A layout_manager is the object responsible for placing
the graphicals on a device. The design mirrors recogniser:
part of the device's responsibilities (here, geometry) is delegated to
an associated object.
A layout_manager is attached to a device via
device->layout_manager. The device asks it
to recompute the layout and to paint any background. Conversely, the
manager assigns each managed graphical a layout_interface
(via
graphical->layout_interface) that
intercepts geometry changes and propagates them back so the manager
knows when to recompute.
Class layout_manager itself is an almost-empty abstract
base. The first concrete realisation is table, implementing
HTML-3-like tables. See also layout_interface.
- See also
-
- class device
- class layout_interface
- class table
- layout_manager <-
device: device*
-
Device on which this manager places graphicals.
- layout_manager <-
request_compute: any*
-
Set when the layout has become invalid and a layout_manager
->compute
is pending; the device polls this slot before the next redraw.
- layout_manager ->initialise:
-
Initialise an abstract instance. Subclasses normally extend this with
their own setup.
- layout_manager ->attach: graphical
-
Attach the manager to a device, taking responsibility for the layout of
the device's graphicals.
- layout_manager ->detach:
-
Detach from the current device.
- layout_manager ->unlink:
-
Called when the manager is destroyed: cleanly detach from
layout_manager
<-device.
- layout_manager ->compute:
-
Virtual method: recompute the layout. Subclasses override.
- layout_manager ->compute_bounding_box:
-
Virtual method: compute the union bounding box of the laid-out
graphicals. The default implementation fails (no contribution).
- layout_manager ->_redraw_area: area
-
Paint background objects for the indicated area. The default
implementation succeeds without drawing.
