Implement hidpi for web platform (#1233)

* fix: use a 'static lifetime for the web backend's `Event` types

* implement hidpi for stdweb (web-sys wip?)

* fix: make all canvas resizes go through backend::set_canvas_size

* update Window docs for web, make `inner/outer_position` return the position in the viewport

src/platform_impl/web/event_loop/runner.rs

@@ -11,7 +11,7 @@ use std::{
     rc::Rc,
 };
 
-pub struct Shared<T>(Rc<Execution<T>>);
+pub struct Shared<T: 'static>(Rc<Execution<T>>);
 
 impl<T> Clone for Shared<T> {
     fn clone(&self) -> Self {
@@ -19,21 +19,21 @@ impl<T> Clone for Shared<T> {
     }
 }
 
-pub struct Execution<T> {
+pub struct Execution<T: 'static> {
     runner: RefCell<Option<Runner<T>>>,
-    events: RefCell<VecDeque<Event<T>>>,
+    events: RefCell<VecDeque<Event<'static, T>>>,
     id: RefCell<u32>,
     redraw_pending: RefCell<HashSet<WindowId>>,
 }
 
-struct Runner<T> {
+struct Runner<T: 'static> {
     state: State,
     is_busy: bool,
-    event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>,
+    event_handler: Box<dyn FnMut(Event<'static, T>, &mut root::ControlFlow)>,
 }
 
 impl<T: 'static> Runner<T> {
-    pub fn new(event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>) -> Self {
+    pub fn new(event_handler: Box<dyn FnMut(Event<'static, T>, &mut root::ControlFlow)>) -> Self {
         Runner {
             state: State::Init,
             is_busy: false,
@@ -55,7 +55,10 @@ impl<T: 'static> Shared<T> {
     // Set the event callback to use for the event loop runner
     // This the event callback is a fairly thin layer over the user-provided callback that closes
     // over a RootEventLoopWindowTarget reference
-    pub fn set_listener(&self, event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>) {
+    pub fn set_listener(
+        &self,
+        event_handler: Box<dyn FnMut(Event<'static, T>, &mut root::ControlFlow)>,
+    ) {
         self.0.runner.replace(Some(Runner::new(event_handler)));
         self.send_event(Event::NewEvents(StartCause::Init));
 
@@ -79,7 +82,7 @@ impl<T: 'static> Shared<T> {
     // Add an event to the event loop runner
     //
     // It will determine if the event should be immediately sent to the user or buffered for later
-    pub fn send_event(&self, event: Event<T>) {
+    pub fn send_event(&self, event: Event<'static, T>) {
         // If the event loop is closed, it should discard any new events
         if self.is_closed() {
             return;
@@ -153,7 +156,7 @@ impl<T: 'static> Shared<T> {
     // handle_event takes in events and either queues them or applies a callback
     //
     // It should only ever be called from send_event
-    fn handle_event(&self, event: Event<T>, control: &mut root::ControlFlow) {
+    fn handle_event(&self, event: Event<'static, T>, control: &mut root::ControlFlow) {
         let is_closed = self.is_closed();
 
         match *self.0.runner.borrow_mut() {