Do not evict visible tiles

Also avoid trying to evict more tiles if the tiles manager is empty (all
tiles were previously removed)

core/document.cpp

@@ -260,7 +260,7 @@ void DocumentPrivate::cleanupPixmapMemory( qulonglong memoryToFree )
             AllocatedPixmap * p = *pIt;
 
             TilesManager *tilesManager = m_pagesVector.at( p->page )->tilesManager( p->id );
-            if ( tilesManager )
+            if ( tilesManager && tilesManager->totalMemory() > 0 )
             {
                 tilesManager->cleanupPixmapMemory( memoryToFree );
                 m_allocatedPixmapsTotalMemory -= p->memory;

core/tilesmanager.cpp

@@ -64,6 +64,7 @@ class TilesManager::Private
         int height;
         long totalPixels;
         Rotation rotation;
+        NormalizedRect visibleRect;
 
         QList<Tile*> rankedTiles;
         QSize tileSize;
@@ -166,6 +167,19 @@ void TilesManager::Private::markDirty( Tile &tile )
     }
 }
 
+void TilesManager::setVisibleRect( const NormalizedRect &rect )
+{
+    if ( d->visibleRect == rect )
+        return;
+
+    d->visibleRect = rect;
+}
+
+NormalizedRect TilesManager::visibleRect() const
+{
+    return d->visibleRect;
+}
+
 void TilesManager::setPixmap( const QPixmap *pixmap, const NormalizedRect &rect )
 {
     for ( int i = 0; i < 16; ++i )
@@ -385,6 +399,9 @@ void TilesManager::cleanupPixmapMemory( qulonglong numberOfBytes )
         if ( !tile->pixmap )
             continue;
 
+        if ( tile->rect.intersects( d->visibleRect ) )
+            continue;
+
         long pixels = tile->pixmap->width()*tile->pixmap->height();
         d->totalPixels -= pixels;
         if ( numberOfBytes < 4*pixels )

core/tilesmanager_p.h

@@ -109,7 +109,6 @@ class OKULAR_EXPORT TilesManager
          */
         void cleanupPixmapMemory( qulonglong numberOfBytes = 1 );
 
-
         /**
          * Inform the new width of the page and mark all tiles to repaint
          */
@@ -124,6 +123,16 @@ class OKULAR_EXPORT TilesManager
         void setRotation( Rotation rotation );
         Rotation rotation() const;
 
+        /**
+         * Sets the visible area of the page
+         */
+        void setVisibleRect( const NormalizedRect &rect );
+
+        /**
+         * Returns the visible area of the page
+         */
+        NormalizedRect visibleRect() const;
+
         /**
          * Returns a rotated NormalizedRect given a @p rotation
          */

ui/pageview.cpp

@@ -3989,7 +3989,12 @@ void PageView::slotRequestVisiblePixmaps( int newValue )
         // if the item doesn't intersect the viewport, skip it
         QRect intersectionRect = viewportRect.intersect( i->croppedGeometry() );
         if ( intersectionRect.isEmpty() )
+        {
+            Okular::TilesManager *tilesManager = i->page()->tilesManager( PAGEVIEW_ID );
+            if ( tilesManager )
+                tilesManager->setVisibleRect( Okular::NormalizedRect() );
             continue;
+        }
 
         // add the item to the 'visible list'
         d->visibleItems.push_back( i );
@@ -4001,6 +4006,10 @@ void PageView::slotRequestVisiblePixmaps( int newValue )
 #endif
 
         visibleRect = vItem->rect;
+        Okular::TilesManager *tilesManager = i->page()->tilesManager( PAGEVIEW_ID );
+        if ( tilesManager )
+            tilesManager->setVisibleRect( vItem->rect );
+
         Okular::NormalizedRect expandedVisibleRect = vItem->rect;
         if ( Okular::Settings::memoryLevel() != Okular::Settings::EnumMemoryLevel::Low )
         {
@@ -4021,7 +4030,6 @@ void PageView::slotRequestVisiblePixmaps( int newValue )
                     PAGEVIEW_ID, i->pageNumber(), i->uncroppedWidth(), i->uncroppedHeight(), PAGEVIEW_PRIO, true );
             requestedPixmaps.push_back( p );
 
-            Okular::TilesManager *tilesManager = i->page()->tilesManager( PAGEVIEW_ID );
             if ( tilesManager )
             {
                 Okular::NormalizedRect tilesRect;