Advanced MFC Programming

Chapter 11. Sample: Simple Paint
1) A region must be selected into DC before being used. The function that can be used to select a region
is CDC::SelectClipRgn(…). To select the region out of the DC, we can simply call this function again
and pass NULL to its parameter.
1) Path can be used to record outputs to the device context. To start path recording, we need to call
function CDC::BeginPath(). To end path recording, we can call function CDC::EndPath(). All the
drawings between the two function calls will be recorded in the path. The output will not appear on the
DC when the recording is undergoing.
1) Function CDC::StrokePath() can be called to stroke the outline of a path. Function CDC::FillPath(…)
can be used to fill the interior of the path. Function CDC::StrokeAndFillPath() can be used to
implement both.
1) Region can be created from an existing path by calling function CRgn::CreateFromPath(…).
1) A region is made up of a series of rectangles. By resizing all the rectangles, we can resize the region.
1) A path is made up of a series of vectors. To resize a path, we can scale all the control points. We can
also change the position of some control points to generate special effects.
1) The standard DIB format that can be used in the clipboard is CF_DIB. To put DIB data to the clipboard,
we need to prepare DIB data with standard DIB format, open the clipboard, empty the clipboard, call
function ::SetClipboardData(…) and pass CF_DIB flag along with the data handle to it. After all these
operations, we must close the clipboard.
1) To obtain DIB data from the clipboard, we can use CF_DIB flag to call function
::GetClipboardData(…).
13) Message WM_PALETTECHANGED is used to notify the applications that the system palette has changed.
Applications that implement logical palettes should realize the logical palette again after receiving this
message to achieve least color distortion.
14) Outputting directly to window may cause flickering sometimes. This is because usually the old
drawings must be erased before the window is updated. To avoid flickering, we can prepare everything
in a memory bitmap, then output the patterns contained in the memory bitmap to the window in one
stroke.
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