position-object

When drawing, the geometry-drawing-object created by position-object computes its own position and size based on the keyword arguments and the position and size of its parent (see drawing-object for the meaning of "parent"). It then establishes a Graphics Ports translation to translate from its parent's left/bottom corner to its own left/bottom corner, and draws its sub-object .

The keyword arguments to position-object specify how to compute the left, right, bottom and top of the positioning object with respect to its parent. For each side, the value is computed by multiplying the ratio by the relevant dimension (width for left and right, height for top and bottom), and then add (for left and bottom) or subtract (for right and top) the margin. Note that the vertical coordinate is 0 at the bottom and increases towards the top.

The default values of right-ratio and top-ratio are 1, and the default values of all the other keyword arguments are 0, making it compute the same position and size as the parent.

fit-object

When drawing, the geometry-drawing-object created by fit-object computes scaling factors for the horizontal and vertical dimensions by dividing its width and height, which it inherits from its parent, by its intended-width and intended-height . It then establishes a Graphics Ports scaling transformation with these factors, and draws its sub-object .

position-and-fit-object

position-and-fit-object creates a drawing-object that performs the equivalent of using position-object with the result of fit-object on the drawing-object argument. In other words, it first positions and then fits.

rotate-object

When drawing, the geometry-drawing-object created by rotate-object computes the transform for rotating the object around the point specified by the keyword arguments (default to left-bottom corner). left-margin , left-ratio , bottom-margin and bottom-ratio are used to compute the center of rotation, using the same algorithm as in position-object.

rotate-object does not affect the width and height of the drawing, but since the drawing itself is rotated, the direction in which the width and height apply are rotated too. For example, if you rotate by pi/2, the width is in the vertical dimension on the screen.

make-absolute-drawing

make-absolute-drawing creates an object that displays its objects in "absolute mode", which means drawing without scaling or rotation, but still taking account of the translation. When using a metafile, the absolute drawing is into the metafile. When the metafile is drawn, it normally scales and this scales everything, including absolute drawings.

data and function

The data argument can be anything, and is stored in the geometry-drawing-object, and can be accessed by compound-drawing-object-data. It can be used to keep arbitrary data, and is also used by compute-drawing-object-from-data.

The function argument is used by compute-drawing-object-from-data only. See compute-drawing-object-from-data.

geometry-drawing-object objects can be used repeatedly and concurrently in the same or different panes. The sub-object can be changed dynamically by using (setf compound-drawing-object-sub-object) from any thread, but if it is already being displayed, you will need to ensure that they are redrawn. See force-objects-redraw.