Improve grid editors placing

Remove the code in wxGrid::ShowCellEditControl() which moves grid
editors unnecessarily and also remove workarounds that were required
because of it in the editors SetSize() functions.

This helps to ensure that the editor is placed at the same position the
renderer draws the cell value, so that it doesn't jump around annoyingly
when editing starts (which was especially noticeable for boolean-valued
cells).

src/generic/grid.cpp

@@ -111,6 +111,9 @@ const int GRID_HASH_SIZE = 100;
 // operation
 const int DRAG_SENSITIVITY = 3;
 
+// the space between the cell edge and the checkbox mark
+const int GRID_CELL_CHECKBOX_MARGIN_X = 2;
+
 } // anonymous namespace
 
 #include "wx/arrimpl.cpp"
@@ -6980,18 +6983,10 @@ void wxGrid::ShowCellEditControl()
             if (rect.x < 0)
                 nXMove = rect.x;
 
-#ifndef __WXQT__
-            // cell is shifted by one pixel
-            // However, don't allow x or y to become negative
-            // since the SetSize() method interprets that as
-            // "don't change."
-            if (rect.x > 0)
-                rect.x--;
-            if (rect.y > 0)
-                rect.y--;
-#else
+#ifdef __WXQT__
             // Substract 1 pixel in every dimension to fit in the cell area.
             // If not, Qt will draw the control outside the cell.
+            // TODO: Check offsets under Qt.
             rect.Deflate(1, 1);
 #endif
 
@@ -10337,4 +10332,44 @@ wxGridCellEditor* wxGridTypeRegistry::GetEditor(int index)
     return editor;
 }
 
+wxRect wxGetGridCheckBoxRect(const wxSize& checkBoxSize,
+                             const wxRect& cellRect,
+                             int hAlign, int WXUNUSED(vAlign))
+{
+    // TODO: support vAlign
+
+    wxRect checkBoxRect;
+    checkBoxRect.SetY(cellRect.y + cellRect.height / 2 - checkBoxSize.y / 2);
+
+    wxCoord minSize = wxMin(cellRect.width, cellRect.height);
+    if ( checkBoxRect.GetWidth() >= minSize || checkBoxRect.GetHeight() >= minSize )
+    {
+        // let the checkbox mark be even smaller than the min size
+        // to leave some space between cell edges and the checkbox
+        const int newSize = wxMax(1, minSize - 2);
+        checkBoxRect.SetWidth(newSize);
+        checkBoxRect.SetHeight(newSize);
+    }
+    else
+    {
+        checkBoxRect.SetSize(checkBoxSize);
+    }
+
+    if ( hAlign & wxALIGN_CENTER_HORIZONTAL )
+    {
+        checkBoxRect.SetX(cellRect.x + cellRect.width / 2 - checkBoxSize.x / 2);
+    }
+    else if ( hAlign & wxALIGN_RIGHT )
+    {
+        checkBoxRect.SetX(cellRect.x + cellRect.width
+                          - checkBoxSize.x - GRID_CELL_CHECKBOX_MARGIN_X);
+    }
+    else // ( hAlign == wxALIGN_LEFT ) and invalid alignment value
+    {
+        checkBoxRect.SetX(cellRect.x + GRID_CELL_CHECKBOX_MARGIN_X);
+    }
+
+    return checkBoxRect;
+}
+
 #endif // wxUSE_GRID