Add basic tests for wxGrid cell attribute presence and count

Do some simple sanity checks with attributes, particularly overwriting
a cell with NULL attribute (as was already checked very usefully in
the grid sample for ref count reasons), and their total count in a grid
when inserting and deleting rows and columns.

While the tests are not particularly useful for the next intended grid
change, they do contain some functions that also work for upcoming tests
so these (harmless) tests are included as well.

tests/controls/gridtest.cpp

@@ -31,7 +31,7 @@
 namespace
 {
 
-// Derive a new class inheriting from wxGrid just to get access to its
+// Derive a new class inheriting from wxGrid, also to get access to its
 // protected GetCellAttr(). This is not pretty, but we don't have any other way
 // of testing this function.
 class TestableGrid : public wxGrid
@@ -46,6 +46,32 @@ public:
     {
         return GetCellAttr(row, col);
     }
+
+    bool HasAttr(int row, int col, wxGridCellAttr::wxAttrKind kind) const
+    {
+        // Can't use GetCellAttr() here as it always returns an attr.
+        wxGridCellAttr* attr = GetTable()->GetAttr(row, col, kind);
+        if ( attr )
+            attr->DecRef();
+
+        return attr != NULL;
+    }
+
+    size_t GetCellAttrCount() const
+    {
+        // Note that only attributes in grid range can easily be checked
+        // and this function only counts those, not any outside of
+        // the grid (e.g. with invalid negative coords).
+        size_t count = 0;
+        for ( int row = 0; row < GetNumberRows(); ++row )
+        {
+            for ( int col = 0; col < GetNumberCols(); ++col )
+                count += HasAttr(row, col, wxGridCellAttr::Cell);
+        }
+
+        return count;
+    }
+
 };
 
 } // anonymous namespace
@@ -106,6 +132,16 @@ protected:
         }
     }
 
+    bool HasCellAttr(int row, int col) const
+    {
+        return m_grid->HasAttr(row, col, wxGridCellAttr::Cell);
+    }
+
+    void SetCellAttr(int row, int col)
+    {
+        m_grid->SetAttr(row, col, new wxGridCellAttr);
+    }
+
     TestableGrid *m_grid;
 
     wxDECLARE_NO_COPY_CLASS(GridTestCase);
@@ -1446,6 +1482,80 @@ TEST_CASE_METHOD(GridTestCase, "Grid::DrawInvalidCell", "[grid][multicell]")
     wxYield();
 }
 
+#define CHECK_ATTR_COUNT(n) CHECK( m_grid->GetCellAttrCount() == n )
+
+TEST_CASE_METHOD(GridTestCase, "Grid::CellAttribute", "[attr][cell][grid]")
+{
+    SECTION("Overwrite")
+    {
+        CHECK_ATTR_COUNT( 0 );
+
+        m_grid->SetAttr(0, 0, NULL);
+        CHECK_ATTR_COUNT( 0 );
+
+        SetCellAttr(0, 0);
+        CHECK_ATTR_COUNT( 1 );
+
+        m_grid->SetAttr(0, 0, NULL);
+        CHECK_ATTR_COUNT( 0 );
+
+        SetCellAttr(0, 0);
+        m_grid->SetCellBackgroundColour(0, 1, *wxGREEN);
+        CHECK_ATTR_COUNT( 2 );
+
+        m_grid->SetAttr(0, 1, NULL);
+        m_grid->SetAttr(0, 0, NULL);
+        CHECK_ATTR_COUNT( 0 );
+    }
+
+
+    // Fill the grid with attributes for next sections.
+
+    const int numRows = m_grid->GetNumberRows();
+    const int numCols = m_grid->GetNumberCols();
+
+    for ( int row = 0; row < numRows; ++row )
+    {
+        for ( int col = 0; col < numCols; ++col )
+            SetCellAttr(row, col);
+    }
+
+    size_t numAttrs = static_cast<size_t>(numRows * numCols);
+
+    CHECK_ATTR_COUNT( numAttrs );
+
+    SECTION("Expanding")
+    {
+        CHECK( !HasCellAttr(numRows, numCols) );
+
+        m_grid->InsertCols();
+        CHECK_ATTR_COUNT( numAttrs );
+        CHECK( !HasCellAttr(0, 0) );
+        CHECK( HasCellAttr(0, numCols) );
+
+        m_grid->InsertRows();
+        CHECK_ATTR_COUNT( numAttrs );
+        CHECK( HasCellAttr(numRows, numCols) );
+    }
+
+    SECTION("Shrinking")
+    {
+        CHECK( HasCellAttr(numRows - 1 , numCols - 1) );
+        CHECK( HasCellAttr(0, numCols - 1) );
+
+        m_grid->DeleteCols();
+        numAttrs -= m_grid->GetNumberRows();
+        CHECK_ATTR_COUNT( numAttrs );
+        CHECK( HasCellAttr(0, 0) );
+        CHECK( !HasCellAttr(0, numCols - 1) );
+
+        m_grid->DeleteRows();
+        numAttrs -= m_grid->GetNumberCols();
+        CHECK_ATTR_COUNT( numAttrs );
+        CHECK( !HasCellAttr(numRows - 1 , numCols - 1) );
+    }
+}
+
 // Test wxGridBlockCoords here because it'a a part of grid sources.
 
 std::ostream& operator<<(std::ostream& os, const wxGridBlockCoords& block) {