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Fix potential cursor redrawing crash #2965

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merged 2 commits into from
Oct 18, 2019
Merged

Fix potential cursor redrawing crash #2965

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30956d7
Added read lock and fix various cursor pos issue
skyline75489 Oct 12, 2019
941b377
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skyline75489 Oct 18, 2019
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19 changes: 19 additions & 0 deletions src/cascadia/TerminalCore/Terminal.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,18 @@ void Terminal::UpdateSettings(winrt::Microsoft::Terminal::Settings::ICoreSetting
proposedTop -= (proposedBottom - bufferSize.Y);
}

Cursor& cursor = _buffer->GetCursor();
auto cursorPosition = cursor.GetPosition();

// If the cursor is positioned beyond the range of the viewport, then
// set the cursor position to a legal value.
cursorPosition.X = std::min(cursorPosition.X, static_cast<SHORT>(viewportSize.X - 1));
cursorPosition.Y = std::min(cursorPosition.Y, static_cast<SHORT>(viewportSize.Y - 1));

cursor.StartDeferDrawing();
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This looks strange but it's necessary. Because SetPosition will call RedrawCursor, and eventually find its way to Terminal::IsCursorDoubleWidth(), causing the crash. So I had to disable redrawing first, correct the position, and enable redrawing. IMO the SetPosition (and related method) are too aggresive doing redrawing, which is not a good design.

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Yeah, you're right. We should likely fix the design on the redrawing and come up with something better. We can take this for now. I know it's ugly and complicated to fix the right way, but I'm glad you found something workable.

cursor.SetPosition(cursorPosition);
cursor.EndDeferDrawing();

_mutableViewport = Viewport::FromDimensions({ 0, proposedTop }, viewportSize);
_scrollOffset = 0;
_NotifyScrollEvent();
Expand Down Expand Up @@ -425,6 +437,11 @@ void Terminal::_WriteBuffer(const std::wstring_view& stringView)
}
}

if (proposedCursorPosition.X > bufferSize.RightInclusive())
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Did you intentionally put this back? It looks like @DHowett-MSFT just removed this in #3212

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The line the caused regression was proposedCursorPosition.Y++;. I only took the first line and reset position.X to a legal value.

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OK.

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This unfortunately caused #3277.

{
proposedCursorPosition.X = 0;
}

// If we're about to scroll past the bottom of the buffer, instead cycle the buffer.
const auto newRows = proposedCursorPosition.Y - bufferSize.Height() + 1;
if (newRows > 0)
Expand Down Expand Up @@ -533,6 +550,8 @@ void Terminal::_InitializeColorTable()
// - isVisible: whether the cursor should be visible
void Terminal::SetCursorVisible(const bool isVisible) noexcept
{
auto lock = LockForWriting();

auto& cursor = _buffer->GetCursor();
cursor.SetIsVisible(isVisible);
}
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