GAM666 – Introduction To Game Programming

1. GAM666 – Introduction To Game Programming Windows Programming in C++ You must use special libraries (aka APIs – application programming interfaces) to make something other than a text-based program. The C++ choices are: • The original Windows SDK (Software Development Kit), a C library • MFC (Microsoft Foundation Classes), a sophisticated wrapper around the Windows SDK • ATL (Active Template Library), a light-duty wrapper around the Windows SDK • .NET, Microsoft's new technology

2. GAM666 – Introduction To Game Programming Why Use the Windows SDK? • Games generally take over the whole screen • Windows SDK is the simplest route to getting to the point where the screen has been taken over • .NET not univerally installed yet • We cover MFC/ATL/.NET in other courses

3. GAM666 – Introduction To Game Programming Basic Windows SDK Concepts • Write a WinMain(), not a classical main() • #include <windows.h> and probably <windowsx.h> • Often #define WIN32_LEAN_AND_MEAN before those #includes to cut down on further #includes of rarely used header files • Use many #define- and typedef-created data types from those header files (e.g. BOOL, HWND) • Use MS-specific declaration modifiers (e.g. WINAPI, CALLBACK) for functions

4. GAM666 – Introduction To Game Programming Basic Windows SDK Concepts Some Data Types are: • BOOL - a boolean value (TRUE or FALSE) • HWND - “handle” to a window • UINT - unsigned integer (32 bit) • WPARAM - “word” parameter (32 bit, originally 16, for passing an integer value, for example) • LPARAM - “long” parameter (32 bit, for passing an address, for example) • LRESULT - 32 bit return code from a function • HINSTANCE - “handle” to a running instance of a program

5. GAM666 – Introduction To Game Programming Messages • MS Windows uses Messages to communicate with the windows in a program • Every window in a windows program (which includes Controls, which are preprogrammed sub-windows like buttons and list boxes) has a Window Procedure, which is the code to handle any message that may be sent to the window • A window is customized by writing a custom window procedure for it, and supplying that procedure's address to Windows, which will call the procedure when needed.

6. GAM666 – Introduction To Game Programming Messages A window procedure is passed four things: • An HWND, identifying the window for whom the message is intended • A UINT, identifying which message it is • A WPARAM, containing a piece of data • An LPARAM, containing another piece of data (typically a pointer to more data, but not necessarily) The WPARAM and LPARAM meaning and usage varies between different messages

7. GAM666 – Introduction To Game Programming Messages Messages can come from: • Windows, based on user interaction or some other operating system activity • Another window (in the same program or another) • The program code itself, using either SendMessage() (waits until message is handled) or PostMessage() (puts the message on a queue but doesn't wait for it to be handled)

8. GAM666 – Introduction To Game Programming Messages • Controls (like buttons) have a window procedure that you don't see • Controls will send a WM_COMMAND message to the parent window when the user interacts with them, its WPARAM identifies the control and the operation • Macros LOWORD() and HIWORD() can extract the low- and high-order 16 bits of a WPARAM or LPARAM (or you can do the bit manipulation operations yourself)

9. GAM666 – Introduction To Game Programming Dialogs • A Dialog is a pop-up window that typically contains a bunch of controls • A dialog can be laid out using a resource file (extension .rc) to describe the controls, rather than creating the controls from within the C++ code • A header file is typically used to interlink the C++ code with the resource code by using symbolic names for IDs, since both languages understand the #define and #include syntax

10. GAM666 – Introduction To Game Programming Dialogs • A dialog is supplied the address of a Dialog Procedure, which is a window procedure specifically designed to handle a dialog (return value is BOOL rather than LRESULT) • Can get the HWND of a control on a dialog using GetDlgItem() • Can send a message to a control on a dialog using SendDlgItemMessage() or PostDlgItemMessage() [alternative to calling GetDlgItem() then Send/PostMessage()]

11. GAM666 – Introduction To Game Programming Dialogs • WM_INITDIALOG is the ID of the message sent to a dialog just after it is first created, giving you a chance to initialize its controls and do other one-time setup • WM_COMMAND is the ID of the message sent to a window when (among other things) one of its controls (ID in low order 16 bits of WPARAM) has something to pass along • IDCANCEL is a predefined control ID that corresponds to a user request to close the window

12. GAM666 – Introduction To Game Programming Dialogs • Each kind of control has different messages that can be sent to it • E.g. CB_GETCURSEL is the ID of the message you send to a ComboBox to get the index of the item in the combobox that is currently selected • E.g. LB_ADDSTRING is the ID of the message you send to a ListBox to add another string (passed in the LPARAM) to the listbox

13. GAM666 – Introduction To Game Programming Dialogs • Dialogs can be modal (application waits until dialog has been completed) or not (dialog and other application windows can be used at the same time) • Modal dialogs can be created by calling DialogBox() • Modal dialogs should be terminated by calling EndDialog()