Merge branch 'grid-autosize'

Optimize wxGrid::AutoSizeColumns() for big grids.

This includes an optimization of wxDC::GetTextExtent() at the price of
slightly reduced precision in wxMSW.

See https://github.com/wxWidgets/wxWidgets/pull/1893

interface/wx/grid.h

@@ -88,6 +88,26 @@ public:
     virtual int GetBestWidth(wxGrid& grid, wxGridCellAttr& attr, wxDC& dc,
                              int row, int col, int height);
 
+    /**
+        Get the maximum possible size for a cell using this renderer, if
+        possible.
+
+        This function may be overridden in the derived class if it can return
+        the maximum size needed for displaying the cells rendered it without
+        iterating over all cells. The base class version simply returns
+        ::wxDefaultSize, indicating that this is infeasible and that
+        GetBestSize() should be called for each cell individually.
+
+        Note that this method will only be used if
+        wxGridTableBase::CanMeasureColUsingSameAttr() is overriden to return
+        @true.
+
+        @since 3.1.4
+     */
+    virtual wxSize GetMaxBestSize(wxGrid& grid,
+                                  wxGridCellAttr& attr,
+                                  wxDC& dc);
+
 protected:
     /**
         The destructor is private because only DecRef() can delete us.
@@ -2517,6 +2537,25 @@ public:
         returns @true.
      */
     virtual bool CanHaveAttributes();
+
+    /**
+        Override to return true if the same attribute can be used for measuring
+        all cells in the given column.
+
+        This function is provided for optimization purposes: it returns @false
+        by default, but can be overridden to return @true when all the cells in
+        the same grid column use sensibly the same attribute, i.e. they use the
+        same renderer (either explicitly, or implicitly, due to their type as
+        returned by GetTypeName()) and the font of the same size.
+
+        Returning @true from this function allows AutoSizeColumns() to skip
+        looking up the attribute and the renderer for each individual cell,
+        which results in very noticeable performance improvements for the grids
+        with many rows.
+
+        @since 3.1.4
+     */
+    virtual bool CanMeasureColUsingSameAttr(int col) const;
 };