Are there clear conventions on where to put a Background on Composables? Or where assumptions about ...

# compose-wear

[yschimke]

Are there clear conventions on where to put a Background on Composables? Or where assumptions about MaterialTheme.colors.background are applied. I just did a deep dive investigating an issue reported for the Media UI and think I've come to the conclusion that user code should almost never set a background, unless it's specific to a Screen such as Artwork.

[yschimke]

My mental model is now

[yschimke]

There is a system level background - for an Activity this is Black (or probably set by the theme?)

[yschimke]

Awkwardly for Android Studio previews it seems to be a washed out dark gray in some cases, but need to investigate more. For Paparazzi it's effectively transparent, so following my new rule above I need to set the background myself in the test case.

[yschimke]

The SwipeDismissableNavHost, has a SwipeToDismissBox, which applies MaterialTheme.colors.background, so typically everything in your app has this background. Nothing above the NavHost affects the background.

[yschimke]

Does Colors.background get used elsewhere, i.e. mixed with other colors for components like Chips? OR if I do apply a screen background, maybe even non uniform like a gradient or image, will colors above that mix correctly?

[yschimke]

message has been deleted

[John Nichol]

We have actually spotted a few places where we didn't have the right background behind our gradients for Chip which we are fixing at the moment

[John Nichol]

Some components like Chip Card and Button will have a natural background (most of time). Most containers should probably not have

[yschimke]

Sounds like I'm doing the right thing with this PR. https://github.com/google/horologist/pull/246

[yschimke]

Thanks