1. Building a Win32API Application
Raw access to the API

2. Resources The resource script (.rc file):
separate from code and dynamic data
compiled by a separate "Resource Compiler”
Resources determine the app’s “look and feel”
Examples:
Keyboard Accelerators, Bitmaps, Cursors, Dialog Box values, Fonts, Icons, Menus, String Tables
Separation of resources and program code
separates tasks of programmer & designer
can change user interface without touching code

3. Message Processing OS User input (mouse, keyboard) interrupt Msg loop:
GetMsg
DispatchMsg
msg
Message queue
msg
WndProc:
Evaluate msg,
take action

4. Basic program flow RegisterClassEx() CreateWindowEx()
(you provide a pointer to a function (usually called WndProc) which handles windows messages such as WM_CREATE, WM_COMMAND, etc.
CreateWindowEx()
returns a handle (pointer) to that control.
When the user clicks on a control you receive the WM_COMMAND message with the ID of that control.
Now handle that event. SetWindowText() and GetWindowText() allow you to set/get the text of any control.
ShowWindow() – displays the window
UpdateWindow() – updates the buffer
Start the message loop
OS then calls WndProc() - Process O/S's messages

5. Message loop MSG msg; // probably a global vbl
while (GetMessage(&msg, NULL, 0, 0)) {
TranslateMessage(&msg);
DispatchMessage(&msg); // tell OS to call my WndProc }
Notes:
the name of the window processor does NOT have to be "WndProc"
The two 0's are filter max/min values

6. About msg loops
O/S only creates a message queue for threads that perform operations which require one.
Must create a window before entering loop
GetMessage blocks until a filter-matching msg arrives See for a discussion of filter max/minvalues

7. Two 32-bit integer values (DWORDs)
Windows Messages
Two 32-bit integer values (DWORDs)
WPARAM – 2 16-bit WORDs inside a DWORD
LPARAM – a 32-bit DWORD
High-order and low order 16 bit WORDs
Extract each WORD with C macros
HIWORD(msg) gets high order
LOWORD(msg) gets low order
Meanings of HI and LO depend on the message

8. WinMain (replaces "main")
Win32API Programs
WinMain (replaces "main")
Primary entry point from OS
Procedure definition
Init
Message processing loop
WinProc (the "callback" function)
Performs actions to process messages
Switch statement based on msg#
Reentered once for each message
Pixel-by-pixel mouse move
Mouse-click, etc.

9. LPARAM & WPARAM LPARAM & WPARAM are datatypes window message design:
if the message takes a pointer,
the pointer is usually passed in the LPARAM,
if the message takes a handle or an integer,
it is passed in the WPARAM
if a message takes both,
the pointer goes in the LPARAM
the integer goes in the WPARAM

10. wParam & lParam Not every message uses these WParam values
Each message uses them differently.
WM_CLOSE message doesn't use either, so ignore both.
WM_COMMAND message uses both,
WParam contains two values,
HIWORD (WParam) - notification message (if applicable)
LOWORD (WParam) - control or menu id that sent the message.
LParam - HWND (window handle) of control which sent the message
NULL if the message isn't from a control.

11. example
Given, some function "fn", extract the string from the parameter (which is a pointer)
LRESULT class::fn (WPARAM wParam, LPARAM lParam)
{ //two steps required
LPTSTR lpMessage = (LPTSTR) lParam; // get ptr to string
CString s = lpMessage; // put string into needed type }

12. Important For WM_LBUTTONDOWN
Caution
Important  For WM_LBUTTONDOWN
Do not use the LOWORD or HIWORD macros to extract the x- and y- coordinates of the cursor position because these macros return incorrect results on systems with multiple monitors. Systems with multiple monitors can have negative x- and y- coordinates, and LOWORD and HIWORD treat the coordinates as unsigned quantities.

13. Two ways to inform a handler
Sending messages
Two ways to inform a handler
PostMessage
Enqueues message for handler
Retrieved with GetMsg
Immediate return to caller (it's a non-blocking call)
SendMessage
Sends message to handler (NO queueing)
BLOCKS until message received!!

14. WndProc Processes System Messages
LRESULT CALLBACK WndProc (HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
Typical operations:
If msg is WM_CREATE, call CreateWindow().
If msg is WM_QUIT, terminate
If msg is WM_PAINT, then redraw the window

15. When a menu item is selected Windows sends WM_COMMAND msg
Menus
When a menu item is selected
Windows sends WM_COMMAND msg
low word of wParam will be the item ID
extract with LOWORD(wParam)
then do
switch/case using LOWORD(wParam) value

16. Menus-1
Double-click your resource file's name (.rc)
Click on menu/menu-name
Enter names as needed

17. Double-click on "Resource.h" Scroll down to your menu items
Menus-2
Double-click on "Resource.h"
Scroll down to your menu items
Change the numeric values
Increment to the next available integer

18. Misc
Msg class specifies what kind of 'control' this window is e.g.; "edit" is a text box and "button" is a button.
Each control (a window) must have a unique ID
Use CString vs. STL string
Remainder of STL is OK in all apps
Note use of new datatypes, "_T", LPSTR
Recommended: use _T() macro vs. char or wchar_t
Use LPTSTR vs. char* or wchar_t*.
Then set MBCS or _UNICODE & rebuild w/o code changes.

