5 ms·

> extremely poor platform APIs As a former member of the Windows accessibility team at Microsoft, I'd appreciate your thoughts on what makes the platform acces

> extremely poor platform APIs As a former member of the Windows accessibility team at Microsoft, I'd appreciate your thoughts on what makes the platform accessibility APIs extremely poor. I have my own thoughts on what makes them difficult to implement, but I'd like to hear your perspective first.

egnehots 5y ago
really the major pain point is more the lack of cross platform APIs.
- zxzax 5y ago
  Such cross platform API would belong in a cross platform toolkit, it really makes no sense for Windows to provide that. For example Qt has a cross platform accessibility API, and GTK is currently working on making theirs cross platform. Maybe somebody should move this functionality out into a standalone library?
  - mwcampbell 5y ago
    > Maybe somebody should move this functionality out into a standalone library? I've been thinking about this for a while. Below is an edited excerpt from a message that I wrote to a colleague a few months ago, about how I think I should go about such a project: --- I've been thinking about the problem of multiple programming languages, and even multiple programming styles within the same language. Do we implement a C library that would make hard-core Unix and Linux folks happy? A library in a subset of C++ that some developers of games and graphics would be comfortable with? A more modern style of C++ that would make some other developers happy? And where would that leave folks working in Java, or C# like the Unity crowd? Of course, different platforms have varying levels of support for different languages. And there are more languages coming into popularity or on the horizon, like Swift and Rust. So I think what we really want is a cross-platform message format or protocol, with multiple implementations: multiple providers on the application/toolkit side, and multiple client libraries on the platform side. The client libraries could be written in each platform's native language (e.g. C++ for Windows, Java for Android, Swift for Apple platforms, or JavaScript for the web), and separately, provider libraries could be implemented in multiple languages. All major programming languages can work with binary data buffers. And since none of us want to work directly with those raw bytes, we could use an existing standard like Google Protocol Buffers, which already has implementations in several languages. Initially, for desktop and mobile platforms as well as web applications, this protocol would just be used internally between components in the same application process. But I can dream about platforms themselves adopting the protocol someday. There would have to be glue layers between cross-platform providers and platform-specific clients, but if we design this right, the glue could be kept pretty thin, with most of the complexity being kept on one side or the other, so we don't have a multiplication of effort for n toolkits or applications on m platforms. I think the protocol should be push-based, rather than pull-based like Windows UI Automation and some other accessibility APIs. That is, the application/toolkit would push full information about objects in the accessibility tree when it first creates that tree, and incremental updates when objects are created or destroyed, when properties change, when text content changes, etc. That's probably the only thing that's going to work for the web platform, and I think it's a model that other platforms would do well to adopt. (It's probably too late for Windows, but I dream of replacing the current accessibility model on desktop Linux someday, after my non-compete with Microsoft expires.) The challenge with a push model is making it efficient; we don't want to re-push the whole contents of a large text box when the user types a single character, and when we do need to push all contents, we need to do so efficiently. And sometimes we really do need to push a lot of information. For example, for a text box, we need the screen coordinates of every character, plus all of the boundaries between words. Luckily, a push-based accessibility architecture has been done before, internally in the Chromium browser engine. As you probably know, Chromium has a multi-process model, where web pages are rendered in sandboxed processes, which communicate with a master browser process that interfaces with the OS. The browser process is not allowed to do blocking IPC requests into the renderer processes, so it can't implement synchronous, pull-based accessibility APIs like UIA in the obvious way. So the Chromium team implemented a protocol where the renderer processes push their accessibility trees, and incremental updates to those trees, over to the browser process, which can then store the trees in memory and then provide information to UIA or other APIs on request. The pushed trees are comprehensive, including the information I mentioned about text. Chromium does this using its own binary protocol called Mojo, which is kind of like Protocol Buffers but strongly tied to Chromium. So, while I'll take design inspiration from Chromium, I probably won't take the actual protocol or code. I