source/modules/juce_gui_basics/mouse/juce_DragAndDropTarget.h

   1 /*
   2   ==============================================================================
   3
   4    This file is part of the JUCE library.
   5    Copyright (c) 2022 - Raw Material Software Limited
   6
   7    JUCE is an open source library subject to commercial or open-source
   8    licensing.
   9
  10    By using JUCE, you agree to the terms of both the JUCE 7 End-User License
  11    Agreement and JUCE Privacy Policy.
  12
  13    End User License Agreement: www.juce.com/juce-7-licence
  14    Privacy Policy: www.juce.com/juce-privacy-policy
  15
  16    Or: You may also use this code under the terms of the GPL v3 (see
  17    www.gnu.org/licenses).
  18
  19    JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
  20    EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
  21    DISCLAIMED.
  22
  23   ==============================================================================
  24 */
  25
  26 namespace juce
  27 {
  28
  29 //==============================================================================
  30 /**
  31     Components derived from this class can have things dropped onto them by a DragAndDropContainer.
  32
  33     To create a component that can receive things drag-and-dropped by a DragAndDropContainer,
  34     derive your component from this class, and make sure that it is somewhere inside a
  35     DragAndDropContainer component.
  36
  37     Note: If all that you need to do is to respond to files being drag-and-dropped from
  38     the operating system onto your component, you don't need any of these classes: instead
  39     see the FileDragAndDropTarget class.
  40
  41     @see DragAndDropContainer, FileDragAndDropTarget
  42
  43     @tags{GUI}
  44 */
  45 class JUCE_API  DragAndDropTarget
  46 {
  47 public:
  48     /** Destructor. */
  49     virtual ~DragAndDropTarget() = default;
  50
  51     //==============================================================================
  52     /** Contains details about the source of a drag-and-drop operation. */
  53     class JUCE_API  SourceDetails
  54     {
  55     public:
  56         /** Creates a SourceDetails object from its various settings. */
  57         SourceDetails (const var& description,
  58                        Component* sourceComponent,
  59                        Point<int> localPosition) noexcept;
  60
  61         /** A descriptor for the drag - this is set DragAndDropContainer::startDragging(). */
  62         var description;
  63
  64         /** The component from the drag operation was started. */
  65         WeakReference<Component> sourceComponent;
  66
  67         /** The local position of the mouse, relative to the target component.
  68             Note that for calls such as isInterestedInDragSource(), this may be a null position.
  69         */
  70         Point<int> localPosition;
  71     };
  72
  73     //==============================================================================
  74     /** Callback to check whether this target is interested in the type of object being
  75         dragged.
  76
  77         @param dragSourceDetails    contains information about the source of the drag operation.
  78         @returns                    true if this component wants to receive the other callbacks regarding this
  79                                     type of object; if it returns false, no other callbacks will be made.
  80     */
  81     virtual bool isInterestedInDragSource (const SourceDetails& dragSourceDetails) = 0;
  82
  83     /** Callback to indicate that something is being dragged over this component.
  84
  85         This gets called when the user moves the mouse into this component while dragging
  86         something.
  87
  88         Use this callback as a trigger to make your component repaint itself to give the
  89         user feedback about whether the item can be dropped here or not.
  90
  91         @param dragSourceDetails    contains information about the source of the drag operation.
  92         @see itemDragExit
  93     */
  94     virtual void itemDragEnter (const SourceDetails& dragSourceDetails);
  95
  96     /** Callback to indicate that the user is dragging something over this component.
  97
  98         This gets called when the user moves the mouse over this component while dragging
  99         something. Normally overriding itemDragEnter() and itemDragExit() are enough, but
 100         this lets you know what happens in-between.
 101
 102         @param dragSourceDetails    contains information about the source of the drag operation.
 103     */
 104     virtual void itemDragMove (const SourceDetails& dragSourceDetails);
 105
 106     /** Callback to indicate that something has been dragged off the edge of this component.
 107
 108         This gets called when the user moves the mouse out of this component while dragging
 109         something.
 110
 111         If you've used itemDragEnter() to repaint your component and give feedback, use this
 112         as a signal to repaint it in its normal state.
 113
 114         @param dragSourceDetails    contains information about the source of the drag operation.
 115         @see itemDragEnter
 116     */
 117     virtual void itemDragExit (const SourceDetails& dragSourceDetails);
 118
 119     /** Callback to indicate that the user has dropped something onto this component.
 120
 121         When the user drops an item this get called, and you can use the description to
 122         work out whether your object wants to deal with it or not.
 123
 124         Note that after this is called, the itemDragExit method may not be called, so you should
 125         clean up in here if there's anything you need to do when the drag finishes.
 126
 127         @param dragSourceDetails    contains information about the source of the drag operation.
 128     */
 129     virtual void itemDropped (const SourceDetails& dragSourceDetails) = 0;
 130
 131     /** Overriding this allows the target to tell the drag container whether to
 132         draw the drag image while the cursor is over it.
 133
 134         By default it returns true, but if you return false, then the normal drag
 135         image will not be shown when the cursor is over this target.
 136     */
 137     virtual bool shouldDrawDragImageWhenOver();
 138 };
 139
 140 } // namespace juce