Presets: Add ability to specify preset_path via env variables

README.md

@@ -21,7 +21,7 @@ A Vulkan and OpenGL overlay for monitoring FPS, temperatures, CPU/GPU load and m
   - [Normal usage](#normal-usage)
   - [OpenGL](#opengl)
   - [Hud configuration](#hud-configuration)
-    - [Environment Variables: **`MANGOHUD_CONFIG`** and **`MANGOHUD_CONFIGFILE`**](#environment-variables-mangohud_config-and-mangohud_configfile)
+    - [Environment Variables: **`MANGOHUD_CONFIG`**, **`MANGOHUD_CONFIGFILE`**, and **`MANGOHUD_PRESETSFILE`**](#environment-variables)
   - [Vsync](#vsync)
     - [OpenGL Vsync](#opengl-vsync)
     - [Vulkan Vsync](#vulkan-vsync)
@@ -289,12 +289,14 @@ You can find an example config in /usr/share/doc/mangohud
 
 ---
 
-### Environment Variables: **`MANGOHUD_CONFIG`** and **`MANGOHUD_CONFIGFILE`**
+### Environment Variables
 
 You can also customize the hud by using the `MANGOHUD_CONFIG` environment variable while separating different options with a comma. This takes priority over any config file.
 
 You can also specify configuration file with `MANGOHUD_CONFIGFILE=/path/to/config` for applications whose names are hard to guess (java, python etc).
 
+You can also specify presets file with `MANGOHUD_PRESETSFILE=/path/to/config`. This is especially useful when running mangohud in a sandbox such as flatpak.
+
 A partial list of parameters are below. See the config file for a complete list.
 Parameters that are enabled by default have to be explicitly disabled. These (currently) are `fps`, `frame_timing`, `cpu_stats` (cpu load), `gpu_stats` (gpu load), and each can be disabled by setting the corresponding variable to 0 (e.g., fps=0).
 

src/overlay_params.cpp

@@ -983,9 +983,9 @@ parse_overlay_config(struct overlay_params *params,
 }
 
 bool parse_preset_config(int preset, struct overlay_params *params){
-   const std::string data_dir = get_data_dir();
+   const char *presets_file_env = getenv("MANGOHUD_PRESETSFILE");
    const std::string config_dir = get_config_dir();
-   std::string preset_path = config_dir + "/MangoHud/" + "presets.conf";
+   std::string preset_path = presets_file_env ? presets_file_env : config_dir + "/MangoHud/" + "presets.conf";
 
    char preset_string[20];
    snprintf(preset_string, sizeof(preset_string), "[preset %d]", preset);
@@ -994,6 +994,7 @@ bool parse_preset_config(int preset, struct overlay_params *params){
    stream.imbue(std::locale::classic());
 
    if (!stream.good()) {
+      SPDLOG_ERROR("Failed to read presets file: '{}'", preset_path);
       return false;
    }