form properties not called during resize

Question

I have a .NET form with a boolean property called _isResized, which is set to true when the SizeChanged event is called and is set to false when the bool isResized() function is called.

ref class net_window : public System::Windows::Forms::Form
{
private:
    bool _isResized;
public:
    net_window(void)
        : _isResized(false){
        InitializeComponent();
    }

    void InitializeComponent(void){
        this->SizeChanged += gcnew EventHandler(this, &net_window::eventResized);
    }

    bool isResized(void){
        bool temp = _isResized;
        _isResized = false;
        return temp;
    }

    Void eventResized(Object^ sender, EventArgs^ e){
        _isResized = true;
    }
};

I also have an native C++ class called window which acts as a layer around the .NET form. This class is updated every frame of the main loop and uses the bool isResized() function of the form to see if the size has changed.

class Window
{
private:
    void* _net_window_handle;
    Window(){
        _net_window_handle = new gcroot<net_window^>;
        (*(gcroot<net_window^>*)_net_window_handle) = gcnew net_window;
    }
    ~Window(){
        delete _net_window_handle;
    }

    void update(void)//Called every frame.
    {
        if( (*(gcroot<net_window^>*)_element)->isResized() )
            //Do stuff.
    }
};

The delegate added to SizeChanged is called whenever the form is being resized, so _isResized is set to true as soon as the form size changes, but for some reason the thread of the main loop freezes whenever the window class uses the bool isResized() function, until the user has released the edge of the form and thus the resizing has finished.

Is it not possible to access .NET form values as long as it is being resized. Is there an alternative?

Thanks

EDIT

I use a main loop which calls System::Windows::Forms::Application::DoEvents() every frame. When the thread of the loop enters this function and the main window is resizing, it freezes. Is there a way to avoid this problem.

Answer 1

DoEvents strikes again. Windows pumps a modal message loop when the user starts dragging a window edge. Which means that your DoEvents loop isn't running anymore. Use a timer instead, SetTimer with a 15 or 31 msec interval is about right. Having your code respond to the Resize event directly of course highly preferred.

Thanks Hans Passant