Don't hardcode rgui.cgp/glslp as default.

In a multi-config environment, shader manager could conflict.
Instead, infer the default RGUI shader cgps/glslps from config path.

Fallback to old rgui.cgp/rgui.glslp if we use a default config.

file.h

@@ -74,6 +74,9 @@ bool path_is_directory(const char *path);
 bool path_file_exists(const char *path);
 const char *path_get_extension(const char *path);
 
+// Removes all text after and including the last '.'
+char *path_remove_extension(char *path);
+
 // Returns basename from path.
 const char *path_basename(const char *path);
 

file_path.c

@@ -185,6 +185,14 @@ const char *path_get_extension(const char *path)
       return "";
 }
 
+char *path_remove_extension(char *path)
+{
+   char *last = strrchr(path, '.');
+   if (*last)
+      *last = '\0';
+   return last;
+}
+
 static int qstrcmp_plain(const void *a_, const void *b_)
 {
    const struct string_list_elem *a = (const struct string_list_elem*)a_; 

frontend/menu/menu_common.c

@@ -40,6 +40,23 @@ void shader_manager_init(rgui_handle_t *rgui)
 {
    memset(&rgui->shader, 0, sizeof(rgui->shader));
    config_file_t *conf = NULL;
+
+   // In a multi-config setting, we can't have conflicts on rgui.cgp/rgui.glslp.
+   if (*g_extern.config_path)
+   {
+      fill_pathname_base(rgui->default_glslp, g_extern.config_path, sizeof(rgui->default_glslp));
+      path_remove_extension(rgui->default_glslp);
+      strlcat(rgui->default_glslp, ".glslp", sizeof(rgui->default_glslp));
+      fill_pathname_base(rgui->default_cgp, g_extern.config_path, sizeof(rgui->default_cgp));
+      path_remove_extension(rgui->default_cgp);
+      strlcat(rgui->default_cgp, ".cgp", sizeof(rgui->default_cgp));
+   }
+   else
+   {
+      strlcpy(rgui->default_glslp, "rgui.glslp", sizeof(rgui->default_glslp));
+      strlcpy(rgui->default_cgp, "rgui.cgp", sizeof(rgui->default_cgp));
+   }
+
    char cgp_path[PATH_MAX];
 
    const char *ext = path_get_extension(g_settings.video.shader_path);

frontend/menu/menu_common.h

@@ -242,6 +242,8 @@ typedef struct
    bool msg_force;
 
    char base_path[PATH_MAX];
+   char default_glslp[PATH_MAX];
+   char default_cgp[PATH_MAX];
 
    const uint8_t *font;
    bool alloc_font;

frontend/menu/rgui.c

@@ -1692,7 +1692,7 @@ static int shader_manager_toggle_setting(rgui_handle_t *rgui, unsigned setting,
 
       if (rgui->shader.passes && type != RARCH_SHADER_NONE)
       {
-         const char *conf_path = type == RARCH_SHADER_GLSL ? "rgui.glslp" : "rgui.cgp";
+         const char *conf_path = type == RARCH_SHADER_GLSL ? rgui->default_glslp : rgui->default_cgp;
 
          char cgp_path[PATH_MAX];
          const char *shader_dir = *g_settings.video.shader_dir ?