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Owner drawing is a really large topic and can be simple or tremendously complex, involving much Canvas-related code. However, often, the kind of drawing you need will be relatively similar. So, if you need checks, arrows, color gradients, and so on, check the procedures into the Vcl.GraphUtil unit. Otherwise, if you need images, you could use TImageList to hold all the images needed by your grid, as we did in this recipe for the Rating field.

The good news is that the drawing code can be reused by different kinds of controls, so try to organize your code in a way that allows code reutilization by avoiding direct dependencies to the form where the control is.

The code in the drawing events should not contain business logic or presentation logic. If you need presentation logic, put it in a separate, testable function or class.