filesystem: SDL_GetUserFolder() now follows the SDL_GetStringRule.

It also now caches at the higher level, so the platform-specific bits don't
change their interface much.

Reference Issue #10229.

src/filesystem/SDL_filesystem.c

@@ -411,14 +411,38 @@ const char *SDL_GetBasePath(void)
     return CachedBasePath;
 }
 
+
+static char *CachedUserFolders[SDL_FOLDER_TOTAL];
+
+const char *SDL_GetUserFolder(SDL_Folder folder)
+{
+    const int idx = (int) folder;
+    if ((idx < 0) || (idx >= SDL_arraysize(CachedUserFolders))) {
+        SDL_InvalidParamError("folder");
+        return NULL;
+    }
+
+    if (!CachedUserFolders[idx]) {
+        CachedUserFolders[idx] = SDL_SYS_GetUserFolder(folder);
+    }
+    return CachedUserFolders[idx];
+}
+
+
+
 void SDL_InitFilesystem(void)
 {
     CachedBasePath = NULL;  // just in case.
+    SDL_zeroa(CachedUserFolders);
 }
 
 void SDL_QuitFilesystem(void)
 {
     SDL_free(CachedBasePath);
     CachedBasePath = NULL;
+    for (int i = 0; i < SDL_arraysize(CachedUserFolders); i++) {
+        SDL_free(CachedUserFolders[i]);
+        CachedUserFolders[i] = NULL;
+    }
 }
 

src/filesystem/SDL_sysfilesystem.h

@@ -24,6 +24,7 @@
 
 // return a string that we can SDL_free(). It will be cached at the higher level.
 extern char *SDL_SYS_GetBasePath(void);
+extern char *SDL_SYS_GetUserFolder(SDL_Folder folder);
 
 int SDL_SYS_EnumerateDirectory(const char *path, const char *dirname, SDL_EnumerateDirectoryCallback cb, void *userdata);
 int SDL_SYS_RemovePath(const char *path);

src/filesystem/android/SDL_sysfilesystem.c

@@ -49,7 +49,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     return NULL;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     /* TODO: see https://developer.android.com/reference/android/os/Environment#lfields
        and https://stackoverflow.com/questions/39332085/get-path-to-pictures-directory */

src/filesystem/cocoa/SDL_sysfilesystem.m

@@ -126,7 +126,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     }
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     @autoreleasepool {
 #ifdef SDL_PLATFORM_TVOS

src/filesystem/dummy/SDL_sysfilesystem.c

@@ -37,7 +37,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     return NULL;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/emscripten/SDL_sysfilesystem.c

@@ -81,7 +81,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     return retval;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     const char *home = NULL;
 

src/filesystem/haiku/SDL_sysfilesystem.cc

@@ -97,7 +97,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     return retval;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     const char *home = NULL;
     char *retval;

src/filesystem/n3ds/SDL_sysfilesystem.c

@@ -60,7 +60,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
 }
 
 /* TODO */
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/ps2/SDL_sysfilesystem.c

@@ -108,7 +108,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
 }
 
 /* TODO */
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/psp/SDL_sysfilesystem.c

@@ -78,7 +78,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
 }
 
 /* TODO */
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/riscos/SDL_sysfilesystem.c

@@ -197,7 +197,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
 }
 
 /* TODO */
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/unix/SDL_sysfilesystem.c

@@ -510,7 +510,7 @@ static char *xdg_user_dir_lookup (const char *type)
     return NULL;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     const char *param = NULL;
     char *retval;

src/filesystem/vita/SDL_sysfilesystem.c

@@ -81,7 +81,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
 }
 
 /* TODO */
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     SDL_Unsupported();
     return NULL;

src/filesystem/windows/SDL_sysfilesystem.c

@@ -174,7 +174,7 @@ char *SDL_GetPrefPath(const char *org, const char *app)
     return retval;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     typedef HRESULT (WINAPI *pfnSHGetKnownFolderPath)(REFGUID /* REFKNOWNFOLDERID */, DWORD, HANDLE, PWSTR*);
     HMODULE lib = LoadLibrary(L"Shell32.dll");

src/filesystem/winrt/SDL_sysfilesystem.cpp

@@ -227,7 +227,7 @@ extern "C" char *SDL_GetPrefPath(const char *org, const char *app)
     return retval;
 }
 
-char *SDL_GetUserFolder(SDL_Folder folder)
+char *SDL_SYS_GetUserFolder(SDL_Folder folder)
 {
     wstring wpath;