also want my protocol to scale down to embedded platforms. Accessibility on devices running embedded software (i.e. not Windows or another general-purpose OS) is basically an unsolved problem; as far as I know, device makers have to implement their own custom self-voicing interfaces, if they do anything about the problem at all. But imagine a standard where a user can pull out their smartphone, connect to the specialized device over Bluetooth or WiFi, and get an accessible interface to the device on their phone. Yeah, I'm swinging for the fence with this project. To pull this off, I think the protocol would need to be not only push-based but streaming, allowing providers to send out accessibility information without having to build up and maintain much extra state in memory. This would also help with the immediate-mode GUIs that are used in some games and game development tools. If we design the protocol right, these immediate-mode toolkits should be able to push out accessibility information and events at the same time that they're making OpenGL (or similar) calls to draw the current frame, again without having to hold much extra state in memory, which is something that these toolkits try to avoid.
    - jcelerier 5y ago
      You can use d-bus on Mac, windows and Linux.
    - zxzax 5y ago
      That seems like it could be interesting. It sounds like you would need to have part of a library store and diff the tree state, and then send updates based on that? You could use that part for immediate mode GUIs, and then retained mode GUIs could skip it and maintain their own trees, and just deal with the protocol, maybe even the raw protobuf bindings or whatever it is you choose. The Linux desktop environments could really use more people working on the accessibility stack, it's really outdated at the moment.
    - neverartful 5y ago
      I've been thinking of something very similar to this and have been working on the implementations. I currently have front-ends written in Java (Swing and SWT), Pascal (Delphi VCL, Delphi FMX, Lazarus LCL), C++ (wxWidgets and Gtk). I also have a HTML/JS prototype. I have backends written in Java, C#, Go, Crystal, and Nim. For the protocol I'm using JSON via HTTP. The more I work with this approach the more advantages I see. I think you're on to something.
      - mwcampbell 5y ago
        Based on the set of front-ends, it sounds like the goal of your project is a cross-language GUI toolkit wrapper. Is that correct? The goal of my project is a cross-platform and cross-language accessibility abstraction.
xyzzy_plugh 5y ago
I've dabbled in this space and it would easily, easily be more code than all of Gio just to get basic accessibility integration in Windows. COM, OLE, a heavy bias towards automatically working with native UI elements which are obviously not used here. It's just not a user friendly API. Hell, that applies to anything that uses COM
- zxzax 5y ago
  Could that be solved by having better golang bindings for COM/OLE? Is it a problem of too much boilerplate?
  - xyzzy_plugh 5y ago
    That's a big part of it. Another part is that most Go developers want to keep their Cgo dependencies as small as possible (preferably zero) for portability and performance reasons. It's also problematic that Go is not really OOP, and in particular immediate mode programming implies that state is inferred by the pass each frame -- meshing this with the COM/OLE model is bananas. You basically need to do everything the library is doing to draw, cache and render the UI again to render the state in COM. It's a ton of bookkeeping. Worse still, while the Gio layout engine is pretty good at culling non-visible stuff, ultimately the framework doesn't know what will be visible until we're in GPU land, so there would have to be a ton of bookkeeping added to test if, for example, some text was clipped or if things were overlapping. In practice, the best way to model things would be to just allow the developer to do something equivalent to pushing fields full of ARIA information like in the browser. But now you're losing all the advantages of the immediate mode and layout engine, etc. It's a lose/lose situation, unfortunately. I think the real solution is somewhere in the middle. I think screen readers need to grow some OCR abilities, and libraries like Gio need to learn some better navigation tech, like supporting tab, keyboard nav, etc. Something like that.
    - zxzax 5y ago
      Screen readers doing OCR is a big no-no. There is no possible way that will have the effect you want it to have. The text-to-speech part is the absolute bare minimum of what a screen reader is actually doing. For example that would break horribly with the situation you describe, where some piece of text gets clipped. Just IMO, it's unrealistic to expect to have an accessible GUI that stores no state, does none of that type of bookkeeping, has no OOP model, and only outputs to pixels. The point with these type of assistive technologies is that the user can't work with that type of visual data, they need more state presented to them. Sure, it makes everything easier to develop when you cut it all out and only use immediate mode, but that's exactly the problem: everything else has been cut out, on purpose.

