Bug 146837 – Media Session: add plumbing for delivering start/end-of-interruption events

• Component: Media
• Status: RESOLVED FIXED

[Matt Rajca]

The platform should be able to send start-of-interruption events to MediaSessions so we can invoke the media session interruption algorithm (4.5.2).

[Radar WebKit Bug Importer]

<rdar://problem/21768356>

[Matt Rajca]

Created attachment 256588 [details]
Patch

[Matt Rajca]

Created attachment 256589 [details]
Patch

[Eric Carlson]

Comment on attachment 256589 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256589&action=review

> Source/WebCore/Modules/mediasession/MediaSessionEvents.h:33
> +enum MediaEventType {

This should be "enum class".

> Source/WebCore/Modules/mediasession/MediaSessionEvents.h:39
> +enum MediaSessionInterruptingCategory {

Ditto.

> Source/WebCore/page/Page.cpp:1230
> +void Page::handleStartOfInterruptionEvent(MediaSessionInterruptingCategory category)
> +{
> +}

Please add notImplemented();

[Matt Rajca]

(In reply to comment #4)
> Comment on attachment 256589 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=256589&action=review
> 
> > Source/WebCore/Modules/mediasession/MediaSessionEvents.h:33
> > +enum MediaEventType {
> 
> This should be "enum class".

These are "enums" so we can cast to them from WKMediaEventTypes. We can't do that with a strongly-typed "enum class".

> 
> > Source/WebCore/Modules/mediasession/MediaSessionEvents.h:39
> > +enum MediaSessionInterruptingCategory {
> 
> Ditto.
> 
> > Source/WebCore/page/Page.cpp:1230
> > +void Page::handleStartOfInterruptionEvent(MediaSessionInterruptingCategory category)
> > +{
> > +}
> 
> Please add notImplemented();

Added.

[Matt Rajca]

Created attachment 256610 [details]
Patch

[Tim Horton]

Comment on attachment 256610 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256610&action=review

> Source/WebKit2/UIProcess/API/C/WKPage.cpp:2197
> +    switch (wkCategory) {

I realize there's only one user, but the enum conversion functions are usually separate static methods. Maybe just keep that in mind if we end up needing this code again?

> Source/WebKit2/WebProcess/WebPage/WebPage.h:746
> +    void handleStartOfInterruptionEvent(uint32_t /* WebCore::MediaSessionInterruptingCategory */);

Since this is on WebPage, it should be more clear that it's about media. Also, maybe just "handleMediaInterruptionEvent", with a state/phase to indicate whether it's starting or ending? Won't you eventually need the end case too?

[Eric Carlson]

Comment on attachment 256610 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256610&action=review

> Source/WebKit2/UIProcess/API/C/WKPage.cpp:2192
> +void WKPageHandleStartOfInterruptionEvent(WKPageRef page, WKMediaSessionInterruptingCategory wkCategory)

You should COMPILE_ASSERT([value in MediaEventType] == [value in WKMediaEventTypes] for each value to make sure the enums stay in sync. See HTMLTrackElement.cpp for an example.

[Eric Carlson]

Comment on attachment 256610 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256610&action=review

>> Source/WebKit2/UIProcess/API/C/WKPage.cpp:2192
>> +void WKPageHandleStartOfInterruptionEvent(WKPageRef page, WKMediaSessionInterruptingCategory wkCategory)
> 
> You should COMPILE_ASSERT([value in MediaEventType] == [value in WKMediaEventTypes] for each value to make sure the enums stay in sync. See HTMLTrackElement.cpp for an example.

Or rather, if you do that then you can use a static_cast to convert values.

[Matt Rajca]

Created attachment 256706 [details]
Patch

[Matt Rajca]

(In reply to comment #7)
> Comment on attachment 256610 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=256610&action=review
> 
> > Source/WebKit2/UIProcess/API/C/WKPage.cpp:2197
> > +    switch (wkCategory) {
> 
> I realize there's only one user, but the enum conversion functions are
> usually separate static methods. Maybe just keep that in mind if we end up
> needing this code again?

