From 8cc311d4a8b3efa4530823047674b2dd935f1f69 Mon Sep 17 00:00:00 2001
From: dodes <dodes@ifosoft.sk>
Date: Wed, 11 Nov 2015 13:16:14 +0100
Subject: [PATCH] WTableView: Support for model data caching

---
 src/Wt/WAbstractItemModel   |  8 ++++++++
 src/Wt/WAbstractItemModel.C |  3 +++
 src/Wt/WTableView.C         | 15 +++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/src/Wt/WAbstractItemModel b/src/Wt/WAbstractItemModel
index 4816a6f..db1e0e3 100644
--- a/src/Wt/WAbstractItemModel
+++ b/src/Wt/WAbstractItemModel
@@ -327,6 +327,14 @@ public:
 						      | MatchWrap))
     const;
 
+  /*! \brief Prepare the data beforehand.
+   *
+   * This is call before the retrieving the data. In some situtations it
+   * it would be better to load the bulk of the data, insted of one by one.
+   * This is mainly used by virtual table views.
+   */
+  virtual void prepareData(int rowFrom, int rowTo);
+
   /*! \brief Returns the data item at the given column and row.
    *
    * This is a convenience method, and is equivalent to:
diff --git a/src/Wt/WAbstractItemModel.C b/src/Wt/WAbstractItemModel.C
index ee3ec07..0b2afa6 100644
--- a/src/Wt/WAbstractItemModel.C
+++ b/src/Wt/WAbstractItemModel.C
@@ -91,6 +91,9 @@ WAbstractItemModel::itemData(const WModelIndex& index) const
   return result;
 }
 
+void WAbstractItemModel::prepareData(int rowFrom, int rowTo)
+{ }
+
 boost::any WAbstractItemModel::data(int row, int column, int role,
 				    const WModelIndex& parent) const
 {
diff --git a/src/Wt/WTableView.C b/src/Wt/WTableView.C
index 78ecb37..776aeb9 100644
--- a/src/Wt/WTableView.C
+++ b/src/Wt/WTableView.C
@@ -581,6 +581,17 @@ void WTableView::renderTable(const int fr, const int lr,
   for (int i = 0; i < -bottomRowsToAdd; ++i)
     removeSection(Bottom);
 
+  //If there are some columns defined
+  if(rowHeaderCount() > 0 || (firstColumn() < lastColumn()))
+  {
+	  // Only if got top rows 
+	  if(topRowsToAdd > 0)
+		model()->prepareData(firstRow() - topRowsToAdd, firstRow());
+	  // Only if got bottom rows 
+	  else if(bottomRowsToAdd > 0)
+		model()->prepareData(lastRow() + 1, lastRow() + bottomRowsToAdd);
+  }
+
   // Add rows
   for (int i = 0; i < topRowsToAdd; i++) {
     int row = firstRow() - 1;
@@ -606,6 +617,10 @@ void WTableView::renderTable(const int fr, const int lr,
     addSection(Bottom, items);
   }
 
+  // Only if there are some columns to add and we've got some rows
+  if((leftColsToAdd > 0 || rightColsToAdd > 0) && firstRow() < lastRow())
+	  model()->prepareData(firstRow(), lastRow());
+
   // Add columns
   for (int i = 0; i < leftColsToAdd; ++i) {
     int col = firstColumn() - 1;
-- 
1.9.5.msysgit.0