lokdocview: add a set_visible_area()

Change-Id: Ib63959ad64fe52b648e0c0d3fe6d49fb282d57ee

include/LibreOfficeKit/LibreOfficeKitGtk.h

@@ -113,6 +113,17 @@ LibreOfficeKitDocument*        lok_doc_view_get_document           (LOKDocView*
  */
 void                           lok_doc_view_set_zoom               (LOKDocView* pDocView,
                                                                     float fZoom);
+/**
+ * lok_doc_view_set_visible_area:
+ * @pDocView: The #LOKDocView instance
+ * @fZoom: The new visible area of pDocView in twips.
+ *
+ * Sets the new visible area of the widget. This helps e.g. the page down key
+ * to jump the correct length, which depends on the amount of visible height of
+ * the document.
+ */
+void                           lok_doc_view_set_visible_area       (LOKDocView* pDocView,
+                                                                    GdkRectangle* pVisibleArea);
 
 /**
  * lok_doc_view_get_zoom:

libreofficekit/qa/gtktiledviewer/gtktiledviewer.cxx

@@ -440,6 +440,9 @@ static void changeZoom( GtkWidget* pButton, gpointer /* pItem */ )
         if ( pDocView )
         {
             lok_doc_view_set_zoom( LOK_DOC_VIEW(pDocView), fZoom );
+            GdkRectangle aVisibleArea;
+            getVisibleAreaTwips(pDocView, &aVisibleArea);
+            lok_doc_view_set_visible_area(LOK_DOC_VIEW(pDocView), &aVisibleArea);
         }
     }
     std::string aZoom = std::to_string(int(fZoom * 100)) + std::string("%");

libreofficekit/source/gtk/lokdocview.cxx

@@ -14,6 +14,7 @@
 #include <vector>
 #include <string>
 #include <sstream>
+#include <iostream>
 #include <boost/property_tree/json_parser.hpp>
 
 #include <com/sun/star/awt/Key.hpp>
@@ -129,6 +130,9 @@ struct LOKDocViewPrivateImpl
     */
     int m_nTileSizeTwips;
 
+    GdkRectangle m_aVisibleArea;
+    bool m_bVisibleAreaSet;
+
     LOKDocViewPrivateImpl()
         : m_aLOPath(nullptr),
         m_aDocPath(nullptr),
@@ -166,7 +170,9 @@ struct LOKDocViewPrivateImpl
         m_bInDragEndHandle(false),
         m_pGraphicHandle(nullptr),
         m_nViewId(0),
-        m_nTileSizeTwips(0)
+        m_nTileSizeTwips(0),
+        m_aVisibleArea({0, 0, 0, 0}),
+        m_bVisibleAreaSet(false)
     {
         memset(&m_aGraphicHandleRects, 0, sizeof(m_aGraphicHandleRects));
         memset(&m_bInDragGraphicHandles, 0, sizeof(m_bInDragGraphicHandles));
@@ -561,6 +567,11 @@ postKeyEventInThread(gpointer data)
                                                  priv->m_nTileSizeTwips);
         priv->m_nTileSizeTwips = 0;
     }
+    if (priv->m_bVisibleAreaSet)
+    {
+        // TODO invoke lok::Document::setVisibleArea() here.
+        priv->m_bVisibleAreaSet = false;
+    }
 
     std::stringstream ss;
     ss << "lok::Document::postKeyEvent(" << pLOEvent->m_nKeyEvent << ", " << pLOEvent->m_nCharCode << ", " << pLOEvent->m_nKeyCode << ")";
@@ -2520,6 +2531,17 @@ lok_doc_view_get_document (LOKDocView* pDocView)
     return priv->m_pDocument;
 }
 
+SAL_DLLPUBLIC_EXPORT void
+lok_doc_view_set_visible_area (LOKDocView* pDocView, GdkRectangle* pVisibleArea)
+{
+    if (!pVisibleArea)
+        return;
+
+    LOKDocViewPrivate& priv = getPrivate(pDocView);
+    priv->m_aVisibleArea = *pVisibleArea;
+    priv->m_bVisibleAreaSet = true;
+}
+
 SAL_DLLPUBLIC_EXPORT void
 lok_doc_view_set_zoom (LOKDocView* pDocView, float fZoom)
 {