## Summary of the Pull Request
When a user had "Disable Scroll Forward" enabled and switched to the alt buffer and maximized the console, then restored down, we'd crash. Now we don't.
## References
## PR Checklist
* [x] Closes#1206
* [x] I work here
* [x] Tests added/passed
## Detailed Description of the Pull Request / Additional comments
The problem is that we'd previously try to "anchor" the viewport to the virtual bottom when resizing like this. This would also cause us to move the top of the viewport down, into the buffer. However, if the alt buffer is getting smaller, we don't want to do this - if we anchor to the old _virtualBottom, the bottom of the viewport will actually be outside the current buffer.
This could theoretically happen with the main buffer too, but it's much easier to repro with the alt buffer.
When the scrollback buffer is empty, the RIS escape sequence (Reset to Initial
State) will fail to clear the screen, or reset any of the state. And when there
is something in the scrollback, it doesn't get cleared completely, and the
screen may get filled with the wrong background color (it should use the
default color, but it actually uses the previously active background color).
This commit attempts to fix those issues.
The initial failure is caused by the `SCREEN_INFORMATION::WriteRect` method
throwing an exception when passed an empty viewport. And the reason it's passed
an empty viewport is because that's what the `Viewport::Subtract` method
returns when the result of the subtraction is nothing. The PR fixes the
problem by making the `Viewport::Subtract` method actually return nothing in
that situation.
This is a change in the defined behavior that also required the associated
viewport tests to be updated. However, it does seem a sensible change, since
the `Subtract` method never returns empty viewports under any other
circumstances. And the only place the method seems to be used is in the
`ScrollRegion` implementation, where the previous behavior is guaranteed to
throw an exception.
The other issues are fixed simply by changing the order in which things are
reset in the `AdaptDispatch::HardReset` method. The call to `SoftReset` needed
to be made first, so that the SGR attributes would be reset before the screen
was cleared, thus making sure that the default background color would be used.
And the screen needed to be cleared before the scrollback was erased, otherwise
the last view of the screen would be retained in the scrollback buffer.
These changes also required existing adapter tests to be updated, but not
because of a change in the expected behaviour. It's just that certain tests
relied on the `SoftReset` happening later in the order, so weren't expecting it
to be called if say the scrollback erase had failed. It doesn't seem like the
tests were deliberately trying to verify that the SoftReset _hadn't_ been
called.
In addition to the updates to existing tests, this PR also add a new screen
buffer test which verifies the display and scrollback are correctly cleared
under the conditions that were previously failing.
Fixes#2307.
* Fix margin boundary tests in the RI, DL, and IL sequences.
* Refactor the margin boundary tests into a reusable SCREEN_INFORMATION method.
* Add screen buffer unit tests for the RI, DL, and IL sequences.
* Add support for origin mode (DECOM).
* Added a state machine unit test for the origin mode.
* Prevent the cursor position moving below the bottom margin of the scrolling region if the origin mode is relative.
* Only adjust the relative cursor position for origin mode if the scrolling region is actually set.
* Add some screenbuffer unit tests for the origin mode.
* Enhance the soft reset screenbuffer tests to verify the origin mode is reset.
* Move the origin mode flag constructor assignments into the intializer list.
* Implement XTerm's private mode escape sequence for enabling DECCOLM support.
* Add output engine and screen buffer units test for the private mode 40 escape sequence.
* Removed using namespace directive from header files and put these in cpp files where they are used
* Fixed tabbing issues by replacing them with spaces.
Also regrouped the using directives.
* Update src/host/exemain.cpp
Co-Authored-By: Mike Griese <migrie@microsoft.com>
* Update src/interactivity/win32/find.cpp
Co-Authored-By: Mike Griese <migrie@microsoft.com>
* Support OSC to set default background and foreground colors
* Update the Terminal theme when the background changes
* Fix whitespace per code-review
* Add Documentation Comments
Also fix a few outdated comments and whitespace
* Update Telemetry codes per code review
* Add Unit Tests for OSC ForegroundColor and BackgroundColor
* Add a couple additional test cases
* Minor doc and whitespace change per PR review
* Update comment help per code review
* Add another OSC 10 & 11 test case, improve output
* Comments and syntax cleanup per code reviews
