fix touch on head units with a second screen

LIVI lists an empty input for its cluster display before the real touchscreen, so every
tap was ignored. Pick the video and input that belong to the main screen.

gearslip/src/test/java/app/seb3thehacker/gearslip/ServiceDiscoveryDisplayTest.kt

@@ -0,0 +1,51 @@
+package app.seb3thehacker.gearslip
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * LIVI 2.0.1 offers a second screen alongside the main one, and lists that screen's input first:
+ *   channel 3:  video sink, no display id (the main screen)
+ *   channel 19: video sink, display_id = 1, display_type = 1 (a cluster)
+ *   channel 20: input service with only display_id = 1
+ *   channel 8:  input service with a 1280x720 touchscreen and keys (the main screen)
+ * Taking the first input service left every touch on the main screen ignored.
+ */
+class ServiceDiscoveryDisplayTest {
+
+    private fun varintField(field: Int, value: Long) = Protobuf.varintField(field, value)
+
+    private fun lenField(field: Int, body: ByteArray): ByteArray =
+        Protobuf.varint(((field shl 3) or 2).toLong()) + Protobuf.varint(body.size.toLong()) + body
+
+    private fun videoSink(id: Int, displayId: Int?): ByteArray {
+        val config = varintField(1, 2L) + varintField(2, 1L) + varintField(5, 180L)
+        var sink = varintField(1, 3L) + lenField(4, config)
+        if (displayId != null) sink += varintField(6, displayId.toLong()) + varintField(7, 1L)
+        return lenField(1, varintField(1, id.toLong()) + lenField(3, sink))
+    }
+
+    private fun input(id: Int, body: ByteArray) = lenField(1, varintField(1, id.toLong()) + lenField(4, body))
+
+    private fun liviResponse(): ByteArray =
+        videoSink(3, null) +
+            videoSink(19, 1) +
+            input(20, varintField(5, 1L)) +
+            input(8, lenField(1, Protobuf.varint(3L) + Protobuf.varint(4L)) + lenField(2, varintField(1, 1280L) + varintField(2, 720L)))
+
+    @Test
+    fun picksTheMainScreensVideo() {
+        val video = ServiceDiscovery.findVideoService(liviResponse())!!
+        assertEquals(3, video.serviceId)
+        assertEquals(0, video.displayId)
+    }
+
+    @Test
+    fun picksTheInputForTheProjectedScreen() {
+        val input = ServiceDiscovery.findInputService(liviResponse(), displayId = 0)!!
+        assertEquals(8, input.serviceId)
+        assertEquals(1280, input.touchWidth)
+        assertEquals(720, input.touchHeight)
+        assertEquals(listOf(3, 4), input.keycodesSupported)
+    }
+}