Fix incorrect size of several wasm demos

Commit 1c73144 (famous resume protocol) change the overal timing and sequence of window creation. As it happens now, when
we set_visibility() is called and we try to preserve a "browser" assigned canvas size,
we do so even for windows where we decided we want to go with the preferred size. This restores the todo/underlay/etc. demos.

With commit bcfa1ea we now end up computing current_size as (10, 10) for the slide puzzle (which has no min-width in Slint),
which differs from (0, 0). But we really shouldn't try to assign a size in the first place.

Author: tronical

internal/backends/winit/winitwindowadapter.rs

@@ -906,7 +906,9 @@ impl WinitWindowAdapter {
             );
 
             #[cfg(target_arch = "wasm32")]
-            if let Some(html_canvas) = winit_window.canvas() {
+            if let Some(html_canvas) =
+                winit_window.canvas().filter(|html_canvas| !is_preferred_sized_canvas(html_canvas))
+            {
                 let existing_canvas_size = winit::dpi::LogicalSize::new(
                     html_canvas.client_width() as f32,
                     html_canvas.client_height() as f32,
@@ -1226,12 +1228,7 @@ impl WindowAdapter for WinitWindowAdapter {
         if let Some(canvas) =
             winit_window_or_none.as_window().and_then(|winit_window| winit_window.canvas())
         {
-            if canvas
-                .dataset()
-                .get("slintAutoResizeToPreferred")
-                .and_then(|val_str| val_str.parse().ok())
-                .unwrap_or_default()
-            {
+            if is_preferred_sized_canvas(&canvas) {
                 let pref = new_constraints.preferred;
                 if pref.width > 0 as Coord || pref.height > 0 as Coord {
                     // TODO: don't ignore error, propgate to caller
@@ -1489,11 +1486,18 @@ fn adjust_window_size_to_satisfy_constraints(
     max_size: Option<winit::dpi::LogicalSize<f64>>,
 ) {
     let sf = adapter.window().scale_factor() as f64;
-    let current_size = adapter
+    let Some(current_size) = adapter
         .pending_requested_size
         .get()
+        .or_else(|| {
+            let existing_adapter_size = adapter.size.get();
+            (existing_adapter_size.width != 0 && existing_adapter_size.height != 0)
+                .then(|| physical_size_to_winit(existing_adapter_size).into())
+        })
         .map(|s| s.to_logical::<f64>(sf))
-        .unwrap_or_else(|| physical_size_to_winit(adapter.size.get()).to_logical(sf));
+    else {
+        return;
+    };
 
     let mut window_size = current_size;
     if let Some(min_size) = min_size {
@@ -1513,3 +1517,12 @@ fn adjust_window_size_to_satisfy_constraints(
         adapter.resize_window(window_size.into()).ok();
     }
 }
+
+#[cfg(target_family = "wasm")]
+fn is_preferred_sized_canvas(canvas: &web_sys::HtmlCanvasElement) -> bool {
+    canvas
+        .dataset()
+        .get("slintAutoResizeToPreferred")
+        .and_then(|val_str| val_str.parse::<bool>().ok())
+        .unwrap_or_default()
+}