linjam/JuceLibraryCode/modules/juce_gui_basics/layout/juce_ResizableBorderComponent.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   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 5 End-User License
   Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
   27th April 2017).

   End User License Agreement: www.juce.com/juce-5-licence
   Privacy Policy: www.juce.com/juce-5-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
{

//==============================================================================
/**
    A component that resizes its parent component when dragged.

    This component forms a frame around the edge of a component, allowing it to
    be dragged by the edges or corners to resize it - like the way windows are
    resized in MSWindows or Linux.

    To use it, just add it to your component, making it fill the entire parent component
    (there's a mouse hit-test that only traps mouse-events which land around the
    edge of the component, so it's even ok to put it on top of any other components
    you're using). Make sure you rescale the resizer component to fill the parent
    each time the parent's size changes.

    @see ResizableCornerComponent

    @tags{GUI}
*/
class JUCE_API  ResizableBorderComponent  : public Component
{
public:
    //==============================================================================
    /** Creates a resizer.

        Pass in the target component which you want to be resized when this one is
        dragged.

        The target component will usually be a parent of the resizer component, but this
        isn't mandatory.

        Remember that when the target component is resized, it'll need to move and
        resize this component to keep it in place, as this won't happen automatically.

        If the constrainer parameter is not a nullptr, then this object will be used to
        enforce limits on the size and position that the component can be stretched to.
        Make sure that the constrainer isn't deleted while still in use by this object.

        @see ComponentBoundsConstrainer
    */
    ResizableBorderComponent (Component* componentToResize,
                              ComponentBoundsConstrainer* constrainer);

    /** Destructor. */
    ~ResizableBorderComponent() override;


    //==============================================================================
    /** Specifies how many pixels wide the draggable edges of this component are.

        @see getBorderThickness
    */
    void setBorderThickness (BorderSize<int> newBorderSize);

    /** Returns the number of pixels wide that the draggable edges of this component are.

        @see setBorderThickness
    */
    BorderSize<int> getBorderThickness() const;


    //==============================================================================
    /** Represents the different sections of a resizable border, which allow it to
        resized in different ways.
    */
    class Zone
    {
    public:
        //==============================================================================
        enum Zones
        {
            centre  = 0,
            left    = 1,
            top     = 2,
            right   = 4,
            bottom  = 8
        };

        //==============================================================================
        /** Creates a Zone from a combination of the flags in \enum Zones. */
        explicit Zone (int zoneFlags) noexcept;

        Zone() noexcept;
        Zone (const Zone&) noexcept;
        Zone& operator= (const Zone&) noexcept;

        bool operator== (const Zone&) const noexcept;
        bool operator!= (const Zone&) const noexcept;

        //==============================================================================
        /** Given a point within a rectangle with a resizable border, this returns the
            zone that the point lies within.
        */
        static Zone fromPositionOnBorder (Rectangle<int> totalSize,
                                          BorderSize<int> border,
                                          Point<int> position);

        /** Returns an appropriate mouse-cursor for this resize zone. */
        MouseCursor getMouseCursor() const noexcept;

        /** Returns true if dragging this zone will move the enire object without resizing it. */
        bool isDraggingWholeObject() const noexcept     { return zone == centre; }
        /** Returns true if dragging this zone will move the object's left edge. */
        bool isDraggingLeftEdge() const noexcept        { return (zone & left) != 0; }
        /** Returns true if dragging this zone will move the object's right edge. */
        bool isDraggingRightEdge() const noexcept       { return (zone & right) != 0; }
        /** Returns true if dragging this zone will move the object's top edge. */
        bool isDraggingTopEdge() const noexcept         { return (zone & top) != 0; }
        /** Returns true if dragging this zone will move the object's bottom edge. */
        bool isDraggingBottomEdge() const noexcept      { return (zone & bottom) != 0; }

        /** Resizes this rectangle by the given amount, moving just the edges that this zone
            applies to.
        */
        template <typename ValueType>
        Rectangle<ValueType> resizeRectangleBy (Rectangle<ValueType> original,
                                                const Point<ValueType>& distance) const noexcept
        {
            if (isDraggingWholeObject())
                return original + distance;

            if (isDraggingLeftEdge())   original.setLeft (jmin (original.getRight(), original.getX() + distance.x));
            if (isDraggingRightEdge())  original.setWidth (jmax (ValueType(), original.getWidth() + distance.x));
            if (isDraggingTopEdge())    original.setTop (jmin (original.getBottom(), original.getY() + distance.y));
            if (isDraggingBottomEdge()) original.setHeight (jmax (ValueType(), original.getHeight() + distance.y));

            return original;
        }

        /** Returns the raw flags for this zone. */
        int getZoneFlags() const noexcept               { return zone; }

    private:
        //==============================================================================
        int zone = centre;
    };

    /** Returns the zone in which the mouse was last seen. */
    Zone getCurrentZone() const noexcept                 { return mouseZone; }

protected:
    /** @internal */
    void paint (Graphics&) override;
    /** @internal */
    void mouseEnter (const MouseEvent&) override;
    /** @internal */
    void mouseMove (const MouseEvent&) override;
    /** @internal */
    void mouseDown (const MouseEvent&) override;
    /** @internal */
    void mouseDrag (const MouseEvent&) override;
    /** @internal */
    void mouseUp (const MouseEvent&) override;
    /** @internal */
    bool hitTest (int x, int y) override;

private:
    WeakReference<Component> component;
    ComponentBoundsConstrainer* constrainer;
    BorderSize<int> borderSize;
    Rectangle<int> originalBounds;
    Zone mouseZone;

    void updateMouseZone (const MouseEvent&);

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ResizableBorderComponent)
};

} // namespace juce