TCustomShape.DrawToCanvas

Draws the Shape for the control on the specified canvas.

Declaration

Source position: extctrls.pp line 291

Description

DrawToCanvas is a method used to draw the shaped control on the TCanvas instance specified in the ACanvas argument. It calculates the drawing area (TRect) needed using the control Width and Height, the width of the Pen on the canvas, and the Shape for the control.

The Brush style and color for the canvas are set in the calling routine. This allows the same method to be used to draw either the content for the shaped control or its Monochrome mask - depending on the settings in the canvas.

DrawToCanvas calls methods in ACanvas to perform drawing operations needed for the value in Shape. For example:

stRectangle, stSquare

Calls the Rectangle method.

stRoundRect, stRoundSquare

Calls the RoundRect method.

stCircle, stEllipse

Calls the Ellipse method.

stSquaredDiamond, stDiamond

Allocates TPoint instances with the four (4) vertices needed for the shape and calls the Polygon method.

stTriangle, stTriangleDown, stTriangleLeft, stTriangleRight

Allocates TPoint instances with the three (3) vertices needed for the shape and calls the Polygon method.

stStar, stStarDown

Calculates the center point and radii needed to scale the width or height for the shape. Allocates the eleven (11) vertices needed for the shape and calls the Polyon method.

stPolygon

Signals the OnShapePoints event handler (when assigned) to get the vertices and polygon winding for a user-specified or irregular polygonal shape. If the event handler returns more than 2 vertices, the Polygon method is called using the points. No actions are performed if 2 (or fewer points) are returned as vertices for the polygon. Please note that the Shape is not drawn on the control canvas at design-time; a rectangle with a dashed border and a red 'X' are drawn to the corners of the designer surface.

DrawToCanvas is called from the UpdateMask and Paint methods.

Version info

Added in LCL version 4.0.

See also