ui: send dropped .webm as video only when it has a video track (#7354)

* ui: send dropped .webm as video only when it has a video track

.webm is as commonly an audio-only container as a video one, so the
extension alone cannot tell whether there is a frame to embed. Read the
container to decide: files with a video track are sent as video, the rest
as files.

Only done for files attached without the user saying how to send them
(drag & drop, paste). An explicitly picked video is still sent as one, so
.webm is now listed in the video file picker too.

* plan: send dropped .webm as video only when it has a video track

apps/multiplatform/common/src/desktopMain/kotlin/chat/simplex/common/platform/VideoPlayer.desktop.kt

@@ -7,6 +7,10 @@ import chat.simplex.common.views.helpers.*
 import chat.simplex.res.MR
 import kotlinx.coroutines.*
 import org.jetbrains.compose.videoplayer.SkiaBitmapVideoSurface
+import uk.co.caprica.vlcj.media.Media
+import uk.co.caprica.vlcj.media.MediaEventAdapter
+import uk.co.caprica.vlcj.media.MediaParsedStatus
+import uk.co.caprica.vlcj.media.ParseFlag
 import uk.co.caprica.vlcj.media.VideoOrientation
 import uk.co.caprica.vlcj.player.base.*
 import uk.co.caprica.vlcj.player.component.CallbackMediaPlayerComponent
@@ -255,6 +259,43 @@ actual class VideoPlayer actual constructor(
       return@withContext VideoPlayerInterface.PreviewAndDuration(preview = preview, timestamp = 0L, duration = duration)
     }
 
+    // Parsing a local container header takes a few dozen ms, this is only a guard against a stuck parse
+    private const val PARSE_TIMEOUT_MS = 3000L
+
+    // Reads container metadata to tell whether there is a video track at all, without decoding a frame.
+    // libvlc signals the end of parsing with an event, so no polling or frame-decoding budget is needed.
+    suspend fun hasVideoTrack(uri: URI): Boolean = withContext(previewThread.asCoroutineDispatcher()) {
+      if (!uri.toFile().exists()) return@withContext false
+      val media = try {
+        vlcPreviewFactory.media().newMedia(uri.toFile().absolutePath)
+      } catch (e: Exception) {
+        Log.e(TAG, "hasVideoTrack unable to create media: ${e.stackTraceToString()}")
+        null
+      } ?: return@withContext false
+      try {
+        val parsed = CompletableDeferred<MediaParsedStatus?>()
+        media.events().addMediaEventListener(object: MediaEventAdapter() {
+          // vlcj maps an unknown status int to null, and a null here would throw on its event thread
+          override fun mediaParsedChanged(parsedMedia: Media?, newStatus: MediaParsedStatus?) {
+            parsed.complete(newStatus)
+          }
+        })
+        if (!media.parsing().parse(PARSE_TIMEOUT_MS.toInt(), ParseFlag.PARSE_LOCAL)) {
+          return@withContext false
+        }
+        if (withTimeoutOrNull(PARSE_TIMEOUT_MS) { parsed.await() } != MediaParsedStatus.DONE) {
+          media.parsing().stop()
+          return@withContext false
+        }
+        media.info().videoTracks().isNotEmpty()
+      } catch (e: Exception) {
+        Log.e(TAG, "hasVideoTrack error: ${e.stackTraceToString()}")
+        false
+      } finally {
+        media.release()
+      }
+    }
+
     val playerThread = Executors.newSingleThreadExecutor()
     private val previewThread = Executors.newSingleThreadExecutor()
     private val playersPool: ArrayList<Component> = ArrayList()

apps/multiplatform/common/src/desktopMain/kotlin/chat/simplex/common/platform/Videos.desktop.kt

@@ -9,5 +9,6 @@ fun isVideo(uri: URI): Boolean {
       path.endsWith(".mp4") ||
       path.endsWith(".mpg") ||
       path.endsWith(".mpeg") ||
-      path.endsWith(".mkv")
+      path.endsWith(".mkv") ||
+      path.endsWith(".webm")
 }

apps/multiplatform/common/src/desktopMain/kotlin/chat/simplex/common/views/helpers/Utils.desktop.kt

@@ -255,6 +255,8 @@ actual suspend fun getBitmapFromVideo(uri: URI, timestamp: Long?, random: Boolea
   return VideoPlayer.getBitmapFromVideo(null, uri, withAlertOnException)
 }
 
+actual suspend fun hasVideoTrack(uri: URI): Boolean = VideoPlayer.hasVideoTrack(uri)
+
 @OptIn(ExperimentalEncodingApi::class)
 actual fun ByteArray.toBase64StringForPassphrase(): String = Base64.encode(this)