X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/dface61ccba162c922b25d18aca2ebc4e6f03312..ab9717339232a7a728dea666c59b73fd6ac78dd3:/docs/latex/wx/dataobj.tex?ds=inline diff --git a/docs/latex/wx/dataobj.tex b/docs/latex/wx/dataobj.tex index 4efc76278e..1c6cce5aa3 100644 --- a/docs/latex/wx/dataobj.tex +++ b/docs/latex/wx/dataobj.tex @@ -1,45 +1,145 @@ +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%% Name: dataobj.tex +%% Purpose: wxDataObject documentation +%% Author: Vadim Zeitlin +%% Modified by: +%% Created: 18.10.99 +%% RCS-ID: $Id$ +%% Copyright: (c) wxWidgets team +%% License: wxWindows license +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + \section{\class{wxDataObject}}\label{wxdataobject} A wxDataObject represents data that can be copied to or from the clipboard, or -dragged and dropped. - -There are several predefined data object classes, such as \helpref{wxFileDataObject}{wxfiledataobject}, -\helpref{wxTextDataObject}{wxtextdataobject}, and \helpref{wxBitmapDataObject}{wxbitmapdataobject}. +dragged and dropped. The important thing about wxDataObject is that this is a +'smart' piece of data unlike 'dumb' data containers such as memory +buffers or files. Being 'smart' here means that the data object itself should +know what data formats it supports and how to render itself in each of +its supported formats. + +A supported format, incidentally, is exactly the format in which the data can +be requested from a data object or from which the data object may be set. In +the general case, an object may support different formats on 'input' and +'output', i.e. it may be able to render itself in a given format but not be +created from data on this format or vice versa. wxDataObject defines an +enumeration type -You may also derive your own data object classes for user-defined types. +\begin{verbatim} +enum Direction +{ + Get = 0x01, // format is supported by GetDataHere() + Set = 0x02 // format is supported by SetData() +}; +\end{verbatim} -TODO: how do user-defined types work? +which distinguishes between them. See +\helpref{wxDataFormat}{wxdataformat} documentation for more about formats. + +Not surprisingly, being 'smart' comes at a price of added complexity. This is +reasonable for the situations when you really need to support multiple formats, +but may be annoying if you only want to do something simple like cut and paste +text. + +To provide a solution for both cases, wxWidgets has two predefined classes +which derive from wxDataObject: \helpref{wxDataObjectSimple}{wxdataobjectsimple} and +\helpref{wxDataObjectComposite}{wxdataobjectcomposite}. +\helpref{wxDataObjectSimple}{wxdataobjectsimple} is +the simplest wxDataObject possible and only holds data in a single format (such +as HTML or text) and \helpref{wxDataObjectComposite}{wxdataobjectcomposite} is +the simplest way to implement a wxDataObject that does support multiple formats +because it achieves this by simply holding several wxDataObjectSimple objects. + +So, you have several solutions when you need a wxDataObject class (and you need +one as soon as you want to transfer data via the clipboard or drag and drop): + +\begin{twocollist}\itemsep=1cm +\twocolitem{{\bf 1. Use one of the built-in classes}}{You may use wxTextDataObject, +wxBitmapDataObject or wxFileDataObject in the simplest cases when you only need +to support one format and your data is either text, bitmap or list of files.} +\twocolitem{{\bf 2. Use wxDataObjectSimple}}{Deriving from wxDataObjectSimple is the simplest +solution for custom data - you will only support one format and so probably +won't be able to communicate with other programs, but data transfer will work +in your program (or between different copies of it).} +\twocolitem{{\bf 3. Use wxDataObjectComposite}}{This is a simple but powerful +solution which allows you to support any number of formats (either +standard or custom if you combine it with the previous solution).} +\twocolitem{{\bf 4. Use wxDataObject directly}}{This is the solution for +maximal flexibility and efficiency, but it is also the most difficult to +implement.} +\end{twocollist} + +Please note that the easiest way to use drag and drop and the clipboard with +multiple formats is by using wxDataObjectComposite, but it is not the most +efficient one as each wxDataObjectSimple would contain the whole data in its +respective formats. Now imagine that you want to paste 200 pages of text in +your proprietary format, as well as Word, RTF, HTML, Unicode and plain text to +the clipboard and even today's computers are in trouble. For this case, you +will have to derive from wxDataObject directly and make it enumerate its +formats and provide the data in the requested format on demand. + +Note that neither the GTK+ data transfer mechanisms for clipboard and +drag and drop, nor OLE data transfer, copy any data until another application +actually requests the data. This is in contrast to the 'feel' offered to the +user of a program who would normally think that the data resides in the +clipboard after having pressed 'Copy' - in reality it is only declared to be +available. + +There are several predefined data object classes derived from +wxDataObjectSimple: \helpref{wxFileDataObject}{wxfiledataobject}, +\helpref{wxTextDataObject}{wxtextdataobject} and +\helpref{wxBitmapDataObject}{wxbitmapdataobject} which can be used without +change. + +You may also derive your own data object classes from +\helpref{wxCustomDataObject}{wxcustomdataobject} for user-defined types. The +format of user-defined data is given as a mime-type string literal, such as +"application/word" or "image/png". These strings are used as they are under +Unix (so far only GTK+) to identify a format and are translated into their +Windows equivalent under Win32 (using the OLE IDataObject for data exchange to +and from the clipboard and for drag and drop). Note that the format string +translation under Windows is not yet finished. + +\pythonnote{At this time this class is not directly usable from wxPython. +Derive a class from \helpref{wxPyDataObjectSimple}{wxdataobjectsimple} +instead.} + +\perlnote{This class is not currently usable from wxPerl; you may +use \helpref{Wx::PlDataObjectSimple}{wxdataobjectsimple} instead.} + +\wxheading{Virtual functions to override} + +Each class derived directly from wxDataObject must override and implement all +of its functions which are pure virtual in the base class. + +The data objects which only render their data or only set it (i.e. work in +only one direction), should return 0 from +\helpref{GetFormatCount}{wxdataobjectgetformatcount}. \wxheading{Derived from} -\helpref{wxObject}{wxobject} +None -\wxheading{Types} +\wxheading{Include files} -\index{wxDataFormat}The following symbols are interchangable with the -Windows equivalents. + -\begin{verbatim} -enum wxDataFormat -{ - wxDF_TEXT = 1, /* CF_TEXT */ - wxDF_BITMAP = 2, /* CF_BITMAP */ - wxDF_METAFILE = 3, /* CF_METAFILEPICT */ - wxDF_DIB = 8, /* CF_DIB */ - wxDF_OEMTEXT = 7, /* CF_OEMTEXT */ - wxDF_FILENAME = 15, /* CF_HDROP */ - wxDF_PRIVATE = 20 -}; -\end{verbatim} +\wxheading{Library} + +\helpref{wxCore}{librarieslist} \wxheading{See also} +\helpref{Clipboard and drag and drop overview}{wxdndoverview}, +\helpref{DnD sample}{samplednd}, \helpref{wxFileDataObject}{wxfiledataobject}, \helpref{wxTextDataObject}{wxtextdataobject}, \helpref{wxBitmapDataObject}{wxbitmapdataobject}, -\helpref{Drag and drop overview}{wxdndoverview}, \helpref{wxDropTarget}{wxdroptarget}, +\helpref{wxCustomDataObject}{wxcustomdataobject}, +\helpref{wxDropTarget}{wxdroptarget}, \helpref{wxDropSource}{wxdropsource}, -\helpref{wxTextDropTarget}{wxtextdroptarget}, \helpref{wxFileDropTarget}{wxfiledroptarget} +\helpref{wxTextDropTarget}{wxtextdroptarget}, +\helpref{wxFileDropTarget}{wxfiledroptarget} \latexignore{\rtfignore{\wxheading{Members}}} @@ -55,9 +155,50 @@ Constructor. Destructor. -\membersection{wxDataObject::GetFormat}\label{wxdataobjectgetformat} +\membersection{wxDataObject::GetAllFormats}\label{wxdataobjectgetallformats} + +\constfunc{virtual void}{GetAllFormats}{ \param{wxDataFormat *}{formats}, \param{Direction}{ dir = Get}} + +Copy all supported formats in the given direction to the array pointed to by +{\it formats}. There is enough space for GetFormatCount(dir) formats in it. + +\perlnote{In wxPerl this method only takes the {\tt dir} parameter. +In scalar context it returns the first format, +in list context it returns a list containing all the supported formats.} + +\membersection{wxDataObject::GetDataHere}\label{wxdataobjectgetdatahere} + +\constfunc{virtual bool}{GetDataHere}{\param{const wxDataFormat\&}{ format}, \param{void }{*buf} } + +The method will write the data of the format {\it format} in the buffer {\it +buf} and return true on success, false on failure. + +\membersection{wxDataObject::GetDataSize}\label{wxdataobjectgetdatasize} + +\constfunc{virtual size\_t}{GetDataSize}{\param{const wxDataFormat\&}{ format} } + +Returns the data size of the given format {\it format}. + +\membersection{wxDataObject::GetFormatCount}\label{wxdataobjectgetformatcount} + +\constfunc{virtual size\_t}{GetFormatCount}{\param{Direction}{ dir = Get}} + +Returns the number of available formats for rendering or setting the data. + +\membersection{wxDataObject::GetPreferredFormat}\label{wxdataobjectgetpreferredformat} + +\constfunc{virtual wxDataFormat}{GetPreferredFormat}{\param{Direction}{ dir = Get}} + +Returns the preferred format for either rendering the data (if {\it dir} is {\tt Get}, +its default value) or for setting it. Usually this will be the +native format of the wxDataObject. + +\membersection{wxDataObject::SetData}\label{wxdataobjectsetdata} + +\func{virtual bool}{SetData}{ \param{const wxDataFormat\&}{ format}, \param{size\_t}{ len}, \param{const void }{*buf} } -\constfunc{virtual wxDataFormat}{GetFormat}{\void} +Set the data in the format {\it format} of the length {\it len} provided in the +buffer {\it buf}. -Returns the format of the object. See \helpref{Types}{wxdataobject}. +Returns true on success, false on failure.