19. ANSI (Windows-1252 = ASCII, ISO-8859) String declaration types
Character strings
Unicode
16 bit characters
Allows for international alphabets/symbols
ANSI (Windows-1252 = ASCII, ISO-8859)
String declaration types
"mystring" will use ANSI characters only
L"mystring" will use Unicode characters only
_T("mystring")
Unicode if #define _UNICODE
ANSI if not

20. Pointers to strings
DO NOT use char* or wchar*
Do use TCHAR* or LPTSTR
LPCTSTR is for usage like: const char*
Replace strcpy with _tcscpy
To convert a byte-buffer to character-size buffer, use: bufflen/sizeof(TCHAR)
pWnd->GetWIndowText(buffer, sizeof(buffer) / sizeof(TCHAR))

21. Callback skeleton for Win32API (for writing text)
LRESULT CALLBACK WndProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { PAINTSTRUCT ps; HDC hDC; TCHAR greeting[ ] = _T ("DJ says, 'Hello World!'"); TCHAR click_greeting[] = _T ("Saw your click"); RECT rect; switch (message) {case WM_PAINT: hDC = BeginPaint (…, &ps); nHeight = -MulDiv (PointSize, GetDeviceCaps (…, LOGPIXELSY), 72); GetClientRect (…, &rect); /* set_font and color where his comment is */ TextOut (…, 5, y_position, greeting, _tcslen (greeting)); EndPaint (…, &ps); DeleteObject (SelectObject (…, hTmp)); break; case WM_LBUTTONDOWN: InvalidateRect (…, NULL, FALSE); // TRUE => erase current content increment_line_num (…); set_font (hDC); TextOut (hDC, 5, y_position, click_greeting, _tcslen (click_greeting)); EndPaint (…, &ps); break; case WM_DESTROY: PostQuitMessage (0); break; default: return DefWindowProc (…, message, wParam, lParam); break; } return 0; // return to the OS from the callback function

22. subroutines
void increment_line_num (HDC hDC) { line_num++; y_position = (-1)*nHeight * line_num; // allow some space to avoid clipping // Remember that y-positions are more negative as you go DOWN the screen!! // i.e.; the top left corner is 0,0 }; Void SetFont () {if (line_num==0) hFont = CreateFont(nHeight, closest_match, escapement, orientation, FW_DONTCARE, no_italic, no_ul, no_xout, ANSI_CHARSET, OUT_TT_PRECIS, CLIP_DEFAULT_PRECIS, DRAFT_QUALITY, VARIABLE_PITCH, TEXT("Times")); // TEXT ≡ _T }

23. Callback skeleton (for drawing)
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {PAINTSTRUCT ps; RECT rect; switch (message) {case WM_LBUTTONDOWN: iPrevX = LOWORD(lParam); iPrevY = HIWORD(lParam); return 0; case WM_MOUSEMOVE: if (wParam & MK_LBUTTON) { hdc = GetDC (hwnd); MoveToEx (…, …, …, …); // update current position. Get old position back in parm 4 LineTo(…, …, …); iPrevX = LOWORD(lParam); iPrevY = HIWORD(lParam); ReleaseDC (hwnd, hdc); } return 0; case WM_LBUTTONUP: InvalidateRect (…, …, …); return 0; case WM_PAINT: GetClientRect (hwnd, &rect); hdc = BeginPaint (hwnd, &ps); InvalidateRect (…, …, …); EndPaint (hwnd, &ps); return 0; case WM_DESTROY: PostQuitMessage(0); return 0; return DefWindowProc(hwnd, message, wParam, lParam);

24. Draw a Circle
case ID_DRAW_CIRCLE: /* draw a blue-bordered magenta-crosshatched circle */ hDC = GetDC(hWnd); /* get a DC for painting */ hPen = CreatePen(PS_SOLID, 3, RGB(0, 0, 255)); /* blue pen */ hBrush = CreateHatchBrush(HS_DIAGCROSS, RGB(255, 0, 255)); hOldPen = (HPEN)SelectObject(hDC, hPen); /* select into DC & */ hOldBrush = (HBRUSH)SelectObject(hDC, hBrush); /* save old object */ Ellipse(hDC, 100, 30, 180, 110); /* draw circle */ SelectObject(hDC, hOldBrush); /* displace brush */ DeleteObject(hBrush); /* delete brush */ SelectObject(hDC, hOldPen); /* same for pen */ DeleteObject(hPen); ReleaseDC(hWnd, hDC); /* release the DC to end painting */ break;

25. Draw a Rectangle
case ID_DRAW_RECTANGLE: /* draw a red-bordered, cyan-filled rectangle */ hDC = GetDC(hWnd); /* get a DC for painting */ hPen = CreatePen(PS_SOLID, 3, RGB(255, 0, 0)); /* red pen */ hBrush = CreateSolidBrush(RGB(0, 255, 255)); /* cyan brush */ hOldPen = (HPEN)SelectObject(hDC, hPen); /* select into DC & */ hOldBrush = (HBRUSH)SelectObject(hDC, hBrush); /* save old object */ Rectangle(hDC, 15, 15, 80, 60); /* draw rectangle */ SelectObject(hDC, hOldBrush); /* displace new brush */ DeleteObject(hBrush); /* delete it from DC */ SelectObject(hDC, hOldPen); /* same for pen */ DeleteObject(hPen); ReleaseDC(hWnd, hDC); /* get rid of DC */ break;

26. Applying defaults ATOM MyRegisterClass(HINSTANCE hInstance) { }
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style= CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc= WndProc;
wcex.cbClsExtra= 0;
wcex.cbWndExtra= 0;
wcex.hInstance= hInstance;
wcex.hIcon= LoadIcon(hInstance, MAKEINTRESOURCE(IDI_WIN32DRAWEXAMPLE));
wcex.hCursor= LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground= (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName= MAKEINTRESOURCE(IDC_WIN32DRAWEXAMPLE);
wcex.lpszClassName= szWindowClass;
wcex.hIconSm= LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassEx(&wcex); }