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On Android the hardware keys are the volume control and the framework mixes our stream against the device level, so a second control inside the app moves something the user already moved. Where that is true the player's level sits at maximum, SetVolume / ChangeVolume / MuteToggle are refused, and nothing persists a level nobody chose: restore remembers the stored value instead of applying it, and saveState writes that same value back rather than recording the synthetic maximum. Mute is in that list because it is a level of zero by another name -- and because with no control rendered it would be the one state on such a platform the user could not get out of. The predicate is named after the capability rather than the platform, because that is what makes it testable. Only platformOwnsVolume is behind a build tag, in two files that declare nothing else; everything else is decided against Player.systemVolume, a field a test sets either way. That is mediacontrols' split, with androidpayload.go's reasoning for keeping the contract out of a tagged file, and the tagged pair is covered by a source sweep since no tier here compiles both halves. SetDuck is deliberately untouched: it applies its attenuation by re-applying the *user's* level through setVolumeLocked, so pinning that level to maximum leaves the offset arithmetic exactly as it was. It is the only thing that may still move the output on such a platform, and TestSystemVolumeStillDucks is that property rather than a comment.
43 lines
2.1 KiB
Go
43 lines
2.1 KiB
Go
package player
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// Who owns the volume, and what follows when it is not us.
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//
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// On Android the hardware keys *are* the volume control and the
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// framework mixes our stream against the device level, so a second
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// control inside the app is a slider that moves something the user
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// already moved (#64). Where that is true the player's own level sits
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// at maximum, nothing changes it, and nothing persists it.
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//
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// **The predicate is named after the capability, not the platform.**
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// The frontend asks "is there a volume for me to control", which is a
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// question about this build; asking "is this a phone" instead would
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// key the answer to a viewport, and an Android tablet at 600px or more
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// would then draw the bottom bar's slider over a level pinned at
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// maximum -- a control that cannot act, which is the thing
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// `library-status-indicator` already settled is worse than none.
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//
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// **Only `platformOwnsVolume` is behind a build tag**, in two files
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// that declare nothing else. A tagged file is compiled by nothing
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// `make lint` or `make test` runs and is untestable off a phone, which
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// is the reasoning `mediacontrols/androidpayload.go` states for
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// keeping its contract out of one -- so everything decidable here is
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// decided against `Player.systemVolume`, a field a test sets either
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// way, and the tag decides only what that field starts as.
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//
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// The one thing this must not disturb is ducking. `SetDuck` applies
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// its attenuation by re-applying the *user's* level through
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// `setVolumeLocked`, so pinning that level to maximum leaves the
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// offset arithmetic exactly as it was: an OS asking us to get out of
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// the way of a navigation prompt is not the user setting a volume, and
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// it is the only thing that may move the output on such a platform.
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// SystemOwnsVolume reports whether the platform's own control is the
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// only volume control there is, so this app neither offers one nor
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// remembers a level.
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//
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// It is bound: the frontend renders no `<volume-control>` when it is
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// true, at any width.
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func (p *Player) SystemOwnsVolume() bool {
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return p.systemVolume
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}
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