fix: layout.rs - use offscreen parking pattern instead of unreliable hide/show on Windows WebView2

src-tauri/src/browser/layout.rs

@@ -1,49 +1,75 @@
-use tauri::{AppHandle, LogicalPosition, LogicalSize, Manager};
-
-use super::tab_manager::{tab_label, ViewportLayout};
-use crate::state::AppState;
-
-const HIDDEN_X: f64 = -32000.0;
-const HIDDEN_Y: f64 = -32000.0;
-
-/// Calculate child WebView bounds from measured React host rect.
-/// React sends getBoundingClientRect() values in logical/CSS pixels.
-pub fn bounds(layout: &ViewportLayout) -> (f64, f64, f64, f64) {
-    let x = layout.x.max(0.0);
-    let y = layout.y.max(0.0);
-    let w = layout.width.max(1.0);
-    let h = layout.height.max(1.0);
-    (x, y, w, h)
-}
-
-pub fn show_tab(app: &AppHandle, tab_id: &str, layout: &ViewportLayout) -> Result<(), String> {
-    let label = tab_label(app, tab_id)?;
-    let (x, y, w, h) = bounds(layout);
-    if let Some(webview) = app.get_webview(&label) {
-        webview.set_position(LogicalPosition::new(x, y)).map_err(|e| e.to_string())?;
-        webview.set_size(LogicalSize::new(w, h)).map_err(|e| e.to_string())?;
-        webview.show().map_err(|e| e.to_string())?;
-        webview.set_focus().map_err(|e| e.to_string())?;
-    }
-    Ok(())
-}
-
-pub fn hide_tab(app: &AppHandle, tab_id: &str) -> Result<(), String> {
-    let label = tab_label(app, tab_id)?;
-    if let Some(webview) = app.get_webview(&label) {
-        let _ = webview.hide();
-        webview.set_position(LogicalPosition::new(HIDDEN_X, HIDDEN_Y)).map_err(|e| e.to_string())?;
-        webview.set_size(LogicalSize::new(1.0, 1.0)).map_err(|e| e.to_string())?;
-    }
-    Ok(())
-}
-
-pub fn resize_active(app: &AppHandle, layout: &ViewportLayout) -> Result<(), String> {
-    let active = {
-        let state = app.state::<AppState>();
-        let tabs = state.tabs.lock().map_err(|_| "lock")?;
-        tabs.active.clone()
-    };
-    if let Some(active_id) = active { show_tab(app, &active_id, layout)?; }
-    Ok(())
-}
+use tauri::{AppHandle, LogicalPosition, LogicalSize, Manager, PhysicalPosition, PhysicalSize};
+
+use super::tab_manager::{tab_label, ViewportLayout};
+use crate::state::AppState;
+
+/// Hidden position — far offscreen. WebView2 stays "visible" (avoids deferred init bug)
+/// but is not renderable. This is the correct pattern for WebView2 on Windows.
+const OFFSCREEN_X: i32 = -32000;
+const OFFSCREEN_Y: i32 = -32000;
+
+/// Calculate child WebView bounds from measured React host rect.
+/// React sends getBoundingClientRect() values in CSS/logical pixels.
+pub fn bounds(layout: &ViewportLayout) -> (f64, f64, f64, f64) {
+    let x = layout.x.max(0.0);
+    let y = layout.y.max(0.0);
+    let w = layout.width.max(1.0);
+    let h = layout.height.max(1.0);
+    (x, y, w, h)
+}
+
+/// Show a tab webview at the specified layout position.
+/// Uses PhysicalPosition with scale factor for correct HiDPI positioning.
+pub fn show_tab(app: &AppHandle, tab_id: &str, layout: &ViewportLayout) -> Result<(), String> {
+    let label = tab_label(app, tab_id)?;
+    let (x, y, w, h) = bounds(layout);
+
+    if let Some(webview) = app.get_webview(&label) {
+        // Get scale factor for coordinate conversion
+        let scale = app.get_window("main")
+            .and_then(|win| win.scale_factor().ok())
+            .unwrap_or(1.0);
+
+        // Convert CSS logical pixels to physical pixels
+        let px = (x * scale) as i32;
+        let py = (y * scale) as i32;
+        let pw = (w * scale).max(1.0) as u32;
+        let ph = (h * scale).max(1.0) as u32;
+
+        // CRITICAL ORDER: position + size FIRST, then show
+        // This avoids the WebView2 "bounds before visible" requirement
+        webview.set_position(PhysicalPosition::new(px, py)).map_err(|e| e.to_string())?;
+        webview.set_size(PhysicalSize::new(pw, ph)).map_err(|e| e.to_string())?;
+
+        // show() is needed on first display after add_child
+        // Subsequent calls are safe (idempotent)
+        let _ = webview.show();
+        let _ = webview.set_focus();
+    }
+    Ok(())
+}
+
+/// Hide a tab webview by parking it offscreen.
+/// We do NOT call webview.hide() because WebView2's hide/show is unreliable.
+/// Instead we move it far offscreen and shrink to 1x1. The webview stays "alive"
+/// and continues processing JS (beneficial for maintaining session state).
+pub fn hide_tab(app: &AppHandle, tab_id: &str) -> Result<(), String> {
+    let label = tab_label(app, tab_id)?;
+    if let Some(webview) = app.get_webview(&label) {
+        // Park offscreen — don't call hide()
+        webview.set_position(PhysicalPosition::new(OFFSCREEN_X, OFFSCREEN_Y)).map_err(|e| e.to_string())?;
+        webview.set_size(PhysicalSize::new(1u32, 1u32)).map_err(|e| e.to_string())?;
+    }
+    Ok(())
+}
+
+/// Resize the active tab to match current layout.
+pub fn resize_active(app: &AppHandle, layout: &ViewportLayout) -> Result<(), String> {
+    let active = {
+        let state = app.state::<AppState>();
+        let tabs = state.tabs.lock().map_err(|_| "lock")?;
+        tabs.active.clone()
+    };
+    if let Some(active_id) = active { show_tab(app, &active_id, layout)?; }
+    Ok(())
+}