Add Settings with fullscreen and windowed options, a config file

(settings.toml) to persist settings, fix a bug in platform code where
innner window size wasn't updated on resize, various other tweaks

platform/src/settings.rs

@@ -0,0 +1,101 @@
+use winit::dpi::LogicalSize;
+use winit::window::{Fullscreen, Window};
+use serde::{Serialize, Deserialize};
+use std::error::Error;
+use std::fs;
+use std::io;
+use std::path::{Path, PathBuf};
+
+pub fn default_config_path() -> PathBuf {
+    let exe_path = std::env::current_exe().unwrap();
+    let exe_dir = exe_path
+        .parent()
+        .ok_or_else(|| std::io::Error::new(std::io::ErrorKind::Other, "executable has no parent")).unwrap();
+
+    exe_dir.join("settings.toml")
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
+#[serde(rename_all = "snake_case")]
+pub enum WindowMode {
+    BorderlessFullscreen,
+    #[default]
+    Windowed,
+}
+
+#[derive(Debug, Default, Serialize, Deserialize)]
+pub struct Settings {
+    pub display_settings: DisplaySettings,
+}
+
+impl Settings {
+    pub fn load_from_file(path: impl AsRef<Path>) -> Result<Self, Box<dyn Error>> {
+        let path = path.as_ref();
+        let text = fs::read_to_string(path)?;
+        let settings: Settings = toml::from_str(&text)?;
+        Ok(settings)
+    }
+
+    pub fn save_to_file(&self, path: impl AsRef<Path>) -> Result<(), Box<dyn Error>> {
+        let path = path.as_ref();
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent)?;
+        }
+        let toml_str = toml::to_string_pretty(self)?;
+        fs::write(path, toml_str)?;
+        Ok(())
+    }
+
+    pub fn load_or_default(path: impl AsRef<Path>) -> Result<Self, Box<dyn Error>> {
+        let path = path.as_ref();
+
+        match fs::read_to_string(path) {
+            Ok(text) => {
+                let settings: Settings = toml::from_str(&text)?;
+                Ok(settings)
+            }
+            Err(err) if err.kind() == io::ErrorKind::NotFound => {
+                let settings = Settings::default();
+                if let Some(parent) = path.parent() {
+                    fs::create_dir_all(parent)?;
+                }
+                let toml_str = toml::to_string_pretty(&settings)?;
+                fs::write(path, toml_str)?;
+                Ok(settings)
+            }
+            Err(err) => Err(Box::new(err)),
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(default)]
+pub struct DisplaySettings {
+    pub fullscreen_mode: WindowMode,
+    #[serde(skip)]
+    pub dirty: bool,
+}
+
+impl Default for DisplaySettings {
+    fn default() -> Self {
+        Self {
+            fullscreen_mode: WindowMode::Windowed,
+            dirty: false,
+        }
+    }
+}
+
+impl DisplaySettings {
+    pub fn apply(&self, window: &Window) {
+        // apply fullscreen mode
+        match self.fullscreen_mode {
+            WindowMode::BorderlessFullscreen => {
+                let monitor = window.current_monitor().or_else(|| window.primary_monitor());
+                window.set_fullscreen(Some(Fullscreen::Borderless(monitor)));
+            }
+            WindowMode::Windowed => {
+                window.set_fullscreen(None);
+            },
+        }
+    }
+}