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1、INCITS/ISO/IEC 9636-2-1991 (R1997) (formerly ANSI/ISO/IEC 9636-2-1991 (R1997) for Information Technology - Computer Graphics - Interfacing Techniques for Dialogues with Graphical Devices (CGI) - Functional Specification - Part 2: Control Copyright American National Standards Institute Provided by IH
2、S under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=USN Ship Repa
3、ir Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/ISO/IEC 9636-2-l 991 Redesignation of ANSI X3.161 (never published) American National Standard for Information Technology - Computer Graphics - Interfaci
4、ng Techniques for Dialogues with Graphical Devices (CGI)- Functional Specification - Part 2: Control Secretariat Computer and Business Equipment Manufacturers Association Approved August 6,1992 American National Standards Institute, Inc. Copyright American National Standards Institute Provided by IH
5、S under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- American National Standard Approval of an American National Standard requires review by ANSI that the requirem
6、ents for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement
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11、merican National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Published by American National Standards Institute 11 West 42nd Street, New York, New York 10036 Copyright 1991 by Information Technology Industry Council (ITI
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14、n National Standards Institute Provided by IHS under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- Contents Page Foreword . Introduction . 1 S-pe 2 Normative refere
15、nces . 3 Concepts . 3.1 Introduction . 3.2 Virtual Device management . 33.1 Device control 3.23 Drawing surface . 3.2.3 Deferral mode . 33.4 Serial synchronous interface . 33 CoLY*.Y BNI: requires that the Viiual Device complete the display of an image “Before the Next Interaction”, that is, before
16、the next interaction with a Logical Input Device gets underway; If an interaction is already underway (i.e. some LID is initialized for events) then BNI is equivalent to ASAP, ASAP: requires that the Virtual Device complete the display of an image “As Soon As Possible”. Note that none of these value
17、s requires an implementation to delay the display of an image. On the other hand, for hard-copy devices, the CGI does not require a page to be printed per function. Explicit control of deferral is provided by the EXECUTE DEPERRED ACTIONS function which ensures that any pending actions are completed
18、(such as rendering any buffered output so that the operator can see it). The CGI requires that any soliciting function immediately following EXECUTE DEPERRED ACTIONS will not return data until all pending actions ate performed and the drawing surface is up to date. NOTE-Some implementations, such as
19、 buffered one-way output devices, may be unable to support Deferral Mode ASAP. 33.4 Serial synchronous interface The CGI is a serial synchronous interface. There are no asynchronous signals over the interface to report events (whether from input interactions or from environmental changes) or the occ
20、urrence of errors. The CGI is therefore able to guarantee synchronization of its soliciting functions, including DEQUEUE ERROR REPORTS, with preceding function executions. Invocation of DEQUEUE ERROR REPORTS will return all errors detected as a result of the execution of the preceding functions prov
21、ided the error queue has not overflowed. This synchronous interface does not preclude implementations that have many parallel processes within them. Deferral allows for this potential parallelism within the implementation and the function EXECUTE DEFERRED ACTIONS provides a client with some degree o
22、f control of this parallelism. 3.3 Coordinate space concepts 33.1 The Virtual Device coordinate system Coordinate data across the CGI is specified in Virtual Device Coordinates (VDCs), except where a direct reference is made to the drawing or display surface. VDC space is an abstract space described
23、 in more detail below. The subset of VDC space specified by the finite VDC extent is mapped to a portion of the physical device drawing surface specified by the device viewport. here are two ways for a CGI client to ensure isotropic mapping from VDC space to the display surface: by asking the CGI to
24、 enForce it, or by using a VDC extent whose aspect ratio matches the visual aspect ratio of the selected device viewport. Entries in the Output Device Description Table provide the information that enables the client to ensure isotropy without resorting to implicit CGI mechanisms. 4 Copyright Americ
25、an National Standards Institute Provided by IHS under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO/IEC 9636-2 : 1991 (E) Coordinate space concepts Concepts Fur
26、thermore, the CGI allows viewport specifications to cause the entire image to be mirrored relative to the normal orientation, in either axes. The Device Viewport Mirroring entry in the Control Description Table provides information on the support of this mirroring capability. 3.32 Device coordinates
27、 The drawing surface and display surface are addressed by means of a Cartesian coordinate system. The Display Surface Bottom-Left Comer and Display Surface Upper-Right comer entries in the Output Device Description Table specify this physical device coordinate system. Although the graphic object pip
28、eline model recognizes an abstract DC space with real coordinates, the only form in which device coordinates are passed across the CGI is as integers. If the implementation uses raster techniques, then the units of DCs correspond to single pixel displacements. 3.33 Device viewport The - in physical
29、device coordinates, which requires either inquiry or prior knowledge of the device. The device viewport is specified in terms of two points (on the diilay surface) at diagonally opposite corners of the rectangle. The order in which the points are specified is significant. The WC-to-Device Mapping en
