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Android: keep the D-pad focus inside mobile dialogs #106

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Merged
keyldev merged 1 commit into from
Nov 3, 2026
Merged

Android: keep the D-pad focus inside mobile dialogs #106

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107 changes: 105 additions & 2 deletions src/OpenIPC.Viewer.App/Services/OverlayDialogPresenter.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Avalonia;
using Avalonia.Animation;
Expand All @@ -15,6 +16,7 @@
using Avalonia.Media.Transformation;
using Avalonia.Reactive;
using Avalonia.Threading;
using Avalonia.VisualTree;

namespace OpenIPC.Viewer.App.Services;

Expand Down Expand Up @@ -85,7 +87,74 @@ public static bool TryDismissTopmost()
return true;
}

private sealed record OpenDialog(Control Content, TaskCompletionSource Dismissed);
private sealed record OpenDialog(Control Content, TaskCompletionSource Dismissed, Control Card);

// Whether the last input on the TopLevel was a key (keyboard, TV remote, gamepad) rather than
// a pointer. A dialog opened from a key puts the focus on its first control right away (the
// remote has nothing else to start from); one opened by a tap does not, so a form whose first
// control is a text field does not pop the soft keyboard on its own.
private static bool _lastInputWasKey;
private static TopLevel? _trackedTopLevel;

private static void TrackInputKind(TopLevel? top)
{
if (top is null || ReferenceEquals(top, _trackedTopLevel)) return;
_trackedTopLevel = top;
top.AddHandler(InputElement.KeyDownEvent, (object? _, KeyEventArgs e) =>
{
_lastInputWasKey = true;
PullFocusBackIntoDialog(top, e);
},
RoutingStrategies.Tunnel, handledEventsToo: true);
top.AddHandler(InputElement.PointerPressedEvent, (object? _, PointerPressedEventArgs _) => _lastInputWasKey = false,
RoutingStrategies.Tunnel, handledEventsToo: true);
}

// A dialog is open but the focus is not in it — its focused control went away (a "Scan again"
// button replaced by the results) or was never set. A navigation key would then move from
// the page, behind the dim; start it from the topmost dialog's first control instead.
// Popups (a ComboBox list) are TopLevels of their own and never route through here.
private static void PullFocusBackIntoDialog(TopLevel top, KeyEventArgs e)
{
if (Open.Count == 0 || e.Handled) return;
if (e.Key is not (Key.Up or Key.Down or Key.Left or Key.Right or Key.Tab or Key.Enter or Key.Space))
return;
var card = Open[^1].Card;
if (top.FocusManager?.GetFocusedElement() is Visual focused
&& (ReferenceEquals(focused, card) || card.IsVisualAncestorOf(focused)))
return;
(FirstFocusable(card) ?? card).Focus(NavigationMethod.Directional);
e.Handled = true;
}

// D-pad / arrow keys inside a dialog move the focus only among the dialog's own controls.
// Without this the XY focus navigation of a TV remote searches the whole TopLevel and walks
// off the sheet onto the page under the dim (the Welcome sheet → the Library search box).
// Arrows a control uses itself (a TextBox caret, a ComboBox) arrive here already handled.
private static void KeepArrowFocusInside(Control card, KeyEventArgs e)
{
if (e.Handled) return;
var direction = e.Key switch
{
Key.Up => NavigationDirection.Up,
Key.Down => NavigationDirection.Down,
Key.Left => NavigationDirection.Left,
Key.Right => NavigationDirection.Right,
_ => (NavigationDirection?)null,
};
if (direction is null) return;
var focusManager = TopLevel.GetTopLevel(card)?.FocusManager;
// The card itself holds the focus (dialog opened by a tap, or at start-up before any key):
// the first arrow goes to the dialog's first control.
if (ReferenceEquals(focusManager?.GetFocusedElement(), card))
FirstFocusable(card)?.Focus(NavigationMethod.Directional);
else
// Directional, so the focus ring shows as it does for the page's own D-pad moves.
(focusManager?.FindNextElement(direction.Value, new FindNextElementOptions { SearchRoot = card })
as InputElement)?.Focus(NavigationMethod.Directional);
// At the sheet's edge there is nothing to move to: stay put rather than leave it.
e.Handled = true;
}

