Use correct canvas size for scale factor change

CHANGELOG.md

@@ -71,6 +71,8 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Web, `EventLoopProxy` now implements `Send`.
 - On Web, `Window` now implements `Send` and `Sync`.
 - **Breaking:** `WindowExtWebSys::canvas()` now returns an `Option`.
+- On Web, use the correct canvas size when calculating the new size during scale factor change,
+  instead of using the output bitmap size.
 
 # 0.28.6
 

examples/web.rs

@@ -59,7 +59,10 @@ mod wasm {
         let body = document.body().unwrap();
 
         // Set a background color for the canvas to make it easier to tell where the canvas is for debugging purposes.
-        canvas.style().set_css_text("background-color: crimson;");
+        canvas
+            .style()
+            .set_property("background-color", "crimson")
+            .unwrap();
         body.append_child(&canvas).unwrap();
 
         let log_header = document.create_element("h2").unwrap();

src/platform_impl/web/event_loop/runner.rs

@@ -327,16 +327,14 @@ impl<T: 'static> Shared<T> {
 
         // Now handle the `ScaleFactorChanged` events.
         for &(id, ref canvas) in &*self.0.all_canvases.borrow() {
-            let canvas = match canvas.upgrade() {
-                Some(rc) => rc.borrow().raw().clone(),
+            let rc = match canvas.upgrade() {
+                Some(rc) => rc,
                 // This shouldn't happen, but just in case...
                 None => continue,
             };
+            let canvas = rc.borrow();
             // First, we send the `ScaleFactorChanged` event:
-            let current_size = crate::dpi::PhysicalSize {
-                width: canvas.width(),
-                height: canvas.height(),
-            };
+            let current_size = canvas.size().get();
             let logical_size = current_size.to_logical::<f64>(old_scale);
             let mut new_size = logical_size.to_physical(new_scale);
             self.handle_single_event_sync(
@@ -351,7 +349,7 @@ impl<T: 'static> Shared<T> {
             );
 
             // Then we resize the canvas to the new size and send a `Resized` event:
-            backend::set_canvas_size(self.window(), &canvas, crate::dpi::Size::Physical(new_size));
+            backend::set_canvas_size(&canvas, crate::dpi::Size::Physical(new_size));
             self.handle_single_event_sync(
                 Event::WindowEvent {
                     window_id: id,

src/platform_impl/web/event_loop/window_target.rs

@@ -16,7 +16,7 @@ use super::{
     runner,
     window::WindowId,
 };
-use crate::dpi::{PhysicalSize, Size};
+use crate::dpi::Size;
 use crate::event::{
     DeviceEvent, DeviceId as RootDeviceId, ElementState, Event, KeyEvent, Touch, TouchPhase,
     WindowEvent,
@@ -89,6 +89,7 @@ impl<T> EventLoopWindowTarget<T> {
         has_focus: Arc<AtomicBool>,
     ) {
         self.runner.add_canvas(RootWindowId(id), canvas);
+        let canvas_clone = canvas.clone();
         let mut canvas = canvas.borrow_mut();
         canvas.set_attribute("data-raw-handle", &id.0.to_string());
 
@@ -502,32 +503,27 @@ impl<T> EventLoopWindowTarget<T> {
             prevent_default,
         );
 
-        let runner = self.runner.clone();
-        let raw = canvas.raw().clone();
-
         // The size to restore to after exiting fullscreen.
-        let mut intended_size = PhysicalSize {
-            width: raw.width(),
-            height: raw.height(),
-        };
+        let mut intended_size = canvas.size().get();
 
         canvas.on_fullscreen_change({
             let window = self.runner.window().clone();
+            let runner = self.runner.clone();
+
             move || {
+                let canvas = canvas_clone.borrow();
+
                 // If the canvas is marked as fullscreen, it is moving *into* fullscreen
                 // If it is not, it is moving *out of* fullscreen
-                let new_size = if backend::is_fullscreen(&window, &raw) {
-                    intended_size = PhysicalSize {
-                        width: raw.width(),
-                        height: raw.height(),
-                    };
+                let new_size = if backend::is_fullscreen(&window, canvas.raw()) {
+                    intended_size = canvas.size().get();
 
                     backend::window_size(&window).to_physical(backend::scale_factor(&window))
                 } else {
                     intended_size
                 };
 
-                backend::set_canvas_size(&window, &raw, Size::Physical(new_size));
+                backend::set_canvas_size(&canvas, Size::Physical(new_size));
                 runner.send_event(Event::WindowEvent {
                     window_id: RootWindowId(id),
                     event: WindowEvent::Resized(new_size),

src/platform_impl/web/web_sys/canvas.rs

@@ -2,13 +2,14 @@ use super::event_handle::EventListenerHandle;
 use super::media_query_handle::MediaQueryListHandle;
 use super::pointer::PointerHandler;
 use super::{event, ButtonsState};
-use crate::dpi::{LogicalPosition, PhysicalPosition, PhysicalSize};
+use crate::dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize};
 use crate::error::OsError as RootOE;
 use crate::event::{Force, MouseButton, MouseScrollDelta};
 use crate::keyboard::{Key, KeyCode, KeyLocation, ModifiersState};
 use crate::platform_impl::{OsError, PlatformSpecificWindowBuilderAttributes};
+use crate::window::WindowAttributes;
 
