feature: add getDefaultViewModelInfo to experimental API

Add the ability to query the default view model name and instance name
for an artboard through the experimental CommandQueue API.

This mirrors the iOS experimental SDK's File.getDefaultViewModelInfo(for:)
which already exists. The name is needed for file-level queries like
getViewModelProperties() and getViewModelInstanceNames() which are keyed
by view model name — without it, ViewModelSource.DefaultForArtboard users
cannot access those APIs.

Changes:
- CommandQueueBridge: add cppGetDefaultViewModelInfo JNI declaration
- CommandQueue: add getDefaultViewModelInfo suspend function + callback
- RiveFile: add public getDefaultViewModelInfo(artboard) API
- DefaultViewModelInfo: new data class for the result
- bindings_command_queue.cpp: JNI binding + ArtboardListener callback

Author: mfazekas

kotlin/src/main/cpp/src/bindings/bindings_command_queue.cpp

@@ -291,6 +291,22 @@ class ArtboardListener : public rive::CommandQueue::ArtboardListener
                      jList.get());
     }
 
+    void onDefaultViewModelInfoReceived(
+        const rive::ArtboardHandle,
+        uint64_t requestID,
+        std::string viewModelName,
+        std::string instanceName) override
+    {
+        auto env = GetJNIEnv();
+        auto jViewModelName = MakeJString(env, viewModelName);
+        auto jInstanceName = MakeJString(env, instanceName);
+        m_queue.call("onDefaultViewModelInfoReceived",
+                     "(JLjava/lang/String;Ljava/lang/String;)V",
+                     requestID,
+                     jViewModelName.get(),
+                     jInstanceName.get());
+    }
+
 private:
     JCommandQueue m_queue;
 };
@@ -985,6 +1001,25 @@ extern "C"
         commandQueue->requestStateMachineNames(artboardHandle, requestID);
     }
 
+    JNIEXPORT void JNICALL
+    Java_app_rive_core_CommandQueueJNIBridge_cppGetDefaultViewModelInfo(
+        JNIEnv*,
+        jobject,
+        jlong ref,
+        jlong requestID,
+        jlong jFileHandle,
+        jlong jArtboardHandle)
+    {
+        auto commandQueue = reinterpret_cast<rive::CommandQueue*>(ref);
+        auto fileHandle = handleFromLong<rive::FileHandle>(jFileHandle);
+        auto artboardHandle =
+            handleFromLong<rive::ArtboardHandle>(jArtboardHandle);
+
+        commandQueue->requestDefaultViewModelInfo(artboardHandle,
+                                                  fileHandle,
+                                                  requestID);
+    }
+
     JNIEXPORT void JNICALL
     Java_app_rive_core_CommandQueueJNIBridge_cppGetViewModelNames(
         JNIEnv*,

kotlin/src/main/kotlin/app/rive/RiveFile.kt

@@ -6,6 +6,7 @@ import androidx.compose.runtime.Stable
 import androidx.compose.runtime.produceState
 import androidx.compose.ui.platform.LocalContext
 import app.rive.core.CloseOnce
+import app.rive.core.DefaultViewModelInfo
 import app.rive.core.FileHandle
 import app.rive.core.RiveWorker
 import app.rive.core.SuspendLazy
@@ -144,6 +145,25 @@ class RiveFile internal constructor(
     private val enumsCache = SuspendLazy {
         riveWorker.getEnums(fileHandle)
     }
+
+    /**
+     * Retrieves the default view model information for an artboard.
+     *
+     * View models define the data structure and bindings for an artboard. This method allows
+     * discovery of which view model and instance are associated with the artboard by default,
+     * as assigned in the Rive editor.
+     *
+     * This is useful when using [ViewModelSource.DefaultForArtboard] to create a view model
+     * instance, since that path does not reveal the view model name. The name is required for
+     * file-level queries like [getViewModelProperties] and [getViewModelInstanceNames].
+     *
+     * @param artboard The artboard to query for default view model information.
+     * @return A [DefaultViewModelInfo] containing the view model name and instance name.
+     * @throws RuntimeException If no default view model is found for the artboard.
+     * @throws CancellationException If the coroutine is cancelled before the operation completes.
+     */
+    suspend fun getDefaultViewModelInfo(artboard: Artboard): DefaultViewModelInfo =
+        riveWorker.getDefaultViewModelInfo(fileHandle, artboard.artboardHandle)
 }
 
