Fix HighDPI on windows with the rust generator and the native style a…

…nd qt backend

We must create the window first to initialize the backend before
the style is called because it would initialize qt as a plugin instead
of as a proper application, and it would then not initialize the high dpi mode

internal/compiler/generator/rust.rs

@@ -853,12 +853,17 @@ fn generate_item_tree(
     } else {
         quote!(&self_rc)
     };
-    let maybe_create_window = parent_ctx.is_none().then(|| {
-        quote!(
-            _self.window.set(slint::create_window().into());
-            _self.window.get().unwrap().window_handle().set_component(&VRc::into_dyn(self_rc.clone()));
+    let (create_window, init_window) = if parent_ctx.is_none() {
+        (
+            Some(quote!(let window = slint::create_window().into();)),
+            Some(quote! {
+                _self.window.set(window);
+                _self.window.get().unwrap().window_handle().set_component(&VRc::into_dyn(self_rc.clone()));
+            }),
         )
-    });
+    } else {
+        (None, None)
+    };
 
     let parent_item_index = parent_ctx.and_then(|parent| {
         parent
@@ -919,11 +924,12 @@ fn generate_item_tree(
             {
                 #![allow(unused)]
                 use slint::re_exports::*;
+                #create_window // We must create the window first to initialize the backend before using the style
                 let mut _self = Self::default();
                 #(_self.parent = parent.clone() as #parent_component_type;)*
                 let self_rc = VRc::new(_self);
                 let _self = self_rc.as_pin_ref();
-                #maybe_create_window;
+                #init_window
                 slint::re_exports::init_component_items(_self, Self::item_tree(), #root_token.window.get().unwrap().window_handle());
                 Self::init(slint::re_exports::VRc::map(self_rc.clone(), |x| x), #root_token, 0, 1);
                 self_rc