refactor: migrate deprecated Kotlin and Compose APIs

Author: WieszczY85

docs/DESIGN.md

@@ -180,7 +180,7 @@ Panels use restrained `#0C2444 → #08192E` depth, with `#135582` outlines. The
 - Use an application-wide Material `Surface` for proper light text over the dark theme. Do not depend on default `Text` content colors after drawing raw backgrounds.
 - The main window chooses an initial size constrained by the desktop work area. The instance panel is vertically scrollable, with a visible scrollbar; crucial controls should be visible without scrolling on typical full-HD screens.
 - Compact hero typography avoids text collisions. Below 760 dp of content width, stack the hero/Play and setup panel with a visible page scrollbar; otherwise keep Play visible and scroll the setup panel independently. Very short windows scroll the page as well. The minimum native window is 400 × 400. Never make unsupported future features appear as active navigation.
-- Optimized JPEG/PNG resources load locally via painterResource without network access, runtime blur, repeated animation or dynamic downloads. Shared vector icons, 18 dp panel radii, 9 dp field radii and typography live in `SyntaxTheme.kt` / `SyntaxComponents.kt`. Account setup details belong behind the Player information action, keeping the normal launch screen concise.
+- Optimized JPEG/PNG resources load locally via `rememberBrandingPainter` and the Compose resources bitmap decoder, retaining the packaged classpath paths. Decoding is remembered per resource path and streams are closed after reading; no network access, runtime blur, repeated animation or dynamic downloads. Shared vector icons, 18 dp panel radii, 9 dp field radii and typography live in `SyntaxTheme.kt` / `SyntaxComponents.kt`. Account setup details belong behind the Player information action, keeping the normal launch screen concise.
 
 ### Startup update screen
 

docs/DEVELOPMENT.md

@@ -351,6 +351,10 @@ remain separate roadmap items.
 
 `MinecraftVersionCatalog` uses the shared HTTP client with a 15-second request deadline. Desktop supplies `cacheDir/minecraft/version_manifest_v2.json`; tests may omit the path. Each fetch requests fresh data, validates JSON and catalog consistency, then publishes the raw Mojang document through a unique sibling temporary file and atomic replacement where supported. This is disposable remote metadata, not a launcher settings schema. Invalid/missing caches are never silently treated as an empty catalog. Failed refreshes can use a re-parsed valid cache, cancellation propagates, and cache-write failures are logged without discarding a valid online result. Disk work runs on the IO dispatcher. Deterministic MockEngine tests cover restart reuse, replacement, malformed/HTTP failures, corruption, unavailable storage and cancellation. Full offline launching remains a separate concern.
 
+## Desktop resource and dialog APIs
+
+Brand PNG/JPEG files remain in `src/main/resources/branding` for the native package, classpath tools and existing image-dimension regressions. Use `rememberBrandingPainter` instead of deprecated `androidx.compose.ui.res.painterResource`: the helper remembers a `BitmapPainter` by path, closes the classpath stream and decodes with `org.jetbrains.compose.resources.decodeToImageBitmap`, following [JetBrains’ classpath migration example](https://github.com/JetBrains/compose-multiplatform-core/pull/1457). Native instance/mod windows use `DialogWindow` with the existing dialog state and close guards. Material3 and resources dependencies use explicit coordinates because the old Compose Gradle accessors are deprecated; keep the resources version aligned with the Compose plugin and retain the resolved Material3 version when changing notation.
+
 ## Interface localization (EN / PL / DE)
 
 `desktop/i18n/UiStrings` loads UTF-8 `resources/i18n/{en,pl,de}.properties` bundles once. Use stable keys with numbered `{0}` placeholders; format runtime values through `strings.text(key, arguments…)` rather than embedding translated content in core. `LocalStrings` scopes language to the application composition. `LauncherLanguageHost` loads the system/saved choice off the UI thread and publishes a new localizer only after an atomic successful preference save. A save failure leaves the current language active and presents a translated retry explanation. No JVM-wide locale mutation is used.

docs/ROADMAP.md

@@ -14,6 +14,7 @@ Agents and contributors MUST keep this file synchronized with actual repository
 
 ## Cross-milestone desktop development ergonomics (October 2026)
 
+- [x] Replace deprecated desktop resource/dialog calls with Compose resource bitmap decoding and `DialogWindow`; align OfflineAccount copy visibility with its private constructor and remove redundant loader null checks. Full local tests/build and Linux package verification pass; native window acceptance remains separate.
 - [x] Embed the semantic product version, CI run number and source SHA at build time; show exact CI build identity in the launcher header and updater without altering release-version comparisons. Local builds have an explicit non-CI label.
 - [ ] 🚧 IN PROGRESS — Consolidate product SemVer in root `gradle.properties` for Gradle modules, embedded metadata, jpackage numeric version derivation, update bundles, GitHub Actions tags and Build Explorer publication; source and deterministic tests committed, final CI acceptance pending.
 - [ ] 🚧 IN PROGRESS — Replace native window decorations with branded controls integrated into the existing Compose header (drag, minimize, maximize/restore, close, 8 resize grips, 400×400 minimum). Source implementation and unit coverage for resize geometry added; real native/manual acceptance on Windows, macOS and Linux X11/Wayland, DPI and small screens remains open.

