In the demo project, I create a simple graph with four series of data. It demonstrates different options of marker, such as shapes, colors, etc. When the cursor hits a marker, the background data value will be displayed by tool tip. Some API functions, such as CRgn::PtInRegion(), in HitTest() work best in device coordinates. It may be a good practice to convert the test-point into device coordinates. In the demo, I create one marker for each data series. If you want to use different marker option within one data series, you have to create one marker for each data point.