[Qgis-developer] index in self.legend.groupLayerRelationship - different behavior between QGIS 1.8 and master?

[Martin Dobias]

On Fri, Oct 5, 2012 at 11:28 AM, Massimo <massimo.endrighi at geopartner.it> wrote:
>
> Thus I propose another solution based on QDomDocument similar to the one
> adopted into the QgsLegend::writeProject method.
> The returned document will contain only groups and layers names and indexes,
> like the following example:
> <!DOCTYPE Group Layer Hierarchy>
> <Legend>
>  <Group Name="G0" Index="0">
>   <Layer GroupIndex="0" Id="L020120904162647883" Name="L0" Index="0"/>
>   <Group Name="G1" Index="1">
>    <Group Name="G2" Index="2">
>     <Layer GroupIndex="2" Id="L120120904162647883" Name="L1" Index="1"/>
>     <Layer GroupIndex="2" Id="L220120904162647382" Name="L2" Index="2"/>
>     <Layer GroupIndex="2" Id="L320120904162644097" Name="L3" Index="3"/>
>    </Group>
>    <Group Name="G3" Index="3">
>     <Layer GroupIndex="3" Id="L40120904162648624" Name="L4" Index="4"/>
>    </Group>
>    <Group Name="G4" Index="4">
>     <Layer GroupIndex="4" Id="L520120904162649445" Name="L5" Index="5"/>
>    </Group>
>   </Group>
>  </Group>
> </Legend>

DOM approach would be fine for read-only access... for operations that
change the hierarchy (e.g. create group G5 within group G3, or move
layer L0 to group G4) it would be good to have classes that represent
the legend items, something like this:

class LegendInterface
{
  LegendItem* root(); // return top-level group (virtual)
}

class LegendItem
{
  ItemType type(); // either group or layer
  LegendItem* parent();
  QList<LegendItem*> children();
  int indexInParent();

  QString name();
  bool isExpanded();
  // + operations: rename, expand/collapse
}

class LegendGroup : LegendItem
{
  bool isVisible();
  // + operations: add child group, remove child group, show/hide ...
}

class LegendLayer : LegendItem
{
  QgsMapLayer* layer();
  bool isVisible();
  // + operations: move to different group, show/hide, refresh
symbology items ...
}

Like this we could get rid of much of the awkwardness of legend
interface. What do you think?

Martin