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OnBeforeRenderData


Unit:SDL_boxplot
Class: TBoxPlot
Declaration: OnBeforeRenderData: TRenderEvent;
{ TRenderEvent = procedure (Sender: TObject; canvas: TCanvas; Top, Left: integer) of object; }

The events OnBeforeRenderData, OnDataRendered and OnScalesRendered  provide hooks for adding user defined graphics to a boxplot. Internally, a box plot is constructed in three phases before the result is copied to the screen: in the first phase the scales are drawn, then the boxes are drawn and finally the crosshairs are rendered. The OnScalesRendered event is triggered after the scales are drawn giving access to the non-data areas of TBoxPlot (i.e. the areas where the scales and captions are drawn). The events OnBeforeRenderData and OnDataRendered are triggered before and after drawing the boxplot diagram.

The event OnBeforeRenderData occurs immediately before the boxplot is drawn. The variable parameter Canvas provides access to the canvas of the data area. The parameters Top and Left contain the offset of the data area relative to the entire chart area.

Hint 1: The declaration of this event has been changed with the introduction of release 10.1 of the SDL Suite. Please see the corresponding type declaration and the section How to Deal with a Canvas Reference Change for details.

Hint 2: In order to avoid unwanted size effects regarding characters displayed on canvases of different resolution (i.e. the screen and a printer) you should never directly assign the font size within the event. Use SetCanvasFontSizeScaled instead. So, for example, the statement Canvas.Font.Size := 12; should be replaced by SetCanvasFontSizeScaled (Canvas, 12);



Last Update: 2012-Oct-26