See inline commentary. I don't really have any energy left to provide
anything else, other than maybe a demonstration of how this dies in
framework:
diff --git a/osu.Framework.Tests/Visual/UserInterface/TestSceneScreenStackUnbindOnExit.cs b/osu.Framework.Tests/Visual/UserInterface/TestSceneScreenStackUnbindOnExit.cs
new file mode 100644
index 000000000..c74ce6636
--- /dev/null
+++ b/osu.Framework.Tests/Visual/UserInterface/TestSceneScreenStackUnbindOnExit.cs
@@ -0,0 +1,59 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics.UserInterface;
+using osu.Framework.Screens;
+
+namespace osu.Framework.Tests.Visual.UserInterface
+{
+ public partial class TestSceneScreenStackUnbindOnExit : FrameworkTestScene
+ {
+ [Cached]
+ private ScreenStack screenStack = new ScreenStack();
+
+ [Test]
+ public void TestScreenExitUnbindDoesNotInterruptLoadComplete()
+ {
+ AddStep("set up the scenario", () =>
+ {
+ Child = screenStack;
+ screenStack.Push(new Screen());
+ screenStack.Push(new BrokenScreen());
+ });
+ AddUntilStep("wait to get to target screen", () => screenStack.CurrentScreen, Is.InstanceOf<Screen>);
+ }
+
+ private partial class BrokenSlider : BasicSliderBar<float>
+ {
+ [Resolved]
+ private ScreenStack screenStack { get; set; } = null!;
+
+ protected override void LoadComplete()
+ {
+ // exiting the current screen provokes the behaviour of unbinding all bindables in the screen's subtree
+ screenStack.CurrentScreen.Exit();
+
+ // ...but the following calls should still take correct effect inside `SliderBar`
+ // (namely one consisting of propagating `{Min,Max}Value` into `currentNumberInstantaneous`)
+ // so that it doesn't have its internal invariants violated
+ CurrentNumber.MinValue = -10;
+ CurrentNumber.MaxValue = 10;
+
+ // this notably calls `Scheduler.AddOnce(updateValue)` inside, which will happen *in the imminent future, in the same frame as `LoadComplete()` here.
+ // if the above mutations of `{Min,Max}Value` don't correctly propagate inside the slider bar due to an overly eager unbind, this will cause a crash.
+ base.LoadComplete();
+ }
+ }
+
+ private partial class BrokenScreen : Screen
+ {
+ [BackgroundDependencyLoader]
+ private void load()
+ {
+ InternalChild = new BrokenSlider();
+ }
+ }
+ }
+}
I attempted to address what I perceive to be the root issue here which
is that `ScreenStack` is allowed to arbitrarily unbind bindables under
drawables which are by all means still in the scene graph. The attempt
consisted of scheduling the unbind until after children of the screen
stack, but that caused 150 game-side tests to fail, seemingly on
something relevant to bindable leases, so I give up.
In order of severity:
- You could actually click on the textbox portion of a disabled textbox,
focus it, select text, input stuff, and commit, which would die
on the spot.
- The slider part had no visual indication that it's not interactable
anymore.
Rather than control the propagation of the value between the slider and
the textbox, add a property that controls the propagation of the value
between the bindables inside the form control to external bindables.
This will help alleviate issues where the external bindable update
incurs overheads due to having heavy change callbacks attached.