[mapserver] Java VM Crashes using the Mapscript API

[Sean Gillies]

Fernando,

This is improper usage and will result in memory leaks. An instance of 
labelObj already holds references to many allocated colorObjs, and if 
you bind new instances to the labelObj the originals will not be freed. 
An example of proper usage is

     label.color.setRGB(0, 0, 0);

All colors should be undefined (-1,-1,-1) by default, so I am at a loss 
how you get a black label background.

Sean

On Jul 28, 2005, at 1:27 PM, Fernando Simon wrote:

> Hi all,
>     I found the same problem with black blackground here some weeks
> ago, I solved the problem when I defined a blank color objects for
> backgoundcolor and backgoundshadowcolor. Like:
>             lObjCor = new colorObj(-1, -1, -1, 0);
>             lObjLabel.setBackgroundcolor(lObjCor);
>             lObjLabel.setBackgroundshadowcolor(lObjCor);
>      So, using this way I can define all my layer using JavaMapscript.
> To check the "mapscript mapfile" you can save it to see all the
> definitions.
>      Thanks.
>
>
> Fernando Simon
>
>
> Citando Rick Innis <rick at INNIS.CA>:
>
>> Im revisiting this somewhat old thread to contribute a few insights
>>
>> I've found while dealing with the same issue, in the hope it saves
>>
>> someone else time and effort in the future. The thread "Mapscript
>>
>> API: for object manipulation, not object creation?" , from earlier
>>
>> this year, also has some info on this topic.
>>
>>>>
>>>> Christian reported a crash in layerObj.delete() which I
>>>> also detected.
>>>> I think I understood the following:
>>>>
>>>> Let's say, we have an initialized  mapObj mO;
>>>>
>>>> layerObj lO = new layerObj(mO);
>>>> // Say lO is the 5th layer now.
>>>> // Now lO.swigCMemOwn == true and
>>>> //     lO.swigCPtr points onto the mO.swigCPtr->layers[4]
>>>>
>>>> ...
>>>> // now the mapObj is deleted but the Java-layerObj continues to
>> live.
>>>> // the C-layer-Object mO.swigCPtr->layers[4] will deleted and
>>>> freed also!
>>>> mO.delete()
>>>> // From now on O.swigCPtr points into invalid piece of
>> C-memory.
>>>> ...
>>
>> I also encountered this a few months back but didn't have time to
>>
>> write it up so coherently. One workaround I was given by Sean was
>> to
>> use insertLayer() to add the layer, which makes a copy, allowing
>> the
>> allocated Java object to be disposed of cleanly. This also requires
>>
>> making and inserting styleObj and classObj instances:
>>
>>                  // initially, layer not associated with any map
>>                  layerObj myLayer = new layerObj(null);
>>                  // initialise layer
>>                  classObj myClass = new classObj(null);
>>                  styleObj myStyle  = new styleObj(null);
>>                  // initialize style, then insert into class
>>                  myClass.insertStyle(styleObj, -1);
>>                  // insert class into layer
>>                  myLayer.insertClass(myClass, -1);
>>                  // insert layer into map - makes copy!
>>                  int ret = map.insertLayer(annos, -1);
>>                  // get reference to inserted copy
>>                  myLayer = map.getLayer(i);
>>
>>
>> However, when  I started labelling my dynamic layers I found that
>> my
>> labels ended up with a black background.  The workaround I found
>> was
>> to define an empty layer in my map, including empty style info, and
>>
>> use cloneLayer() to make copies as needed.
>>
>> The layer definition looks like this:
>>
>>          # Blank generic annotation layer
>>          LAYER
>>                  NAME user_layer
>>                  STATUS OFF
>>                  TYPE POINT
>>                  CLASS
>>                      STYLE
>>                          COLOR 255 255 255
>>                      END
>>                      LABEL
>>                          COLOR 255 255 255
>>                      END
>>                  END
>>          END
>>
>> To use it, I grab the layer from the map, clone it, initialize it,
>>
>> and insert the clone into the map:
>>
>>                  layerObj myLayer = map.getLayerByName
>> ("blank_layer").cloneLayer();
>>                  // initialise...
>>                  int ret = map.insertLayer(annos, -1);
>>
>> The layer's type can be changed on the fly, so one definition
>> suffices for all layers.
>>
>>      --Rick.
>>
>
>
>
>
> -------------------------------------------------
>   Univali - Webmail - http://webmail.univali.br
>
>
--
Sean Gillies
sgillies at frii dot com
http://zcologia.com