SDL_windows.h

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Date : 2013-10-18T00:13:51

Fixed bug 2139 - SDL_CreateWindow/WIN_GL_LoadLibrary fails due to external iconv not being able to convert path J?nis R?cis Brief history: We recently ported a game from SDL 1.2 to SDL 2. While doing Windows testing, I soon discovered that the game exits without opening a window with my cross-compiled SDL2.dll, but works great with the SDL2.dll from the MinGW SDK on libsdl.org. It was as simple as swapping out the DLLs to make it work. Running the game in Wine showed that the game actually does run, up until the call to SDL_CreateWindow, which fails and leads the game to print out an error: Failure to create window (LoadLibrary("OPENGL32.DLL"): (null)) Which basically says that there was no error, but maybe that's a Wine quirk. The error string originates in SDL_windowsopengl.c, in WIN_GL_LoadLibrary, which contains this piece of code: wpath = WIN_UTF8ToString(path); _this->gl_config.dll_handle = LoadLibrary(wpath); SDL_free(wpath); if (!_this->gl_config.dll_handle) { char message[1024]; SDL_snprintf(message, SDL_arraysize(message), "LoadLibrary(\"%s\")", path); return WIN_SetError(message); } After some digging, I discovered the culprit: WIN_UTF8ToString returns NULL. Why? Because it calls iconv_open from an iconv.dll that does not support the UCS-2-INTERNAL encoding. Why does the official SDL2.dll work? Because it calls no external iconv functions at all. It turns out that the Fedora MinGW infrastructure (from which I obtained the conventiently prebuilt iconv.dll) does not provide a DLL from libiconv, but instead provides a DLL from a minimal Windows library called win-iconv. Which knows a good bit, but doesn't know anything about UCS-2-INTERNAL: http://code.google.com/p/win-iconv/source/browse/trunk/win_iconv.c#155 So there are two problems here: 1) The error message is clearly useless, because LoadLibrary is an innocent bystander. Instead wpath should probably checked for NULL, and a more appropriate error should be set. Ideally something that makes it clear than an external iconv is causing trouble. 2) SDL doomed itself at the ./configure step, by finding an existing iconv and happily using it without confirming support for the mandatory encodings required by SDL. There are certainly a few easy ways out of the situation (although I didn't yet manage to figure out how to prevent ./configure from looking for external iconv), but this had me completely stomped for a good while, so I figured it's worth writing down if anything. (Search also found this, which talks a little about using UTF-16LE instead of UCS-2-INTERNAL: https://bugzilla.libsdl.org/show_bug.cgi?id=2075)

src/core/windows/SDL_windows.h

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

/* This is an include file for windows.h with the SDL build settings */

#ifndef _INCLUDED_WINDOWS_H
#define _INCLUDED_WINDOWS_H

#define WIN32_LEAN_AND_MEAN
#define STRICT
#ifndef UNICODE
#define UNICODE 1
#endif
#undef _WIN32_WINNT
#define _WIN32_WINNT  0x501   /* Need 0x410 for AlphaBlend() and 0x500 for EnumDisplayDevices(), 0x501 for raw input */

#include <windows.h>

/* Routines to convert from UTF8 to native Windows text */
#if UNICODE
#define WIN_StringToUTF8(S) SDL_iconv_string("UTF-8", "UTF-16LE", (char *)(S), (SDL_wcslen(S)+1)*sizeof(WCHAR))
#define WIN_UTF8ToString(S) (WCHAR *)SDL_iconv_string("UTF-16LE", "UTF-8", (char *)(S), SDL_strlen(S)+1)
#else
/* !!! FIXME: UTF8ToString() can just be a SDL_strdup() here. */
#define WIN_StringToUTF8(S) SDL_iconv_string("UTF-8", "ASCII", (char *)(S), (SDL_strlen(S)+1))
#define WIN_UTF8ToString(S) SDL_iconv_string("ASCII", "UTF-8", (char *)(S), SDL_strlen(S)+1)
#endif

/* Sets an error message based on GetLastError(). Always return -1. */
extern int WIN_SetError(const char *prefix);

/* Wrap up the oddities of CoInitialize() into a common function. */
extern HRESULT WIN_CoInitialize(void);
extern void WIN_CoUninitialize(void);

#endif /* _INCLUDED_WINDOWS_H */

/* vi: set ts=4 sw=4 expandtab: */

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