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1 @c -*-texinfo-*-
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2 @c This is part of the XEmacs Lisp Reference Manual.
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3 @c Copyright (C) 1998 Oliver Graf <ograf@fga.de>
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4 @c Original reference is (c) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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5 @c See the file lispref.texi for copying conditions.
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6 @setfilename ../../info/dragndrop.texi
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7 @node Drag and Drop, Modes, Scrollbars, Top
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8 @chapter Drag and Drop
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9 @cindex drag and drop
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10
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11 @emph{WARNING}: the Drag'n'Drop API is still under development and the
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12 interface may change! The current implementation is considered experimental.
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13
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14 Drag'n'drop is a way to transfer information between multiple applications.
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15 To do this several GUIs define their own protocols. Examples are OffiX, CDE,
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16 Motif, KDE, MSWindows, GNOME, and many more. To catch all these protocols,
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17 XEmacs provides a generic API.
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18
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19 One prime idea behind the API is to use a data interface that is
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20 transparent for all systems. The author thinks that this is best
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21 archived by using URL and MIME data, cause any internet enabled system
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22 must support these for email already. XEmacs also already provides
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23 powerful interfaces to support these types of data (tm and w3).
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24
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25 @menu
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26 * Supported Protocols:: Which low-level protocols are supported.
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27 * Drop Interface:: How XEmacs handles a drop from another application.
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28 * Drag Interface:: Calls to initiate a drag from XEmacs.
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29 @end menu
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30
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31 @node Supported Protocols
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32 @section Supported Protocols
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33
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34 The current release of XEmacs only support a small set of Drag'n'drop
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35 protocols. Some of these only support limited options available in the API.
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36
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37 @menu
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38 * OffiX DND:: A generic X based protocol.
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39 * CDE dt:: Common Desktop Environment used on suns.
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40 * MSWindows OLE:: Mr. Gates way of live.
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41 * Loose ends:: The other protocols.
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42 @end menu
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43
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44 @node OffiX DND
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45 @subsection OffiX DND
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46 @cindex OffiX DND
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47
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48 @emph{WARNING}: If you compile in OffiX, you may not be able to use
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49 multiple X displays successfully. If the two servers are from
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50 different vendors, the results may be unpredictable.
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51
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52 The OffiX Drag'n'Drop protocol is part of a X API/Widget library created by
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53 Cesar Crusius. It is based on X-Atoms and ClientMessage events, and works with
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54 any X platform supporting them.
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55
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56 OffiX is supported if 'offix is member of the variable dragdrop-protocols, or
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57 the feature 'offix is defined.
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58
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59 Unfortunately it uses it's own data types. Examples are: File, Files,
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60 Exe, Link, URL, MIME. The API tries to choose the right type for the data that
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61 is dragged from XEmacs (well, not yet...).
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62
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63 XEmacs supports both MIME and URL drags and drops using this API. No application
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64 interaction is possible while dragging is in progress.
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65
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66 For information about the OffiX project have a look at http://leb.net/~offix/
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67
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68 @node CDE dt
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69 @subsection CDE dt
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70 @cindex CDE dt
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71
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72 CDE stands for Common Desktop Environment. It is based on the Motif
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73 widget library. It's drag'n'drop protocol is also an abstraction of the
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74 Motif protocol (so it might be possible, that XEmacs will also support
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75 the Motif protocol soon).
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76
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77 CDE has three different types: file, buffer, and text. XEmacs only uses
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78 file and buffer drags. The API will disallow full URL drags, only file
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79 method URLs are passed through.
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80
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81 Buffer drags are always converted to plain text.
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82
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83 @node MSWindows OLE
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84 @subsection MSWindows OLE
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85 @cindex MSWindows OLE
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86
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87 Only allows file drags and drops.
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88
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89 @node Loose ends
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90 @subsection Loose ends
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91
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92 The following protocols will be supported soon: Xdnd, Motif, Xde (if I
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93 get some specs), KDE OffiX (if KDE can find XEmacs windows).
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94
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95 In particular Xdnd will be one of the protocols that can benefit from
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96 the XEmacs API, cause it also uses MIME types to encode dragged data.
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97
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98 @node Drop Interface
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99 @section Drop Interface
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100 @cindex drop
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101 @cindex Drop API
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102
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103 For each activated low-level protocol, a internal routine will catch
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104 incoming drops and convert them to a dragdrop-drop type
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105 misc-user-event.
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106
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107 This misc-user-event has its function argument set to
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108 @code{dragdrop-drop-dispatch} and the object contains the data of the drop
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109 (converted to URL/MIME specific data). This function will search the variable
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110 @code{experimental-dragdrop-drop-functions} for a function that can handle the
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111 dropped data.
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112
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113 To modify the drop behavior, the user can modify the variable
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114 @code{experimental-dragdrop-drop-functions}. Each element of this list
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115 specifies a possible handler for dropped data. The first one that can handle
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116 the data will return @code{t} and exit. Another possibility is to set a
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117 extent-property with the same name. Extents are checked prior to the
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118 variable.
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119
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120 The customization group @code{drag-n-drop} shows all variables of user
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121 interest.
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122
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123 @node Drag Interface
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124 @section Drag Interface
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125 @cindex drag
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126 @cindex Drag API
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127
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128 This describes the drag API (not implemented yet).
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