fix: improve single-pixel resize handling on Windows (#44723)

* fix: improve single-pixel resize handling

Co-authored-by: Shelley Vohr <[email protected]>

* Update spec/api-browser-window-spec.ts

Co-authored-by: Niklas Wenzel <[email protected]>

Co-authored-by: Shelley Vohr <[email protected]>

* Update shell/browser/native_window_views.cc

Co-authored-by: Niklas Wenzel <[email protected]>

Co-authored-by: Shelley Vohr <[email protected]>

---------

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <[email protected]>

shell/browser/native_window_views.cc

@@ -1643,18 +1643,28 @@ void NativeWindowViews::OnWidgetBoundsChanged(views::Widget* changed_widget,
   if (changed_widget != widget())
     return;
 
-  // |GetWindowBoundsInScreen| has a ~1 pixel margin of error, so if we check
-  // existing bounds directly against the new bounds without accounting for that
-  // we'll have constant false positives when the window is moving but the user
-  // hasn't changed its size at all.
-  auto areWithinOnePixel = [](gfx::Size old_size, gfx::Size new_size) -> bool {
+#if BUILDFLAG(IS_WIN)
+  // OnWidgetBoundsChanged is emitted both when a window is moved and when a
+  // window is resized. If the window is moving, then
+  // WidgetObserver::OnWidgetBoundsChanged is being called from
+  // Widget::OnNativeWidgetMove() and not Widget::OnNativeWidgetSizeChanged.
+  // |GetWindowBoundsInScreen| has a ~1 pixel margin
+  // of error because it converts from floats to integers between calculations,
+  // so if we check existing bounds directly against the new bounds without
+  // accounting for that we'll have constant false positives when the window is
+  // moving but the user hasn't changed its size at all.
+  auto isWithinOnePixel = [](gfx::Size old_size, gfx::Size new_size) -> bool {
     return base::IsApproximatelyEqual(old_size.width(), new_size.width(), 1) &&
            base::IsApproximatelyEqual(old_size.height(), new_size.height(), 1);
   };
 
+  if (is_moving_ && isWithinOnePixel(widget_size_, bounds.size()))
+    return;
+#endif
+
   // We use |GetBounds| to account for minimized windows on Windows.
   const auto new_bounds = GetBounds();
-  if (!areWithinOnePixel(widget_size_, new_bounds.size())) {
+  if (widget_size_ != new_bounds.size()) {
     NotifyWindowResize();
     widget_size_ = new_bounds.size();
   }

spec/api-browser-window-spec.ts

@@ -1543,6 +1543,16 @@ describe('BrowserWindow module', () => {
           await expect(once(w, 'resized')).to.eventually.be.fulfilled();
         });
       });
+
+      it('does not emits the resize event for move-only changes', async () => {
+        const [x, y] = w.getPosition();
+
+        w.once('resize', () => {
+          expect.fail('resize event should not be emitted');
+        });
+
+        w.setBounds({ x: x + 10, y: y + 10 });
+      });
     });
 
     describe('BrowserWindow.setSize(width, height)', () => {
@@ -1556,6 +1566,17 @@ describe('BrowserWindow module', () => {
         expectBoundsEqual(w.getSize(), size);
       });
 
+      it('emits the resize event for single-pixel size changes', async () => {
+        const [width, height] = w.getSize();
+        const size = [width + 1, height - 1];
+
+        const resized = once(w, 'resize');
+        w.setSize(size[0], size[1]);
+        await resized;
+
+        expectBoundsEqual(w.getSize(), size);
+      });
+
       ifit(process.platform === 'darwin')('on macOS', () => {
         it('emits \'resized\' event after animating', async () => {
           const size = [300, 400];