Writing a Platform and GUI Toolkit Independent OpenGL Class

/*
 * =====================================================================================
 *
 *       Filename:  glviewmotifapp.cpp
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  10/17/2010 03:44:27 PM
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Sharjith N. (SSN), sharjith@gmail.com
 *        Company:  Sharjith's Inc.
 *
 * =====================================================================================
 */

#include <X11/Intrinsic.h>
#include <X11/Xutil.h>

#include <Xm/Xm.h>
#include <Xm/MainW.h>
#include <Xm/Form.h>
#include <Xm/DrawingA.h>
#include <Xm/PushB.h>
#include <Xm/RowColumn.h>
#include <Xm/CascadeB.h>
#include <Xm/MessageB.h>
#include <Xm/Label.h>

#include <cstdlib>
#include <iostream>
using std::cout;
using std::endl;

#include <GLView.h>

#define WIDTH    900
#define HEIGHT   700
#define MENU_QUIT       1
#define MENU_ABOUT		2

Widget toplevel, drawing_area, message_area;
static CGLView* pGLView = NULL;
Widget quit_option, about_option;

void show_about(Widget parent)
{
	Widget           dialog;
	Arg              arg[5];
	XmString         xms;
	int              n = 0;
#ifdef DEBUG
	cout << "show_about" << endl;
#endif

	xms = XmStringCreateLocalized ("GLView Test Motif Application");
	XtSetArg (arg[n], XmNmessageString, xms); n++;
	dialog = XmCreateInformationDialog (parent, "About", arg, n);
	XtVaSetValues (dialog, XmNdialogStyle, XmDIALOG_SYSTEM_MODAL,     
			NULL);

	XmStringFree (xms);
	XtUnmanageChild (XtNameToWidget (dialog, "Cancel"));
	XtManageChild (dialog);
}

void quitCB(Widget w,
		XtPointer client_data,
		XtPointer call_data)
{
	if(pGLView)
	{
		delete pGLView;
	}
	exit(0);
}

void quit_app(Widget parent)
{
	Widget         dialog;
	XmString       msg, yes, no;
	extern void    my_callback(Widget, XtPointer, XtPointer);

	dialog = XmCreateQuestionDialog (parent, "Question", NULL, 0);
	yes = XmStringCreateLocalized ("Yes");
	no = XmStringCreateLocalized ("No");
	msg = XmStringCreateLocalized ("Do you want to quit?");
	XtVaSetValues (dialog, XmNmessageString, msg, XmNokLabelString, yes,
			XmNcancelLabelString, no, NULL);
	XtAddCallback (dialog, XmNokCallback, quitCB, NULL);

	XmStringFree (yes);
	XmStringFree (no);
	XmStringFree (msg);
	XtUnmanageChild (XtNameToWidget (dialog, "Help"));
	XtManageChild (dialog);
}

void exposeCB(Widget w,
		int client_data,
		XmDrawingAreaCallbackStruct *cd)
{
#ifdef DEBUG
	cout << "exposeCB" << endl;
#endif
	if(pGLView != NULL)
	{
		pGLView->RenderScene();
	}

}

void resizeCB(Widget w,
		int client_data,
		XmDrawingAreaCallbackStruct *cd)
{
	Arg args[5];
	int n = 0;
	Dimension width, height;
	XtSetArg (args[n], XmNwidth, &width);  n++;
	XtSetArg (args[n], XmNheight, &height);  n++;
	XtGetValues (w, args, n);
#ifdef DEBUG
	cout << "resizeCB width=" << width << " height=" << height << endl;
#endif
	if(pGLView != NULL)
	{
		pGLView->Resize(width, height);
	}
}

void menuCB(Widget w,
		int client_data,
		XmAnyCallbackStruct *call_data)
/* handles menu options. */
{
	switch (client_data)
	{
		case MENU_QUIT:
			quit_app(drawing_area);
			break;
		case MENU_ABOUT:
			show_about(drawing_area);
			break;
	}
}

Widget make_menu_option(char *option_name,int client_data,Widget menu)
{
	int ac;
	Arg al[10];
	Widget b;

	ac = 0;
	XtSetArg(al[ac], XmNlabelString,
			XmStringCreateLtoR(option_name,
				XmSTRING_DEFAULT_CHARSET)); ac++;
	b=XtCreateManagedWidget(option_name,xmPushButtonWidgetClass,
			menu,al,ac);
	XtAddCallback (b, XmNactivateCallback, (XtCallbackProc)menuCB, (XtPointer)client_data);
	return(b);
}

