1695116 - Make Windows use RemoteAccessible for tree navigation and role

Status: RESOLVED FIXED

(Core :: Disability Access APIs, task)

Description

[James Teh [:Jamie]]

Once Windows has a separate class hierarchy, it should be possible to have it use RemoteAccessible for anything that doesn't require a sync IPC call. For now, this is only tree navigation and role. Of course, this should be done behind a pref.

This will require a lot of fail-early checks for other IAccessible methods to prevent crashes.

Comment 1

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 1: When the cache is enabled, use a real MsaaAccessible for RemoteAccessibles.

With the cache disabled (which was previously always the case), we create a RemoteAccessibleWrap for each RemoteAccessible, stored as the RemoteAccessible's "Wrapper".
This in turn creates an MsaaAccessible.
However, both of these are little more than stubs: the MsaaAccessible itself is never returned to clients and most of the methods would crash if called.
They exist only to store the MSAA id received from the content process and to return the COM proxy from the content process to clients.

With the cache enabled, we now create a real MsaaAccessible for each RemoteAccessible, stored as the RemoteAccessible's "Wrapper".
This MsaaAccessible is directly returned to clients.
Soon, it will generate its own id in the parent process and will delegate to the underlying RemoteAccessible to serve queries from clients.

As part of this:

1. We stop managing COM proxies in the parent process when the cache is enabled, since we don't need those and can't store them anyway.
2. We stop setting the id on the MsaaAccessible when the cache is enabled, since it will soon generate its own id like local MsaaAccessibles do.
3. OuterDocAccessible::ChildCount had to be tweaked so it doesn't try to return a RemoteAccessibleWrap when the cache is enabled. (It previously called RemoteChildDocAccessible, which fetches a RemoteAccessibleWrap.)

Comment 2

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 2: Support RemoteAccessible in various utility functions.

1. Add support for RemoteAccessible in MsaaAccessible::GetFrom.
2. Add an overload of MsaaDocAccessible::GetFrom which accepts a (remote) DocAccessibleParent.
3. Add MsaaDocAccessible::GetFromOwned to return the containing document's MsaaDocAccessible for a given Accessible.
4. MsaaAccessible::LocalAcc now returns null for a RemoteAccessible, rather than just assuming the accessible is local.
5. MsaaAccessible::NativeAccessible now supports retrieving a native client pointer for LocalAccessibles, RemoteAccessibles and RemoteAccessibleWraps.

Comment 3

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 3: Id management for remote MsaaAccessibles with the cache enabled.

1. Make MsaaDocAccessible id maps contain Accessibles instead of AccessibleWraps. This allows us to put RemoteAccessibles in the id map.
2. Make MsaaAccessible::MsaaShutdown and GetChildIDFor handle RemoteAccessibles. GetChildIDFor lazily generates an id, Just as it does for LocalAccessible.

Comment 4

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 4: Support events for RemoteAccessibles with the cache enabled.

1. GetHWNDFor and FireWinEvent now take an Accessible and support RemoteAccessible.
2. The Proxy*Event methods pass a RemoteAccessible instead of a RemoteAccessibleWrap, since RemoteAccessibleWraps aren't used with the cache enabled. FireWinEvent retrieves the RemoteAccessibleWrap if the cache is disabled.

Comment 5

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 5: Initial support for RemoteAccessibles in QueryInterface.

For now, a lot of interfaces are disabled, since they don't support RemoteAccessibles at all.

Comment 6

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 6: Support retrieval of remote MsaaAccessibles via MSAA child id.

Comment 7

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 7: Support MSAA accParent, accChildCount and accNavigate for RemoteAccessibles.

Comment 8

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 8: Support MSAA accRole for RemoteAccessibles.

Comment 9

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 9: Fail gracefully for MSAA methods which don't support RemoteAccessible yet instead of crashing.

Comment 10

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 10: When the cache is enabled, don't send COM proxies and MSAA ids from the content process.

Sending these doesn't really do any harm, as we already disregard them in the parent process.
However, it's certainly unnecessary and wasteful.

Comment 11

[James Teh [:Jamie]]

Attachment: Bug 1695116 part 11: When the cache is enabled, don't generate an MSAA id for each content process.

This isn't used and thus isn't necessary.
Also, we can currently only support 127 content processes because of this id allocation, so avoiding this removes that restriction.

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/56ac84b2eae0
part 1: When the cache is enabled, use a real MsaaAccessible for RemoteAccessibles. r=morgan
https://hg.mozilla.org/integration/autoland/rev/517f726f1c3e
part 2: Support RemoteAccessible in various utility functions. r=morgan
https://hg.mozilla.org/integration/autoland/rev/b441f1c4bf99
part 3: Id management for remote MsaaAccessibles with the cache enabled. r=morgan
https://hg.mozilla.org/integration/autoland/rev/d52bb54ca76a
part 4: Support events for RemoteAccessibles with the cache enabled. r=morgan
https://hg.mozilla.org/integration/autoland/rev/232ba8d9bcd2
part 5: Initial support for RemoteAccessibles in QueryInterface. r=morgan
https://hg.mozilla.org/integration/autoland/rev/b067a69fc41b
part 6: Support retrieval of remote MsaaAccessibles via MSAA child id. r=morgan
https://hg.mozilla.org/integration/autoland/rev/84745f573a55
part 7: Support MSAA accParent, accChildCount and accNavigate for RemoteAccessibles. r=morgan
https://hg.mozilla.org/integration/autoland/rev/55273d675037
part 8: Support MSAA accRole for RemoteAccessibles. r=morgan
https://hg.mozilla.org/integration/autoland/rev/52c836904523
part 9: Fail gracefully for MSAA methods which don't support RemoteAccessible yet instead of crashing. r=morgan
https://hg.mozilla.org/integration/autoland/rev/185d685563d9
part 10: When the cache is enabled, don't send COM proxies and MSAA ids from the content process. r=morgan
https://hg.mozilla.org/integration/autoland/rev/804044733a13
part 11: When the cache is enabled, don't generate an MSAA id for each content process. r=morgan

Comment 13

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/56ac84b2eae0
https://hg.mozilla.org/mozilla-central/rev/517f726f1c3e
https://hg.mozilla.org/mozilla-central/rev/b441f1c4bf99
https://hg.mozilla.org/mozilla-central/rev/d52bb54ca76a
https://hg.mozilla.org/mozilla-central/rev/232ba8d9bcd2
https://hg.mozilla.org/mozilla-central/rev/b067a69fc41b
https://hg.mozilla.org/mozilla-central/rev/84745f573a55
https://hg.mozilla.org/mozilla-central/rev/55273d675037
https://hg.mozilla.org/mozilla-central/rev/52c836904523
https://hg.mozilla.org/mozilla-central/rev/185d685563d9
https://hg.mozilla.org/mozilla-central/rev/804044733a13