From 7f51178371e9a3f4c098436ec3ef8a18316fad73 Mon Sep 17 00:00:00 2001
From: Mitchell Cohen <mitch.cohen@me.com>
Date: Fri, 1 May 2026 17:06:40 -0400
Subject: [PATCH] fix: ensure stable bounds on Windows when toggling
 setResizable for frameless windows (#51427)

---
 shell/browser/ui/views/win_frame_view.cc           |  3 +--
 .../win/electron_desktop_window_tree_host_win.cc   |  7 ++++---
 spec/api-browser-window-spec.ts                    | 14 ++++++++++++++
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/shell/browser/ui/views/win_frame_view.cc b/shell/browser/ui/views/win_frame_view.cc
index 2193492b3c..0ff50e3046 100644
--- a/shell/browser/ui/views/win_frame_view.cc
+++ b/shell/browser/ui/views/win_frame_view.cc
@@ -295,8 +295,7 @@ gfx::Size WinFrameView::GetMaximumSize() const {
 }
 
 gfx::Insets WinFrameView::RestoredFrameBorderInsets() const {
-  if (window_->has_frame() || !window_->has_thick_frame() ||
-      !window_->IsResizable())
+  if (window_->has_frame() || !window_->has_thick_frame())
     return {};
 
   const int thickness =
diff --git a/shell/browser/ui/win/electron_desktop_window_tree_host_win.cc b/shell/browser/ui/win/electron_desktop_window_tree_host_win.cc
index fbd5b2a45e..ba68f7c117 100644
--- a/shell/browser/ui/win/electron_desktop_window_tree_host_win.cc
+++ b/shell/browser/ui/win/electron_desktop_window_tree_host_win.cc
@@ -124,10 +124,11 @@ bool ElectronDesktopWindowTreeHostWin::GetClientAreaInsets(
       // monitors with different DPIs before changing this code.
       *insets = gfx::Insets::TLBR(thickness, thickness, thickness, thickness);
       return true;
-    } else if (native_window_view_->has_thick_frame() &&
-               native_window_view_->IsResizable()) {
+    } else if (native_window_view_->has_thick_frame()) {
       // Grow the insets to support resize targets past the frame edge like in
-      // windows with standard frames.
+      // windows with standard frames. Non-resizable windows still get input
+      // insets for stable bounds and so they can be dragged from outer edges,
+      // also like in windows with standard frames.
       *insets = gfx::Insets::TLBR(0, thickness, thickness, thickness);
       return true;
     }
diff --git a/spec/api-browser-window-spec.ts b/spec/api-browser-window-spec.ts
index 7a231f1744..3a1019456b 100755
--- a/spec/api-browser-window-spec.ts
+++ b/spec/api-browser-window-spec.ts
@@ -5564,6 +5564,20 @@ describe('BrowserWindow module', () => {
         expectBoundsEqual(w.getContentSize(), [10, 10]);
       });
 
+      it('does not change window size when disabled and enabled for frameless window', () => {
+        const w = new BrowserWindow({
+          show: false,
+          width: 400,
+          height: 300,
+          frame: false
+        });
+
+        w.setResizable(false);
+        expectBoundsEqual(w.getSize(), [400, 300]);
+        w.setResizable(true);
+        expectBoundsEqual(w.getSize(), [400, 300]);
+      });
+
       ifit(process.platform === 'win32')('do not change window with frame bounds when maximized', () => {
         const w = new BrowserWindow({
           show: true,