///////////////////////////////////////////////////////////////////////////////
// Name:        src/msw/overlay.cpp
// Author:      Ali Kettab
// Copyright:   (c) 2022 Ali Kettab
// Licence:     wxWindows licence
///////////////////////////////////////////////////////////////////////////////

#include "wx/wxprec.h"

#include "wx/private/overlay.h"
#include "wx/dcclient.h"
#include "wx/dcmemory.h"
#include "wx/msw/dc.h"
#include "wx/msw/private.h"

namespace // anonymous
{

wxWindow* wxCreateOverlayWindow(const wxRect& rect)
{
    auto overlayWin = new wxWindow();

    overlayWin->MSWCreate
                (
                    overlayWin->GetMSWClassName(0),
                    nullptr, // No title
                    rect.GetPosition(),
                    rect.GetSize(),
                    WS_POPUP,
                    WS_EX_LAYERED |
                    WS_EX_TRANSPARENT |
                    WS_EX_NOACTIVATE
                );

    overlayWin->SetBackgroundStyle(wxBG_STYLE_PAINT);

    if ( !::SetLayeredWindowAttributes(GetHwndOf(overlayWin), 0, 128,
                                       LWA_COLORKEY | LWA_ALPHA) )
    {
        wxLogLastError(wxS("SetLayeredWindowAttributes()"));
    }

    // We intentionally don't use WS_VISIBLE when creating this window to avoid
    // stealing activation from the parent, so show it using SWP_NOACTIVATE now.
    ::SetWindowPos(GetHwndOf(overlayWin), nullptr, 0, 0, 0, 0,
                   SWP_NOSIZE |
                   SWP_NOMOVE |
                   SWP_NOREDRAW |
                   SWP_NOOWNERZORDER |
                   SWP_NOACTIVATE |
                   SWP_SHOWWINDOW);

    return overlayWin;
}

} // anonymous namespace

class wxOverlayImpl : public wxOverlay::Impl
{
public:
    wxOverlayImpl() = default;
    ~wxOverlayImpl() = default;

    virtual void Reset() override;
    virtual bool IsOk() override;
    virtual void Init(wxDC* dc, int x , int y , int width , int height) override;
    virtual void BeginDrawing(wxDC* dc) override;
    virtual void EndDrawing(wxDC* dc) override;
    virtual void Clear(wxDC* dc) override;

public:
    // window the overlay is associated with
    wxWindow* m_window = nullptr;
    // the overlay window itself. doesn't have to be child of any window
    // and is totally managed by this class
    wxWindow* m_overlayWindow = nullptr;

    wxRect      m_rect;

    // Drawing on the overlay window is achieved by hijacking the existing wxDC.
    // i.e. any drawing done through wxDC should go to the offscreen bitmap m_bitmap
    // which will eventually be drawn on the overlay window.
    wxBitmap    m_bitmap;
    wxMemoryDC  m_memDC;    // for memory dc construction only.
    WXHDC       m_hdc = 0;  // the original HDC

    wxDECLARE_NO_COPY_CLASS(wxOverlayImpl);
};

bool wxOverlayImpl::IsOk()
{
    return m_overlayWindow != nullptr;
}

void wxOverlayImpl::Init(wxDC* dc, int , int , int , int )
{
    if ( IsOk() )
        return;

    m_window = dc->GetWindow();

    m_rect.SetSize(m_window->GetClientSize());
    m_rect.SetPosition(m_window->GetScreenPosition());

    m_bitmap.CreateWithLogicalSize(m_rect.GetSize(), m_window->GetDPIScaleFactor());

    m_overlayWindow = wxCreateOverlayWindow(m_rect);
}

void wxOverlayImpl::BeginDrawing(wxDC* dc)
{
    wxCHECK_RET( IsOk(), wxS("overlay not initialized") );

    m_memDC.SelectObject(m_bitmap);

    auto impl = dc->GetImpl();
    auto msw_impl = static_cast<wxMSWDCImpl*>(impl);

    m_hdc = GetHdcOf(*msw_impl); // save the original hdc

    msw_impl->SetHDC(GetHdcOf(m_memDC));
    msw_impl->UpdateClipBox();
}

void wxOverlayImpl::EndDrawing(wxDC* dc)
{
    wxCHECK_RET( IsOk(), wxS("overlay not initialized") );

    m_memDC.SelectObject(wxNullBitmap);

    auto impl = dc->GetImpl();
    auto msw_impl = static_cast<wxMSWDCImpl*>(impl);

    msw_impl->SetHDC(m_hdc); // restore the original hdc
    msw_impl->UpdateClipBox();

    wxWindowDC winDC(m_overlayWindow);
    winDC.DrawBitmap(m_bitmap, wxPoint(0, 0));
}

void wxOverlayImpl::Clear(wxDC* WXUNUSED(dc))
{
    wxCHECK_RET( IsOk(), wxS("overlay not initialized") );

    // Note that the colour used here is the same one that we specify as
    // LWA_COLORKEY when creating the layered window, so it is actually
    // transparent.
    m_memDC.SetBackground(*wxBLACK);
    m_memDC.Clear();
}

void wxOverlayImpl::Reset()
{
    if ( IsOk() )
    {
        m_overlayWindow->Destroy();
        m_overlayWindow = nullptr;
    }
}

wxOverlay::Impl* wxOverlay::Create()
{
    return new wxOverlayImpl;
}