docs/WORKLOG.md

@@ -8,6 +8,45 @@ Every code/build/documentation/CI task must add an entry according to `AGENTS.md
 
 ---
 
+## 2026-10-21 — Migrate deprecated Kotlin and Compose APIs
+
+**Milestone:** v0.1 — existing core/UI maintenance; v0.12 — build compatibility
+**Author/Agent:** Codex / GPT-6
+**Status:** Completed
+
+### Completed
+- Applied `@ConsistentCopyVisibility` to OfflineAccount so the generated copy method respects its private constructor; all repository creation remains through validated `create`.
+- Removed redundant Elvis/safe calls where Kotlin already proves that the delayed installer has a selected loader and registry. Loader resolution, preparation order and errors for missing services remain unchanged.
+- Replaced deprecated image calls in the main window, header, hero and startup updater with one remembered classpath bitmap helper using the Compose resources decoder. Existing PNG/JPEG paths, artwork, sizing and native package icon remain intact; input streams close after reading.
+- Migrated the instance and local-mod native windows from Dialog to DialogWindow, preserving size/state, resize support, busy close guards and content.
+- Declared Material3 explicitly at its existing resolved version and Compose resources at the plugin version, avoiding deprecated Gradle dependency accessors. No warning suppressions or product-version bump introduced.
+
+### Changed files
+- `launcher-core/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/core/account/OfflineAccount.kt` — consistent generated-copy visibility.
+- `launcher-core/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/core/launch/MinecraftLaunchCoordinator.kt` — remove proven-unnecessary null handling.
+- `launcher-desktop/build.gradle.kts` — explicit Material3 and resources dependencies.
+- `launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/ui/BrandingResources.kt` — shared remembered painter using Compose resources bitmap decoding.
+- `launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/Main.kt`, `ui/{LauncherArtwork,StartupUpdateGate,SyntaxLauncherApp}.kt` — migrate all branding painter calls.
+- `launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/ui/{InstanceWorkspace,LocalModsDialog}.kt` — migrate native window API.
+- `docs/{DESIGN,DEVELOPMENT,ROADMAP,WORKLOG}.md` — current resource/dependency conventions, maintenance progress and evidence.
+
+### Verification
+- `./gradlew test` — PASS via `./gradlew --offline --no-daemon -PlauncherBuildNumber=156 -PlauncherCommit=e96b70e7be7a41a3ee0e15f32cf9fc3d1145ef67 -PlauncherUpdateChannel=dev test build :launcher-desktop:createDistributable --rerun-tasks --no-build-cache --warning-mode all`; 136 core and 25 desktop tests passed, two opt-in live tests skipped. All 19 actionable tasks executed.
+- `./gradlew build` — PASS in the same invocation; zero Kotlin source or Gradle-script compiler warnings. Only the two upstream plugin deprecations listed below remain.
+- `:launcher-desktop:createDistributable` — PASS for Linux. Verified that the packaged desktop JAR includes the new helper and all three original branding files. `scripts/package_update.py` and `:launcher-desktop:verifyUpdateBundle` also PASS for the complete Linux update archive.
+- Manual verification — inspected regenerated Polish home (1440×810) and startup updater (440×600) renders. Branding, transparency and geometry preserved; native dialogs and Windows/macOS still require platform acceptance.
+- `git diff --check` — PASS.
+
+### Roadmap updates
+- `[x] Cross-milestone desktop development ergonomics / Deprecated core/Compose APIs` — local migration/verification complete.
+- `[ ] Native UI and Windows/macOS/platform acceptance` — remains open; headless rendering and Linux packaging do not replace native checks.
+
+### Follow-ups / known issues
+- Two upstream Compose/Hot Reload Gradle deprecations remain: Configuration.setVisible and the HotReloadUsageType attribute value type. No repository calls use these APIs; upgrading or disabling plugins is outside the supplied source-warning cleanup.
+- No authentication, loader feature, persistence-schema, artwork, canonical product-version or release-policy change. Hosted CI and native dialog focus/resize acceptance remain separate.
+
+---
+
 ## 2026-10-21 — Fix nested home scrolling in CI render tests
 
 **Milestone:** v0.1 — translated home regression coverage; v0.12 — CI reliability

launcher-core/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/core/account/OfflineAccount.kt

@@ -3,6 +3,7 @@ package pl.syntaxdevteam.syntaxlauncher.core.account
 import java.nio.charset.StandardCharsets
 import java.util.UUID
 