Widget make_menu(char *menu_name, Widget menu_bar)
{
	int ac;
	Arg al[10];
	Widget menu, cascade;

	ac = 0;
	menu = XmCreatePulldownMenu (menu_bar, menu_name, al, ac);

	ac = 0;
	XtSetArg (al[ac], XmNsubMenuId, menu);  ac++;
	XtSetArg(al[ac], XmNlabelString,
			XmStringCreateLtoR(menu_name, XmSTRING_DEFAULT_CHARSET)); ac++;
	cascade = XmCreateCascadeButton (menu_bar, menu_name, al, ac);
	XtManageChild (cascade); 

	return(menu);
}

void create_menus(Widget menu_bar)
{
	int ac;
	Arg al[10];
	Widget menu;

	menu=make_menu("File",menu_bar);
	quit_option = make_menu_option("Quit",MENU_QUIT,menu);

	menu=make_menu("Help",menu_bar);
	about_option = make_menu_option("About",MENU_ABOUT,menu);

	/* Tell the menubar which button is the help menu  */
    if (menu = XtNameToWidget (menu_bar, "Help"))
        XtVaSetValues (menu_bar, XmNmenuHelpWidget, menu, NULL);
}

int main(int argc, char *argv[])
{
	Widget toplevel, main_w, form, label, menu_bar, command_w;
	Arg al[10];
	int ac;

	toplevel=XtInitialize(argv[0],"",NULL,0,&argc,argv);

	/* default window size. */
	ac=0;
	XtSetArg(al[ac],XmNheight, HEIGHT); ac++;
	XtSetArg(al[ac],XmNwidth, WIDTH); ac++;
	XtSetArg(al[ac], XmNcommandWindowLocation,
			XmCOMMAND_BELOW_WORKSPACE); ac++;
	XtSetValues(toplevel,al,ac);

	main_w = XmCreateMainWindow (toplevel, "main_w", al, ac);
	/* create a form widget. */
	ac=0;
	form=XtCreateManagedWidget("form",xmFormWidgetClass,
			main_w,al,ac);

	/* create a menu bar and attach it to the form. */
	ac=0;
	XtSetArg(al[ac], XmNtopAttachment,    XmATTACH_FORM); ac++;
	XtSetArg(al[ac], XmNrightAttachment, XmATTACH_FORM); ac++;
	XtSetArg(al[ac], XmNleftAttachment,   XmATTACH_FORM); ac++;
	menu_bar=XmCreateMenuBar(form,"menu_bar",al,ac);

	XtManageChild(menu_bar);

	create_menus(menu_bar);


	/* create a drawing area widget. */
	ac=0;

	XtSetArg(al[ac], XmNtopAttachment,    XmATTACH_WIDGET); ac++;
	XtSetArg(al[ac], XmNtopWidget, menu_bar); ac++;
	XtSetArg(al[ac], XmNrightAttachment, XmATTACH_FORM); ac++;
	XtSetArg(al[ac], XmNleftAttachment,   XmATTACH_FORM); ac++;
	XtSetArg(al[ac], XmNbottomAttachment,   XmATTACH_FORM); ac++;
	XtSetArg(al[ac], XmNeditMode,XmMULTI_LINE_EDIT); ac++;
	drawing_area=XtCreateManagedWidget("drawing_area", xmDrawingAreaWidgetClass, form,al,ac);

	XtAddCallback (drawing_area, XmNexposeCallback,
			(XtCallbackProc)exposeCB, NULL);
	XtAddCallback (drawing_area, XmNresizeCallback,
			(XtCallbackProc)resizeCB, NULL);


	/* message  area */
    message_area = XtVaCreateManagedWidget ("Ready",
	xmLabelWidgetClass, main_w,
	XmNalignment,   XmALIGNMENT_BEGINNING,
	NULL);

	XtManageChild (main_w);
	XtRealizeWidget(toplevel);

	pGLView = new CGLView();
	if(pGLView == NULL)
	{
		cout << "Failed to create CGLView!" << endl;
		exit(0);
	}
	else
	{
		Arg args[5];
		int n = 0;
		Dimension width, height;
		XtSetArg (args[n], XmNwidth, &width);  n++;
		XtSetArg (args[n], XmNheight, &height);  n++;
		XtGetValues (drawing_area, args, n);
		pGLView->SetWindow(XtDisplay(drawing_area), XtWindow(drawing_area));
		pGLView->SetupGLContext(true);
		pGLView->Resize(width, height);
	}


	XtMainLoop();
}