ViddikScreenshot
Marks a @Composable as a viddik fixture: one golden image, and one entry in the showroom.
Every descriptive parameter is optional. What is left out is read from an androidx.compose.ui.tooling.preview.Preview annotation on the same function, when there is one, so a composable that already carries a preview for the IDE does not have to spell its name and size a second time:
@ViddikScreenshot
@Preview(name = "Primary", group = "Buttons", widthDp = 320)
@Composable
fun PrimaryButton() { ... }That is the whole reason this annotation carries no parameters in the example: @Preview is a superset of what viddik needs, it means the same thing to the IDE preview pane and to Android's own screenshot tooling, and in Compose Multiplatform 1.12 it is the very same androidx.compose.ui.tooling.preview.Preview on both. Reading it keeps one declaration serving all three.
This annotation stays the opt-in, though, and is not going away: scanning every @Preview in a codebase would silently turn previews written purely for the IDE into goldens, including the many that cannot render headless at all.
Precedence for each field is: an argument given here, then the matching @Preview field, then the default. Arguments given here therefore keep working exactly as before.
Parameters
golden-file and showroom name; defaults to the @Preview name, then to the function's own name.
showroom grouping; defaults to the @Preview group, then to "Default".
capture width in pixels; defaults to @Preview.widthDp, then to 400. viddik renders at density 1, so a dp from @Preview is a pixel here — see ViddikDensityTest, which pins that.
capture height in pixels; defaults to @Preview.heightDp, then to AUTO_HEIGHT, which measures the content and crops to it.
emit a second, dark entry alongside the light one. Distinct from @Preview(uiMode = UI_MODE_NIGHT_YES), which says this one fixture is dark rather than asking for another one; setting both is an error.
share of pixels this fixture alone may differ by, overriding the run's own setting (viddik.tolerancePercent, otherwise 0.05%). Unset by default, and meant for the fixture that provably can't hold the strict number — a known-unportable rendering path, not a fixture that has started failing. The engine's 16-pixel floor still applies underneath, so this loosens a fixture rather than tightening it below a handful of pixels. @Preview has no counterpart, so this one is only ever read here.