JUCE/modules/juce_gui_extra/native/juce_mac_NSViewFrameWatcher.h

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

   This file is part of the JUCE library.
   Copyright (c) 2020 - 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 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-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.

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

#if JUCE_MAC

namespace juce
{

JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wundeclared-selector")
const auto nsViewFrameChangedSelector = @selector (frameChanged:);
JUCE_END_IGNORE_WARNINGS_GCC_LIKE

struct NSViewCallbackInterface
{
    virtual ~NSViewCallbackInterface() = default;
    virtual void frameChanged() = 0;
};

//==============================================================================
struct NSViewFrameChangeCallbackClass   : public ObjCClass<NSObject>
{
    NSViewFrameChangeCallbackClass()
        : ObjCClass ("JUCE_NSViewCallback_")
    {
        addIvar<NSViewCallbackInterface*> ("target");

        addMethod (nsViewFrameChangedSelector, frameChanged);

        registerClass();
    }

    static void setTarget (id self, NSViewCallbackInterface* c)
    {
        object_setInstanceVariable (self, "target", c);
    }

private:
    static void frameChanged (id self, SEL, NSNotification*)
    {
        if (auto* target = getIvar<NSViewCallbackInterface*> (self, "target"))
            target->frameChanged();
    }

    JUCE_DECLARE_NON_COPYABLE (NSViewFrameChangeCallbackClass)
};

//==============================================================================
class NSViewFrameWatcher : private NSViewCallbackInterface
{
public:
    NSViewFrameWatcher (NSView* viewToWatch, std::function<void()> viewResizedIn)
        : viewResized (std::move (viewResizedIn)), callback (makeCallbackForView (viewToWatch))
    {
    }

    ~NSViewFrameWatcher() override
    {
        [[NSNotificationCenter defaultCenter] removeObserver: callback];
        [callback release];
        callback = nil;
    }

    JUCE_DECLARE_NON_COPYABLE (NSViewFrameWatcher)
    JUCE_DECLARE_NON_MOVEABLE (NSViewFrameWatcher)

private:
    id makeCallbackForView (NSView* view)
    {
        static NSViewFrameChangeCallbackClass cls;
        auto* result = [cls.createInstance() init];
        NSViewFrameChangeCallbackClass::setTarget (result, this);

        [[NSNotificationCenter defaultCenter]  addObserver: result
                                                  selector: nsViewFrameChangedSelector
                                                      name: NSViewFrameDidChangeNotification
                                                    object: view];

        return result;
    }

    void frameChanged() override { viewResized(); }

    std::function<void()> viewResized;
    id callback;
};

} // namespace juce

#endif