## Summary of the Pull Request
This forces the `TermControl` to only use `ControlCore` and `ControlInteractivity` via their WinRT projections. We want this, because WinRT projections can be used across process boundaries. In the future, `ControlCore` and `ControlInteractivity` are going to be living in a different process entirely from `TermControl`. By enforcing this boundary now, we can make sure that they will work seamlessly in the future.
## References
* Tear-out: #1256
* Megathread: #5000
* Project: https://github.com/microsoft/terminal/projects/5
## PR Checklist
* [x] Closes https://github.com/microsoft/terminal/projects/5#card-50760270
* [x] I work here
* [x] Tests added/passed
* [n/a] Requires documentation to be updated
## Detailed Description of the Pull Request / Additional comments
Most all this was just converting pure c++ types to winrt types when possible. I've added a couple helper projections with `til` converters, which made most of this really easy.
The "`MouseButtonState` needs to be composed of `Int32`s instead of `bool`s" is MENTAL. I have no idea why this is, but when I had the control OOP in the sample, that would crash when trying to de-marshal the bools. BODGY.
The biggest changes are in the way the UIA stuff is hooked up. The UiaEngine needs to be attached directly to the `Renderer`, and it can't be easily projected, so it needs to live next to the `ControlCore`. But the `TermControlAutomationPeer` needed the `UiaEngine` to help implement some interfaces.
Now, there's a new layer we've introduced. `InteractivityAutomationPeer` does the `ITextProvider`, `IControlAccessibilityInfo` and the `IUiaEventDispatcher` thing. `TermControlAutomationPeer` now has a
`InteractivityAutomationPeer` stashed inside itself, so that it can ask the interactivity layer to do the real work. We still need the `TermControlAutomationPeer` though, to be able to attach to the real UI tree.
## Validation Steps Performed
The terminal behaves basically the same as before.
Most importantly, I whipped out Accessibility Insights, and the Terminal looks the same as before.
**BE NOT AFRAID**. I know that there's 107 files in this PR, but almost
all of it is just find/replacing `TerminalControl` with `Control`.
This is the start of the work to move TermControl into multiple pieces,
for #5000. The PR starts this work by:
* Splits `TerminalControl` into separate lib and dll projects. We'll
want control tests in the future, and for that, we'll need a lib.
* Moves `ICoreSettings` back into the `Microsoft.Terminal.Core`
namespace. We'll have other types in there soon too.
* I could not tell you why this works suddenly. New VS versions? New
cppwinrt version? Maybe we're just better at dealing with mdmerge
bugs these days.
* RENAMES `Microsoft.Terminal.TerminalControl` to
`Microsoft.Terminal.Control`. This touches pretty much every file in
the sln. Sorry about that (not sorry).
An upcoming PR will move much of the logic in TermControl into a new
`ControlCore` class that we'll add in `Microsoft.Terminal.Core`.
`ControlCore` will then be unittest-able in the
`UnitTests_TerminalCore`, which will help prevent regressions like #9455
## Detailed Description of the Pull Request / Additional comments
You're really gonna want to clean the sln first, then merge this into
your branch, then rebuild. It's very likely that old winmds will get
left behind. If you see something like
```
Error MDM2007 Cannot create type
Microsoft.Terminal.TerminalControl.KeyModifiers in read-only metadata
file Microsoft.Terminal.TerminalControl.
```
then that's what happened to you.
This PR makes use of the UiaRenderer by attaching it to the TerminalControl and setting up selectionChanged events for accessibility.
Part 1: attaching the UiaRenderer
The uiaRenderer is treated very similarly to the dxRenderer. We have a unique_ptr ref to it in the TermControl. This gets populated when the TermControlAutomationPeer is created (thus enabling accessibility).
To prevent every TermControl from sending signals simultaneously, we specifically only enable whichever one is in an active pane.
The UiaRenderer needs to send encoded events to the automation provider (in this case, TermControlAutomationPeer). We needed our own automation events so that we can reuse this model for ConHost. This is the purpose of IUiaEventDispatcher.
We need a dispatcher for the UiaRenderer. Otherwise, we would do a lot of work to find out when to fire an event, but we wouldn't have a way of doing that.
Part 2: hooking up selection events
This provides a little bit of polish to hooking it up before. Primarily to actually make it work. This includes returning S_FALSE instead of E_NOTIMPL.
The main thing here really is just how to detect if a selection has changed. This also shows how clean adding more events will be in the future!
Builds on the work of #1691 and #1915
Let's start with the easy change:
- `TermControl`'s `controlRoot` was removed. `TermControl` is a `UserControl`
now.
