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| | 11 | <H1 ALIGN=CENTER>Whitepaper: wxWidgets on the GNOME desktop</H1> |
| | 12 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>Introduction</FONT></FONT></P> |
| | 13 | <P>wxWidgets<A HREF="http://www.wxwidgets.org/"><SUP>[1]</SUP></A> |
| | 14 | (formely known as wxWindows) is a C++ cross-platform GUI library, |
| | 15 | whose distintive feature is the use of native calls and native |
| | 16 | widgets on the respective platform, i.e. an application compiled for |
| | 17 | the Linux platform will use the GTK+<A HREF="http://www.gtk.org/"><SUP>[2]</SUP></A> |
| | 18 | library for displaying the various widgets. There is also a version |
| | 19 | („port“) of wxWidgets which uses the Motif toolkit for |
| | 20 | displaying its widgets (this port is commonly referred to as wxMotif) |
| | 21 | and another one, which only uses X11 calls and which draws its |
| | 22 | widgets entirely itself, without using any outside library. This port |
| | 23 | is called wxX11 or sometimes more generally wxUniv (short for |
| | 24 | wxUniversal), since this widget set (implemented entirely within |
| | 25 | wxWidgets) is available whereever wxWidgets is available. Since this |
| | 26 | short overview is mainly about how to write wxWidgets applications |
| | 27 | for the GNOME<A HREF="http://www.gnome.org/"><SUP>[3]</SUP></A> |
| | 28 | desktop, I will focus on the GTK+ port, which is generally referred |
| | 29 | to as wxGTK. |
| | 30 | </P> |
| | 31 | <P>wxGTK still supports the old version GTK+ 1.2, but it now defaults |
| | 32 | to the uptodate version GTK+ 2.X, which is the basis for the current |
| | 33 | GNOME desktop. By way of using GTK+ 2.X and its underlying text |
| | 34 | rendering library Pango<A HREF="http://www.pango.org/"><SUP>[4]</SUP></A>, |
| | 35 | wxGTK fully supports the Unicode character set and it can render text |
| | 36 | in any language and script, that is supported by Pango.</P> |
| | 37 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>wxWidgets' |
| | 38 | design principles sofar</FONT></FONT></P> |
| | 39 | <P>The three main design goals of the wxWidgets library are |
| | 40 | portability across the supported platforms, complete integration with |
| | 41 | the supported platforms and a broad range of functionality covering |
| | 42 | most aspects of GUI and non-GUI application programming. Sometimes, |
| | 43 | various aspects of these design goals contradict each other and this |
| | 44 | holds true especially for the Linux platform which – from the |
| | 45 | point of view of the desktop environment integration – is |
| | 46 | lagging behind the other two major desktops (Windows and MacOS X) |
| | 47 | mostly because of the schism between the GTK+ based GNOME desktop and |
| | 48 | the Qt<A HREF="http://www.trolltech.com/"><SUP>[5]</SUP></A> based |
| | 49 | KDE<A HREF="http://www.kde.org/"><SUP>[6]</SUP></A> desktop. So far, |
| | 50 | the typical wxWidgets user targeted Windows, maybe MacOS X and Linux |
| | 51 | <I>in general</I>, so the aim was to make wxGTK applications run as |
| | 52 | well as possible on as many versions of Linux as possible, including |
| | 53 | those using the KDE environment. Luckily, most of these distributions |
| | 54 | included the GTK+ library (for running applications like the GIMP, |
| | 55 | GAIM, Evolution or Mozilla) whereas the GNOME libraries were not |
| | 56 | always installed by default. Also, the GNOME libraries didn't really |
| | 57 | offer substantial value so that the hassle of installing them was |
| | 58 | hardly justified. Therefore, much effort was spent on making wxGTK |
| | 59 | fully functional without relying on the GNOME libraries, mostly by |
| | 60 | reimplementing as much as sensible of the missing functionality. This |
| | 61 | included a usable file selection dialog, a printing system for |
| | 62 | PostScript output, code for querying MIME-types and file-icon |
| | 63 | associations, classes for storing application preferences and |
| | 64 | configurations, the possibility to display mini-apps in the taskbar, |
