Unify onOpen and onDrag, and support more cases

I don't think it matters whether the open comes from onOpen (opening
magnet, .torrent file, dragging file to dock, menu item) or from
dragging to the window.

These should use the same code path. The only relevant information is
the page of the app that we're on.

This change unifies the two methods, and supports dragging .torrent
files or creating a torrent when the player is active, if the dragged
files are not .srt or .vtt. We go back to the list, or to the create
torrent page in these situations, so it's not confusing for the user.

Always close open modals when handling an open.

renderer/index.js

@@ -87,7 +87,7 @@ function init () {
 
   // OS integrations:
   // ...drag and drop a torrent or video file to play or seed
-  dragDrop('body', onDrag)
+  dragDrop('body', onOpen)
 
   // ...same thing if you paste a torrent
   document.addEventListener('paste', onPaste)
@@ -273,15 +273,14 @@ function dispatch (action, ...args) {
     playPause()
   }
   if (action === 'play') {
-    if (state.location.pending()) return
     state.location.go({
       url: 'player',
       onbeforeload: function (cb) {
+        play()
         openPlayer(args[0] /* infoHash */, args[1] /* index */, cb)
       },
       onbeforeunload: closePlayer
     })
-    play()
   }
   if (action === 'playbackJump') {
     jumpToTime(args[0] /* seconds */)
@@ -431,18 +430,18 @@ function openSubtitles () {
 function backToList () {
   // Exit any modals and screens with a back button
   state.modal = null
-  while (state.location.hasBack()) state.location.back()
+  state.location.backToFirst(function () {
+    // If we were already on the torrent list, scroll to the top
+    var contentTag = document.querySelector('.content')
+    if (contentTag) contentTag.scrollTop = 0
 
-  // If we were already on the torrent list, scroll to the top
-  var contentTag = document.querySelector('.content')
-  if (contentTag) contentTag.scrollTop = 0
-
-  // Work around virtual-dom issue: it doesn't expose its redraw function,
-  // and only redraws on requestAnimationFrame(). That means when the user
-  // closes the window (hide window / minimize to tray) and we want to pause
-  // the video, we update the vdom but it keeps playing until you reopen!
-  var mediaTag = document.querySelector('video,audio')
-  if (mediaTag) mediaTag.pause()
+    // Work around virtual-dom issue: it doesn't expose its redraw function,
+    // and only redraws on requestAnimationFrame(). That means when the user
+    // closes the window (hide window / minimize to tray) and we want to pause
+    // the video, we update the vdom but it keeps playing until you reopen!
+    var mediaTag = document.querySelector('video,audio')
+    if (mediaTag) mediaTag.pause()
+  })
 }
 
 // Checks whether we are connected and already casting
@@ -555,41 +554,29 @@ function saveState () {
   update()
 }
 
-// Called when the user clicks a magnet link or torrent, or uses the Open dialog
+// Called when the user drag-drops files onto the app
 function onOpen (files) {
   if (!Array.isArray(files)) files = [ files ]
 
-  // Return to the home screen
-  backToList()
-
-  if (files.every(isTorrent)) {
-    // All .torrent files? Start downloading
-    files.forEach(addTorrent)
-  } else {
-    // Show the Create Torrent screen. Let's seed those files.
-    showCreateTorrent(files)
+  if (state.modal) {
+    state.modal = null
   }
-}
 
-// Called when the user drag-drops files onto the app
-function onDrag (files) {
-  if (!Array.isArray(files)) files = [ files ]
+  var subtitles = files.filter(isSubtitle)
 
-  var isInPlayer = state.location.current().url === 'player'
-  var isHome = state.location.current().url === 'home' && !state.modal
-
-  if (isInPlayer) {
-    // In the player, the only drag-drop function is adding subtitles
-    addSubtitles(files.filter(isSubtitle), true)
-  } else if (isHome) {
-    // Otherwise, you can only drag-drop onto the home screen
+  if (state.location.url() === 'home' || subtitles.length === 0) {
     if (files.every(isTorrent)) {
-      // All .torrent files? Start downloading
+      if (state.location.url() !== 'home') {
+        backToList()
+      }
+      // All .torrent files? Add them.
       files.forEach(addTorrent)
     } else {
       // Show the Create Torrent screen. Let's seed those files.
       showCreateTorrent(files)
     }
+  } else if (state.location.url() === 'player') {
+    addSubtitles(subtitles, true)
   }
 
   update()
@@ -757,7 +744,6 @@ function startTorrentingSummary (torrentSummary) {
 // Shows the Create Torrent page with options to seed a given file or folder
 function showCreateTorrent (files) {
   if (Array.isArray(files)) {
-    if (state.location.pending() || state.location.current().url !== 'home') return
     state.location.go({
       url: 'create-torrent',
       files: files