Accessibility: Finalized Shared UIA Tree Model #1915
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Both projects must now implement the virtual functions. ConHost should be MOSTLY set up. WT needs a way to implement these (need access to Terminal info) NEXT: Fix IScreenInfoUiaProvider's references to Selection and UiaTextRange
TODOs: - bugfix: get rects for Min/Max/Close buttons - Clean public/protected/private functions from UIA Providers (some are in wrong place) - re-attach tracing - Hook up Windows Terminal
Got WindowsTerminal UIA Tree up and running again TODO ConHost: - bugfix: get rects for Caption buttons - re-attach tracing TODO WT: - attach ScreenInfoUiaProvider to TermControl
miniksa
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zadjii-msft
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miniksa
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This was referenced Jul 16, 2019
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Just gonna merge this into my I'll mark it ready for review when it's ready for review (so, like, later today) |
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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.
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Summary of the Pull Request
The UIA provider classes are now shared properly. They're hooked up to ConHost and Windows Terminal. You should actually have a UIA Tree when you try to use them.
The actual text buffer UIA element is not hooked up for Windows Terminal, however. That'll be a later PR.
References
Extension of #1691
Please read the description in that PR for background information.
Detailed Description of the Pull Request / Additional comments
Changes to the WindowUiaProvider
As mentioned earlier, the WindowUiaProvider is the top-level UIA provider for our projects. To reuse as much code as possible, I created
Microsoft::Console::Types::WindowUiaProviderBase. Any existing functions that reference aScreenInfoUiaProviderwere virtual-ized.In each project, a
WindowUiaProvider : WindowUiaProviderBasewas created to define those virtual functions. Note that that will be the main difference between ConHost and Windows Terminal moving forward: how many TextBuffers are on the screen.So, ConHost should be the same as before, with only one
ScreenInfoUiaProvider, whereas Windows Terminal needs to (1) update which one is on the screen and (2) may have multiple on the screen.🚨 Windows Terminal doesn't have the
ScreenInfoUiaProviderhooked up yet. We'll have all the XAML elements in the UIA tree. But, sinceTermControlis a custom XAML Control, I need to hook up theScreenInfoUiaProviderto it. This work will be done in a new PR and resolve GitHub Issue #1352.Moved to
Microsoft::Console::TypesThese files got moved to a shared area so that they can be used by both ConHost and Windows Terminal.
This means that any references to the
ServiceLocatorhad to be removed.IConsoleWindowIslandWindow : IConsoleWindowScreenInfoUiaProviderServiceLocatorandSCREEN_INFORMATIONwere removed.IRenderDatawas used to accomplish this. Refer to next section for more details.UiaTextRangeServiceLocatorandSCREEN_INFORMATIONwere removed.IRenderDatawas used to accomplish this. Refer to next section for more details.static, that means that anIRenderDatahad to be added into most of them.Changes to IRenderData
Since
IRenderDatais now being used to abstract outServiceLocatorandSCREEN_INFORMATION, I had to add a few functions here:bool IsAreaSelected()void ClearSelection()void SelectNewRegion(...)HRESULT SearchForText(...)SearchForText()is a problem here. The overall new design is great! But Windows Terminal doesn't have a way to search for text in the buffer yet, whereas ConHost does. So I'm punting on this issue for now. It looks nasty, but just look at all the other pretty things here. :)Miscellaneous Known Issues
Tracingneeds to be reattachedScreenInfoUiaProviderneeds to be attached to theTermControl.Things I'll fix in this PR (just need to add commits on top of it):
Validation Steps Performed