Advanced MFC Programming

Chapter 8. DC, Pen, Brush and Palette
CGDIDoc *ptrDoc;
……
}
ptrDoc=(CGDIDoc *)GetDocument();
if((nFlags & MK_LBUTTON) && ptrDoc->GetFloodFill() == FALSE)
{
void CGDIView::OnLButtonUp(UINT nFlags, CPoint point)
{
CClientDC dc(this);
CPen pen;
CPen *ptrPenOld;
int nMode;
CGDIDoc *ptrDoc;
……
}
ptrDoc=(CGDIDoc *)GetDocument();
if(ptrDoc->GetFloodFill() == FALSE)
{
This will enable flood filling.
Sample 8.5-2\GDI is exactly the same with sample 8.5-1\GDI except that here we use function CDC::
ExtFloodFill(…) instead of CDC::FloodFill(…). The following is the difference between the function
calling in two samples:
8.5-1\GDI:
dc.FloodFill(point.x, point.y, RGB(255, 0, 0));
8.5-2\GDI:
dc.ExtFloodFill(point.x, point.y, dc.GetPixel(point), FLOODFILLSURFACE);
We call function CDC::GetPixel(…) to retrieve the color of the pixel specified by point, and fill the
area that has the same color with it. The flood filling will stretch out to all directions until borders with
different colors are reached. For samples 8.5-1\GDI and 8.5-2\GDI, we don’t see much difference between
function CDC::ExtFloodFill(…) and CDC::FloodFill(…). However, in the sample, if the lines can be
drawn with different colors, we need to use CDC::ExtFloodFill(…) rather than CDC::FloodFill(…) to
implement flood filling.
8.6 Pattern Brush
Pattern brush is very useful in filling an area with a specific pattern. We already know how to create a
hatch brush, which could have several simple patterns. By using pattern brush, we are able to create a brush
with any custom pattern.
The pattern brush can be created from a bitmap with a dimension of 8×8. If we use a larger bitmap
image, only the upper-left portion of the image (with a size of 8×8) will be used. The bitmap used to create
pattern brush must be stored in a CBitamp declared variable.
The simplest way of implementing pattern brush is to prepare a bitmap resource, load it with a CBitmap
type variable, then create the brush. The function that can be used to create pattern brush is CBrush::
CreatePatternBrush(…), which has the following format:
BOOL CBrush::CreatePatternBrush(CBitmap* pBitmap);
Sample 8.6\GDI demonstrates how to create and use pattern brush. It is based on sample 8.2-1\GDI. In
the new sample, pattern brush is used to fill the interior of the rectangles instead of solid brush.
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