An updated preview of a slide should be broadcast to all document clients

Amazingly, this (my third attempt) seems to work.

Add a boolean 'forAllClients' parameter to the loleafget getPreview()
function, and pass it as true in the location where a new preview of
an edited slide is requested.

Add a parameter 'broadcast' to the 'tile' (request) message. Set to
'yes' in the above case. When subscribing to a such tile rendering,
subscribe all sessions of the document.

While at it, drop the default values for the parameters of the
TileDesc constructor. I dislike default values...

Change-Id: Idb438f11c953d791fafe4c890e0497d8dfbaa733
Reviewed-on: https://gerrit.libreoffice.org/29591
Reviewed-by: pranavk <pranavk@collabora.co.uk>
Tested-by: pranavk <pranavk@collabora.co.uk>
(cherry picked from commit 8fe58df7594dad926eefaa22dbdb300e9bfa3de9)

8 files changed, 55 insertions, 23 deletions

diff --git a/loleaflet/README b/loleaflet/README
index 9a01968127..bfbadf51cd 100644
--- a/loleaflet/README
+++ b/loleaflet/README
@@ -178,11 +178,14 @@ Parts (like slides in presentation, or sheets in spreadsheets):
         map.setPart('next' | 'prev' | partNumber)
         map.getNumberOfParts()
         map.getCurrentPartNumber()
-        map.getPreview(id, index, maxWidth, maxHeight, [options])
+        map.getPreview(id, index, maxWidth, maxHeight, [options], forAllClients)
             + id = the ID of the request so that the response can be identified
             + index = the part / page 's number
             + maxWidth / maxHeight = max dimensions so that the ratio is preserved
-            + options = {autoUpdate: true} - automatically updates the previews
+            + options = {autoUpdate: <boolean>, broadcast: <boolean>} -
+	      + autoUpdate - boolean, automatically updates the previews
+	      + broadcast - boolean, whether the response (a preview of a slide) should be sent to all clients
+                viewing the same presentation
         map.getCustomPreview(id, part, width, height, tilePosX, tilePosY, tileWidth, tileHeight, [options])
             + id = the ID of the request so that the response can be identified
             + part = the part containing the desired preview
diff --git a/loleaflet/reference.html b/loleaflet/reference.html
index 0b67eb02bc..839d072ac5 100644
--- a/loleaflet/reference.html
+++ b/loleaflet/reference.html
@@ -1648,8 +1648,7 @@ unexpected behaviour.</h4>
 		</code></td>
 		<td><code>undefined</code></td>
 		<td>Triggers the creation of a preview with the given id, of maximum maxWidth X maxHeight size, of the
-            page / part with number 'index', keeping the original ration. By passing an
-            optional parameter {autoUpdate: true}, the preview will be automatically invalidated.</td>
+            page / part with number 'index', keeping the original ration.</td>
 	</tr>
 	<tr>
 		<td><code><b>getCustomPreview</b>(
@@ -1665,8 +1664,7 @@ unexpected behaviour.</h4>
 		</code></td>
 		<td><code>undefined</code></td>
 		<td>Triggers the creation of a preview with the given id, of width X height size, of the
-            [(tilePosX,tilePosY), (tilePosX + tileWidth, tilePosY + tileHeight)] section of the document. By passing an
-            optional parameter {autoUpdate: true}, the preview will be automatically invalidated.</td>
+            [(tilePosX,tilePosY), (tilePosX + tileWidth, tilePosY + tileHeight)] section of the document.</td>
 	</tr>
 	<tr>
 		<td><code><b>removePreviewUpdate</b>(
@@ -1711,7 +1709,14 @@ unexpected behaviour.</h4>
 	<tr>
 		<td><code><b>autoUpdate</b></code></td>
 		<td><code>Boolean</code></td>
-        <td>Whether a new preview is generated automatically when it becomes invalid.</td>
+        <td>Whether a new preview is generated automatically when it becomes
+        invalid.</td>
+	</tr>
+	<tr>
+	  <td><code><b>broadcast</b></code></td>
+	  <td><code>Boolean</code></td>
+          <td>Whether new preview should be broadcasted to other clients of same
+            document.</td>
 	</tr>
 </table>
 
