v0.21.0

[Origogi]

Name a file in commonMain and its previews come up in the browser and redraw on save, the same way Android ones do — Kotlin Multiplatform and Compose Multiplatform modules work end to end. Prevue also gets going on a Mac without Android Studio, finding an installed JDK by itself and saying what is missing (Java or the Android SDK) before anything is approved, and saving stays under a second even when you pause between edits.

Kotlin Multiplatform

Prevue now draws commonMain previews of Kotlin Multiplatform and Compose Multiplatform modules. Like Android Studio, it draws them from the module's Android compilation, and iOS · web targets alongside are fine. It takes AGP 9's com.android.kotlin.multiplatform.library (variant androidMain) and the older kotlin.multiplatform + com.android.library pair. If you warmed up an app module with an earlier version, warm it up once more to pick all of this up.

_{PartyAnimationPreview from the commonMain of the KotlinConf app (Apache 2.0), opened in Prevue's interactive mode.}

• Warmup. Previews come up from the dump of the Android app that includes the module. Warming up with a file of a KMP module takes that app's dump, even on a fresh clone where nothing is built yet (when several apps include it, it asks which one), and a module with no Android target says why.
• Saving. Prevue watches commonMain · androidMain and the intermediate source sets Android takes part in, so saving redraws without Gradle. That includes KMP modules of an included build under the repository (includeBuild("components"), as in Thunderbird's components/ui/bolt).
• expect · actual. Saving or opening a file with expect · actual declarations says it needs a Gradle build. It used to try compiling and fail with "'expect' and 'actual' declarations can be used only in multiplatform projects" plus advice to warm up the module. Now the picture stays as it was, marked stale with "needs a Gradle build", and redraws on its own when the build outputs change. Opening such a file changed since the last Gradle build, or bringing back an empty tab by saving one, draws from the Gradle build with the same mark instead of failing.
• Compose Multiplatform resources (Res). Fonts, images and strings from composeResources used to fail with "Missing resource … .cvr" or fall back to the default font. Prevue now takes the app's merged assets from the dump and draws them as the app does. A KMP module's src/androidMain/res and manifest are also watched for resource changes.
• The older JetBrains @Preview (org.jetbrains.compose.ui.tooling.preview.Preview) reads like the androidx one. Multipreview annotations built from it now expand, constants in its arguments (widthDp = WIDE) are read from the compiled class, and an aliased import still counts. Its @PreviewParameter providers already worked.
• Viewer. A KMP module's file names its source set in the subtitle (feature:pearl · commonMain · debug). In the open-files rail, a shared source set's file icon carries the Kotlin Multiplatform mark and a KMP module's androidMain an Android robot, in the official one-color logo (black, white in dark mode); Android-only files keep the plain file icon, and the icons are 18px. A shared source set's tab tooltip adds "Shared code · rendered with the Android build", and the first time you open such a file in a checkout, a note at the bottom says "commonMain renders with the app's Android build too. expect calls run the Android actual." until you close it (it steps aside while you look at other files). prevue status gains kmp, and sourceSet for the shown file and for each tab of a KMP module.
• README. The subtitle names Jetpack Compose and Compose Multiplatform, and a Compose Multiplatform badge joins the badge row, now regrouped into plain build, version and license badges and brand-colored ones for Claude Code, Codex, Jetpack Compose, Compose Multiplatform and JDK. Get started says to name a file in commonMain the same way, the board section says commonMain Previews are drawn from the module's Android compilation, and Supported lists which KMP modules work and which stop.