-use std::cell::RefCell;
+use std::cell::{Cell, RefCell};
 use std::rc::Rc;
 
 use js_sys::Promise;
@@ -39,15 +40,17 @@ pub struct Common {
     pub window: web_sys::Window,
     /// Note: resizing the HTMLCanvasElement should go through `backend::set_canvas_size` to ensure the DPI factor is maintained.
     pub raw: HtmlCanvasElement,
+    size: Rc<Cell<PhysicalSize<u32>>>,
     wants_fullscreen: Rc<RefCell<bool>>,
 }
 
 impl Canvas {
     pub fn create(
         window: web_sys::Window,
-        attr: PlatformSpecificWindowBuilderAttributes,
+        attr: &WindowAttributes,
+        platform_attr: PlatformSpecificWindowBuilderAttributes,
     ) -> Result<Self, RootOE> {
-        let canvas = match attr.canvas {
+        let canvas = match platform_attr.canvas {
             Some(canvas) => canvas,
             None => {
                 let document = window
@@ -66,16 +69,28 @@ impl Canvas {
         // sequential keyboard navigation, but its order is defined by the
         // document's source order.
         // https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/tabindex
-        if attr.focusable {
+        if platform_attr.focusable {
             canvas
                 .set_attribute("tabindex", "0")
                 .map_err(|_| os_error!(OsError("Failed to set a tabindex".to_owned())))?;
         }
 
-        Ok(Canvas {
+        let size = attr
+            .inner_size
+            .unwrap_or(
+                LogicalSize {
+                    width: 1024.0,
+                    height: 768.0,
+                }
+                .into(),
+            )
+            .to_physical(super::scale_factor(&window));
+
+        let canvas = Canvas {
             common: Common {
                 window,
                 raw: canvas,
+                size: Rc::new(Cell::new(size)),
                 wants_fullscreen: Rc::new(RefCell::new(false)),
             },
             on_touch_start: None,
@@ -88,7 +103,11 @@ impl Canvas {
             on_fullscreen_change: None,
             on_dark_mode: None,
             pointer_handler: PointerHandler::new(),
-        })
+        };
+
+        super::set_canvas_size(&canvas, size.into());
+
+        Ok(canvas)
     }
 
     pub fn set_cursor_lock(&self, lock: bool) -> Result<(), RootOE> {
@@ -121,11 +140,12 @@ impl Canvas {
         }
     }
 
-    pub fn size(&self) -> PhysicalSize<u32> {
-        PhysicalSize {
-            width: self.common.raw.width(),
-            height: self.common.raw.height(),
-        }
+    pub fn window(&self) -> &web_sys::Window {
+        &self.common.window
+    }
+
+    pub fn size(&self) -> &Rc<Cell<PhysicalSize<u32>>> {
+        &self.common.size
     }
 
     pub fn raw(&self) -> &HtmlCanvasElement {

src/platform_impl/web/web_sys/mod.rs

@@ -76,12 +76,19 @@ pub fn scale_factor(window: &web_sys::Window) -> f64 {
     window.device_pixel_ratio()
 }
 
-pub fn set_canvas_size(window: &web_sys::Window, raw: &HtmlCanvasElement, size: Size) {
-    let scale_factor = scale_factor(window);
-    let logical_size = size.to_logical::<f64>(scale_factor);
-
-    set_canvas_style_property(raw, "width", &format!("{}px", logical_size.width));
-    set_canvas_style_property(raw, "height", &format!("{}px", logical_size.height));
+pub fn set_canvas_size(canvas: &Canvas, new_size: Size) {
+    let scale_factor = scale_factor(canvas.window());
+
+    let physical_size = new_size.to_physical(scale_factor);
+    canvas.size().set(physical_size);
+
+    let logical_size = new_size.to_logical::<f64>(scale_factor);
+    set_canvas_style_property(canvas.raw(), "width", &format!("{}px", logical_size.width));
+    set_canvas_style_property(
+        canvas.raw(),
+        "height",
+        &format!("{}px", logical_size.height),
+    );
 }
 
 pub fn set_canvas_style_property(raw: &HtmlCanvasElement, property: &str, value: &str) {

src/platform_impl/web/window.rs

@@ -1,4 +1,4 @@
-use crate::dpi::{LogicalSize, PhysicalPosition, PhysicalSize, Position, Size};
+use crate::dpi::{PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error::{ExternalError, NotSupportedError, OsError as RootOE};
 use crate::event;
 use crate::icon::Icon;
@@ -48,7 +48,7 @@ impl Window {
         let prevent_default = platform_attr.prevent_default;
 
         let window = target.runner.window();
-        let canvas = backend::Canvas::create(window.clone(), platform_attr)?;
+        let canvas = backend::Canvas::create(window.clone(), &attr, platform_attr)?;
         let canvas = Rc::new(RefCell::new(canvas));
 
         let register_redraw_request = Box::new(move || runner.request_redraw(RootWI(id)));
@@ -67,15 +67,6 @@ impl Window {
         let runner = target.runner.clone();
         let destroy_fn = Box::new(move || runner.notify_destroy_window(RootWI(id)));
 
-        backend::set_canvas_size(
-            window,
-            canvas.borrow().raw(),
-            attr.inner_size.unwrap_or(Size::Logical(LogicalSize {
-                width: 1024.0,
-                height: 768.0,
-            })),
-        );
-
         let window = Window {
             id,
             has_focus,
@@ -171,7 +162,7 @@ impl Window {
     pub fn set_inner_size(&self, size: Size) {
         self.inner.dispatch(move |inner| {
             let old_size = inner.inner_size();
-            backend::set_canvas_size(&inner.window, inner.canvas.borrow().raw(), size);
+            backend::set_canvas_size(&inner.canvas.borrow(), size);
             let new_size = inner.inner_size();
             if old_size != new_size {
                 (inner.resize_notify_fn)(new_size);
@@ -454,7 +445,7 @@ impl Inner {
 
     #[inline]
     pub fn inner_size(&self) -> PhysicalSize<u32> {
-        self.canvas.borrow().size()
+        self.canvas.borrow().size().get()
     }
 }