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Fix SubViewNeedsDraw handling and improve test coverage

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Refactored `View` class to ensure `SuperView.SubViewNeedsDraw`
is managed correctly. Added logic to prevent clearing the flag
prematurely when sibling subviews still require drawing.

Introduced a new `SubViewNeedsDraw` property with a private
setter and added `TODO` comments for potential future
improvements, such as making it a computed property.

Updated and added tests in `NeedsDrawTests` and `StaticDrawTests`
to validate the corrected behavior and prevent regressions.
Re-enabled a previously skipped test after fixing the related bug.
This commit is contained in:
Tig
2025-12-04 12:36:54 -07:00
parent 193a5873d1
commit 96151201f6
4 changed files with 30 additions and 9 deletions
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5
Terminal.Gui/ViewBase/View.Drawing.cs
View File

@@ -35,6 +35,11 @@ public partial class View // Drawing APIs
foreach (View view in viewsArray)
{
view.ClearNeedsDraw ();
// ClearNeedsDraw does not clear view.SuperView.SubViewsNeedDraw, so we have to do it here
if (view.SuperView is { })
{
view.SuperView.SubViewNeedsDraw = false;
}
}
}

24
Terminal.Gui/ViewBase/View.NeedsDraw.cs
View File

@@ -39,6 +39,12 @@ public partial class View
}
}
// TODO: This property is decoupled from the actual state of the subviews (and adornments)
// TODO: It is a 'cache' that is set when any subview or adornment requests a redraw
// TODO: As a result the code is fragile and can get out of sync.
// TODO: Consider making this a computed property that checks all subviews and adornments for their NeedsDraw state
// TODO: But that may have performance implications.
/// <summary>Gets whether any SubViews need to be redrawn.</summary>
public bool SubViewNeedsDraw { get; private set; }
@@ -161,10 +167,20 @@ public partial class View
SubViewNeedsDraw = false;
if (SuperView is { })
{
SuperView.SubViewNeedsDraw = false;
}
// DO NOT clear SuperView.SubViewNeedsDraw here!
// The SuperView is responsible for clearing its own SubViewNeedsDraw flag.
// Previously this code cleared it:
//if (SuperView is { })
//{
// SuperView.SubViewNeedsDraw = false;
//}
// This caused a bug where drawing one subview would incorrectly clear the SuperView's
// SubViewNeedsDraw flag even when sibling subviews still needed drawing.
//
// The SuperView will clear its own SubViewNeedsDraw after all its subviews are drawn,
// either via:
// 1. The superview's own Draw() method calling ClearNeedsDraw()
// 2. The static View.Draw(peers) method calling ClearNeedsDraw() on all peers
// This ensures LineCanvas' get redrawn
if (!SuperViewRendersLineCanvas)

2
Tests/UnitTestsParallelizable/ViewBase/Draw/NeedsDrawTests.cs
View File

@@ -557,7 +557,7 @@ public class NeedsDrawTests : FakeDriverBase
}
[Fact (Skip = "This is a real bug discovered in PR #4431 that needs to be fixed")]
[Fact]
public void IndividualViewDraw_DoesNotClearSuperViewSubViewNeedsDraw ()
{
// This test validates that individual view Draw() calls should NOT clear the superview's

4
Tests/UnitTestsParallelizable/ViewBase/Draw/StaticDrawTests.cs
View File

@@ -95,7 +95,7 @@ public class StaticDrawTests : FakeDriverBase
// at the very end, cleaning up any SubViewNeedsDraw flags set
// by Margin.DrawMargins()
Assert.False (superview.SubViewNeedsDraw,
"SuperView's SubViewNeedsDraw should be false after all subviews are drawn and cleared");
"superview's SubViewNeedsDraw should be false after static Draw(). All subviews were drawn in the call to View.Draw");
Assert.False (subview1.SubViewNeedsDraw,
"SubView1's SubViewNeedsDraw should be false after its subviews are drawn and cleared");
}
@@ -188,7 +188,7 @@ public class StaticDrawTests : FakeDriverBase
// All SubViewNeedsDraw flags should be cleared after the static Draw
Assert.False (topView.SubViewNeedsDraw,
"TopView's SubViewNeedsDraw should be false after static Draw()");
"TopView's SubViewNeedsDraw should be false after static Draw(). All subviews were drawn in the call to View.Draw");
Assert.False (middleView1.SubViewNeedsDraw,
"MiddleView1's SubViewNeedsDraw should be false after its subviews are drawn");
Assert.False (middleView2.SubViewNeedsDraw,