fix(linux): position gtk::Fixed child webviews via move_ (honor set_bounds)

.changes/fix-linux-gtk-fixed-webview-position.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+On Linux, fix positioned child webviews in a `gtk::Fixed` losing their position after a layout pass. `WebView::set_bounds` now positions the webview via `gtk::Fixed::move_` (plus `set_size_request`) rather than a bare `size_allocate`, which the `gtk::Fixed` resets to the child's stored put-coordinate on the next size-allocate. This makes positioned multi-webview layouts created with `WebViewBuilderExtUnix::new_gtk` / `build_gtk` over a `gtk::Fixed` hold their bounds across resizes.

src/webkitgtk/mod.rs

@@ -866,6 +866,20 @@ impl InnerWebView {
     }
 
     if self.is_in_fixed_parent {
+      // Position the webview via its parent `gtk::Fixed`'s `move_` (which persists
+      // across layout passes) and `set_size_request`, in addition to the
+      // immediate `size_allocate`. A bare `size_allocate` only sets a transient
+      // allocation that the `gtk::Fixed` resets to the child's stored
+      // put-coordinate on the next size-allocate, so the requested position was
+      // dropped on the first relayout.
+      if let Some(fixed) = self
+        .webview
+        .parent()
+        .and_then(|p| p.downcast::<gtk::Fixed>().ok())
+      {
+        fixed.move_(&self.webview, x, y);
+      }
+      self.webview.set_size_request(width, height);
       self
         .webview
         .size_allocate(&gtk::Allocation::new(x, y, width, height));