Setup without Android Studio

• Without Android Studio, Prevue finds an installed JDK by itself, and says so when there is none. It used to run only on Android Studio's bundled Java or the JDK in PREVUE_JDK: a Mac with JDK 25 from Homebrew still stopped at "Java is missing", and with neither, health reported only the server as missing and start then failed with "FileNotFoundError: [Errno 2] No such file or directory". Now, with no PREVUE_JDK, it looks at Android Studio (/Applications and ~/Applications), then JAVA_HOME, Library/Java/JavaVirtualMachines, Homebrew's openjdk* and SDKMAN, reading each JDK's version itself, and takes 25 first, then 21–24, then 26 or later. When none is 21 or later, health lists jdk under missing first, before any download or Gradle run is approved, saying where it looked (jdkSearched) and to run brew install openjdk@25 (no sudo), and start stops with the same message before it opens the preparation screen or touches a running server; call again after installing and it is found with nothing to set. A Java older than 21 counts as missing too, so a PREVUE_JDK pointing at JDK 17 no longer passes health only for the server to fail after setup and warmup; the response names the version it found in jdkVersion. Previews were byte-identical on Android Studio's JBR 25, Temurin 21 and Temurin 25; 25 or later starts about a second faster. Thanks to @Dwite for the fix (#29).
• Without an Android SDK, health says so before anything is approved. The preview server draws against the SDK's android.jar, found through ANDROID_HOME, then ANDROID_SDK_ROOT, then ~/Library/Android/sdk. With none there, setup and warmup went ahead and the server then failed to start, leaving only "android.jar를 찾지 못했다" in its log. Now health lists sdk under missing right after jdk, with the folder it checked and how to install the SDK, and start stops with the same message before it opens the preparation screen. An SDK folder with no platform downloaded counts as missing, and an empty ANDROID_HOME is skipped the same way by both.

Performance

• Saving stays under a second when you pause between edits. The preview server used to start the Kotlin compiler's environment over on every save, so with saves half a minute apart, compiling one file could climb from about 0.3 s to 0.6–1 s after a few saves and a save took longer than a second (KotlinConf's PageTitle.kt, a commonMain file). Now it keeps that environment between saves, as the Kotlin daemon does. On an Apple M4 Max, six to ten saves 30 seconds apart took a median of 0.64–0.79 s across four runs, against 0.63–1.19 s across five runs without it; a jar that Gradle rewrites in the meantime is still read fresh.

Fixes

• Projects whose module directories don't follow their Gradle paths work end to end. When settings.gradle (or a settings plugin) moves a module with projectDir — :widgets living in core/design/widgets — saving a file failed to compile with "Unresolved reference" because it borrowed the app's classpath, and wait · focus · scroll · touch answered "No daemon" (#30). The dump now records each module's directory from settings, so warm up once more to pick it up. Thanks to @sergei-lapin for the report and the fix (#31).
• A component no longer stretches when you pick a device in interactive mode. A preview that sizes itself to its content, such as a card or a row, used to be drawn only as tall as its content. The viewer then stretched that picture to fill the device screen, so text looked tall and squeezed. It now draws at the device's screen size like a custom size does, with the component at the top left and the rest of the screen empty. The posture pictures drawn ahead and the CLI's PNG change the same way. The renderer takes whole dp only, so on devices whose screen does not divide evenly into dp (Pixel 9, Pixel 9 Pro Fold, Galaxy Z Fold8 and Fold8 Ultra) the picture can be one pixel off the panel size, for example 1079×2423 on a Pixel 9.
• When the renderer or a project's ui-tooling doesn't pair with Prevue, the preview fails and names what's missing. If a project's androidx.compose.ui:ui-tooling lacked the tree accessor Prevue reads, the picture still came out but pointing at it found nothing, with only the warning "Compose 노드 없음 — 렌더는 성공했지만 Preview가 그린 노드가 없다", which blamed the preview. Now that render fails with "Couldn't read the Compose tree from ComposeViewAdapter — this project's androidx.compose.ui:ui-tooling doesn't pair with Prevue's renderer (ComposeViewAdapter.getViewInfos$ui_tooling is missing)". On the renderer side, the internals Prevue uses to load, preload and swap your classes are now opened when the server starts, and when any is missing it stops there listing all of them ("The renderer doesn't pair with this Prevue — couldn't open renderer internals: …"), instead of failing partway through a later render or save.
• When the preview server fails on its first start, start gives the reason. On the first start after installing or updating, the JVM writes its startup cache to the log after the server exits, so the error read "The daemon didn't start — Removed temporary AOT configuration file …". Now it quotes the server's own failure line.
• In Codex, the approval question keeps its reason. When Prevue needed approval to read the build settings or reread resources, Codex often swapped the question's first clause for a note that the Prevue skill requires approval, so "This is the first time opening this module" or "Resources have changed" never reached you. Now the question is passed on whole, and any note on where the request comes from follows it as a separate short paragraph.

Thanks

@Dwite (#29) · @sergei-lapin (#30, #31)

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This discussion was created from the release v0.21.0.