juce_LassoComponent.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
template <class SelectableItemType>
class LassoSource
{
public:
    virtual ~LassoSource() = default;
 
    virtual void findLassoItemsInArea (Array<SelectableItemType>& itemsFound,
                                       const Rectangle<int>& area) = 0;
 
    virtual SelectedItemSet<SelectableItemType>& getLassoSelection() = 0;
};
 
 
//==============================================================================
template <class SelectableItemType>
class LassoComponent  : public Component
{
public:
    //==============================================================================
    LassoComponent() = default;
 
    //==============================================================================
    void beginLasso (const MouseEvent& e, LassoSource<SelectableItemType>* lassoSource)
    {
        jassert (source == nullptr);  // this suggests that you didn't call endLasso() after the last drag...
        jassert (lassoSource != nullptr); // the source can't be null!
        jassert (getParentComponent() != nullptr);  // you need to add this to a parent component for it to work!
 
        source = lassoSource;
 
        if (lassoSource != nullptr)
            originalSelection = lassoSource->getLassoSelection().getItemArray();
 
        setSize (0, 0);
        dragStartPos = e.getMouseDownPosition();
    }
 
    void dragLasso (const MouseEvent& e)
    {
        if (source != nullptr)
        {
            setBounds (Rectangle<int> (dragStartPos, e.getPosition()));
            setVisible (true);
 
            Array<SelectableItemType> itemsInLasso;
            source->findLassoItemsInArea (itemsInLasso, getBounds());
 
            if (e.mods.isShiftDown())
            {
                itemsInLasso.removeValuesIn (originalSelection); //  to avoid duplicates
                itemsInLasso.addArray (originalSelection);
            }
            else if (e.mods.isCommandDown() || e.mods.isAltDown())
            {
                auto originalMinusNew = originalSelection;
                originalMinusNew.removeValuesIn (itemsInLasso);
 
                itemsInLasso.removeValuesIn (originalSelection);
                itemsInLasso.addArray (originalMinusNew);
            }
 
            source->getLassoSelection() = SelectedItemSet<SelectableItemType> (itemsInLasso);
        }
    }
 
    void endLasso()
    {
        source = nullptr;
        originalSelection.clear();
        setVisible (false);
    }
 
    //==============================================================================
    enum ColourIds
    {
        lassoFillColourId       = 0x1000440, 
        lassoOutlineColourId    = 0x1000441, 
    };
 
    //==============================================================================
    void paint (Graphics& g) override
    {
        getLookAndFeel().drawLasso (g, *this);
 
        // this suggests that you've left a lasso comp lying around after the
        // mouse drag has finished.. Be careful to call endLasso() when you get a
        // mouse-up event.
        jassert (isMouseButtonDownAnywhere());
    }
 
    bool hitTest (int, int) override        { return false; }
 
private:
    //==============================================================================
    Array<SelectableItemType> originalSelection;
    LassoSource<SelectableItemType>* source = nullptr;
    Point<int> dragStartPos;
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (LassoComponent)
};
 
} // namespace juce