feat: add support for read & listen windows text scale factor

.changes/add-text-scale-factor-support.md

@@ -0,0 +1,5 @@
+---
+"tao": patch
+---
+
+feat(windows): add text scale factor support

.gitignore

@@ -5,6 +5,7 @@
 target/
 rls/
 .vscode/
+.idea/
 *~
 *.ts
 *.js

Cargo.toml

@@ -64,9 +64,10 @@ unicode-segmentation = "1.11"
 windows-version = "0.1"
 windows-core = "0.61"
 
-  [target."cfg(target_os = \"windows\")".dependencies.windows]
-  version = "0.61"
-  features = [
+[target."cfg(target_os = \"windows\")".dependencies.windows]
+version = "0.61"
+features = [
+  "UI_ViewManagement",
   "Win32_Devices_HumanInterfaceDevice",
   "Win32_Foundation",
   "Win32_Globalization",

src/event.rs

@@ -405,6 +405,12 @@ pub enum WindowEvent<'a> {
     new_inner_size: &'a mut PhysicalSize<u32>,
   },
 
+  /// The system text scale factor has changed.
+  ///
+  /// ## Platform-specific
+  /// - **Linux /  Android / iOS:** Unsupported
+  TextScaleFactorChanged(f64),
+
   /// The system window theme has changed.
   ///
   /// Applications might wish to react to this to change the theme of the content of the window
@@ -510,6 +516,7 @@ impl Clone for WindowEvent<'static> {
       ScaleFactorChanged { .. } => {
         unreachable!("Static event can't be about scale factor changing")
       }
+      TextScaleFactorChanged(f) => TextScaleFactorChanged(*f),
       DecorationsClick => DecorationsClick,
     }
   }
@@ -595,6 +602,7 @@ impl<'a> WindowEvent<'a> {
       Touch(touch) => Some(Touch(touch)),
       ThemeChanged(theme) => Some(ThemeChanged(theme)),
       ScaleFactorChanged { .. } => None,
+      TextScaleFactorChanged(factor) => Some(TextScaleFactorChanged(factor)),
       DecorationsClick => Some(DecorationsClick),
     }
   }

src/platform_impl/android/mod.rs

@@ -539,6 +539,8 @@ impl Window {
     MonitorHandle.scale_factor()
   }
 
+  pub fn text_scale_factor(&self) -> f64 { 1.0 }
+
   pub fn request_redraw(&self) {
     // TODO
   }

src/platform_impl/ios/window.rs

@@ -206,6 +206,10 @@ impl Inner {
     }
   }
 
+  pub fn text_scale_factor(&self) -> f64 {
+    1.0
+  }
+
   pub fn set_cursor_icon(&self, _cursor: CursorIcon) {
     debug!("`Window::set_cursor_icon` ignored on iOS")
   }

src/platform_impl/macos/window.rs

@@ -887,6 +887,9 @@ impl UnownedWindow {
     NSWindow::backingScaleFactor(&self.ns_window) as _
   }
 
+  #[inline]
+  pub fn text_scale_factor(&self) -> f64 { 1.0 }
+
   #[inline]
   pub fn set_cursor_position(&self, cursor_position: Position) -> Result<(), ExternalError> {
     let physical_window_position = self.inner_position().unwrap();

src/platform_impl/windows/event_loop.rs

@@ -645,6 +645,12 @@ lazy_static! {
     pub static ref CHANGE_THEME_MSG_ID: u32 = unsafe {
         RegisterWindowMessageA(s!("Tao::ChangeTheme"))
     };
+    /// Message sent by event loop when TextScaleFactorChanged
+    /// WPARAM and LPARAM are unused.
+    pub static ref TEXT_SCALE_FACTOR_CHANGED_MSG_ID: u32 = unsafe {
+        RegisterWindowMessageA(s!("Tao::TextScaleFactorChanged"))
+    };
+
     /// When the taskbar is created, it registers a message with the "TaskbarCreated" string and then broadcasts this message to all top-level windows
     /// When the application receives this message, it should assume that any taskbar icons it added have been removed and add them again.
     pub static ref S_U_TASKBAR_RESTART: u32 = unsafe {
@@ -2147,6 +2153,7 @@ unsafe fn public_window_callback_inner<T: 'static>(
 
     win32wm::WM_SETTINGCHANGE => {
       update_theme(subclass_input, window, true);
+      update_text_scale_factor(subclass_input, window, true);
     }
 
