).
      $ > geoConverter -compact2description -input file:<compact-input-xml-file> -output <detector>.description
      $ > <SimDist>/scripts/slic.sh -o output.slcio -g SiD.description -m <geant4-macro>.mac -r 100