Added a README file regarding WinRT support

To note, this file is currently formatted with CRLF line endings, rather than
LF, to allow the file to be viewed with Notepad.

src/filesystem/winrt/SDL_sysfilesystem.cpp

@@ -0,0 +1,174 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2014 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.
+*/
+#include "../../SDL_internal.h"
+
+/* TODO, WinRT: include copyright info in SDL_winrtpaths.cpp
+   TODO, WinRT: remove the need to compile this with C++/CX (/ZW) extensions, and if possible, without C++ at all
+*/
+
+#ifdef __WINRT__
+
+extern "C" {
+#include "SDL_filesystem.h"
+#include "SDL_error.h"
+#include "SDL_stdinc.h"
+#include "SDL_system.h"
+#include "../../core/windows/SDL_windows.h"
+}
+
+#include <string>
+#include <unordered_map>
+
+using namespace std;
+using namespace Windows::Storage;
+
+extern "C" const wchar_t *
+SDL_WinRTGetFSPathUNICODE(SDL_WinRT_Path pathType)
+{
+    switch (pathType) {
+        case SDL_WINRT_PATH_INSTALLED_LOCATION:
+        {
+            static wstring path;
+            if (path.empty()) {
+                path = Windows::ApplicationModel::Package::Current->InstalledLocation->Path->Data();
+            }
+            return path.c_str();
+        }
+
+        case SDL_WINRT_PATH_LOCAL_FOLDER:
+        {
+            static wstring path;
+            if (path.empty()) {
+                path = ApplicationData::Current->LocalFolder->Path->Data();
+            }
+            return path.c_str();
+        }
+
+#if WINAPI_FAMILY != WINAPI_FAMILY_PHONE_APP
+        case SDL_WINRT_PATH_ROAMING_FOLDER:
+        {
+            static wstring path;
+            if (path.empty()) {
+                path = ApplicationData::Current->RoamingFolder->Path->Data();
+            }
+            return path.c_str();
+        }
+
+        case SDL_WINRT_PATH_TEMP_FOLDER:
+        {
+            static wstring path;
+            if (path.empty()) {
+                path = ApplicationData::Current->TemporaryFolder->Path->Data();
+            }
+            return path.c_str();
+        }
+#endif
+
+        default:
+            break;
+    }
+
+    SDL_Unsupported();
+    return NULL;
+}
+
+extern "C" const char *
+SDL_WinRTGetFSPathUTF8(SDL_WinRT_Path pathType)
+{
+    typedef unordered_map<SDL_WinRT_Path, string> UTF8PathMap;
+    static UTF8PathMap utf8Paths;
+
+    UTF8PathMap::iterator searchResult = utf8Paths.find(pathType);
+    if (searchResult != utf8Paths.end()) {
+        return searchResult->second.c_str();
+    }
+
+    const wchar_t * ucs2Path = SDL_WinRTGetFSPathUNICODE(pathType);
+    if (!ucs2Path) {
+        return NULL;
+    }
+
+    char * utf8Path = WIN_StringToUTF8(ucs2Path);
+    utf8Paths[pathType] = utf8Path;
+    SDL_free(utf8Path);
+    return utf8Paths[pathType].c_str();
+}
+
+extern "C" char *
+SDL_GetBasePath(void)
+{
+    const char * srcPath = SDL_WinRTGetFSPathUTF8(SDL_WINRT_PATH_INSTALLED_LOCATION);
+    size_t destPathLen;
+    char * destPath = NULL;
+
+    if (!srcPath) {
+        SDL_SetError("Couldn't locate our basepath: %s", SDL_GetError());
+        return NULL;
+    }
+
+    destPathLen = SDL_strlen(srcPath) + 2;
+    destPath = (char *) SDL_malloc(destPathLen);
+    if (!destPath) {
+        SDL_OutOfMemory();
+        return NULL;
+    }
+
+    SDL_snprintf(destPath, destPathLen, "%s\\", srcPath);
+    return destPath;
+}
+
+extern "C" char *
+SDL_GetPrefPath(const char *org, const char *app)
+{
+    /* WinRT note: The 'SHGetFolderPath' API that is used in Windows 7 and
+     * earlier is not available on WinRT or Windows Phone.  WinRT provides
+     * a similar API, but SHGetFolderPath can't be called, at least not
+     * without violating Microsoft's app-store requirements.
+     */
+
+#if WINAPI_FAMILY == WINAPI_FAMILY_PHONE_APP
+    /* A 'Roaming' folder is not available in Windows Phone 8, however a 'Local' folder is. */
+    const char * srcPath = SDL_WinRTGetFSPathUTF8(SDL_WINRT_PATH_LOCAL_FOLDER);
+#else
+    /* A 'Roaming' folder is available on Windows 8 and 8.1.  Use that. */
+    const char * srcPath = SDL_WinRTGetFSPathUTF8(SDL_WINRT_PATH_ROAMING_FOLDER);
+#endif
+
+    size_t destPathLen;
+    char * destPath = NULL;
+
+    if (!srcPath) {
+        SDL_SetError("Couldn't locate our basepath: %s", SDL_GetError());
+        return NULL;
+    }
+
+    destPathLen = SDL_strlen(srcPath) + SDL_strlen(org) + SDL_strlen(app) + 4;
+    destPath = (char *) SDL_malloc(destPathLen);
+    if (!destPath) {
+        SDL_OutOfMemory();
+        return NULL;
+    }
+
+    SDL_snprintf(destPath, destPathLen, "%s\\%s\\%s\\", srcPath, org, app);
+    return destPath;
+}
+
+#endif /* __WINRT__ */