30、try in the Control State List may force isotropic mapping. If the current VDC extent, device viewport, and device viewport mapping would not lead to an isotropic mapping, the VDC extent is mapped onto a subset of the specified device viewport. This subset is defined by shrinking either the vertical
31、or horizontal dimension of the current device viewport, as needed, to reach the required aspect ratio. This smaller effective device viewport is used to define the coordinate mapping from VDC to the device s coordinates. The placement of the effective viewport rectangle within the original one can b
32、e specified. This placement can be one of LEFT, RIGHT, or CENTRED when the shrinking is horizontal, and TOP, BOTTOM or CENTRED when the shrinking is vertical. These meanings are relative to the display surface. (See figure 1.) 3.3.4 VDC space and range Graphics output functions are used to define vi
33、rtual images. The coordinate data given as parameters to these functions (that is, points in the virtual image) are specified as absolute two-dimensional Virtual Device Coordinates (WCs). VDC space is a two-dimensional Cartesian coordinate space of infinite precision and infinite extent. Only a subs
34、et of VDC space, the VDC range, is realizable by the CGI client. The VDC range comprises all coordinates representable in the format specified by the declared VDC type and limited by any applicable precision; thus, the VDC range is not directly set by the client. The VDC range is a finite discrete s
35、ubset of VDC space (i.e. it does not provide a continuous range of values). VDC space can be addressed with either integer or real coordinate data, determined by the VDC Type entry in the Control State List and controlled by the VDC TYPE function. The granularity and realizable extent of the VDC ran
36、ge is affected by either the VDC INTEGER PRECISION REQUIREMENT function or the VDC REAL PRECISION REQUIREMENTS function, depending on the VDC Type. The Control Description Table indicates which of integer and real types am supporWl for WCs. Refer to 3.5.1 for further information on precision control
37、. 3.3.5 VDC extent The VDC extent is the portion of VDC space that is to be mapped onto the effective device viewport on the drawing surface of the Virtual Device. The extent is set by specifying the addresses (in VDC space) of two opposite comers of a rectangular region. Values outside the VDC exte
38、nt are permitted in CGI functions. 5 Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo reproduction or networking permitted without license from IHS -,-,- ._._ g _I_-
39、. _ - I -_- _. _L_ ._.w_i_ . -. ISO/IEC 9636-2 : 1991 Q Concepts Coordinate space concepts VDC Extent VDC-to-Device Mapping VDC Extent = (0, 0), (32676.32676) Isotropy = FORCED Horizontal Alignment = LEFT Vettical Alignment = BOTTOM Specification Mode of Current Device Viewport = FRACI ION OF DISPLA
40、Y SURFACE Metric Scale Factor of Current Device Viewport = 1 .O Requested Device Viewport = (0.0.0.0). (1 .O. 1 .O) Effective Device Viewpott = (0.0,O.O). (0X566.1.0) Display Surface Effective Device Viewport Figure 1 - An example VDC-to-Device Mapping. The values of the coordinates for either dimen
41、sion may be either increasing or decreasing from the first to the second corner. In this way, the sense of the coordinate system of VDC space relative to the dmwing surface is established (see ligure 2). The transformation which maps VDC points to the drawing surface is called the VDC-to-Device Mapp
42、ing. The VDC-to-Device Mapping maps the fmt point specifying the VDC extent onto the comer of the effective device viewport corresponding to the fust point specifying the device viewport, and similarly for the second point. The mapping is linear in each dimension, but is not necessarily isotropic (e
43、.g. a circle in VDC may not appear round to the viewer). If the values of the device viewport mapping entries do not force isotropy, an isotropic transformation can still be assured if the numerical aspect ratio of VDC extent matches ihe physical (not necessarily numerical) aspect ratio of the devic
44、e viewport. Angular directions are defined as follows: positive 90-degrees is defined to be the right angle from the positive x-axis to the positive y-axis (see figure 2). Whether changes to the VDC-to-Device Mapping take place immediately, can be simulated, or lead to an implicit regeneration, is d
45、etermined by the Dynamic Modification Accepted For VDC-to-Device Mapping entry in the Output Device Description Table. The terminology used in the description of primitives and attributes refers to increasing coordinates from the fast to the second corner relative to the device viewport. If a coordi
46、nate system is chosen with decreasing coordinates from the first to the second corner in one of x or y, the rendered objects shall be mirrored. If decreasing in both x and y. the rendered objects shall be rotated by an angle of 1800. 3.3.6 VDC tailoring The ability to specify the VDC range and the V
47、DC extent provides the flexibility to configure the Virtual Device coordinate space to match various needs. It may be configured as an abstract, normalized coordinate range for maximum device independence. It may also be configured to match the address range and resolution of some target device (e.g
48、. in order to avoid abasing problems or increase performance). If the Virtual Device coordinate space is configured to match the address range and resolution of a raster device, it may be necessary to know whether or not the pixels lie on or between the coordinates. Where pixels lie relative to the
49、coordinates is indicated by an entry in the Output Device Description Table. The preferred behaviour is that coordinates lie between pixels. Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=USN Ship Repair Facility Yokosuka/9961031100 Not for Resale, 05/08/2007 20:13:49 MDTNo