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Improve "Actions" section in vector layer properties context help

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Signed-off-by: Tim Sutton <tim@linfiniti.com>
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Giuseppe Sucameli 2012-03-28 03:37:39 +02:00 committed by Tim Sutton
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resources/context_help/QgsVectorLayerProperties-en_US
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@ -104,11 +104,31 @@ The <label>Metadata</label> tab contains information about the layer, including
<h4>Actions</h4>
</a>
QGIS provides the ability to perform an action based on the attributes of a feature. This can be used to perform any number of actions, for example, running a program with arguments built from the attributes of a feature or passing parameters to a web reporting tool. <br/>
Actions are useful when you frequently want to run an external application or view a web page based on one or more values in your vector layer. An example is performing a search based on an attribute value.<p>
Actions are useful when you frequently want to run an external application or view a web page based on one or more values in your vector layer.<p>
The new implementation of actions uses the QGis expression engine to do evaluations. Each expression is evaluated and replaced by its result at runtime.<p>
An expression must be enclosed between <code>[%</code> and <code>%]</code>, anyway the GUI has some buttons which do that for you.
The <label>Insert expression...</label> button launches the <label>Expression builder</label> which allows to write an expression in a easy way, the <label>Insert field</label> button inserts into the action a placeholder like <code>[% "fieldname" %]</code> where fieldname is the name of the field selected in the dropdown list close to the button.<p>
See the User Guide for further information.
<h5>Using Actions</h5>
Actions can be invoked from the <label>Identify Results</label> dialog.
Actions can be invoked from the <label>Identify Results</label> dialog or using the <label>Run feature action</label> tool.<p>
Each of them adds a little set of custom expressions to the default set available in the <label>Expression builder</label>.<br/>
While running actions from the <label>Identify Results</label> dialog the custom expression <code>$currfield</code> will be replaced with the value of the selected field in the dialog, using the <label>Run feature action</label> tool the following custom expression are instead available:
<ul>
<li><code>$clickx</code> returns the x coordinate of the clicked point in canvas</li>
<li><code>$clicky</code> returns the y coordinate of the clicked point in canvas</li>
<li><code>$layerid</code> returns the ID of the selected layer in the legend</li>
</ul>
Note: the <label>Run feature action</label> tool execute the actions on all the matching features, the <label>Identify Results</label> allows you to select which feature to run action on.<p>
<h5>Action Examples</h5>
You can add some example actions by clicking on the <label>Add default actions</label> button.
<a name="diagram">
<h4>Diagram Overlay</h4>