Page 44 Table of Contents Index Page 46
Chapters
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30
A, B, C, D, E



CHAPTER 6. OVERVIEW OF WINDOW FACILITIES

make it visible. Ports and grafts provide the functionality for managing this capability. A port
is an abstract connection to a display service that is responsible for managing host display server
resources and for processing input events received from the host display server. A graft is a
special kind of sheet that represents a host window, typically a root window (that is, a screen-
level window). A sheet is attached to a display by making it a child of a graft, which represents
an appropriate host window. The sheet will then appear to be a child of that host window. So,
a sheet is put onto a particular screen by making it a child of an appropriate graft and enabling
it. Ports and grafts are described in detail in Chapter 9.

6.2 Properties of Sheets

Sheets have the following properties:

A coordinate system Provides the ability to refer to locations in a sheet's abstract plane.

A region Defines an area within a sheet's coordinate system that indicates the area of interest
within the plane, that is, a clipping region for output and input. This typically corresponds
to the visible region of the sheet on the display.

A parent A sheet that is the parent in a windowing relationship in which this sheet is a child.

Children An ordered set of sheets that are each a child in a windowing relationship in which
this sheet is a parent. The ordering of the set corresponds to the stacking order of the
sheets. Not all sheets have children.

A transformation Determines how points in this sheet's coordinate system are mapped into
points in its parents.

An enabled flag Indicates whether the sheet is currently actively participating in the window-
ing relationship with its parent and siblings.

An event handler A procedure invoked when the display server wishes to inform CLIM of
external events.

Output state A set of values used when CLIM causes graphical or textual output to appear
on the display. This state is often represented by a medium.

6.3 Sheet Protocols
A sheet is a participant in a number of protocols. Every sheet must provide methods for the
generic functions that make up these protocols. These protocols are:

The windowing protocol Describes the relationships between the sheet and its parent and
children (and, by extension, all of its ancestors and descendants).


Page 44 Table of Contents Index Page 46
Chapters
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30
A, B, C, D, E