// fullScreen → fill the whole TopLevel (no bottom-sheet card / scroll wrapper).
// Used for the SSH terminal and file manager, which are full-screen pages on
Expand All @@ -102,6 +171,9 @@ public static async Task<TResult> ShowAsync<TResult>(Control content, Task<TResu
// We size the dim explicitly to the TopLevel client area instead, and
// track it so rotation / soft-keyboard insets keep it full-bleed.
var top = TopLevel.GetTopLevel(overlay);
TrackInputKind(top);
// Given back when the dialog closes, so a remote user lands where they were.
var focusBefore = top?.FocusManager?.GetFocusedElement();

var card = new Border
{
Expand All @@ -117,6 +189,9 @@ public static async Task<TResult> ShowAsync<TResult>(Control content, Task<TResu
// inner content caps its width; content controls also paint Bg1.
Background = ResolveBrush("Bg1Brush"),
ClipToBounds = true,
// Holds the focus while no control of the dialog has it (opened by a tap); not a tab
// stop itself (set below).
Focusable = true,
BoxShadow = fullScreen
? default
: new BoxShadows(new BoxShadow
Expand Down Expand Up @@ -211,6 +286,13 @@ void ApplySafeArea()

card.AddHandler(InputElement.GotFocusEvent, (object? _, RoutedEventArgs _) => ScrollFocusedIntoView(),
RoutingStrategies.Bubble);
KeyboardNavigation.SetIsTabStop(card, false);

// Keyboard / remote focus stays in the dialog: Tab wraps around inside it, arrows are
// searched within the card only.
KeyboardNavigation.SetTabNavigation(dim, KeyboardNavigationMode.Cycle);
dim.AddHandler(InputElement.KeyDownEvent, (object? _, KeyEventArgs e) => KeepArrowFocusInside(card, e),
RoutingStrategies.Bubble);

// Drive the dim to cover the full client area and cap the sheet to that
// height (minus the top peek) so long forms scroll inside the card
Expand All @@ -235,7 +317,7 @@ void ApplySize(Size s)
sizeSub = top.GetObservable(TopLevel.ClientSizeProperty).Subscribe(ApplySize);
}

var entry = new OpenDialog(content, new TaskCompletionSource());
var entry = new OpenDialog(content, new TaskCompletionSource(), card);
overlay.Children.Add(dim);
Open.Add(entry);
ActiveChanged?.Invoke();
Expand All @@ -247,6 +329,13 @@ void ApplySize(Size s)
dim.Opacity = 1;
if (!fullScreen)
card.RenderTransform = TransformOperations.Parse("translateY(0)");
// Opened from a key: start the remote on the dialog's first control. Opened by a tap:
// only take the focus off the page underneath, without a focus ring or a keyboard.
var first = _lastInputWasKey ? FirstFocusable(card) : null;
if (first is not null)
first.Focus(NavigationMethod.Directional);
else
card.Focus(NavigationMethod.Unspecified);
}, DispatcherPriority.Background);

try
Expand All @@ -266,9 +355,23 @@ void ApplySize(Size s)
overlay.Children.Remove(dim);
Open.Remove(entry);
ActiveChanged?.Invoke();
// Keyboard / remote only: after a tap there is no focus ring to restore, and giving the
// focus back to a text field would pop the soft keyboard. Posted: the button that opened
// the dialog is usually disabled until its async command, which awaits this dialog, ends.
if (_lastInputWasKey && focusBefore is InputElement before)
Dispatcher.UIThread.Post(() =>
{
if (before.IsEffectivelyVisible && before.IsEffectivelyEnabled)
before.Focus(NavigationMethod.Directional);
}, DispatcherPriority.Background);
}
}

// The dialog's first control in visual (= reading) order that the keyboard can focus.
private static InputElement? FirstFocusable(Control card) =>
card.GetVisualDescendants().OfType<InputElement>().FirstOrDefault(e =>
e.Focusable && e.IsEffectivelyVisible && e.IsEffectivelyEnabled && KeyboardNavigation.GetIsTabStop(e));

private static double Clamp(double inset) => Math.Clamp(inset, 0, MaxSafeInset);


Expand Down
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