FLTK MDI

application.cpp

#include "base.h"
#include "application.h"

MainApplication app;

MainApplication::MainApplication(const char* caption)
	: Fl_Double_Window(640, 480, caption)
	, menubar( 0, 0, 480, menuHeight)
	, workspace( 0, 0, 280, 60, "")
{
	menubar.box(FL_FLAT_BOX);
	menubar.menu(menu);
	
	workspace.color((Fl_Color) 30);
	workspace.box(FL_DOWN_BOX);
	
	workspace.align(Fl_Align(FL_ALIGN_CENTER|FL_ALIGN_INSIDE));
	workspace.labelcolor((Fl_Color) 0);
	
	resizable(this);
	show();
}
	
void MainApplication::resize(int x, int y, int width, int height) {
	menubar.resize(0, 0, w(), menuHeight);
	workspace.resize(1, menuHeight, w(), (h() - menuHeight) - 1);
	Fl_Double_Window::resize(x, y, width, height);
}

uint32_t MainApplication::menuHeight = 28;

Fl_Menu_Item MainApplication::menu[] = {
	{ "&File", 0, 0, 0, 0, (uchar)FL_NORMAL_LABEL, 0, 14, 0 },
	{ "&Edit", 0, 0, 0, 0, (uchar)FL_NORMAL_LABEL, 0, 14, 0 },
	{ "&Window", 0, 0, 0, 0, (uchar)FL_NORMAL_LABEL, 0, 14, 0 },
	{ "", 0, 0, 0, 0, (uchar)FL_NORMAL_LABEL, 0, 14, 0 },
	{ "&Help", 0, 0, 0, 0, (uchar)FL_NORMAL_LABEL, 0, 14, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 }
};

int main() {
	return Fl::run();
}

application.h

#include "child.h"

class MainApplication: public Fl_Double_Window {
	Fl_Menu_Bar menubar;
	Fl_Scroll workspace;
	static Fl_Menu_Item menu[];
	static uint32_t menuHeight;
	
	std::vector<MDIChildWindow*> children;
	friend class MDIChildWindow;
	
	MDIChildWindow *form = new MDIChildWindow( *this, 12, 12, 250, 100 );
	
public:
	MainApplication(const char* caption = "Application Window");
	virtual void resize(int x, int y, int width, int height);
};

child.cpp

#include "base.h"
#include "application.h"

uint32_t MDIChildWindow::titleHeight = 30;

MDIWindowDecorations::MDIWindowDecorations(MDIChildWindow& parent, const char* caption)
	: Fl_Box(parent.x(), parent.y(), parent.w(), parent.titleHeight, caption)
	, window(parent)
{
	
}

MDIChildWindow::MDIChildWindow(MainApplication& parent, int offsetX, int offsetY, int width, int h )
	: Fl_Group( parent.x() + offsetX, parent.y() + offsetY, width + offsetX, h + titleHeight + offsetY, "MDI Child")
	, titlebar( *this, "MDI Child" )
	, parent( parent )
{	
	box(FL_UP_BOX);
	color((Fl_Color)31);
	
	align(FL_ALIGN_CLIP|FL_ALIGN_INSIDE);
	clip_children(true);
	
	initialize();
	
	parent.children.push_back(this);
	show();
}

void MDIChildWindow::initialize() {
	titlebar.box(FL_FLAT_BOX);
	titlebar.labelcolor((Fl_Color)31);
	
	titlebar.color((Fl_Color)176);
	titlebar.align(292 | FL_ALIGN_CLIP | FL_ALIGN_INSIDE);
}

int MDIWindowDecorations::handle( int event_id ) {
	switch (event_id) {
	case FL_ENTER:
	case FL_LEAVE:
		break;
	
	case FL_PUSH:
	case FL_RELEASE:
		switch (event_id) {
		case FL_PUSH:
			handleMotion = true;
			originX = Fl::event_x();
			originY = Fl::event_y();
			break;
		
		case FL_RELEASE:
			handleMotion = false;
			break;
		}
		return 1;
		
		
	case FL_DRAG:
		int eventX = Fl::event_x(),
			eventY = Fl::event_y();
		
		if (handleMotion) {
			switch (Fl::event_button()) {
			case 1:
				window.position(eventX + window.x() - originX,
								eventY + window.y() - originY),
				
				window.redraw();
				window.parent.redraw();
				
				printf( "React to dragging. (%d, %d)\n", 
						Fl::event_x() + window.x() - originX, 
						Fl::event_y() + window.y() - originY);
				break;
			}
		}
	}
	
	return 0;
}

child.h

class MDIChildWindow;
class MainApplication;

class MDIWindowDecorations: public Fl_Box {
	MDIChildWindow& window;
	
protected:	
	bool handleMotion = false;
	uint32_t originX, originY;
	
	int handle( int event_id );
	
public:
	MDIWindowDecorations(MDIChildWindow& parent, const char* caption);
};

class MDIChildWindow: public Fl_Group {
	MDIWindowDecorations titlebar;
	MainApplication& parent;
	
	static uint32_t titleHeight;
	friend class MDIWindowDecorations;
	
	void initialize();
	
public:
	MDIChildWindow(MainApplication& parent, int offsetX, int offsetY, int w, int h );
};