Will do.

> 
> > Source/WebKit2/WebProcess/WebPage/WebPage.h:746
> > +    void handleStartOfInterruptionEvent(uint32_t /* WebCore::MediaSessionInterruptingCategory */);
> 
> Since this is on WebPage, it should be more clear that it's about media.
> Also, maybe just "handleMediaInterruptionEvent", with a state/phase to
> indicate whether it's starting or ending? Won't you eventually need the end
> case too?

I renamed it to 'handleMediaSessionInterruptionEvent' and added an enum for the event type (currently either start-of-interruption and end-of-interruption).

[Matt Rajca]

(In reply to comment #9)
> Comment on attachment 256610 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=256610&action=review
> 
> >> Source/WebKit2/UIProcess/API/C/WKPage.cpp:2192
> >> +void WKPageHandleStartOfInterruptionEvent(WKPageRef page, WKMediaSessionInterruptingCategory wkCategory)
> > 
> > You should COMPILE_ASSERT([value in MediaEventType] == [value in WKMediaEventTypes] for each value to make sure the enums stay in sync. See HTMLTrackElement.cpp for an example.
> 
> Or rather, if you do that then you can use a static_cast to convert values.

Added the static assertions.

[Tim Horton]

Comment on attachment 256706 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256706&action=review

> Source/WebKit2/WebProcess/WebPage/WebPage.cpp:191
> +#include "WKPagePrivate.h"

Put the enums in a new header (probably in Shared/API/C) that you include in both places (and install as a private header), do not import UIProcess API headers here!

[Matt Rajca]

Created attachment 256708 [details]
Patch

[Matt Rajca]

(In reply to comment #13)
> Comment on attachment 256706 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=256706&action=review
> 
> > Source/WebKit2/WebProcess/WebPage/WebPage.cpp:191
> > +#include "WKPagePrivate.h"
> 
> Put the enums in a new header (probably in Shared/API/C) that you include in
> both places (and install as a private header), do not import UIProcess API
> headers here!

That header import was left over from a previous revision of the patch. Removed.

[Tim Horton]

Comment on attachment 256708 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256708&action=review

> Source/WebKit2/UIProcess/API/C/WKPage.cpp:2193
> +// NOTE: The values in the WKMediaSessionInterruptingCategory enum must stay in sync with those in WebCore::MediaSessionInterruptingCategory.

Why must they? You do a proper conversion below.

[Matt Rajca]

(In reply to comment #16)
> Comment on attachment 256708 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=256708&action=review
> 
> > Source/WebKit2/UIProcess/API/C/WKPage.cpp:2193
> > +// NOTE: The values in the WKMediaSessionInterruptingCategory enum must stay in sync with those in WebCore::MediaSessionInterruptingCategory.
> 
> Why must they? You do a proper conversion below.

We cast from a WKMediaSessionInterruptionEvent to a MediaSessionInterruptionEvent in WebPage.cpp. We need to ensure the enums' values are the same, otherwise we'll get them mixed up after casting.

[Matt Rajca]

Committed r186791: <http://trac.webkit.org/changeset/186791>

[Tim Horton]

(In reply to comment #17)
> (In reply to comment #16)
> > Comment on attachment 256708 [details]
> > Patch
> > 
> > View in context:
> > https://bugs.webkit.org/attachment.cgi?id=256708&action=review
> > 
> > > Source/WebKit2/UIProcess/API/C/WKPage.cpp:2193
> > > +// NOTE: The values in the WKMediaSessionInterruptingCategory enum must stay in sync with those in WebCore::MediaSessionInterruptingCategory.
> > 
> > Why must they? You do a proper conversion below.
> 
> We cast from a WKMediaSessionInterruptionEvent to a
> MediaSessionInterruptionEvent in WebPage.cpp. We need to ensure the enums'
> values are the same, otherwise we'll get them mixed up after casting.

I'm not sure why we have a proper conversion function in one direction and just cast in the other direction?