Button class

module winglib.buttons;
//---------------------------------------------------
private import core.runtime;
private import core.sys.windows.windows ;
private import core.sys.windows.commctrl ;
private import std.stdio ;
private import std.string ;
private import std.conv;
//----------------------------------------------------
private import winglib.commons ;
private import winglib.controls : Control;
private import winglib.events;

//------------------------------------------------------

private DWORD btnStyle = WS_CHILD | BS_NOTIFY | WS_TABSTOP | WS_VISIBLE;
private DWORD btnExStyle = 0;
private Button[] buttonList;
private static int btnNumber = 1;
private static int mIdNum = 101;
private static int subClsID = 1001;
//---------------------------------------------------------

class Button : Control {

    import winglib.window : Window;
    import winglib.application : hInst = gModuleInstance;
    import winglib.enums : ControlType ;
    //-----------------------------------------------------------------------

    ButtonEvents events ;
    alias events this;

    this(Window pParent){
        with(this){
            mText = format("Button%s", btnNumber.to!string());
            mWidth = 100;
            mHeight = 35;
            mXpos = 30;
            mYpos = 30;
            mParent = pParent;
            this.mFont = this.mParent.font;
            this.mControlType = ControlType.button;
            ++btnNumber;
        }
    }
//--------------------------------------------------------------------------------------------
    this(Window pParent, string btnText, int x, int y, int pWidth = 100, int pHeight = 35){
        with(this){
            mText = btnText;
            mWidth = pWidth;
            mHeight = pHeight;
            mXpos = x;
            mYpos = y;
            mParent = pParent;
            this.mFont = this.mParent.font;
            ++btnNumber;
            this.create();
        }
    }
//------------------------------------------------------------------------------------------
    ~this() {
        RemoveWindowSubclass(this.handle, this.btnWindProc, this.ownSubClsId);
        writeln("A button's subclass data is removed");
    }
//------------------------------------------------------------------------

    HWND create() {
        this.mHandle = CreateWindowEx(  btnExStyle,
                                        cast(LPCWSTR) WC_BUTTON,
                                        toUString(this.mText),
                                        btnStyle,
                                        this.mXpos,
                                        this.mYpos,
                                        this.mWidth,
                                        this.mHeight,
                                        this.mParent.handle,
                                        cast(HMENU) mIdNum,
                                        hInst,
                                        null);
        this.misHandleCreated = true;
        this.setFont();
        ++mIdNum;
        setSubClass();      \\-------------------This is the function which causes error.

        this.mParent.controls ~= this;
        buttonList~= this;
        return this.mHandle;
    }
    //-------------------------------------------------------------------------
    protected MsgHandler[] msgHandlerList;

    /// Adding event handler functions to button events.
    void addHandler(uint evt, EvtFuncPtr fnp){
        auto mh = MsgHandler();
        mh.handle = this.mHandle;
        mh.message = evt;
        mh.fnPtr = fnp;
        mh.isActive = true;
        this.msgHandlerList ~= mh;
    }
    //---------------------------------------------------------------------------------
    private :
    Button me;
    SUBCLASSPROC btnWindProc;
    int ownSubClsId ;
    //-----------------------------------------------------------------------
    /// Find the correct MsgHandler struct for given message and hwnd.
    MsgHandler findHandler(HWND hw, uint uMsg) {
        MsgHandler result ;
        foreach (MsgHandler mh; this.msgHandlerList) {
            if (mh.handle == hw && mh.message == uMsg) {
                result = mh;
                break;
            }
        }
        return result;
    }
    //------------------------------------------------------------------------

    void setSubClass() {
        this.btnWindProc = &btnWndProc;
        this.ownSubClsId = subClsID;
        SetWindowSubclass(this.mHandle, SUBCLASSPROC(&btnWndProc), UINT_PTR(subClsID), cast(DWORD_PTR) &this);
        ++subClsID;
    }
    //------------------------------------------------------------------------
}// End Button Class---------------------------------------------------------


extern(Windows)
private LRESULT btnWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam, UINT_PTR scID, DWORD_PTR refData) {
    try  {

        Button thisBtn = *cast(Button*) refData; //findButton(hWnd);
        if (thisBtn.msgHandlerList.length > 0) {
            MsgHandler mh = thisBtn.findHandler(hWnd, message);
            if(mh.isActive) {
                EventArgs e = EventArgs(hWnd, message, wParam, lParam);
                with(e) {
                    // msg = message;
                    // handle = hWnd;
                    wpm = wParam;
                    lpm = lParam;
                }
                mh.fnPtr(e);
                return 0 ;
            }
    }
}
    catch (Exception e) {}
    return DefSubclassProc(hWnd, message, wParam, lParam);
}

struct ButtonEvents {
    uint click = WM_LBUTTONDOWN;
    uint mouseEnter;
    uint mouseMove = WM_MOUSEMOVE;
    uint mouseLeave = WM_MOUSELEAVE;
}