2. OpenGL in a Window System

Size: px

Start display at page:

Download "2. OpenGL in a Window System"

Dwain Strickland
6 years ago
Views:

1 2. OpenGL in a Window System OpenGL is purely a graphics API It provides no support for - performing windowing tasks - obtaining user input - rendering fonts Every windowing system must provide some library extensions to support OpenGL rendering - X Windows - GLX routines - MS Windows - WGL routines - OS/2 - PGL routines Windows libraries - Older libraries such as Xlib, Xt Intrinsics and SDK (Software Development Kit) largely written in C - Newer libraries are Object Oriented and make heavy use of inheritance (C++) OSF/Motif (Open Software Foundation) Microsoft Foundation Classes (MFC) Object Window Library (OWL) (Borland) E.R. Bachmann & P.L. McDowell MV 4202 Page 1 of 8

2 Most Windows libraries follow the smalltalk paradigm Programs were broken into three parts - Model, or database - Provided View of the data - Controller (manipulated the model and view) Controller shared between the windows system and the applications processing messages MFC - Document/View Architecture Motif - Gadgets and Widgets Windows programming is done using Interactive Development Tools (IDT s) such as - RapidApp - MicroSoft Visual C++ - Borland C++ These authoring tools help to reduce the learning curve for windows programming. E.R. Bachmann & P.L. McDowell MV 4202 Page 2 of 8

3 Microsoft Windows Windows programs following the event-driven programming model - Applications respond to events by processing messages sent by the operating system - WinMain is the entry point for a Windows program Creates a window Enters a messaging processing loop - The window procedure processes messages sent to the window of an application In Windows 9x, mouse and keyboard messages are first buffered in hardware - After buffering, messages are passed to the appropriate thread message queue - i.e., each application has its own queue Windows 9x uses preemptive scheduling to distribute processor time among active processes Applications process messages through - functions local to the application - API functions in the Windows kernel E.R. Bachmann & P.L. McDowell MV 4202 Page 3 of 8

4 API functions are contained in dynamic link libraries (DLL s) Messages Windows 9x defines 200 different messages - Each message name begins with WM_ - Programmers may define their own messages Messages contain four parts - window handle unique identifier for the targeted window - message identifier numeric value which identifies the message type - wparam (Word Parameter) bit flags identifying the state of the control and shift keys and the mouse buttons - lparam (long Parameter) Two 16 bit values describing the location of the mouse E.R. Bachmann & P.L. McDowell MV 4202 Page 4 of 8

5 Microsoft Foundation Class (MFC) Library Places an object-oriented wrapper around the Windows API - Version 4 consists of nearly 200 classes - Provides an application framework - Windows API is called through class member functions Variable Naming Convention Names begin with one or more lowercase characters identifying the data type - prefixes are sometimes combined - m_ indicates a class data member c dw h l i p str w wnd char DWORD handle LONG int pointer CString WORD CWnd E.R. Bachmann & P.L. McDowell MV 4202 Page 5 of 8

6 Document/View Architecture MFC applications should be written in the document/ view architecture framework Document objects: - abstract representation of a program s data - Base class: CDocument View objects: - Present views of the program s data - Base class: CView CWinApp, CFrameWnd, and CDoctemplate work in conjunction with CDocument and CView to complete the framework MFC Class Hierarchy The majority of MFC classes are derived from CObject Application Architecture Classes Basic architectural elements of a program - CWinApp,CDocument,CCmdTarget E.R. Bachmann & P.L. McDowell MV 4202 Page 6 of 8

7 Window Classes Encapsulates the properties of a window - default handling of many messages - member functions perform window operations - CWnd, CFrameWnd, CView, CDialog GDI (Graphics Device Interface) Classes Encapsulates the functionality of the Windows Device Context - CDC File Classes Provide object-oriented interface to files - CFile Exception Classes Exception classes designed to work with try/throw/ catch of C++ - CException OLE Classes Abstract the OLE protocol E.R. Bachmann & P.L. McDowell MV 4202 Page 7 of 8

8 Database Classes Abstract the Open Database Connectivity (ODBC) API Threading Classes Encapsulate threads of execution and aid in synchronizing concurrent threads - CWinThread, CSyncObject Collection Classes and Templates Class library support for common data structures - CByteArray, CPtrArray, CStringArray General-Purpose Classes Simple data types - CString, CPoint, CSize, CRect, Ctime, CtimeSpan Afx Functions Non-member helper functions - AfxAbort, AfxBeginThread, AfxEndThread,AfxFormatString1, AfxMessageBox, AfxGetApp, AfxGetAppName, AfxGetMainWnd, AfxGetInstanceHandle, AfxRegisterWndClass E.R. Bachmann & P.L. McDowell MV 4202 Page 8 of 8

Module 2: Getting Started with Visual C AppWizard

Module 2: Getting Started with Visual C++ 6.0 AppWizard Program examples compiled using Visual C++ 6.0 (MFC 6.0) compiler on Windows XP Pro machine with Service Pack 2. Topics and sub topics for this Tutorial