SWI-Prolog -- Get methods

1.38.3 Get methods

device <-catch_all: name -> graphical

Find a displayed graphical by it's name. To find a graphical named hello, type

?- get(Device, hello_member, Hello).

NOTE: Graphicals may also be found using device<-member.

Diagnostics: Asking for a graphical that does not exist will trap the no_behaviour error.

See also: device<-member

device <-contains: -> chain

Implementation of the visual part-of hierarchy. Equivalent to‘Device device<-graphicals’.

See also: - device-graphicals
- visual<-contains

device <-find: at=[point|event], condition=[code] -> graphical

Find the most local graphical overlapping with at for which condition succeeds.

This methods uses a similar search technique as used by device->event and is first of all intended to help writing gestures that have to relate two graphical objects, possibly not placed on the same device object. Examples are class connect_gesture or a drag-and-drop gesture.

device<-find performs the following steps:

Traverse the list device<-graphicals from tail to head (i.e. starting at the topmost graphical). For each graphical:
if at is given and graphical->in_event_area fails Continue with the next graphical
if the graphical is a device object Recursively call device<-find on the device. Return with the result if any.
if the graphical is not a device Evaluate the condition and return the graphical if the condition succeeds.
Finally, evaluate the condition on the device itself and return the device if the condition succeeds.
The following example finds a graphical that defines the send-method drop in the same window as where the event occurred:
```
...
get(@event?window, find, @event,
        message(@arg1, has_send_method, drop), Gr),
...
```

device <-inside: area -> chain

Returns a new chain object with all graphicals that are entirely inside the argument area. If no graphicals can be found, an empty chain is returned. Described with selection because it is commonly used to implement selecting multiple graphicals by dragging a box around them. See PceDraw.

See also: - device->room
- area->inside

device <-member: graphical_name=name -> graphical

Return the first graphical of device<-graphicals that has name name. This mechanism is commonly used to address parts of a device.

Diagnostics: Fails if no graphical with the requested name exists.

See also: - device<-catch_all
- device<-get_catch_all
- graphical-name
- device-graphicals

device <-offset: -> point

Inherits description from: device-offset

See also: - device<-y
- device<-x
- device<-position

device <-pointed_objects: at=point|event, append_to=[chain] -> chain

Determines all objects that overlap with some position. This method is used internally to determine the objects to which an event should be send. The first argument describes the position. It is either a point or an event. In the latter case the position of the event is taken.

If chain is supplied, this chain is filled with the matching graphicals. This chain is chain->cleared first. If it is @default, a new chain object with the matching graphicals it returned.

The matching graphicals are the graphicals for which‘Graphical graphical->in_event_area’succeeds. The graphicals are stored in the chain, such that the top-most graphical is the head of the chain.

See also: - device-pointed
- graphical->in_event_area

device <-position: -> point

Inherits description from: device-offset

See also: device<-offset

device <-selection: -> chain

Returns a new chain with all graphicals that have‘Graphical graphical<-selected: @on’. If there are no such graphicals, an empty chain is returned.