diff --git a/loleaflet/src/control/Parts.js b/loleaflet/src/control/Parts.js
index 1542b1cee8..cbca779602 100644
--- a/loleaflet/src/control/Parts.js
+++ b/loleaflet/src/control/Parts.js
@@ -53,7 +53,8 @@ L.Map.include({
 		if (!this._docPreviews) {
 			this._docPreviews = {};
 		}
-		var autoUpdate = options ? options.autoUpdate : false;
+		var autoUpdate = options ? !!options.autoUpdate : false;
+		var forAllClients = options ? !!options.broadcast : false;
 		this._docPreviews[id] = {id: id, index: index, maxWidth: maxWidth, maxHeight: maxHeight, autoUpdate: autoUpdate};
 
 		var docLayer = this._docLayer;
@@ -91,7 +92,8 @@ L.Map.include({
 							'tileposy=' + tilePosY + ' ' +
 							'tilewidth=' + tileWidth + ' ' +
 							'tileheight=' + tileHeight + ' ' +
-							'id=' + id);
+							'id=' + id + ' ' +
+							'broadcast=' + (forAllClients ? 'yes' : 'no'));
 	},
 
 	getCustomPreview: function (id, part, width, height, tilePosX, tilePosY, tileWidth, tileHeight, options) {
@@ -109,7 +111,8 @@ L.Map.include({
 							'tileposy=' + tilePosY + ' ' +
 							'tilewidth=' + tileWidth + ' ' +
 							'tileheight=' + tileHeight + ' ' +
-							'id=' + id);
+							'id=' + id + ' ' +
+							'broadcast=no');
 	},
 
 	removePreviewUpdate: function (id) {
diff --git a/loleaflet/src/layer/tile/TileLayer.js b/loleaflet/src/layer/tile/TileLayer.js
index 7d6aa7a0ff..8eca6a840c 100644
--- a/loleaflet/src/layer/tile/TileLayer.js
+++ b/loleaflet/src/layer/tile/TileLayer.js
@@ -1878,7 +1878,7 @@ L.TileLayer = L.GridLayer.extend({
 				preview = this._map._docPreviews[key];
 				if (preview.autoUpdate) {
 					if (preview.index >= 0) {
-						this._map.getPreview(preview.id, preview.index, preview.maxWidth, preview.maxHeight, {autoUpdate: true});
+						this._map.getPreview(preview.id, preview.index, preview.maxWidth, preview.maxHeight, {autoUpdate: true, broadcast: true});
 					}
 					else {
 						this._map.getCustomPreview(preview.id, preview.part, preview.width, preview.height, preview.tilePosX,
diff --git a/loolwsd/DocumentBroker.cpp b/loolwsd/DocumentBroker.cpp
index 52f60c78ba..39702cc159 100644
--- a/loolwsd/DocumentBroker.cpp
+++ b/loolwsd/DocumentBroker.cpp
@@ -680,7 +680,17 @@ void DocumentBroker::handleTileRequest(TileDesc& tile,
         return;
     }
 
-    tileCache().subscribeToTileRendering(tile, session);
+    if (tile.getBroadcast())
+    {
+        for (auto& it: _sessions)
+        {
+            tileCache().subscribeToTileRendering(tile, it.second);
+        }
+    }
+    else
+    {
+        tileCache().subscribeToTileRendering(tile, session);
+    }
 
     // Forward to child to render.
     LOG_DBG("Sending render request for tile (" << tile.getPart() << ',' <<
diff --git a/loolwsd/TileDesc.hpp b/loolwsd/TileDesc.hpp
index 8ba44bdf6d..5c39e48023 100644
--- a/loolwsd/TileDesc.hpp
+++ b/loolwsd/TileDesc.hpp
@@ -25,7 +25,7 @@
 class TileDesc
 {
 public:
-    TileDesc(int part, int width, int height, int tilePosX, int tilePosY, int tileWidth, int tileHeight, int ver = -1, int imgSize = 0, int id = -1) :
+    TileDesc(int part, int width, int height, int tilePosX, int tilePosY, int tileWidth, int tileHeight, int ver, int imgSize, int id, bool broadcast) :
         _part(part),
         _width(width),
         _height(height),
@@ -35,7 +35,8 @@ public:
         _tileHeight(tileHeight),
         _ver(ver),
         _imgSize(imgSize),
-        _id(id)
+        _id(id),
+        _broadcast(broadcast)
     {
         if (_part < 0 ||
             _width <= 0 ||
@@ -62,6 +63,7 @@ public:
     int getImgSize() const { return _imgSize; }
     void setImgSize(const int imgSize) { _imgSize = imgSize; }
     int getId() const { return _id; }
+    bool getBroadcast() const { return _broadcast; }
 
