XeviQueryExtension, XeviQueryVersion, XeviGetVisualInfo - X Extended Visual Information functions


#include <X11/extensions/XEVI.h>

Bool XeviQueryExtension (Display *dpy);

Bool XeviQueryVersion (Display *dpy,
int *major_version_return,
int *minor_version_return);

int XeviGetVisualInfo (Display *dpy, VisualID *visual,
int n_visual, ExtendedVisualInfo ** evi_return,
int * n_info_return);


The X11 Extended Visual Information extension (EVI) allows a client to determine information about core X visuals beyond what the core protocol provides.

The EVI application programming library contains the interfaces described below. With the exception of XeviQueryExtension, if any of these routines are called with a display that does not support the extension, the ExtensionErrorHandler (which can be set with XSetExtensionErrorHandler and functions the same way as XSetErrorHandler) will be called and the function will then return.

XeviQueryExtension returns True if the Extended Visual Information extension is available on the given display. A client must call XeviQueryExtension before calling any other EVI function in order to negotiate a compatible protocol version; otherwise the client will get undefined behavior (EVI may or may not work).

XeviQueryVersion returns True if the request succeeded; the values of the major and minor protocol version supported by the server are returned in major_version_return and minor_version_return.

XeviGetVisualInfo returns a list of ExtendedVisualInfo structures that describe visual information beyond that supported by the core protocol. This includes layer information relevant for systems supporting overlays and/or underlay planes, and information that allows applications better to determine the level of hardware support for multiple colormaps. XeviGetVisualInfo returns Success if successful, or an X error otherwise. If the argument visual is NULL, then information for all visuals of all screens is returned. Otherwise, it’s a pointer to a list of visuals for which extended visual information is desired. n_visual is the number of elements in the array visual. evi_return returns a pointer to a list of ExtendedVisualInfo. When done, the client should free the list using XFree. n_info_return returns the number of elements in the array evi_return.

The ExtendedVisualInfo structure has the following fields:







unsigned int


unsigned int


unsigned int


unsigned int


unsigned int


VisualID *


The combination of core_visual_id and screen number uniquely specify the visual being described.

level returns the level number for the visual, 0 for normal planes, > 0 for overlays, < 0 for underlays.

transparency_type returns the type of transparency supported by the visual. XEVI_TRANSPARENCY_NONE if there are no transparent pixels, XEVI_TRANSPARENCY_PIXEL if the visual supports a transparent pixel, XEVI_TRANSPARENCY_MASK if the visual supports transparent plane(s).

transparency_value returns the pixel/plane value to set for transparency if transparency_type isn’t XEVI_TRANSPARENCY_NONE.

min_hw_colormaps and max_hw_colormaps return the minimum and maximum number of hardware colormaps backing up the visual.

num_colormap_conflicts returns the number of elements in colormap_conflicts. This array returns a list of visuals that may cause conflicts in the use of the hardware colormap. For example, if a 12-bit hardware colormap is overloaded to support 8-bit colormaps, the corresponding 8-bit visuals would conflict with the 12-bit visuals.


XeviGetVisualInfo will return BadValue if passed an illegal visual ID, BadAccess if the X server does not respond, BadAlloc if there is a memory allocation failure.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.