[Qgis-developer] Editing the geometry of a feature

[Tim Sutton]

Hi Roger

Which provider and data format are you using? Not all formats support
write operations. I suspect you need to indicate to the layer that
editing is started and then commit your changes when editing is done.
Take a look at the code behind the start and stop editing options in
the legend it may give you some hints.

Regards

Tim

2007/10/22, Tait, Roger <roger.tait at ntu.ac.uk>:
> Hi,
>
>
>
> I have a QGis::WKBPoint based vector layer containing a single feature.
>
> I want to change the position of the feature using a single click of a button embedded in the tool bar.
>
> I have unsuccessfully tried to change the position using the following:
>
>
>
>
>
> void QgisApp::trackWayPoint()
>
> {
>
>
>
>    ...
>
>    ...
>
>
>
>    QgsFeature *feature = pointLayer->getFirstFeature(true,false);
>
>    QgsGeometry *geometry = feature->geometry();
>
>
>
>    unsigned char *wkb = geometry->wkbBuffer();
>
>
>
>    memcpy(&wkb[5], &newPosX, sizeof(double));
>
>    memcpy(&wkb[5]+sizeof(double), &newPosY, sizeof(double));
>
>
>
> }
>
>
>
>
>
>
>
> The correct feature and geometry are referenced however for some reason the new position is lost before the feature is drawn to screen.
>
> I have also tried commitAttributeChanges(const std::set<QString>& deleted, ... ,std::map<QString,QString> >& changed); without success.
>
>
>
> Please tell me how I can change the position of a feature?
>
>
>
> Thanks Roger
>
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Tim Sutton
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