     bool intersectsWithRect(int x, int y, int w, int h) const
     {
@@ -131,6 +133,11 @@ public:
             oss << " id=" << _id;
         }
 
+        if (_broadcast)
+        {
+            oss << " broadcast=yes";
+        }
+
         return oss.str();
     }
 
@@ -155,12 +162,14 @@ public:
                 pairs[name] = value;
             }
         }
+        std::string s;
+        bool broadcast = (LOOLProtocol::getTokenString(tokens, "broadcast", s) && s == "yes");
 
         return TileDesc(pairs["part"], pairs["width"], pairs["height"],
                         pairs["tileposx"], pairs["tileposy"],
                         pairs["tilewidth"], pairs["tileheight"],
                         pairs["ver"],
-                        pairs["imgsize"], pairs["id"]);
+                        pairs["imgsize"], pairs["id"], broadcast);
     }
 
     /// Deserialize a TileDesc from a string format.
@@ -182,6 +191,7 @@ private:
     int _ver; //< Versioning support.
     int _imgSize; //< Used for responses.
     int _id;
+    bool _broadcast;
 };
 
 /// One or more tile header.
@@ -243,7 +253,7 @@ private:
                 throw BadArgumentException("Invalid tilecombine descriptor.");
             }
 
-            _tiles.emplace_back(_part, _width, _height, x, y, _tileWidth, _tileHeight, ver, size, id);
+            _tiles.emplace_back(_part, _width, _height, x, y, _tileWidth, _tileHeight, ver, size, id, false);
         }
     }
 
diff --git a/loolwsd/protocol.txt b/loolwsd/protocol.txt
index 9de16062e7..c316b32d1f 100644
--- a/loolwsd/protocol.txt
+++ b/loolwsd/protocol.txt
@@ -123,14 +123,15 @@ status
 styles
 
 tile part=<partNumber> width=<width> height=<height> tileposx=<xpos> tileposy=<ypos> tilewidth=<tileWidth>
-tileheight=<tileHeight> [timestamp=<time>] [id=<id>]
+tileheight=<tileHeight> [timestamp=<time>] [id=<id> broadcast=<yesOrNo>]
 
-    All parameters are numbers.
+    Parameters are numbers except broadcast which is 'yes' or 'no'.
 
-    Note: id must be echoed back in the response verbatim. It is used
-    when rendering slide thumbnails of presentation documents, and not
-    for anything else. It is only useful to loleaflet and will break
-    it if not returned in the response.
+    Note: id must be echoed back in the response verbatim. It and the
+    following parameter, broadcast, are used when rendering slide
+    previews of presentation documents, and not for anything else. It
+    is only useful to loleaflet and will break it if not returned in
+    the response.
 
 tilecombine <parameters>
 
diff --git a/loolwsd/test/TileCacheTests.cpp b/loolwsd/test/TileCacheTests.cpp
index 53430924b0..da115cc69a 100644
--- a/loolwsd/test/TileCacheTests.cpp
+++ b/loolwsd/test/TileCacheTests.cpp
@@ -152,7 +152,7 @@ void TileCacheTests::testSimple()
     int tilePosY = 0;
     int tileWidth = 3840;
     int tileHeight = 3840;
-    TileDesc tile(part, width, height, tilePosX, tilePosY, tileWidth, tileHeight);
+    TileDesc tile(part, width, height, tilePosX, tilePosY, tileWidth, tileHeight, -1, 0, -1, false);
 
     // No Cache
     auto file = tc.lookupTile(tile);