 /**

kotlin/src/main/kotlin/app/rive/core/CommandQueue.kt

@@ -560,6 +560,51 @@ class CommandQueue(
         (pendingContinuations.remove(requestID) as? Continuation<List<String>>)?.resume(names)
     }
 
+    /**
+     * Query the default view model info for an artboard. Returns on
+     * [onDefaultViewModelInfoReceived].
+     *
+     * @param fileHandle The handle of the file containing the artboard.
+     * @param artboardHandle The handle of the artboard to query.
+     * @return A [DefaultViewModelInfo] containing the view model name and instance name.
+     * @throws RuntimeException If the artboard or file handle is invalid, or no default view model
+     *    is found.
+     * @throws IllegalStateException If the CommandQueue has been released.
+     * @throws CancellationException If the coroutine is cancelled before the operation completes.
+     */
+    @Throws(RuntimeException::class, IllegalStateException::class, CancellationException::class)
+    suspend fun getDefaultViewModelInfo(
+        fileHandle: FileHandle,
+        artboardHandle: ArtboardHandle
+    ): DefaultViewModelInfo =
+        suspendNativeRequest { requestID ->
+            bridge.cppGetDefaultViewModelInfo(
+                cppPointer.pointer,
+                requestID,
+                fileHandle.handle,
+                artboardHandle.handle
+            )
+        }
+
+    /**
+     * Callback when the default view model info is received, from [getDefaultViewModelInfo].
+     *
+     * @param requestID The request ID used when querying, used to complete the continuation.
+     * @param viewModelName The name of the default view model for the artboard.
+     * @param instanceName The name of the default view model instance for the artboard.
+     */
+    @Keep // Called from JNI
+    @Suppress("Unused")
+    @JvmName("onDefaultViewModelInfoReceived")
+    internal fun onDefaultViewModelInfoReceived(
+        requestID: Long,
+        viewModelName: String,
+        instanceName: String
+    ) {
+        (pendingContinuations.remove(requestID) as? Continuation<DefaultViewModelInfo>)
+            ?.resume(DefaultViewModelInfo(viewModelName, instanceName))
+    }
+
     /**
      * Query the file for available view model names. Returns on [onViewModelsListed].
      *
@@ -2347,6 +2392,20 @@ value class FontHandle(val handle: Long) {
     override fun toString(): String = "FontHandle($handle)"
 }
 
+/**
+ * Information about the default view model for an artboard.
+ *
+ * Returned by [CommandQueue.getDefaultViewModelInfo]. Contains the name of the default view model
+ * and the name of its default instance, as assigned in the Rive editor.
+ *
+ * @param viewModelName The name of the default view model type for the artboard.
+ * @param instanceName The name of the default view model instance for the artboard.
+ */
+data class DefaultViewModelInfo(
+    val viewModelName: String,
+    val instanceName: String
+)
+
 /**
  * A key used to uniquely identify a draw operation in the CommandQueue. This is useful when the
  * same CommandQueue issues multiple draw calls. If the same key is used before the render loop

kotlin/src/main/kotlin/app/rive/core/CommandQueueBridge.kt

@@ -30,6 +30,13 @@ interface CommandQueueBridge {
         artboardHandle: Long
     )
 
+    fun cppGetDefaultViewModelInfo(
+        pointer: Long,
+        requestID: Long,
+        fileHandle: Long,
+        artboardHandle: Long
+    )
+
     fun cppGetViewModelNames(
         pointer: Long,
         requestID: Long,
@@ -466,6 +473,13 @@ internal class CommandQueueJNIBridge : CommandQueueBridge {
         artboardHandle: Long
     )
 
+    external override fun cppGetDefaultViewModelInfo(
+        pointer: Long,
+        requestID: Long,
+        fileHandle: Long,
+        artboardHandle: Long
+    )
+
     external override fun cppGetViewModelNames(
         pointer: Long,
         requestID: Long,