Add VFS support to imageviewer (should get Unicode filenames working on Windows too, even without VFS)

cores/libretro-imageviewer/Makefile

@@ -1,5 +1,6 @@
-image_core.so:
+image_core.so: image_core.c
 	gcc \
+		-g \
 		image_core.c \
 		../../libretro-common/file/file_path.c \
 		../../libretro-common/lists/dir_list.c \
@@ -7,10 +8,13 @@ image_core.so:
 		../../libretro-common/compat/compat_strcasestr.c \
 		../../libretro-common/lists/string_list.c \
 		../../libretro-common/file/retro_dirent.c \
+		../../libretro-common/streams/file_stream.c \
+		../../libretro-common/vfs/vfs_implementation.c \
 		-o image_core.so \
 		-DHAVE_STB_IMAGE \
 		-I ../../libretro-common/include/ \
 		-I../../deps/stb \
+		-Wl,--no-undefined \
 		-shared \
 		-fPIC \
 		-lm

cores/libretro-imageviewer/image_core.c

@@ -10,6 +10,8 @@
 #include <compat/strl.h>
 #include <retro_environment.h>
 
+#include <streams/file_stream.h>
+
 #if defined(HAVE_RPNG) || defined(HAVE_RJPEG) || defined(HAVE_RTGA) || defined(HAVE_RBMP)
 #define PREFER_NON_STB_IMAGE
 #endif
@@ -157,10 +159,19 @@ void IMAGE_CORE_PREFIX(retro_set_environment)(retro_environment_t cb)
    static const struct retro_variable vars[] = {
       { NULL, NULL },
    };
+   
+   
+   struct retro_vfs_interface_info vfs_iface_info = { 1, NULL };
 
    IMAGE_CORE_PREFIX(environ_cb) = cb;
 
    cb(RETRO_ENVIRONMENT_SET_VARIABLES, (void*)vars);
+   
+#ifndef RARCH_INTERNAL
+   /* I don't trust filestream_vfs_init to work inside rarch */
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VFS_INTERFACE, &vfs_iface_info))
+      filestream_vfs_init(&vfs_iface_info);
+#endif
 }
 
 void IMAGE_CORE_PREFIX(retro_set_video_refresh)(retro_video_refresh_t cb)
@@ -227,6 +238,9 @@ static bool imageviewer_load(const char *path, int image_index)
 {
 #ifdef STB_IMAGE_IMPLEMENTATION
    int comp;
+   RFILE* f;
+   size_t len;
+   void* buf;
 #endif
 #ifdef RARCH_INTERNAL
    extern bool video_driver_supports_rgba(void);
@@ -235,12 +249,17 @@ static bool imageviewer_load(const char *path, int image_index)
    imageviewer_free_image();
 
 #ifdef STB_IMAGE_IMPLEMENTATION
-   image_buffer           = (uint32_t*)stbi_load(
+   f = filestream_open(path, RETRO_VFS_FILE_ACCESS_READ, 0);
-         path,
+   len = filestream_get_size(f);
-         &image_width,
+   buf = malloc(len);
-         &image_height,
+   filestream_read(f, buf, len);
-         &comp,
+   filestream_close(f);
-         4);
+   
+   image_buffer           = (uint32_t*)stbi_load_from_memory(
+         buf, len,
+         &image_width, &image_height,
+         &comp, 4);
+   free(buf);
 #else
 #ifdef RARCH_INTERNAL
    image_texture.supports_rgba = video_driver_supports_rgba();

libretro-common/vfs/vfs_implementation.c

@@ -182,6 +182,11 @@ libretro_vfs_implementation_file *retro_vfs_file_open_impl(const char *path, uns
    const char *mode_str    = NULL;
    libretro_vfs_implementation_file *stream = (libretro_vfs_implementation_file*)calloc(1, sizeof(*stream));
 
+#ifdef VFS_FRONTEND
+   const char * dumb_prefix = "vfsonly://";
+   if (!memcmp(path, dumb_prefix, strlen(dumb_prefix))) path += strlen(dumb_prefix);
+#endif
+
    if (!stream)
       return NULL;