     win32wm::WM_NCCALCSIZE => {
@@ -2278,6 +2285,9 @@ unsafe fn public_window_callback_inner<T: 'static>(
       } else if msg == *S_U_TASKBAR_RESTART {
         let window_state = subclass_input.window_state.lock();
         let _ = set_skip_taskbar(window, window_state.skip_taskbar);
+      } else if msg == *TEXT_SCALE_FACTOR_CHANGED_MSG_ID {
+        update_text_scale_factor(subclass_input, window, false);
+        result = ProcResult::Value(LRESULT(0));
       }
     }
   };
@@ -2319,6 +2329,28 @@ fn update_theme<T>(
   }
 }
 
+fn update_text_scale_factor<T>(
+  subclass_input: &SubclassInput<T>,
+  window: HWND,
+  from_settings_change_event: bool,
+) {
+  let mut window_state = subclass_input.window_state.lock();
+  if from_settings_change_event {
+    return;
+  }
+  let new_text_scale_factor = util::get_cur_text_scale_factor().unwrap_or(1.0);
+  if window_state.text_scale_factor != new_text_scale_factor {
+    window_state.text_scale_factor = new_text_scale_factor;
+    mem::drop(window_state);
+    unsafe {
+      subclass_input.send_event(Event::WindowEvent {
+        window_id: RootWindowId(WindowId(window.0 as _)),
+        event: WindowEvent::TextScaleFactorChanged(new_text_scale_factor),
+      })
+    };
+  }
+}
+
 fn is_show_window_contents_while_dragging_enabled() -> bool {
   let mut is_enabled: BOOL = BOOL(0);
   let result = unsafe {

src/platform_impl/windows/util.rs

@@ -20,6 +20,7 @@ use crate::{
 use once_cell::sync::Lazy;
 use windows::{
   core::{BOOL, HRESULT, PCSTR, PCWSTR},
+  UI::ViewManagement::UISettings,
   Win32::{
     Foundation::{COLORREF, FARPROC, HWND, LPARAM, LRESULT, POINT, RECT, WPARAM},
     Globalization::lstrlenW,
@@ -509,3 +510,9 @@ pub unsafe fn get_system_metrics_for_dpi(nindex: SYSTEM_METRICS_INDEX, dpi: u32)
     GetSystemMetrics(nindex)
   }
 }
+
+// Read text_scale_factor from system settings
+pub(crate) fn get_cur_text_scale_factor() -> Result<f64, windows::core::Error> {
+  let ui_settings = UISettings::new()?;
+  ui_settings.TextScaleFactor()
+}

src/platform_impl/windows/window.rs

@@ -509,6 +509,11 @@ impl Window {
     self.window_state.lock().scale_factor
   }
 
+  #[inline]
+  pub fn text_scale_factor(&self) -> f64 {
+    self.window_state.lock().text_scale_factor
+  }
+
   #[inline]
   pub fn set_cursor_position(&self, position: Position) -> Result<(), ExternalError> {
     let scale_factor = self.scale_factor();

src/platform_impl/windows/window_state.rs

@@ -29,6 +29,7 @@ pub struct WindowState {
 
   pub saved_window: Option<SavedWindow>,
   pub scale_factor: f64,
+  pub text_scale_factor: f64,
 
   pub dragging: bool,
 
@@ -132,6 +133,8 @@ impl WindowState {
     preferred_theme: Option<Theme>,
     background_color: Option<RGBA>,
   ) -> WindowState {
+    let text_scale_factor = util::get_cur_text_scale_factor().unwrap_or(1.0);
+
     WindowState {
       mouse: MouseProperties {
         cursor: CursorIcon::default(),
@@ -147,6 +150,7 @@ impl WindowState {
 
       saved_window: None,
       scale_factor,
+      text_scale_factor,
 
       dragging: false,
 

src/window.rs

@@ -662,6 +662,15 @@ impl Window {
     self.window.scale_factor()
   }
 
+  /// Returns the text scale factor
+  ///
+  /// ## Platform-specific
+  /// Android/iOS/Linux: Unsupported, always returns 1.0
+  #[inline]
+  pub fn text_scale_factor(&self) -> f64 {
+    self.window.text_scale_factor()
+  }
+
   /// Emits a `WindowEvent::RedrawRequested` event in the associated event loop after all OS
   /// events have been processed by the event loop.
   ///