1.67.1 Instance variables

figure <- background: colour|gradient|image|{foreground,background}*

Colour used as background. Commonly used to prevent the figure from being transparent (figure->background: background).

figure <- status: name

The figure<-status of a figure is a name indicating which graphicals of the figure should be visible: if figure<-status equals all_active, all device<-graphicals are visible, otherwise only graphicals with the same name as figure<-status are made visible.

This mechanism may be used to define graphical objects that should be switched between different states. Consider the example where we want to have a diagram which can be displayed opened and as an icon. The code below outlines a possible approach:

create_closable_diagram(F) :-
        new(F, figure),
        send(F, status, opened),
        send(F, display, new(BM, bitmap('my_icon'))),
        send(BM, name, closed),
        send(BM, recogniser,
                 click_gesture(left, '', double,
                               message(F, status, opened),
        send(F, display, new(F2, figure)),
        send(F2, name, opened),
        ...
        <create the real diagram on F2>

figure <- border: num

Extra empty pixels added around the children's bounding box. Used together with graphical<-pen to draw a visible frame at a distance from the contents.

figure <- radius: num

Corner radius for the outline drawn by graphical<-pen/figure<-elevation. 0 yields a square outline.

figure <- elevation: elevation*

elevation object describing a 3-D appearance (raised, sunken, shadow, ...) of the figure's box. @nil disables the effect.

figure <- shadow: 0..|shadow*

Drop shadow painted outside the box of the figure. See class shadow. An integer N is a soft shadow N pixels to the bottom right; 0 is no shadow. The default is @nil (no shadow).

figure <- blend: {normal,multiply,screen,overlay,darken,lighten,color_dodge,color_burn,hard_light,soft_light,difference,exclusion,hue,saturation,color,luminosity,add}

How the figure, with its contents, is composited onto what is below it. normal paints it over what is below. The other modes are those of Cairo and CSS mix-blend-mode, e.g., multiply darkens what is below by the colours of the figure, as overlapping transparent inks would. A figure that is not normal is drawn on a temporary surface, as is one with graphical<-opacity below 1, which is combined with the blend mode.

Defaults: normal

figure <- clip_path: path*

If not @nil, the graphicals of the figure are only drawn where they are inside this path, as determined by path<-fill_rule. The points of the path are in the coordinate system of the graphicals of the figure, so the clipping region moves, rotates and scales with them under figure<-transform. The path itself is not displayed. Clipping affects drawing only: graphicals that are clipped away still receive events. After modifying the path, send figure->clip_path again to redraw the figure.

Defaults: @nil

figure <- transform: transform*

Optional 2-D affine transform applied to the figure's contents. @nil means no transform. The transform is applied to the children while drawing, hit-testing and computing the bounding box, so a rotated/scaled figure is still selectable by the mouse and reports a tight bounding box in its parent's coordinates. The convenience methods figure->translate, figure->scale, figure->rotate and figure->shear compose operations into this transform without the caller having to manage the transform object explicitly.

figure <- local_area: area

Bounding box of the children in the figure's local (pre-transform, pre-offset) coordinate system. Refreshed by figure->compute. Damage handling and child event dispatch use this to keep paint and hit tests correct under rotation/scale.