Terminal: Crashes when a custom scaling size is set

[alostsock]

Environment

Windows build number: Microsoft Windows [Version 10.0.19033.1]
Windows Terminal version (if applicable): 0.7.3291.0, also built from master (7bcb060)

Steps to reproduce

1. Set a custom scaling factor in Settings > System > Display > "Advanced scaling settings", for example:

   

2. Start the terminal

Expected behavior

The terminal should start

Actual behavior

The terminal crashes almost immediately after loading a blank screen.

In trying to fix this I've reinstalled and also removed profiles.json to get a fresh one. Afterwards I attempted to debug, and got the following call stack:

TerminalControl.dll!gsl::details::terminate() Line 127  C++
TerminalControl.dll!gsl::details::throw_exception<gsl::narrowing_error>(gsl::narrowing_error && __formal) Line 136  C++
TerminalControl.dll!gsl::narrow<float,double>(double u) Line 126    C++
TerminalControl.dll!ScaleRect(winrt::Windows::Foundation::Rect rect, double scale) Line 31  C++
TerminalControl.dll!winrt::Microsoft::Terminal::TerminalControl::implementation::TSFInputControl::_layoutRequestedHandler(winrt::Windows::UI::Text::Core::CoreTextEditContext sender, const winrt::Windows::UI::Text::Core::CoreTextLayoutRequestedEventArgs & args) Line 164   C++

Based on this I realized my display's scaling factor had been set to a custom value (115% or something). I changed it back to the default 100% and it started fine.

Feedback Hub link: https://aka.ms/AA6q09q

[DHowett-MSFT]

Fascinating! Thanks. This might explain a number of the crash-on-startup issues.

[mkitzan]

I had a look through the code implicated in the stack trace, and it's a classic floating point comparison failure. ScaleRect takes a double which it tries to cast to a float using gsl::narrow. The exception is emitted from gsl::narrow after a failed comparison between floating point values (float and double). After writing a ScaleRect which only uses the gsl::narrow_cast (which just wraps a static_cast) the crash disappears.

[mkitzan]

ScaleRect is coming from Utils.h in External Dependencies in WinRTUtils and TerminalControl (when viewed in VS19). Would there be any problem editing Utils.h? Would the new ScaleRect function be better?

[DHowett-MSFT]

No problem editing that file, it’s definitely one of ours :)

[mkitzan]

Great, I'll PR the fix

[msftbot[bot]]

:tada:This issue was addressed in #3784, which has now been successfully released as Windows Terminal Preview v0.7.3382.0.:tada:

Handy links:

• Release Notes
• Store Download

[johnc44]

Just installed Version: 0.7.3382.0 and can confirm that it's all working now. Thanks for the quick response!