[desktop] improve theme detection and add manual theme selection.

desktop/tauri/src-tauri/src/config.rs

@@ -0,0 +1,45 @@
+use std::fs;
+
+use log::{debug, error};
+use serde::{Deserialize, Serialize};
+use tauri::{AppHandle, Manager};
+
+#[derive(Serialize, Deserialize)]
+pub enum Theme {
+    Light,
+    Dark,
+    System,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct Config {
+    pub theme: Theme,
+}
+
+const CONFIG_FILE_NAME: &'static str = "config.json";
+
+pub fn save(app: &AppHandle, config: Config) -> tauri::Result<()> {
+    let config_dir = app.path().app_config_dir()?;
+
+    let config_path = config_dir.join(CONFIG_FILE_NAME);
+    debug!("saving config file: {:?}", config_path);
+    let json = serde_json::to_string_pretty(&config)?;
+    fs::write(config_path, json)?;
+    Ok(())
+}
+
+pub fn load(app: &AppHandle) -> tauri::Result<Config> {
+    let config_dir = app.path().app_config_dir()?;
+
+    let config_path = config_dir.join(CONFIG_FILE_NAME);
+    if let Ok(json) = fs::read_to_string(config_path) {
+        if let Ok(config) = serde_json::from_str(&json) {
+            return Ok(config);
+        }
+    }
+
+    error!("failed to load config file returning default config");
+    Ok(Config {
+        theme: Theme::System,
+    })
+}