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DragAndDropContainer Class Reference

Enables drag-and-drop behaviour for a component and all its sub-components. More...

Inherited by Toolbar, and ToolbarItemPalette.

Public Member Functions

 DragAndDropContainer ()
 Creates a DragAndDropContainer.
 
virtual ~DragAndDropContainer ()
 Destructor.
 
void startDragging (const var &sourceDescription, Component *sourceComponent, Image dragImage=Image::null, bool allowDraggingToOtherJuceWindows=false, const Point< int > *imageOffsetFromMouse=nullptr)
 Begins a drag-and-drop operation.
 
bool isDragAndDropActive () const
 Returns true if something is currently being dragged.
 
var getCurrentDragDescription () const
 Returns the description of the thing that's currently being dragged.
 

Static Public Member Functions

static DragAndDropContainerfindParentDragContainerFor (Component *childComponent)
 Utility to find the DragAndDropContainer for a given Component.
 
static bool performExternalDragDropOfFiles (const StringArray &files, bool canMoveFiles)
 This performs a synchronous drag-and-drop of a set of files to some external application.
 
static bool performExternalDragDropOfText (const String &text)
 This performs a synchronous drag-and-drop of a block of text to some external application.
 

Protected Member Functions

virtual bool shouldDropFilesWhenDraggedExternally (const DragAndDropTarget::SourceDetails &sourceDetails, StringArray &files, bool &canMoveFiles)
 Override this if you want to be able to perform an external drag a set of files when the user drags outside of this container component.
 

Detailed Description

Enables drag-and-drop behaviour for a component and all its sub-components.

For a component to be able to make or receive drag-and-drop events, one of its parent components must derive from this class. It's probably best for the top-level component to implement it.

Then to start a drag operation, any sub-component can just call the startDragging() method, and this object will take over, tracking the mouse and sending appropriate callbacks to any child components derived from DragAndDropTarget which the mouse moves over.

Note: If all that you need to do is to respond to files being drag-and-dropped from the operating system onto your component, you don't need any of these classes: you can do this simply by overriding Component::filesDropped().

See Also
DragAndDropTarget

Constructor & Destructor Documentation

DragAndDropContainer::DragAndDropContainer ( )

Creates a DragAndDropContainer.

The object that derives from this class must also be a Component.

virtual DragAndDropContainer::~DragAndDropContainer ( )
virtual

Destructor.

Member Function Documentation

void DragAndDropContainer::startDragging ( const var sourceDescription,
Component sourceComponent,
Image  dragImage = Image::null,
bool  allowDraggingToOtherJuceWindows = false,
const Point< int > *  imageOffsetFromMouse = nullptr 
)

Begins a drag-and-drop operation.

This starts a drag-and-drop operation - call it when the user drags the mouse in your drag-source component, and this object will track mouse movements until the user lets go of the mouse button, and will send appropriate messages to DragAndDropTarget objects that the mouse moves over.

findParentDragContainerFor() is a handy method to call to find the drag container to use for a component.

Parameters
sourceDescriptiona string or value to use as the description of the thing being dragged - this will be passed to the objects that might be dropped-onto so they can decide whether they want to handle it
sourceComponentthe component that is being dragged
dragImagethe image to drag around underneath the mouse. If this is a null image, a snapshot of the sourceComponent will be used instead.
allowDraggingToOtherJuceWindowsif true, the dragged component will appear as a desktop window, and can be dragged to DragAndDropTargets that are the children of components other than this one.
imageOffsetFromMouseif an image has been passed-in, this specifies the offset at which the image should be drawn from the mouse. If it isn't specified, then the image will be centred around the mouse. If an image hasn't been passed-in, this will be ignored.
bool DragAndDropContainer::isDragAndDropActive ( ) const

Returns true if something is currently being dragged.

var DragAndDropContainer::getCurrentDragDescription ( ) const

Returns the description of the thing that's currently being dragged.

If nothing's being dragged, this will return a null var, otherwise it'll return the var that was passed into startDragging().

See Also
startDragging
static DragAndDropContainer* DragAndDropContainer::findParentDragContainerFor ( Component childComponent)
static

Utility to find the DragAndDropContainer for a given Component.

This will search up this component's parent hierarchy looking for the first parent component which is a DragAndDropContainer.

It's useful when a component wants to call startDragging but doesn't know the DragAndDropContainer it should to use.

Obviously this may return nullptr if it doesn't find a suitable component.

static bool DragAndDropContainer::performExternalDragDropOfFiles ( const StringArray files,
bool  canMoveFiles 
)
static

This performs a synchronous drag-and-drop of a set of files to some external application.

You can call this function in response to a mouseDrag callback, and it will block, running its own internal message loop and tracking the mouse, while it uses a native operating system drag-and-drop operation to move or copy some files to another application.

Parameters
filesa list of filenames to drag
canMoveFilesif true, the app that receives the files is allowed to move the files to a new location (if this is appropriate). If false, the receiver is expected to make a copy of them.
Returns
true if the files were successfully dropped somewhere, or false if it was interrupted
See Also
performExternalDragDropOfText
static bool DragAndDropContainer::performExternalDragDropOfText ( const String text)
static

This performs a synchronous drag-and-drop of a block of text to some external application.

You can call this function in response to a mouseDrag callback, and it will block, running its own internal message loop and tracking the mouse, while it uses a native operating system drag-and-drop operation to move or copy some text to another application.

Parameters
textthe text to copy
Returns
true if the text was successfully dropped somewhere, or false if it was interrupted
See Also
performExternalDragDropOfFiles
virtual bool DragAndDropContainer::shouldDropFilesWhenDraggedExternally ( const DragAndDropTarget::SourceDetails sourceDetails,
StringArray files,
bool &  canMoveFiles 
)
protectedvirtual

Override this if you want to be able to perform an external drag a set of files when the user drags outside of this container component.

This method will be called when a drag operation moves outside the Juce-based window, and if you want it to then perform a file drag-and-drop, add the filenames you want to the array passed in, and return true.

Parameters
sourceDetailsinformation about the source of the drag operation
fileson return, the filenames you want to drag
canMoveFileson return, true if it's ok for the receiver to move the files; false if it must make a copy of them (see the performExternalDragDropOfFiles() method)
See Also
performExternalDragDropOfFiles

The documentation for this class was generated from the following file: