Qt 5.13 | GNU Free Documentation License (FDL)

Qt 5.13.2 Reference Documentation

# GNU Free Documentation License (FDL)

Qt documentation is available under commercial licenses from The Qt Company. In addition, is is available under the terms of the GNU Free Documentation License version 1.3, as published by the Free Software Foundation.

Example code embedded in the Qt documentation is also licensed under a BSD 3-Clause "New" or "Revised" License. See License of Qt examples for further details.

The Qt Toolkit is Copyright (C) 2018 The Qt Company Ltd. and other contributors.
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Reference: GNU Free Documentation License

                      GNU Free Documentation License
                       Version 1.3, 3 November 2008

       Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
           <http://fsf.org/>
       Everyone is permitted to copy and distribute verbatim copies
       of this license document, but changing it is not allowed.

      0. PREAMBLE

      The purpose of this License is to make a manual, textbook, or other
      functional and useful document "free" in the sense of freedom: to
      assure everyone the effective freedom to copy and redistribute it,
      with or without modifying it, either commercially or noncommercially.
      Secondarily, this License preserves for the author and publisher a way
      to get credit for their work, while not being considered responsible
      for modifications made by others.

      This License is a kind of "copyleft", which means that derivative
      works of the document must themselves be free in the same sense.  It
      complements the GNU General Public License, which is a copyleft
      license designed for free software.

      We have designed this License in order to use it for manuals for free
      software, because free software needs free documentation: a free
      program should come with manuals providing the same freedoms that the
      software does.  But this License is not limited to software manuals;
      it can be used for any textual work, regardless of subject matter or
      whether it is published as a printed book.  We recommend this License
      principally for works whose purpose is instruction or reference.

      1. APPLICABILITY AND DEFINITIONS

      This License applies to any manual or other work, in any medium, that
      contains a notice placed by the copyright holder saying it can be
      distributed under the terms of this License.  Such a notice grants a
      world-wide, royalty-free license, unlimited in duration, to use that
      work under the conditions stated herein.  The "Document", below,
      refers to any such manual or work.  Any member of the public is a
      licensee, and is addressed as "you".  You accept the license if you
      copy, modify or distribute the work in a way requiring permission
      under copyright law.

      A "Modified Version" of the Document means any work containing the
      Document or a portion of it, either copied verbatim, or with
      modifications and/or translated into another language.

      A "Secondary Section" is a named appendix or a front-matter section of
      the Document that deals exclusively with the relationship of the
      publishers or authors of the Document to the Document's overall
      subject (or to related matters) and contains nothing that could fall
      directly within that overall subject.  (Thus, if the Document is in
      part a textbook of mathematics, a Secondary Section may not explain
      any mathematics.)  The relationship could be a matter of historical
      connection with the subject or with related matters, or of legal,
      commercial, philosophical, ethical or political position regarding
      them.

      The "Invariant Sections" are certain Secondary Sections whose titles
      are designated, as being those of Invariant Sections, in the notice
      that says that the Document is released under this License.  If a
      section does not fit the above definition of Secondary then it is not
      allowed to be designated as Invariant.  The Document may contain zero
      Invariant Sections.  If the Document does not identify any Invariant
      Sections then there are none.

      The "Cover Texts" are certain short passages of text that are listed,
      as Front-Cover Texts or Back-Cover Texts, in the notice that says that
      the Document is released under this License.  A Front-Cover Text may
      be at most 5 words, and a Back-Cover Text may be at most 25 words.

      A "Transparent" copy of the Document means a machine-readable copy,
      represented in a format whose specification is available to the
      general public, that is suitable for revising the document
      straightforwardly with generic text editors or (for images composed of
      pixels) generic paint programs or (for drawings) some widely available
      drawing editor, and that is suitable for input to text formatters or
      for automatic translation to a variety of formats suitable for input
      to text formatters.  A copy made in an otherwise Transparent file
      format whose markup, or absence of markup, has been arranged to thwart
      or discourage subsequent modification by readers is not Transparent.
      An image format is not Transparent if used for any substantial amount
      of text.  A copy that is not "Transparent" is called "Opaque".

      Examples of suitable formats for Transparent copies include plain
      ASCII without markup, Texinfo input format, LaTeX input format, SGML
      or XML using a publicly available DTD, and standard-conforming simple
      HTML, PostScript or PDF designed for human modification.  Examples of
      transparent image formats include PNG, XCF and JPG.  Opaque formats
      include proprietary formats that can be read and edited only by
      proprietary word processors, SGML or XML for which the DTD and/or
      processing tools are not generally available, and the
      machine-generated HTML, PostScript or PDF produced by some word
      processors for output purposes only.

      The "Title Page" means, for a printed book, the title page itself,
      plus such following pages as are needed to hold, legibly, the material
      this License requires to appear in the title page.  For works in
      formats which do not have any title page as such, "Title Page" means
      the text near the most prominent appearance of the work's title,
      preceding the beginning of the body of the text.

      The "publisher" means any person or entity that distributes copies of
      the Document to the public.

      A section "Entitled XYZ" means a named subunit of the Document whose
      title either is precisely XYZ or contains XYZ in parentheses following
      text that translates XYZ in another language.  (Here XYZ stands for a
      specific section name mentioned below, such as "Acknowledgements",
      "Dedications", "Endorsements", or "History".)  To "Preserve the Title"
      of such a section when you modify the Document means that it remains a
      section "Entitled XYZ" according to this definition.

      The Document may include Warranty Disclaimers next to the notice which
      states that this License applies to the Document.  These Warranty
      Disclaimers are considered to be included by reference in this
      License, but only as regards disclaiming warranties: any other
      implication that these Warranty Disclaimers may have is void and has
      no effect on the meaning of this License.

      2. VERBATIM COPYING

      You may copy and distribute the Document in any medium, either
      commercially or noncommercially, provided that this License, the
      copyright notices, and the license notice saying this License applies
      to the Document are reproduced in all copies, and that you add no
      other conditions whatsoever to those of this License.  You may not use
      technical measures to obstruct or control the reading or further
      copying of the copies you make or distribute.  However, you may accept
      compensation in exchange for copies.  If you distribute a large enough
      number of copies you must also follow the conditions in section 3.

      You may also lend copies, under the same conditions stated above, and
      you may publicly display copies.

      3. COPYING IN QUANTITY

      If you publish printed copies (or copies in media that commonly have
      printed covers) of the Document, numbering more than 100, and the
      Document's license notice requires Cover Texts, you must enclose the
      copies in covers that carry, clearly and legibly, all these Cover
      Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
      the back cover.  Both covers must also clearly and legibly identify
      you as the publisher of these copies.  The front cover must present
      the full title with all words of the title equally prominent and
      visible.  You may add other material on the covers in addition.
      Copying with changes limited to the covers, as long as they preserve
      the title of the Document and satisfy these conditions, can be treated
      as verbatim copying in other respects.

      If the required texts for either cover are too voluminous to fit
      legibly, you should put the first ones listed (as many as fit
      reasonably) on the actual cover, and continue the rest onto adjacent
      pages.

      If you publish or distribute Opaque copies of the Document numbering
      more than 100, you must either include a machine-readable Transparent
      copy along with each Opaque copy, or state in or with each Opaque copy
      a computer-network location from which the general network-using
      public has access to download using public-standard network protocols
      a complete Transparent copy of the Document, free of added material.
      If you use the latter option, you must take reasonably prudent steps,
      when you begin distribution of Opaque copies in quantity, to ensure
      that this Transparent copy will remain thus accessible at the stated
      location until at least one year after the last time you distribute an
      Opaque copy (directly or through your agents or retailers) of that
      edition to the public.

      It is requested, but not required, that you contact the authors of the
      Document well before redistributing any large number of copies, to
      give them a chance to provide you with an updated version of the
      Document.

      4. MODIFICATIONS

      You may copy and distribute a Modified Version of the Document under
      the conditions of sections 2 and 3 above, provided that you release
      the Modified Version under precisely this License, with the Modified
      Version filling the role of the Document, thus licensing distribution
      and modification of the Modified Version to whoever possesses a copy
      of it.  In addition, you must do these things in the Modified Version:

      A. Use in the Title Page (and on the covers, if any) a title distinct
         from that of the Document, and from those of previous versions
         (which should, if there were any, be listed in the History section
         of the Document).  You may use the same title as a previous version
         if the original publisher of that version gives permission.
      B. List on the Title Page, as authors, one or more persons or entities
         responsible for authorship of the modifications in the Modified
         Version, together with at least five of the principal authors of the
         Document (all of its principal authors, if it has fewer than five),
         unless they release you from this requirement.
      C. State on the Title page the name of the publisher of the
         Modified Version, as the publisher.
      D. Preserve all the copyright notices of the Document.
      E. Add an appropriate copyright notice for your modifications
         adjacent to the other copyright notices.
      F. Include, immediately after the copyright notices, a license notice
         giving the public permission to use the Modified Version under the
         terms of this License, in the form shown in the Addendum below.
      G. Preserve in that license notice the full lists of Invariant Sections
         and required Cover Texts given in the Document's license notice.
      H. Include an unaltered copy of this License.
      I. Preserve the section Entitled "History", Preserve its Title, and add
         to it an item stating at least the title, year, new authors, and
         publisher of the Modified Version as given on the Title Page.  If
         there is no section Entitled "History" in the Document, create one
         stating the title, year, authors, and publisher of the Document as
         given on its Title Page, then add an item describing the Modified
         Version as stated in the previous sentence.
      J. Preserve the network location, if any, given in the Document for
         public access to a Transparent copy of the Document, and likewise
         the network locations given in the Document for previous versions
         it was based on.  These may be placed in the "History" section.
         You may omit a network location for a work that was published at
         least four years before the Document itself, or if the original
         publisher of the version it refers to gives permission.
      K. For any section Entitled "Acknowledgements" or "Dedications",
         Preserve the Title of the section, and preserve in the section all
         the substance and tone of each of the contributor acknowledgements
         and/or dedications given therein.
      L. Preserve all the Invariant Sections of the Document,
         unaltered in their text and in their titles.  Section numbers
         or the equivalent are not considered part of the section titles.
      M. Delete any section Entitled "Endorsements".  Such a section
         may not be included in the Modified Version.
      N. Do not retitle any existing section to be Entitled "Endorsements"
         or to conflict in title with any Invariant Section.
      O. Preserve any Warranty Disclaimers.

      If the Modified Version includes new front-matter sections or
      appendices that qualify as Secondary Sections and contain no material
      copied from the Document, you may at your option designate some or all
      of these sections as invariant.  To do this, add their titles to the
      list of Invariant Sections in the Modified Version's license notice.
      These titles must be distinct from any other section titles.

      You may add a section Entitled "Endorsements", provided it contains
      nothing but endorsements of your Modified Version by various
      parties--for example, statements of peer review or that the text has
      been approved by an organization as the authoritative definition of a
      standard.

      You may add a passage of up to five words as a Front-Cover Text, and a
      passage of up to 25 words as a Back-Cover Text, to the end of the list
      of Cover Texts in the Modified Version.  Only one passage of
      Front-Cover Text and one of Back-Cover Text may be added by (or
      through arrangements made by) any one entity.  If the Document already
      includes a cover text for the same cover, previously added by you or
      by arrangement made by the same entity you are acting on behalf of,
      you may not add another; but you may replace the old one, on explicit
      permission from the previous publisher that added the old one.

      The author(s) and publisher(s) of the Document do not by this License
      give permission to use their names for publicity for or to assert or
      imply endorsement of any Modified Version.

      5. COMBINING DOCUMENTS

      You may combine the Document with other documents released under this
      License, under the terms defined in section 4 above for modified
      versions, provided that you include in the combination all of the
      Invariant Sections of all of the original documents, unmodified, and
      list them all as Invariant Sections of your combined work in its
      license notice, and that you preserve all their Warranty Disclaimers.

      The combined work need only contain one copy of this License, and
      multiple identical Invariant Sections may be replaced with a single
      copy.  If there are multiple Invariant Sections with the same name but
      different contents, make the title of each such section unique by
      adding at the end of it, in parentheses, the name of the original
      author or publisher of that section if known, or else a unique number.
      Make the same adjustment to the section titles in the list of
      Invariant Sections in the license notice of the combined work.

      In the combination, you must combine any sections Entitled "History"
      in the various original documents, forming one section Entitled
      "History"; likewise combine any sections Entitled "Acknowledgements",
      and any sections Entitled "Dedications".  You must delete all sections
      Entitled "Endorsements".

      6. COLLECTIONS OF DOCUMENTS

      You may make a collection consisting of the Document and other
      documents released under this License, and replace the individual
      copies of this License in the various documents with a single copy
      that is included in the collection, provided that you follow the rules
      of this License for verbatim copying of each of the documents in all
      other respects.

      You may extract a single document from such a collection, and
      distribute it individually under this License, provided you insert a
      copy of this License into the extracted document, and follow this
      License in all other respects regarding verbatim copying of that
      document.

      7. AGGREGATION WITH INDEPENDENT WORKS

      A compilation of the Document or its derivatives with other separate
      and independent documents or works, in or on a volume of a storage or
      distribution medium, is called an "aggregate" if the copyright
      resulting from the compilation is not used to limit the legal rights
      of the compilation's users beyond what the individual works permit.
      When the Document is included in an aggregate, this License does not
      apply to the other works in the aggregate which are not themselves
      derivative works of the Document.

      If the Cover Text requirement of section 3 is applicable to these
      copies of the Document, then if the Document is less than one half of
      the entire aggregate, the Document's Cover Texts may be placed on
      covers that bracket the Document within the aggregate, or the
      electronic equivalent of covers if the Document is in electronic form.
      Otherwise they must appear on printed covers that bracket the whole
      aggregate.

      8. TRANSLATION

      Translation is considered a kind of modification, so you may
      distribute translations of the Document under the terms of section 4.
      Replacing Invariant Sections with translations requires special
      permission from their copyright holders, but you may include
      translations of some or all Invariant Sections in addition to the
      original versions of these Invariant Sections.  You may include a
      translation of this License, and all the license notices in the
      Document, and any Warranty Disclaimers, provided that you also include
      the original English version of this License and the original versions
      of those notices and disclaimers.  In case of a disagreement between
      the translation and the original version of this License or a notice
      or disclaimer, the original version will prevail.

      If a section in the Document is Entitled "Acknowledgements",
      "Dedications", or "History", the requirement (section 4) to Preserve
      its Title (section 1) will typically require changing the actual
      title.

      9. TERMINATION

      You may not copy, modify, sublicense, or distribute the Document
      except as expressly provided under this License.  Any attempt
      otherwise to copy, modify, sublicense, or distribute it is void, and
      will automatically terminate your rights under this License.

      However, if you cease all violation of this License, then your license
      from a particular copyright holder is reinstated (a) provisionally,
      unless and until the copyright holder explicitly and finally
      terminates your license, and (b) permanently, if the copyright holder
      fails to notify you of the violation by some reasonable means prior to
      60 days after the cessation.

      Moreover, your license from a particular copyright holder is
      reinstated permanently if the copyright holder notifies you of the
      violation by some reasonable means, this is the first time you have
      received notice of violation of this License (for any work) from that
      copyright holder, and you cure the violation prior to 30 days after
      your receipt of the notice.

      Termination of your rights under this section does not terminate the
      licenses of parties who have received copies or rights from you under
      this License.  If your rights have been terminated and not permanently
      reinstated, receipt of a copy of some or all of the same material does
      not give you any rights to use it.

      10. FUTURE REVISIONS OF THIS LICENSE

      The Free Software Foundation may publish new, revised versions of the
      GNU Free Documentation License from time to time.  Such new versions
      will be similar in spirit to the present version, but may differ in
      detail to address new problems or concerns.  See
      http://www.gnu.org/copyleft/.

      Each version of the License is given a distinguishing version number.
      If the Document specifies that a particular numbered version of this
      License "or any later version" applies to it, you have the option of
      following the terms and conditions either of that specified version or
      of any later version that has been published (not as a draft) by the
      Free Software Foundation.  If the Document does not specify a version
      number of this License, you may choose any version ever published (not
      as a draft) by the Free Software Foundation.  If the Document
      specifies that a proxy can decide which future versions of this
      License can be used, that proxy's public statement of acceptance of a
      version permanently authorizes you to choose that version for the
      Document.

      11. RELICENSING

      "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
      World Wide Web server that publishes copyrightable works and also
      provides prominent facilities for anybody to edit those works.  A
      public wiki that anybody can edit is an example of such a server.  A
      "Massive Multiauthor Collaboration" (or "MMC") contained in the site
      means any set of copyrightable works thus published on the MMC site.

      "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
      license published by Creative Commons Corporation, a not-for-profit
      corporation with a principal place of business in San Francisco,
      California, as well as future copyleft versions of that license
      published by that same organization.

      "Incorporate" means to publish or republish a Document, in whole or in
      part, as part of another Document.

      An MMC is "eligible for relicensing" if it is licensed under this
      License, and if all works that were first published under this License
      somewhere other than this MMC, and subsequently incorporated in whole or
      in part into the MMC, (1) had no cover texts or invariant sections, and
      (2) were thus incorporated prior to November 1, 2008.

      The operator of an MMC Site may republish an MMC contained in the site
      under CC-BY-SA on the same site at any time before August 1, 2009,
      provided the MMC is eligible for relicensing.

      ADDENDUM: How to use this License for your documents

      To use this License in a document you have written, include a copy of
      the License in the document and put the following copyright and
      license notices just after the title page:

          Copyright (c)  YEAR  YOUR NAME.
          Permission is granted to copy, distribute and/or modify this document
          under the terms of the GNU Free Documentation License, Version 1.3
          or any later version published by the Free Software Foundation;
          with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
          A copy of the license is included in the section entitled "GNU
          Free Documentation License".

      If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
      replace the "with...Texts." line with this:

          with the Invariant Sections being LIST THEIR TITLES, with the
          Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

      If you have Invariant Sections without Cover Texts, or some other
      combination of the three, merge those two alternatives to suit the
      situation.

      If your document contains nontrivial examples of program code, we
      recommend releasing these examples in parallel under your choice of
      free software license, such as the GNU General Public License,
      to permit their use in free software.