Problem with resizing (FormBorderStyle = None) - c++

Question

I got a problem. When I set FormBorderStyle to None to make the form stripped down, it loses its expandability. I need to make it so that I can drag the edge of the form and it expands. That is, return the ability to resizing. How I can make it?
I tried to google it but found solutions for C# and I need to do it in C++

Answer 1

Redrawing WinForm can meet your needs.
You need to set FormBorderStyle to None then use following code.
public:
MyForm(void)
{
InitializeComponent();
this->DoubleBuffered = true;
this->SetStyle(
System::Windows::Forms::ControlStyles::ResizeRedraw,
true);
//
//TODO: Add the constructor code here
//
}
int cGrip = 16; // Grip size
int cCaption = 32;
protected:
virtual void WndProc(System::Windows::Forms::Message %
m) override {
if (m.Msg == 0x84) { // Trap WM_NCHITTEST
Point pos = Point(m.LParam.ToInt32());
pos = this->PointToClient(pos);
if (pos.Y < cCaption) {
m.Result = (IntPtr)2; // HTCAPTION
return;
}
if (pos.X >= this->ClientSize.Width - cGrip &&
pos.Y >= this->ClientSize.Height - cGrip) {
m.Result = (IntPtr)17; // HTBOTTOMRIGHT
return;
}
if (pos.X <= this->ClientSize.Width - cGrip &&
pos.Y >= this->ClientSize.Height - cGrip) {
m.Result = (IntPtr)16;
return;
}
if (pos.X <= this->ClientSize.Width - cGrip &&
pos.Y <= this->ClientSize.Height - cGrip) {
m.Result = (IntPtr)13;
return;
}
if (pos.X >= this->ClientSize.Width - cGrip &&
pos.Y <= this->ClientSize.Height - cGrip) {
m.Result = (IntPtr)14;
return;
}
}
__super::WndProc(m);
}