+--------------+
   |              |
   +---+----------+
   |   |          |
   |   |          |
   |   |          |
   +---+----------+

#include <CtrlLib/CtrlLib.h>

// Refer to "Browse topics - src - CtrlCore - Ctrl" to see how positioning works

// initial window width
const int window_width = 600;
// initial window heighth
const int window_height = 400;

// fixed height of top rectangle
const int fixed_top = 100;
// fixed width of left rectangle
const int fixed_left = 50;

class App : public TopWindow
{
private:
	StaticRect top_left_to_right;
	StaticRect bottom_left;
	StaticRect bottom_right;
	
public:
	App()
	{
		// create StaticRect "top_left_to_right" with variable width and fixed height
		// set up variable width from left to right edge of window
		top_left_to_right.HSizePos(); // same as HSizePos(0, 0)
		// set up fixed height from top edge of window
		top_left_to_right.TopPos(0, fixed_top);
		// add color to make rectangle distinguishable
		top_left_to_right.Color(Red);
		// add rectangle to window
		Add(top_left_to_right);
		
		// create StaticRect "bottom_left" with fixed width and variable height
		// set up fixed width from left edge of window with fixed size
		bottom_left.HSizePos(0, fixed_left);
		// set up variable height from bottom edge of top_left_to_right to bottom edge of window
		bottom_left.VSizePos(fixed_top); // same as VSizePos(fixed_top, 0)
		// add color to make rectangle distinguishable
		bottom_left.Color(Green);
		// add rectangle to window
		Add(bottom_left);

		// create StaticRect "bottom_right" with variable width and variable height
		// set up variable width from left edge of bottom_left to right edge of window
		bottom_right.HSizePos(fixed_left); // same as HSizePos(fixed_left, 0)
		// set up fixed height from bottom edge of top_left_to_right to bottom edge of window
		bottom_right.VSizePos(fixed_top); // same as VSizePos(fixed_top, 0)
		// add color to make rectangle distinguishable
		bottom_right.Color(Blue);
		// add rectangle to window
		Add(bottom_right);
	}
};

GUI_APP_MAIN
{
    // window smaller than the fixed sizes seems not reasonable
    Size min_size;
    // double minimal width - otherwise resizing conflicts with fixed width (try out!)
    min_size.cx = fixed_left * 2;
    // minimal height
    min_size.cy = fixed_top;
    
    App app;
    app.Title("Resize window to see what happens");

    // window size: left edge, top edge, width, height - 0, 0, ..., ... means "center window"
    app.SetRect(0, 0, window_width, window_height);
    app.SetMinSize(min_size);
    app.Sizeable();
    app.Run();
}

#include <CtrlLib/CtrlLib.h>

#define LAYOUTFILE <staticrect/layout.lay>
#include <CtrlCore/lay.h>

class App : public WithFramesLayout<TopWindow> {
public:

	typedef App CLASSNAME;

	App();
};

App::App()
{
	CtrlLayout(*this, "Resize window to see what happens");
	top_left_to_right.Color(Red);
	bottom_left.Color(Green);
	bottom_right.Color(Blue);
	this -> Sizeable();
}

GUI_APP_MAIN
{
    App app;
    app.Run();
}

FrameLeft<StaticRect> myframe;
Button b;
.....
mywidget.AddFrame(myframe);
myframe.Add(b.HSizePos().TopPos(0, 10));
.....