Windows API Tutorials

The constant, ID_MAIN, for instance, refers to the main program's icons (large and small in the same resource), the main menu, and the string with the Windows class name. ID_CAPTION refers to the window caption string. Such organization promotes code reusability, not to mention the ease of localization.

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, char * cmdParam, int cmdShow) {

_set_new_handler (& NewHandler);

// Using exceptions here helps debugging your program

// and protects from unexpected incidents.

try {

// Create top window class

TopWinClass topWinClass (ID_MAIN, hInst, MainWndProc);

// Is there a running instance of this program?

HWND hwndOther = topWinClass.GetRunningWindow ();

if (hwndOther != 0) {

::SetForegroundWindow (hwndOther);

if (::IsIconic (hwndOther)) ::ShowWindow (hwndOther, SW_RESTORE);

return 0;

}

topWinClass.Register ();

// Create top window

ResString caption (hInst, ID_CAPTION);

TopWinMaker topWin (topWinClass, caption);

topWin.Create ();

topWin.Show (cmdShow);

// The main message loop

MSG msg;

int status;

while ((status = ::GetMessage (&msg, 0, 0, 0)) != 0) {

if (status == –1) return –1;

::TranslateMessage (&msg);

::DispatchMessage (&msg);

}

return msg.wParam;

}

catch ( WinException e ) {

char buf [50];

wsprintf (buf, "%s, Error %d", e.GetMessage (), e.GetError ());

::MessageBox (0, buf, "Exception", MB_ICONEXCLAMATION | MB_OK);

}

catch (…) {

::MessageBox (0, "Unknown", "Exception", MB_ICONEXCLAMATION | MB_OK);

}

return 0;

}

Let's have a look at the WinClassclass. It encapsulates a Windows-defined structure called WNDCLASSEX and provides reasonable defaults for all its fields. It is derived from a simple WinSimpleClass class, which you might use to encapsulate some built-in Windows classes (like buttons, list views, etc.).

I have provided examples of methods that can be used to override the defaults. For instance, SetBgSysColorchanges the default background color of the user area of the window to one of the predefined system colors. The method SetResIconsloads appropriate icons from resources and attaches them to the window class. These icons will then appear in the upper left corner of the main window and on the windows' taskbar.

TopWinClassderived from WinClassmakes use of this method. It also assigns the menu to the top Window class.

class WinSimpleClass{

public:

WinSimpleClass (char const * name, HINSTANCE hInst) : _name (name), _hInstance (hInst) {}

WinSimpleClass (int resId, HINSTANCE hInst); char const * GetName () const {

return _name.c_str ();

}

HINSTANCE GetInstance () const {

return _hInstance;

}

HWND GetRunningWindow ();

protected:

HINSTANCE _hInstance;

std::string _name;

};

WinSimpleClass::WinSimpleClass(int resid, hinstance hinst) : _hInstance (hInst) {

ResString resStr (hInst, resId);

_name = resStr;

}

HWND WinSimpleClass::GetRunningWindow() {

HWND hwnd = :: FindWindow(getname (), 0);

if (:: IsWindow(hwnd)) {

HWND hwndPopup = :: GetLastActivePopup(hwnd);

if (:: IsWindow(hwndpopup)) hwnd = hwndPopup;

} else hwnd = 0;

return hwnd;

}

class WinClass: public WinSimpleClass{

public:

WinClass (char const * className, HINSTANCE hInst, WNDPROC wndProc);

WinClass (int resId, HINSTANCE hInst, WNDPROC wndProc);

void SetBgSysColor (int sysColor) {

_class.hbrBackground = reinterpret_cast (sysColor + 1);

}

void SetResIcons (int resId);

void Register ();

protected:

void SetDefaults ();

WNDCLASSEX_class;

};

WinClass::WinClass(char const * className, HINSTANCE hInst, WNDPROC wndProc) : WinSimpleClass (className, hInst) {

_class.lpfnWndProc = wndProc;

SetDefaults ();

}

WinClass::WinClass(int resId, HINSTANCE hInst, WNDPROC wndProc) : WinSimpleClass (resId, hInst) {

_class.lpfnWndProc = wndProc;

SetDefaults ();

}

void WinClass::SetDefaults() {

// Provide reasonable default values

_class.cbSize = sizeof (WNDCLASSEX);

_class.style = 0;

_class.lpszClassName = GetName ();

_class.hInstance = GetInstance ();

_class.hIcon = 0;

_class.hIconSm = 0;

_class.lpszMenuName = 0;

_class.cbClsExtra = 0;

_class.cbWndExtra = 0;

_class.hbrBackground = reinterpret_cast (COLOR_WINDOW + 1);

_class.hCursor = ::LoadCursor (0, IDC_ARROW);

}

void WinClass::SetResIcons(int resid) {

_class.hIcon = reinterpret_cast (

:: LoadImage(

_class.hInstance,

MAKEINTRESOURCE (resId),

IMAGE_ICON,

:: GetSystemMetrics(sm_cxicon),

:: GetSystemMetrics(sm_cyicon),

0));

// Small icon can be loaded from the same resource

_class.hIconSm = reinterpret_cast (

:: LoadImage(

_class.hInstance,

MAKEINTRESOURCE (resId),

IMAGE_ICON,

:: GetSystemMetrics(sm_cxsmicon),

:: GetSystemMetrics(sm_cysmicon),

0));

}

void WinClass::Register() {

if (:: RegisterClassEx(&_class) == 0) throw WinException ("Internal error: RegisterClassEx failed.");

}

class TopWinClass: public WinClass{

public:

TopWinClass (int resId, HINSTANCE hInst, WNDPROC wndProc);

};

TopWinClass::TopWinClass(int resId, HINSTANCE hInst, WNDPROC wndProc) : WinClass (resId, hInst, wndProc) {

SetResIcons (resId);

_class.lpszMenuName = MAKEINTRESOURCE (resId);