ARC Media View: Mojo definitions.

components/arc/common/file_system.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Next MinVersion: 2
+// Next MinVersion: 3
 
 module arc.mojom;
 
+// Represents a document in Android DocumentsProvider.
+// See Android docs of DocumentsContract.Document for details.
+[Extensible]
+struct Document {
+  // ID of the document.
+  string document_id;
+
+  // Display name of the document.
+  string display_name;
+
+  // MIME type of the document.
+  // A directory is represented by a document having MIME_TYPE_DIR MIME type.
+  string mime_type;
+
+  // Size of the document in bytes. If the size is unknown, -1 is set.
+  int64 size;
+
+  // Timestamp when the document was modified last time, in milliseconds
+  // since UNIX epoch.
+  uint64 last_modified;
+};
+
 // Next method ID: 3
 interface FileSystemInstance {
+  // Queries the child documents of the directory specified by |authority| and
+  // |parent_document_id|.
+  // If such a directory does not exist, null is returned.
+  [MinVersion=2] GetChildDocuments@4(string authority,
+                                     string parent_document_id) =>

[hashimoto, 2016/12/07 10:02:22]

qq #1: Existing methods like GetFileSize() and OpenFileToRead() take URLs
(content: and file:) while these new methods take URL components.
Isn't it going to be confusing?

qq #2: Android's documentation[1] says a content URL consists of an authority, a
path, and an ID, while these new methods don't take paths. Why can we ignore
paths here? It'd be nice to put the reasoning as comments.

[1]: https://developer.android.com/reference/android/content/ContentUris.html

[Shuhei Takahashi, 2016/12/07 10:35:32]

We can make IPC interface to solely use content URLs instead of document ID, but
I want to use knowledge about authority/documentID in Chrome anyway to write
authority-specific logic etc. For example we are discussing to hide "Download"
directory in media views because files there are duplicated with ones in Chrome
OS Downloads directory.
Document ID is a concept of Documents Provider. I added mentions of Documents
Provider. I'm not sure if it is clear enough, so I welcome suggestion to update
the comment.

[hashimoto, 2016/12/07 10:51:00]

How about putting an Android doc URL?
https://developer.android.com/reference/android/provider/DocumentsContract.html

[Shuhei Takahashi, 2016/12/08 05:38:03]

Thanks, added a link.

+      (array<Document>? documents);
+
+  // Queries the document specified by |authority| and |document_id|.
+  // If such a document does not exist, null is returned.
+  [MinVersion=2] GetDocument@3(string authority, string document_id) =>
+      (Document? document);
+
   // Asks the ContentResolver for the size of the file specified by the URL.
   // If the file does not exist or the size is unknown, -1 is returned.
   [MinVersion=1] GetFileSize@1(string url) => (int64 size);
 
   // Asks the ContentResolver to get a FD to read the file specified by the
   // URL.
   [MinVersion=1] OpenFileToRead@2(string url) => (handle? fd);
 
   // Requests MediaProvider to scan specified files.
   // When the specified file does not exist, the corresponding entry in
   // MediaProvider is removed.
   RequestMediaScan@0(array<string> paths);
 };