replace media_kit's video widget with a custom impl

Fixes #48

This helps Linux touchscreen devices like Linux phones, where the old widget didn't work correctly.

lib/widgets/players/player_controls.dart

@@ -0,0 +1,84 @@
+import "dart:math";
+
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_hooks/flutter_hooks.dart";
+import "package:material_ui/material_ui.dart";
+import "package:media_kit/media_kit.dart";
+
+/// Play/pause, position and seeking controls for a media_kit [Player].
+class const PlayerControls(
+  final Player player, {
+  final bool loading = false,
+  final Color? color,
+  final IList<Widget> actions = const .empty(),
+  super.key,
+}) extends HookWidget {
+  @override
+  Widget build(BuildContext context) {
+    final playing = useStream(
+      player.stream.playing,
+      initialData: player.state.playing,
+    ).requireData;
+    final buffering = useStream(
+      player.stream.buffering,
+      initialData: player.state.buffering,
+    ).requireData;
+    final position = useStream(
+      player.stream.position,
+      initialData: player.state.position,
+    ).requireData;
+    final duration = useStream(
+      player.stream.duration,
+      initialData: player.state.duration,
+    ).requireData;
+
+    String format(Duration duration) {
+      final minutes = duration.inMinutes
+          .remainder(60)
+          .toString()
+          .padLeft(2, "0");
+      final seconds = duration.inSeconds
+          .remainder(60)
+          .toString()
+          .padLeft(2, "0");
+
+      return "$minutes:$seconds";
+    }
+
+    final textStyle = Theme.of(context).textTheme.bodySmall
+        ?.copyWith(color: color);
+    final max = duration.inMilliseconds <= 0
+        ? 1.0
+        : duration.inMilliseconds.toDouble();
+
+    return Row(
+      children: [
+        if (loading || buffering)
+          SizedBox.square(
+            dimension: 48,
+            child: CircularProgressIndicator(padding: .all(12), color: color),
+          )
+        else
+          IconButton(
+            onPressed: player.playOrPause,
+            color: color,
+            tooltip: playing ? "Pause" : "Play",
+            icon: Icon(playing ? Icons.pause_circle : Icons.play_circle),
+          ),
+        SizedBox(width: 8),
+        Text(format(position), style: textStyle),
+        Expanded(
+          child: Slider(
+            max: max,
+            value: min(position.inMilliseconds.toDouble(), max),
+            onChanged: loading
+                ? null
+                : (value) => player.seek(.new(milliseconds: value.toInt())),
+          ),
+        ),
+        Text(format(duration), style: textStyle),
+        ...actions,
+      ],
+    );
+  }
+}