Call this member function to fill a given rectangle using the specified brush.
The function fills the complete rectangle, including the left and top borders, but it does not fill the right and bottom borders.
When filling the specified rectangle, FillRect does not include the rectangle's right and bottom sides. GDI fills a rectangle up to, but does not include, the right column and bottom row, regardless of the current mapping mode. FillRect compares the values of the top, bottom, left, and right members of the specified rectangle. If bottom is less than or equal to top, or if right is less than or equal to left, the rectangle is not drawn.
FillRect is similar to CDC::FillSolidRect; however, FillRect takes a brush and therefore can be used to fill a rectangle with a solid color, a dithered color, hatched brushes, or a pattern. FillSolidRect uses only solid colors (indicated by a COLORREF parameter). FillRect usually is slower than FillSolidRect.