[Windows] Fix TitleBar.IsVisible = false the caption buttons become unresponsive

[devanathan-vaithiyanathan]

Issue Details

On Windows, when TitleBar.IsVisible is set to false, the system caption buttons (minimize, maximize, close) become unresponsive after resizing the window.

Description of Change

Updated WindowRootView.UpdateTitleBarContentSize() to apply passthrough regions only when the TitleBar is visible and to clear them when it is hidden, preventing stale regions from blocking caption button interactions.

Issues Fixed

Fixes #33171

Tested the behavior in the following platforms.

• Android
• Windows
• iOS
• Mac

Before	After
Windows After.mov	Windows Before.mov

[sheiksyedm]

/rebase

[Copilot]

Pull request overview

This pull request fixes a Windows-specific issue where system caption buttons (minimize, maximize, close) become unresponsive after resizing the window when TitleBar.IsVisible is set to false.

Key Changes

• Updated WindowRootView.UpdateTitleBarContentSize() to conditionally apply passthrough regions based on TitleBar visibility
• Added Windows-specific UI test helper methods to interact with system caption buttons via Appium
• Created comprehensive UI test to verify caption button responsiveness when TitleBar is hidden

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Core/src/Platform/Windows/WindowRootView.cs	Added visibility check to only set passthrough regions when TitleBar is visible, and clear them when hidden to prevent blocking caption buttons
src/TestUtils/src/UITest.Appium/HelperExtensions.cs	Added TapMinimizeButton(), TapMaximizeButton(), and FindSystemButton() helper methods for Windows UI automation testing of system caption buttons
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue33171.cs	Created Windows-specific NUnit test that verifies caption buttons remain responsive when TitleBar visibility is toggled and window is resized
src/Controls/tests/TestCases.HostApp/Issues/Issue33171.cs	Created test page with TitleBar, visibility toggle button, window resize button, and window size label to reproduce and test the issue

[Copilot]

The test verifies that the maximize button works after toggling TitleBar visibility and reducing window width. However, the PR description states that caption buttons become unresponsive "after resizing the window". The test should verify this specific scenario by:

1. Setting TitleBar.IsVisible = false
2. Resizing the window (currently done via ReduceWidthButton)
3. Attempting to click caption buttons to verify they are responsive

The current test flow doesn't clearly demonstrate the bug scenario described in the PR - it toggles visibility, reduces width, maximizes, and checks the size change. Consider adding a more explicit test that demonstrates caption buttons are responsive after window resize with TitleBar.IsVisible = false.

[jeremy-visionaid]

LGTM, thanks!

[sheiksyedm]

/rebase

[PureWeen]

/rebase

[PureWeen]

Code Review - Suggested Simplifications

After testing multiple alternative approaches and having 4 different AI models evaluate the implementation, all models unanimously identified two optimization opportunities in the current fix.

✅ Current Implementation: CORRECT

The fix successfully solves the caption button responsiveness issue. However, it can be simplified for better performance and clarity.

---

🔴 Issue #1: Duplicate Visibility Check

Current code checks visibility twice:

• Line 204: AppTitleBarContentControl.Visibility == UI.Xaml.Visibility.Visible
• Line 234: AppTitleBarContentControl.Visibility == UI.Xaml.Visibility.Visible

Suggested: Cache the visibility check once at the start:

bool isTitleBarVisible = AppTitleBarContentControl.Visibility == UI.Xaml.Visibility.Visible;

---

🔴 Issue #2: Unnecessary Loop Execution (Performance)

Current code (lines 217-225) always executes the loop even when title bar is hidden:

The code performs expensive TransformToVisual() calculations, then checks visibility afterward and discards the results if hidden.

Suggested: Gate the loop behind the visibility check:

if (isTitleBarVisible && PassthroughTitlebarElements.Count > 0)
{
    // Only calculate rects when actually needed
    var rectArray = new List<Rect32>();
    foreach (var child in PassthroughTitlebarElements)
    {
        // ... expensive calculations ...
    }
    nonClientInputSrc.SetRegionRects(...);
}
else
{
    nonClientInputSrc.ClearRegionRects(...);
}

---

💡 Recommended Refactor

Click to see full optimized implementation

internal void UpdateTitleBarContentSize()
{
    if (AppTitleBarContentControl is null)
        return;

    // Cache visibility check (fixes issue #1)
    bool isTitleBarVisible = AppTitleBarContentControl.Visibility == UI.Xaml.Visibility.Visible;

    // Update height logic
    if (isTitleBarVisible && _appTitleBarHeight != AppTitleBarContentControl.ActualHeight)
    {
        UpdateRootNavigationViewMargins(AppTitleBarContentControl.ActualHeight);

        if (AppWindowId.HasValue)
        {
            AppWindow.GetFromWindowId(AppWindowId.Value).TitleBar.PreferredHeightOption =
                _appTitleBarHeight >= 48 ? TitleBarHeightOption.Tall : TitleBarHeightOption.Standard;
        }

        this.RefreshThemeResources();
    }

    // Update passthrough regions
    if (AppWindowId.HasValue)
    {
        var nonClientInputSrc = InputNonClientPointerSource.GetForWindowId(AppWindowId.Value);

        // Only calculate rects when needed (fixes issue #2)
        if (isTitleBarVisible && PassthroughTitlebarElements.Count > 0)
        {
            var rectArray = new List<Rect32>();
            foreach (var child in PassthroughTitlebarElements)
            {
                var transform = child.TransformToVisual(null);
                var bounds = transform.TransformBounds(
                    new FRect(0, 0, child.ActualWidth, child.ActualHeight));
                rectArray.Add(GetRect(bounds, XamlRoot.RasterizationScale));
            }

            nonClientInputSrc.SetRegionRects(NonClientRegionKind.Passthrough, [.. rectArray]);
        }
        else
        {
            nonClientInputSrc.ClearRegionRects(NonClientRegionKind.Passthrough);
        }
    }
}

---

📊 Benefits

Benefit	Impact
Performance	Avoids expensive transform calculations when title bar is hidden
Clarity	Single cached visibility variable makes logic obvious
Correctness	Same behavior, just more efficient
Maintainability	Easier to understand the visibility gating logic

---

🤖 Model Agreement (4/4 Consensus)

All models (Claude Sonnet, Claude Opus, Gemini, GPT-5.2 Codex) identified these exact same issues and suggested identical fixes.

---

Verdict: Current implementation is correct and solves the bug, but the suggested refactor improves performance and clarity without changing behavior.

[PureWeen]

/azp run

[PureWeen]

@devanathan-vaithiyanathan let me know if my last commit is alright and you agree with the changes

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[devanathan-vaithiyanathan]

let me know if my last commit is alright and you agree with the changes

Yes @PureWeen , changes are fine