+@ConsistentCopyVisibility
 data class OfflineAccount private constructor(
     override val username: String,
     override val uuid: UUID,

launcher-core/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/core/launch/MinecraftLaunchCoordinator.kt

@@ -109,10 +109,9 @@ class MinecraftLaunchCoordinator(
             }
 
             val prepared = if (delayedInstaller) {
-                val selected = loader ?: error("Missing installed loader selection")
+                val selected = loader
                 stage(LaunchPhase.PREPARING_LOADER, "Installing " + selected.id + " " + selected.version)
-                val installed = loaders?.install(version, selected, instanceLayout, runtime)
-                    ?: throw ModLoaderException("Mod loader installer is not configured.")
+                val installed = loaders.install(version, selected, instanceLayout, runtime)
                 stage(LaunchPhase.PREPARING_GAME, "Verifying installed ${selected.id} files")
                 preparation.prepare(installed, platform, instanceLayout) { event ->
                     if (event is MinecraftPreparationEvent.Download) downloaded(event.event)

launcher-desktop/build.gradle.kts

@@ -15,7 +15,8 @@ dependencies {
     // Desktop itself owns HttpClient lifecycle and therefore needs this API directly.
     implementation("io.ktor:ktor-client-core:3.6.0")
     implementation(compose.desktop.currentOs)
-    implementation(compose.material3)
+    implementation("org.jetbrains.compose.material3:material3:1.9.0")
+    implementation("org.jetbrains.compose.components:components-resources:1.12.2")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-swing:1.11.0")
     runtimeOnly("ch.qos.logback:logback-classic:1.6.5")
     testImplementation(kotlin("test-junit5"))

launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/Main.kt

@@ -9,7 +9,6 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.foundation.window.WindowDraggableArea
 import androidx.compose.ui.window.WindowPlacement
 import androidx.compose.ui.window.rememberWindowState
-import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.WindowState
 import androidx.compose.ui.window.application
@@ -35,6 +34,7 @@ import pl.syntaxdevteam.syntaxlauncher.core.storage.LauncherPreferencesStore
 import pl.syntaxdevteam.syntaxlauncher.core.storage.MinecraftInstallationLayout
 import pl.syntaxdevteam.syntaxlauncher.desktop.i18n.LauncherLanguageHost
 import pl.syntaxdevteam.syntaxlauncher.desktop.ui.SyntaxLauncherApp
+import pl.syntaxdevteam.syntaxlauncher.desktop.ui.rememberBrandingPainter
 import pl.syntaxdevteam.syntaxlauncher.desktop.ui.StartupUpdateGate
 import pl.syntaxdevteam.syntaxlauncher.desktop.ui.WindowControls
 import pl.syntaxdevteam.syntaxlauncher.desktop.ui.WindowResizeHandles
@@ -104,7 +104,7 @@ fun main(args: Array<String>) {
         Window(
             onCloseRequest = closeLauncher,
             title = "SyntaxLauncher · v" + LauncherBuildInfo.version + " · " + LauncherBuildInfo.buildLabel,
-            icon = painterResource("branding/syntaxlauncher-icon.png"),
+            icon = rememberBrandingPainter("branding/syntaxlauncher-icon.png"),
             state = windowState,
             undecorated = true,
             resizable = true,

launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/ui/BrandingResources.kt

@@ -0,0 +1,18 @@
+package pl.syntaxdevteam.syntaxlauncher.desktop.ui
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.graphics.painter.BitmapPainter
+import androidx.compose.ui.graphics.painter.Painter
+import org.jetbrains.compose.resources.decodeToImageBitmap
+
+/** Keep packaged branding on the classpath while using the current Compose bitmap decoder. */
+@Composable
+internal fun rememberBrandingPainter(path: String): Painter = remember(path) {
+    val bytes = checkNotNull(BrandingResources::class.java.getResourceAsStream("/$path")) {
+        "Missing packaged branding resource: $path"
+    }.use { it.readAllBytes() }
+    BitmapPainter(bytes.decodeToImageBitmap())
+}
+
+private object BrandingResources

launcher-desktop/src/main/kotlin/pl/syntaxdevteam/syntaxlauncher/desktop/ui/InstanceWorkspace.kt

@@ -45,7 +45,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.DpSize
 import androidx.compose.ui.unit.dp
-import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.window.DialogWindow
 import androidx.compose.ui.window.rememberDialogState
 import pl.syntaxdevteam.syntaxlauncher.core.instance.InstanceCopyProgress
 import pl.syntaxdevteam.syntaxlauncher.core.instance.MinecraftInstance
@@ -162,7 +162,7 @@ fun InstanceWorkspace(
         )
     }
 
-    Dialog(
+    DialogWindow(
         onCloseRequest = { if (!isBusy) onDismiss() },
         title = strings.text("ui.syntaxlauncher_instances"),
         state = rememberDialogState(size = DpSize(width, height)),