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python/gui/qgscustomdrophandler.sip

@@ -12,12 +12,25 @@ class QgsCustomDropHandler : QObject
 {
 %Docstring
  Abstract base class that may be implemented to handle new types of data to be dropped in QGIS.
- Implementations will be used when a QgsMimeDataUtils.Uri has layerType equal to "custom",
- and the providerKey is equal to key() returned by the implementation.
 
- Alternatively, implementations can override the handleMimeData() or handleFileDrop()
- methods to handle QMimeData and file drops directly. Reimplementation of these methods
- does not rely on key() matching.
+ Implementations have three approaches they can use to handle drops.
+
+ 1. The simplest approach is to implement handeFileDrop() when they need to handle
+ dropped files (i.e. with mime type "text/uri-list").
+
+ 2. Reimplement handleCustomUriDrop() when they want to handle dropped custom
+ QgsMimeDataUtils.Uri entries, for instance handling dropping custom entries
+ from the browser tree (with mime type "application/x-vnd.qgis.qgis.uri"). In
+ this case the implementation's customUriProviderKey() must match the uri
+ entry's providerKey.
+
+ 3. Reimplement handleMimeData() to directly handle dropped QMimeData.
+ Subclasses should take care when overriding this method. When a drop event
+ occurs, Qt will lock the source application of the drag for the duration
+ of the drop event handling via handleMimeData() (e.g. dragging files from
+ explorer to QGIS will lock the explorer window until the drop handling has
+ been complete). Accordingly handleMimeData() implementations must return
+ quickly and defer any intensive or slow processing.
 
 .. versionadded:: 3.0
 %End
@@ -28,15 +41,25 @@ class QgsCustomDropHandler : QObject
   public:
     virtual ~QgsCustomDropHandler();
 
-    virtual QString key() const = 0;
+    virtual QString customUriProviderKey() const;
 %Docstring
-Type of custom URI recognized by the handler
+ Type of custom URI recognized by the handler. This must match
+ the URI entry's providerKey in order for handleCustomUriDrop()
+ to be called.
+
+.. seealso:: handleCustomUriDrop()
  :rtype: str
 %End
 
-    virtual void handleDrop( const QgsMimeDataUtils::Uri &uri ) const;
+    virtual void handleCustomUriDrop( const QgsMimeDataUtils::Uri &uri ) const;
 %Docstring
-Method called from QGIS after a drop event with custom URI known by the handler
+ Called from QGIS after a drop event with custom URI known by the handler.
+
+ In order for handleCustomUriDrop() to be called, subclasses must
+ also implement customUriProviderKey() to indicate the providerKey
+ value which the handler accepts.
+
+.. seealso:: customUriProviderKey()
 %End
 
     virtual void handleMimeData( const QMimeData *data );

src/app/qgisapp.cpp

@@ -1491,9 +1491,9 @@ void QgisApp::handleDropUriList( const QgsMimeDataUtils::UriList &lst )
     {
       Q_FOREACH ( QgsCustomDropHandler *handler, mCustomDropHandlers )
       {
-        if ( handler && handler->key() == u.providerKey )
+        if ( handler && handler->customUriProviderKey() == u.providerKey )
         {
-          handler->handleDrop( u );
+          handler->handleCustomUriDrop( u );
           break;
         }
       }

src/gui/qgscustomdrophandler.cpp

@@ -15,7 +15,12 @@
 
 #include "qgscustomdrophandler.h"
 
-void QgsCustomDropHandler::handleDrop( const QgsMimeDataUtils::Uri &uri ) const
+QString QgsCustomDropHandler::customUriProviderKey() const
+{
+  return QString();
+}
+
+void QgsCustomDropHandler::handleCustomUriDrop( const QgsMimeDataUtils::Uri &uri ) const
 {
   Q_UNUSED( uri );
 }

src/gui/qgscustomdrophandler.h

@@ -21,12 +21,25 @@
 
 /** \ingroup gui
  * Abstract base class that may be implemented to handle new types of data to be dropped in QGIS.
- * Implementations will be used when a QgsMimeDataUtils::Uri has layerType equal to "custom",
- * and the providerKey is equal to key() returned by the implementation.
  *
- * Alternatively, implementations can override the handleMimeData() or handleFileDrop()
- * methods to handle QMimeData and file drops directly. Reimplementation of these methods
- * does not rely on key() matching.
+ * Implementations have three approaches they can use to handle drops.
+ *
+ * 1. The simplest approach is to implement handeFileDrop() when they need to handle
+ * dropped files (i.e. with mime type "text/uri-list").
+ *
+ * 2. Reimplement handleCustomUriDrop() when they want to handle dropped custom
+ * QgsMimeDataUtils::Uri entries, for instance handling dropping custom entries
+ * from the browser tree (with mime type "application/x-vnd.qgis.qgis.uri"). In
+ * this case the implementation's customUriProviderKey() must match the uri
+ * entry's providerKey.
+ *
+ * 3. Reimplement handleMimeData() to directly handle dropped QMimeData.
+ * Subclasses should take care when overriding this method. When a drop event
+ * occurs, Qt will lock the source application of the drag for the duration
+ * of the drop event handling via handleMimeData() (e.g. dragging files from
+ * explorer to QGIS will lock the explorer window until the drop handling has
+ * been complete). Accordingly handleMimeData() implementations must return
+ * quickly and defer any intensive or slow processing.
  *
  * \since QGIS 3.0
  */
@@ -37,11 +50,25 @@ class GUI_EXPORT QgsCustomDropHandler : public QObject
   public:
     virtual ~QgsCustomDropHandler() = default;
 
-    //! Type of custom URI recognized by the handler
-    virtual QString key() const = 0;
+    /**
+     * Type of custom URI recognized by the handler. This must match
+     * the URI entry's providerKey in order for handleCustomUriDrop()
+     * to be called.
+     *
+     * \see handleCustomUriDrop()
+     */
+    virtual QString customUriProviderKey() const;
 
-    //! Method called from QGIS after a drop event with custom URI known by the handler
-    virtual void handleDrop( const QgsMimeDataUtils::Uri &uri ) const;
+    /**
+     * Called from QGIS after a drop event with custom URI known by the handler.
+     *
+     * In order for handleCustomUriDrop() to be called, subclasses must
+     * also implement customUriProviderKey() to indicate the providerKey
+     * value which the handler accepts.
+     *
+     * \see customUriProviderKey()
+     */
+    virtual void handleCustomUriDrop( const QgsMimeDataUtils::Uri &uri ) const;
 
     /**
      * Called when the specified mime \a data has been dropped onto QGIS.