display_manager.md
In rswipl: Embed 'SWI'-'Prolog'

class display_manager {#class-display_manager}

Class display_manager has a single instance @display_manager, created at boot time. Its responsibilities are:

Maintain the set of attached display objects (<-members, <-member, <-primary, <-current). On SDL3 the set is updated dynamically as monitors are added or removed.
Drive the top-level event loop (->dispatch) and flush damage to the screen (->redraw).

@see class display @see display<-display_manager

display_manager<-members: chain Chain of currently attached display objects. Normally holds just @display on a single-monitor setup; gains and loses entries as monitors are hotplugged.
display_manager<->test_queue: bool When @on, redraw passes are interrupted whenever events become available, yielding faster perceived response while typing or dragging. Default is @on everywhere.
display_manager<->focus_message: code* Optional code object invoked with the frame that gained keyboard focus. Used by tools (e.g. the symbol picker) to track the active window without polling.

display_manager->initialise Create the manager. Called once at boot to build @display_manager; not used directly.
display_manager->append: display Attach a new display to the manager. Called by display's constructor; applications normally do not invoke this.
display_manager->redraw Flush all pending changes to the screen. Called from the top-level event loop to repaint windows queued in @changed_windows; may be overridden for special event-loop hooks.

@see display->flush @see display->synchronise @see graphical->compute
display_manager->has_visible_frames Succeeds if any attached display has at least one visible frame (used to decide when the application can exit).

display_manager<-contains: -> chain Equivalent to <-members: chain holding every currently attached display.
display_manager<-primary: -> display The display the OS designates as primary. Falls back to the first member when no primary is set.
display_manager<-current: -> display The display that received the last event, or <-primary when no event has happened yet. Use this when you need to open a new frame "where the user is".
display_manager<-member: name|1.. -> display Look up a display by its <-name or <-number.
display_manager<-window_of_last_event: -> window Find the window object that received the last event. Fails if that window has been destroyed. Used internally to choose the first window to repaint; available for similar scheduling tasks in user code.