theForger's Win32 API Programming Tutorial
Basics
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A Simple WindowExample: simple_window ![[images/simple_window.gif]](images/simple_window.gif)
Sometimes people come on IRC and ask "How do I make a window?"...Well it's not
entirely that simple I'm afraid. It's not difficult once you know what you're
doing but there are quite a few things you need to do to get a window to show up; And
they're more than can be simply explained over a chat room, or a quick note.
I always liked to do things first and learn them later...so here is the code to a simple window which will be explained shortly.
#include <windows.h>
const char g_szClassName[] = "myWindowClass";
// Step 4: the Window Procedure
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX wc;
HWND hwnd;
MSG Msg;
//Step 1: Registering the Window Class
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wc.lpszMenuName = NULL;
wc.lpszClassName = g_szClassName;
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if(!RegisterClassEx(&wc))
{
MessageBox(NULL, "Window Registration Failed!", "Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
// Step 2: Creating the Window
hwnd = CreateWindowEx(
WS_EX_CLIENTEDGE,
g_szClassName,
"The title of my window",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, 240, 120,
NULL, NULL, hInstance, NULL);
if(hwnd == NULL)
{
MessageBox(NULL, "Window Creation Failed!", "Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
ShowWindow(hwnd, nCmdShow);
UpdateWindow(hwnd);
// Step 3: The Message Loop
while(GetMessage(&Msg, NULL, 0, 0) > 0)
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return Msg.wParam;
}
For most part this is the simplest windows program you can write that actually
creates a functional window, a mere 70 or so lines. If you got the first example
to compile then this one should work with no problems.
Step 1: Registering the Window ClassA Window Class stores information about a type of window, including it's Window Procedure which controls the window, the small and large icons for the window, and the background color. This way, you can register a class once, and create as many windows as you want from it, without having to specify all those attributes over and over. Most of the attributes you set in the window class can be changed on a per-window basis if desired.A Window Class has NOTHING to do with C++ classes. const char g_szClassName[] = "myWindowClass";The variable above stores the name of our window class, we will use it shortly to register our window class with the system.
WNDCLASSEX wc;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wc.lpszMenuName = NULL;
wc.lpszClassName = g_szClassName;
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if(!RegisterClassEx(&wc))
{
MessageBox(NULL, "Window Registration Failed!", "Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
This is the code we use in The members of the struct affect the window class as follows:
We then call Step 2: Creating the Window
Once the class is registered, we can create a window with it. You should look
up the paramters for
HWND hwnd;
hwnd = CreateWindowEx(
WS_EX_CLIENTEDGE,
g_szClassName,
"The title of my window",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, 240, 120,
NULL, NULL, hInstance, NULL);
The first parameter (
Next we have the class name (
The parameter we have as
The next four parameters (
Next (
If you're wondering what this magic
Number one cause of people not knowing what the heck is wrong with their programs is probably
that they didn't check the return values of their calls to see if they failed or not.
if(hwnd == NULL)
{
MessageBox(NULL, "Window Creation Failed!", "Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
After we've created the window and checked to make sure we have a valid handle
we show the window, using the last parameter in ShowWindow(hwnd, nCmdShow); UpdateWindow(hwnd);
The Step 3: The Message LoopThis is the heart of the whole program, pretty much everything that your program does passes through this point of control.
while(GetMessage(&Msg, NULL, 0, 0) > 0)
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return Msg.wParam;
Step 4: the Window ProcedureIf the message loop is the heart of the program, the window procedure is the brain. This is where all the messages that are sent to our window get processed.
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
The window procedure is called for each message, the
When we call Step 5: There is no Step 5Phew. Well that's it! If I haven't explained stuff clearly enough yet, just hang in there and hopefully things will become more clear as we get into more usefull programs. |
![[x]](images/button_close.gif)
or types Alt-F4. This will cause the window
to be destroyed by default, but I like to handle it explicitly, since this is the perfect
spot to do cleanup checks, or ask the user to save files etc. before exiting the program.