Ok. Now we've got a story to tell here....
### TermControlAP - the Automation Peer
Here's an in-depth guide on custom automation peers:
https://docs.microsoft.com/en-us/windows/uwp/design/accessibility/custom-automation-peers
We have a custom XAML element (TermControl). So XAML can't really hold our
hands and determine an accessible behavior for us. So this automation peer is
responsible for enabling that interaction.
We made it a FrameworkElementAutomationPeer to get as much accessibility as
possible from it just being a XAML element (i.e.: where are we on the screen?
what are my dimensions?). This is recommended. Any functions with "Core" at the
end, are overwritten here to tweak this automation peer into what we really
need.
But what kind of interactions can a user expect from this XAML element?
Introducing ControlPatterns! There's a ton of interfaces that just define "what
can I do". Thankfully, we already know that we're supposed to be
`ScreenInfoUiaProvider` and that was an `ITextProvider`, so let's just make the
TermControlAP an `ITextProvider` too.
So now we have a way to define what accessible actions can be performed on us,
but what should those actions do? Well let's just use the automation providers
from ConHost that are now in a shared space! (Note: this is a great place to
stop and get some coffee. We're about to hop into the .cpp file in the next
section)
### Wrapping our shared Automation Providers
Unfortunately, we can't just use the automation providers from ConHost. Or, at
least not just hook them up as easily as we wish. ConHost's UIA Providers were
written using UIAutomationCore and ITextRangeProiuder. XAML's interfaces
ITextProvider and ITextRangeProvider are lined up to be exactly the same.
So we need to wrap our ConHost UIA Providers (UIAutomationCore) with the XAML
ones. We had two providers, so that means we have two wrappers.
#### TermControlAP (XAML) <----> ScreenInfoUiaProvider (UIAutomationCore)
Each of the functions in the pragma region `ITextProvider` for
TermControlAP.cpp is just wrapping what we do in `ScreenInfoUiaProvider`, and
returning an acceptable version of it.
Most of `ScreenInfoUiaProvider`'s functions return `UiaTextRange`s. So we need
to wrap that too. That's this next section...
#### XamlUiaTextRange (XAML) <----> UiaTextRange (UIAutomationCore)
Same idea. We're wrapping everything that we could do with `UiaTextRange` and
putting it inside of `XamlUiaTextRange`.
### Additional changes to `UiaTextRange` and `ScreenInfoUiaProvider`
If you don't know what I just said, please read this background:
- #1691: how accessibility works and the general responsibility of these two
classes
- #1915: how we pulled these Accessibility Providers into a shared area
TL;DR: `ScreenInfoUiaProvider` lets you interact with the displayed text.
`UiaTextRange` is specific ranges of text in the display and navigate the text.
Thankfully, we didn't do many changes here. I feel like some of it is hacked
together but now that we have a somewhat working system, making changes
shouldn't be too hard...I hope.
#### UiaTextRange
We don't have access to the window handle. We really only need it to draw the
bounding rects using WinUser's `ScreenToClient()` and `ClientToScreen()`. I
need to figure out how to get around this.
In the meantime, I made the window handle optional. And if we don't have
one....well, we need to figure that out. But other than that, we have a
`UiaTextRange`.
#### ScreenInfoUiaProvider
At some point, we need to hook up this automation provider to the
WindowUiaProvider. This should help with navigation of the UIA Tree and make
everything just look waaaay better. For now, let's just do the same approach
and make the pUiaParent optional.
This one's the one I'm not that proud of, but it works. We need the parent to
get a bounding rect of the terminal. While we figure out how to attach the
WindowUiaProvider, we should at the very least be able to get a bunch of info
from our xaml automation peer. So, I've added a _getBoundingRect optional
function. This is what's called when we don't have a WindowUiaProvider as our
parent.
## Validation Steps Performed
I've been using inspect.exe to see the UIA tree.
I was able to interact with the terminal mostly fine. A few known issues below.
Unfortunately, I tried running Narrator on this and it didn't seem to like it
(by that I mean WT crashed). Then again, I don't really know how to use
narrator other than "click on object" --> "listen voice". I feel like there's a
way to get the other interactions with narrator, but I'll be looking into more
of that soon. I bet if I fix the two issues below, Narrator will be happy.
## Miscellaneous Known Issues
- `GetSelection()` and `GetVisibleRanges()` crashes. I need to debug through
these. I want to include them in this PR.
Fixes#1353.
Mike Griese
Carlos Zamora