refactored window storage;

new helper window events (Destroyed, Created);
clippy + fmt;

core/src/window/settings/macos.rs

@@ -0,0 +1,12 @@
+//! Platform specific settings for macOS.
+
+/// The platform specific window settings of an application.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct PlatformSpecific {
+    /// Hides the window title.
+    pub title_hidden: bool,
+    /// Makes the titlebar transparent and allows the content to appear behind it.
+    pub titlebar_transparent: bool,
+    /// Makes the window content appear behind the titlebar.
+    pub fullsize_content_view: bool,
+}

core/src/window/settings/other.rs

@@ -0,0 +1,3 @@
+/// The platform specific window settings of an application.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct PlatformSpecific;

core/src/window/settings/wasm.rs

@@ -0,0 +1,11 @@
+//! Platform specific settings for WebAssembly.
+
+/// The platform specific window settings of an application.
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub struct PlatformSpecific {
+    /// The identifier of a DOM element that will be replaced with the
+    /// application.
+    ///
+    /// If set to `None`, the application will be appended to the HTML body.
+    pub target: Option<String>,
+}

core/src/window/settings/windows.rs

@@ -0,0 +1,21 @@
+//! Platform specific settings for Windows.
+use raw_window_handle::RawWindowHandle;
+
+/// The platform specific window settings of an application.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct PlatformSpecific {
+    /// Parent window
+    pub parent: Option<RawWindowHandle>,
+
+    /// Drag and drop support
+    pub drag_and_drop: bool,
+}
+
+impl Default for PlatformSpecific {
+    fn default() -> Self {
+        Self {
+            parent: None,
+            drag_and_drop: true,
+        }
+    }
+}