egnehots 5y ago

really the major pain point is more the lack of cross platform APIs.

zxzax 5y ago
Such cross platform API would belong in a cross platform toolkit, it really makes no sense for Windows to provide that. For example Qt has a cross platform accessibility API, and GTK is currently working on making theirs cross platform. Maybe somebody should move this functionality out into a standalone library?
- mwcampbell 5y ago
  > Maybe somebody should move this functionality out into a standalone library? I've been thinking about this for a while. Below is an edited excerpt from a message that I wrote to a colleague a few months ago, about how I think I should go about such a project: --- I've been thinking about the problem of multiple programming languages, and even multiple programming styles within the same language. Do we implement a C library that would make hard-core Unix and Linux folks happy? A library in a subset of C++ that some developers of games and graphics would be comfortable with? A more modern style of C++ that would make some other developers happy? And where would that leave folks working in Java, or C# like the Unity crowd? Of course, different platforms have varying levels of support for different languages. And there are more languages coming into popularity or on the horizon, like Swift and Rust. So I think what we really want is a cross-platform message format or protocol, with multiple implementations: multiple providers on the application/toolkit side, and multiple client libraries on the platform side. The client libraries could be written in each platform's native language (e.g. C++ for Windows, Java for Android, Swift for Apple platforms, or JavaScript for the web), and separately, provider libraries could be implemented in multiple languages. All major programming languages can work with binary data buffers. And since none of us want to work directly with those raw bytes, we could use an existing standard like Google Protocol Buffers, which already has implementations in several languages. Initially, for desktop and mobile platforms as well as web applications, this protocol would just be used internally between components in the same application process. But I can dream about platforms themselves adopting the protocol someday. There would have to be glue layers between cross-platform providers and platform-specific clients, but if we design this right, the glue could be kept pretty thin, with most of the complexity being kept on one side or the other, so we don't have a multiplication of effort for n toolkits or applications on m platforms. I think the protocol should be push-based, rather than pull-based like Windows UI Automation and some other accessibility APIs. That is, the application/toolkit would push full information about objects in the accessibility tree when it first creates that tree, and incremental updates when objects are created or destroyed, when properties change, when text content changes, etc. That's probably the only thing that's going to work for the web platform, and I think it's a model that other platforms would do well to adopt. (It's probably too late for Windows, but I dream of replacing the current accessibility model on desktop Linux someday, after my non-compete with Microsoft expires.) The challenge with a push model is making it efficient; we don't want to re-push the whole contents of a large text box when the user types a single character, and when we do need to push all contents, we need to do so efficiently. And sometimes we really do need to push a lot of information. For example, for a text box, we need the screen coordinates of every character, plus all of the boundaries between words. Luckily, a push-based accessibility architecture has been done before, internally in the Chromium browser engine. As you probably know, Chromium has a multi-process model, where web pages are rendered in sandboxed processes, which communicate with a master browser process that interfaces with the OS. The browser process is not allowed to do blocking IPC requests into the renderer processes, so it can't implement synchronous, pull-based accessibility APIs like UIA in the obvious way. So the Chromium team implemented a protocol where the renderer processes push their accessibility trees, and incremental updates to those trees, over to the browser process, which can then store the trees in memory and then provide information to UIA or other APIs on request. The pushed trees are comprehensive, including the information I mentioned about text. Chromium does this using its own binary protocol called Mojo, which is kind of like Protocol Buffers but strongly tied to Chromium. So, while I'll take design inspiration from Chromium, I probably won't take the actual protocol or code. I also want my protocol to scale down to embedded platforms. Accessibility on devices running embedded software (i.e. not Windows or another general-purpose OS) is basically an unsolved problem; as far as I know, device makers have to implement their own custom self-voicing interfaces, if they do anything about the problem at all. But imagine a standard where a user can pull out their smartphone, connect to the specialized device over Bluetooth or WiFi, and get an accessible interface to the device on their phone. Yeah, I'm swinging for the fence with this project. To pull this off, I think the protocol would need to be not only push-based but streaming, allowing providers to send out accessibility information without having to build up and maintain much extra state in memory. This would also help with the immediate-mode GUIs that are used in some games and game development tools. If we design the protocol right, these immediate-mode toolkits should be able to push out accessibility information and events at the same time that they're making OpenGL (or similar) calls to draw the current frame, again without having to hold much extra state in memory, which is something that these toolkits try to avoid.
  - jcelerier 5y ago
    You can use d-bus on Mac, windows and Linux.
  - zxzax 5y ago
    That seems like it could be interesting. It sounds like you would need to have part of a library store and diff the tree state, and then send updates based on that? You could use that part for immediate mode GUIs, and then retained mode GUIs could skip it and maintain their own trees, and just deal with the protocol, maybe even the raw protobuf bindings or whatever it is you choose. The Linux desktop environments could really use more people working on the accessibility stack, it's really outdated at the moment.
  - neverartful 5y ago
    I've been thinking of something very similar to this and have been working on the implementations. I currently have front-ends written in Java (Swing and SWT), Pascal (Delphi VCL, Delphi FMX, Lazarus LCL), C++ (wxWidgets and Gtk). I also have a HTML/JS prototype. I have backends written in Java, C#, Go, Crystal, and Nim. For the protocol I'm using JSON via HTTP. The more I work with this approach the more advantages I see. I think you're on to something.
    - mwcampbell 5y ago
      Based on the set of front-ends, it sounds like the goal of your project is a cross-language GUI toolkit wrapper. Is that correct? The goal of my project is a cross-platform and cross-language accessibility abstraction.

