lokdocview: Separate "painting" and "saving" of tiles

Lets separate the task of painting the tile, and saving the tile
in tile buffer using GAsyncReadyCallback. This will provide us
with better control over tiles -- cancelling the painting operation,
and filtering tiles that should not be saved in the tile buffer.

Change-Id: I6aae928d8cc0c906034570ed0e9a054763d493a3
Reviewed-on: https://gerrit.libreoffice.org/19725Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>

libreofficekit/source/gtk/lokdocview.cxx

@@ -873,6 +873,47 @@ renderGraphicHandle(LOKDocView* pDocView,
     }
 }
 
+/// Finishes the paint tile operation and returns the result, if any
+static gpointer
+paintTileFinish(LOKDocView* pDocView, GAsyncResult* res, GError **error)
+{
+    GTask* task = G_TASK(res);
+
+    g_return_val_if_fail(LOK_IS_DOC_VIEW(pDocView), NULL);
+    g_return_val_if_fail(g_task_is_valid(res, pDocView), NULL);
+    g_return_val_if_fail(error == NULL || *error == NULL, NULL);
+
+    return g_task_propagate_pointer(task, error);
+}
+
+/// Callback called in the main UI thread when paintTileInThread in LOK thread has finished
+static void
+paintTileCallback(GObject* sourceObject, GAsyncResult* res, gpointer userData)
+{
+    LOKDocView* pDocView = LOK_DOC_VIEW(sourceObject);
+    LOKDocViewPrivate& priv = getPrivate(pDocView);
+    LOEvent* pLOEvent = static_cast<LOEvent*>(userData);
+    std::unique_ptr<TileBuffer>& buffer = priv->m_pTileBuffer;
+    int index = pLOEvent->m_nPaintTileX * buffer->m_nWidth + pLOEvent->m_nPaintTileY;
+    GError* error;
+
+    error = NULL;
+    GdkPixbuf* pPixBuf = static_cast<GdkPixbuf*>(paintTileFinish(pDocView, res, &error));
+    if (error != NULL)
+    {
+        g_warning("Unable to get painted GdkPixbuf: %s", error->message);
+        g_error_free(error);
+        return;
+    }
+
+    buffer->m_mTiles[index].setPixbuf(pPixBuf);
+    buffer->m_mTiles[index].valid = true;
+    gdk_threads_add_idle(queueDraw, GTK_WIDGET(pDocView));
+
+    g_object_unref(pPixBuf);
+}
+
+
 static gboolean
 renderDocument(LOKDocView* pDocView, cairo_t* pCairo)
 {
@@ -921,7 +962,13 @@ renderDocument(LOKDocView* pDocView, cairo_t* pCairo)
 
             if (bPaint)
             {
-                GTask* task = g_task_new(pDocView, NULL, NULL, NULL);
+                LOEvent* pLOEvent = new LOEvent(LOK_PAINT_TILE);
+                pLOEvent->m_nPaintTileX = nRow;
+                pLOEvent->m_nPaintTileY = nColumn;
+                pLOEvent->m_fPaintTileZoom = priv->m_fZoom;
+                GTask* task = g_task_new(pDocView, NULL, paintTileCallback, pLOEvent);
+                g_task_set_task_data(task, pLOEvent, LOEvent::destroy);
+
                 Tile& currentTile = priv->m_pTileBuffer->getTile(nRow, nColumn, priv->m_fZoom, task, priv->lokThreadPool);
                 GdkPixbuf* pPixBuf = currentTile.getBuffer();
                 gdk_cairo_set_source_pixbuf (pCairo, pPixBuf,
@@ -1516,12 +1563,7 @@ paintTileInThread (gpointer data)
                                          pixelToTwip(nTileSizePixels, pLOEvent->m_fPaintTileZoom),
                                          pixelToTwip(nTileSizePixels, pLOEvent->m_fPaintTileZoom));
 
-    //create a mapping for it
-    buffer->m_mTiles[index].setPixbuf(pPixBuf);
-    buffer->m_mTiles[index].valid = true;
-    gdk_threads_add_idle(queueDraw, GTK_WIDGET(pDocView));
-
-    g_object_unref(pPixBuf);
+    g_task_return_pointer(task, pPixBuf, g_object_unref);
 }
 
 

libreofficekit/source/gtk/tilebuffer.cxx

@@ -87,11 +87,6 @@ Tile& TileBuffer::getTile(int x, int y, float fZoom, GTask* task,
 
     if (m_mTiles.find(index) != m_mTiles.end() && !m_mTiles[index].valid)
     {
-        LOEvent* pLOEvent = new LOEvent(LOK_PAINT_TILE);
-        pLOEvent->m_nPaintTileX = x;
-        pLOEvent->m_nPaintTileY = y;
-        pLOEvent->m_fPaintTileZoom = fZoom;
-        g_task_set_task_data(task, pLOEvent, LOEvent::destroy);
         g_thread_pool_push(lokThreadPool, g_object_ref(task), &error);
         if (error != NULL)
         {
@@ -102,11 +97,6 @@ Tile& TileBuffer::getTile(int x, int y, float fZoom, GTask* task,
     }
     else if(m_mTiles.find(index) == m_mTiles.end())
     {
-        LOEvent* pLOEvent = new LOEvent(LOK_PAINT_TILE);
-        pLOEvent->m_nPaintTileX = x;
-        pLOEvent->m_nPaintTileY = y;
-        pLOEvent->m_fPaintTileZoom = fZoom;
-        g_task_set_task_data(task, pLOEvent, LOEvent::destroy);
         g_thread_pool_push(lokThreadPool, g_object_ref(task), &error);
         if (error != NULL)
         {