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win32 create a window question


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#1 Assassinbeast   Members   -  Reputation: 271

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Posted 10 October 2012 - 10:34 AM

Hello, im very new to win32 and at the moment im learning some stuff in this homepage http://www.directxtu...11/A-A/AA3.aspx

But can anybody tell me why i get red lines(errors) under my code on line:
32 (below the assignment operator)
39 (below L)
40 (below L)

[source lang="cpp"]// include the basic windows header file#include <windows.h>#include <windowsx.h>// the WindowProc function prototypeLRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);// the entry point for any Windows programint WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){ // the handle for the window, filled by a function HWND hWnd; // this struct holds information for the window class WNDCLASSEX wc; // clear out the window class for use ZeroMemory(&wc, sizeof(WNDCLASSEX)); // fill in the struct with the needed information wc.cbSize = sizeof(WNDCLASSEX); wc.style = CS_HREDRAW | CS_VREDRAW; wc.lpfnWndProc = WindowProc; wc.hInstance = hInstance; wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)COLOR_WINDOW; wc.lpszClassName = L"WindowClass1"; // <--------------- LINE 32 // register the window class RegisterClassEx(&wc); // create the window and use the result as the handle hWnd = CreateWindowEx(NULL, L"WindowClass1", // name of the window class <------------- LINE 39 L"Our First Windowed Program", // title of the window <-------- LINE 40 WS_OVERLAPPEDWINDOW, // window style 300, // x-position of the window 300, // y-position of the window 500, // width of the window 400, // height of the window NULL, // we have no parent window, NULL NULL, // we aren't using menus, NULL hInstance, // application handle NULL); // used with multiple windows, NULL // display the window on the screen ShowWindow(hWnd, nCmdShow); // enter the main loop: // this struct holds Windows event messages MSG msg; // wait for the next message in the queue, store the result in 'msg' while(GetMessage(&msg, NULL, 0, 0)) { // translate keystroke messages into the right format TranslateMessage(&msg); // send the message to the WindowProc function DispatchMessage(&msg); } // return this part of the WM_QUIT message to Windows return msg.wParam;}// this is the main message handler for the programLRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam){ // sort through and find what code to run for the message given switch(message) { // this message is read when the window is closed case WM_DESTROY: { // close the application entirely PostQuitMessage(0); return 0; } break; } // Handle any messages the switch statement didn't return DefWindowProc (hWnd, message, wParam, lParam);}[/source]

When i put the cursor on the assignment operator on line 32, it says:
Error: a value of type "const wchar_t *"Cannot be assigned to an entity of type "LPCSTR"

I actually tried to removed the L on line 32, 39 and 40.
Then i got no errors and could run the program and got the window to pop up.
But why on this directx tutorial homepage do they write L behind it?
I dont know if this is gonna be a big deal in the future when i program in win32, so i just wanna be sure if this is gonna be a big deal Posted Image
Hope you can help me... Thanks alot Posted Image

Edited by Assassinbeast, 10 October 2012 - 10:36 AM.


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#2 Radikalizm   Crossbones+   -  Reputation: 2793

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Posted 10 October 2012 - 10:53 AM

The L before a string literal means that the string should be represented with wide characters (wchar_t) instead of regular ANSI characters (char). If your compile options do not specify that you want to use wide unicode characters the windows API will assume you're using ANSI characters, hence the error you're getting.
The tutorial probably assumed that you would be using wide characters, but since you're not there's probably no harm in removing the L in front of the string.

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#3 Assassinbeast   Members   -  Reputation: 271

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Posted 10 October 2012 - 03:03 PM

The L before a string literal means that the string should be represented with wide characters (wchar_t) instead of regular ANSI characters (char). If your compile options do not specify that you want to use wide unicode characters the windows API will assume you're using ANSI characters, hence the error you're getting.
The tutorial probably assumed that you would be using wide characters, but since you're not there's probably no harm in removing the L in front of the string.


Ahh ok, thanks alot bro Posted Image

#4 SIC Games   Members   -  Reputation: 508

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Posted 10 October 2012 - 10:39 PM

also check to see if your Win32 application us being compiled in Multi-Byte code or in ASCII code - I believe that's it. This too makes the difference. I realized that as well. LPCSTR stands for Long Pointer Constant STRing. LPCWSTR stands for Long-Pointer Constant Wide STRing. Additional notes, L"blah blah blah" will convert the blah blah blah part into a Long-Pointer Constant Wide STRing. Because L is shortly defined as LPCWSTR. When you don't use the L this will create the window because you're implying the title of the window or what not is a Constant String (LPCSTR). :) Hope this helps!

Game Engine's WIP Videos - http://www.youtube.com/sicgames88





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