Carla/source/modules/juce_events/native/juce_win32_HiddenMessageWindow.h

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

   This file is part of the JUCE library.
   Copyright (c) 2015 - ROLI Ltd.

   Permission is granted to use this software under the terms of either:
   a) the GPL v2 (or any later version)
   b) the Affero GPL v3

   Details of these licenses can be found at: www.gnu.org/licenses

   JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

   ------------------------------------------------------------------------------

   To release a closed-source product which uses JUCE, commercial licenses are
   available: visit www.juce.com for more information.

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

#ifndef JUCE_WIN32_HIDDENMESSAGEWINDOW_H_INCLUDED
#define JUCE_WIN32_HIDDENMESSAGEWINDOW_H_INCLUDED

//==============================================================================
class HiddenMessageWindow
{
public:
    HiddenMessageWindow (const TCHAR* const messageWindowName, WNDPROC wndProc)
    {
        String className ("JUCE_");
        className << String::toHexString (Time::getHighResolutionTicks());

        HMODULE moduleHandle = (HMODULE) Process::getCurrentModuleInstanceHandle();

        WNDCLASSEX wc = { 0 };
        wc.cbSize         = sizeof (wc);
        wc.lpfnWndProc    = wndProc;
        wc.cbWndExtra     = 4;
        wc.hInstance      = moduleHandle;
        wc.lpszClassName  = className.toWideCharPointer();

        atom = RegisterClassEx (&wc);
        jassert (atom != 0);

        hwnd = CreateWindow (getClassNameFromAtom(), messageWindowName,
                             0, 0, 0, 0, 0, 0, 0, moduleHandle, 0);
        jassert (hwnd != 0);
    }

    ~HiddenMessageWindow()
    {
        DestroyWindow (hwnd);
        UnregisterClass (getClassNameFromAtom(), 0);
    }

    inline HWND getHWND() const noexcept     { return hwnd; }

private:
    ATOM atom;
    HWND hwnd;

    LPCTSTR getClassNameFromAtom() noexcept  { return (LPCTSTR) (pointer_sized_uint) atom; }
};

//==============================================================================
class JuceWindowIdentifier
{
public:
    static bool isJUCEWindow (HWND hwnd) noexcept
    {
        return GetWindowLongPtr (hwnd, GWLP_USERDATA) == getImprobableWindowNumber();
    }

    static void setAsJUCEWindow (HWND hwnd, bool isJuceWindow) noexcept
    {
        SetWindowLongPtr (hwnd, GWLP_USERDATA, isJuceWindow ? getImprobableWindowNumber() : 0);
    }

private:
    static LONG_PTR getImprobableWindowNumber() noexcept
    {
        static LONG_PTR number = (LONG_PTR) Random::getSystemRandom().nextInt64();
        return number;
    }
};

//==============================================================================
class DeviceChangeDetector  : private Timer
{
public:
    DeviceChangeDetector (const wchar_t* const name)
        : messageWindow (name, (WNDPROC) deviceChangeEventCallback)
    {
        SetWindowLongPtr (messageWindow.getHWND(), GWLP_USERDATA, (LONG_PTR) this);
    }

    virtual ~DeviceChangeDetector() {}

    virtual void systemDeviceChanged() = 0;

    void triggerAsyncDeviceChangeCallback()
    {
        // We'll pause before sending a message, because on device removal, the OS hasn't always updated
        // its device lists correctly at this point. This also helps avoid repeated callbacks.
        startTimer (500);
    }

private:
    HiddenMessageWindow messageWindow;

    static LRESULT CALLBACK deviceChangeEventCallback (HWND h, const UINT message,
                                                       const WPARAM wParam, const LPARAM lParam)
    {
        if (message == WM_DEVICECHANGE
             && (wParam == 0x8000 /*DBT_DEVICEARRIVAL*/
                  || wParam == 0x8004 /*DBT_DEVICEREMOVECOMPLETE*/
                  || wParam == 0x0007 /*DBT_DEVNODES_CHANGED*/))
        {
            ((DeviceChangeDetector*) GetWindowLongPtr (h, GWLP_USERDATA))
                ->triggerAsyncDeviceChangeCallback();
        }

        return DefWindowProc (h, message, wParam, lParam);
    }

    void timerCallback() override
    {
        stopTimer();
        systemDeviceChanged();
    }
};

#endif   // JUCE_WIN32_HIDDENMESSAGEWINDOW_H_INCLUDED