xyzzy_plugh 5y ago

I've dabbled in this space and it would easily, easily be more code than all of Gio just to get basic accessibility integration in Windows. COM, OLE, a heavy bias towards automatically working with native UI elements which are obviously not used here. It's just not a user friendly API. Hell, that applies to anything that uses COM

zxzax 5y ago
Could that be solved by having better golang bindings for COM/OLE? Is it a problem of too much boilerplate?
- xyzzy_plugh 5y ago
  That's a big part of it. Another part is that most Go developers want to keep their Cgo dependencies as small as possible (preferably zero) for portability and performance reasons. It's also problematic that Go is not really OOP, and in particular immediate mode programming implies that state is inferred by the pass each frame -- meshing this with the COM/OLE model is bananas. You basically need to do everything the library is doing to draw, cache and render the UI again to render the state in COM. It's a ton of bookkeeping. Worse still, while the Gio layout engine is pretty good at culling non-visible stuff, ultimately the framework doesn't know what will be visible until we're in GPU land, so there would have to be a ton of bookkeeping added to test if, for example, some text was clipped or if things were overlapping. In practice, the best way to model things would be to just allow the developer to do something equivalent to pushing fields full of ARIA information like in the browser. But now you're losing all the advantages of the immediate mode and layout engine, etc. It's a lose/lose situation, unfortunately. I think the real solution is somewhere in the middle. I think screen readers need to grow some OCR abilities, and libraries like Gio need to learn some better navigation tech, like supporting tab, keyboard nav, etc. Something like that.
  - zxzax 5y ago
    Screen readers doing OCR is a big no-no. There is no possible way that will have the effect you want it to have. The text-to-speech part is the absolute bare minimum of what a screen reader is actually doing. For example that would break horribly with the situation you describe, where some piece of text gets clipped. Just IMO, it's unrealistic to expect to have an accessible GUI that stores no state, does none of that type of bookkeeping, has no OOP model, and only outputs to pixels. The point with these type of assistive technologies is that the user can't work with that type of visual data, they need more state presented to them. Sure, it makes everything easier to develop when you cut it all out and only use immediate mode, but that's exactly the problem: everything else has been cut out, on purpose.