| | 65 | a full-featured HTML based help system etc. With all that in place |
| | 66 | you can write a pretty fully featured wxWidgets application on an |
| | 67 | old Linux system with little more installed than X11 and GTK+.</P> |
| | 68 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>Recent |
| | 69 | developments</FONT></FONT></P> |
| | 70 | <P>Recently, several key issues have been addressed by the GNOME |
| | 71 | project. Sometimes integrated into the newest GTK+ releases (such as |
| | 72 | the file selecter), sometimes as part of the GNOME libraries (such as |
| | 73 | the new printing system with Pango integration or the mime-types |
| | 74 | handling in gnome-vfs), sometimes as outside projects (such as the |
| | 75 | media/video backend based on the Gstreamer<A HREF="http://gstreamer.freedesktop.org/"><SUP>[7]</SUP></A> |
| | 76 | project). Also, care has been taken to unify the look and feel of |
| | 77 | GNOME applications by writing down a number of rules (modestly called |
| | 78 | „Human Interface Guidelines“<A HREF="http://developer.gnome.org/projects/gup/hig"><SUP>[8]</SUP></A>) |
| | 79 | and more and more decisions are taken in a desktop neutral way (for |
| | 80 | both GNOME and KDE), mostly as part of the FreeDesktop<A HREF="http://www.freedesktop.org/"><SUP>[9]</SUP></A> |
| | 81 | initiative. This development together with the rising number of |
| | 82 | OpenSource projects using wxWidgets mainly for the Linux and more |
| | 83 | specifically GNOME desktop has led to a change of direction within |
| | 84 | the wxWidgets project, now working on making more use of GNOME |
| | 85 | features when present. The general idea is to call the various GNOME |
| | 86 | libraries if they are present and to offer a reasonable fallback if |
| | 87 | not. I'll detail on the various methods chosen below:</P> |
| | 88 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>Printing |
| | 89 | system</FONT></FONT></P> |
| | 90 | <P>The old printing system ....</P> |
| | 91 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>MIME-type |
| | 92 | handling</FONT></FONT></P> |
| | 93 | <P>The old mime-type system used to simply query some files stored in |
| | 94 | „typical“ locations for the respective desktop |
| | 95 | environment. Since both the format and the location of these files |
| | 96 | changed rather frequently, this system was never fully working as |
| | 97 | desired for reading the MIME-types and it never worked at all for |
| | 98 | writing MIME-types or icon/file associations. ...</P> |
| | 99 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>The |
| | 100 | new file dialog</FONT></FONT></P> |
| | 101 | <P>Previously, wxGTK application made use of a file dialog written in |
| | 102 | wxWidgets itself, since the default GTK+ file dialog was simplistic |
| | 103 | to say the least. This has changed with version GTK+ 2.4, where a |
| | 104 | nice and powerful dialog has been added. We now query the GTK+ |
| | 105 | library, if the new file dialog functions are available and wxGTK |
| | 106 | applications will show and use them if that is the case, otherwise, |
| | 107 | they will fall back to the old generic one.</P> |
| | 108 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>File |
| | 109 | configuration and preferences</FONT></FONT></P> |
| | 110 | <P>The usual Unix way of saving file configuration and preferences is |
| | 111 | to write and read a so called „dot-file“, basically a |
| | 112 | text file in a user's home directory starting with a dot. This was |
| | 113 | deemed insufficient by the GNOME desktop project and therefore they |
| | 114 | introduced the so called GConf system, for storing and retrieving |
| | 115 | application and sessions information....</P> |
| | 116 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>Results |
| | 117 | and discussion</FONT></FONT></P> |
| | 118 | <P>One of wxWidgets' greatest merits is the ability to write an |
| | 119 | application that not only runs on different operating systems but |
| | 120 | especially under Linux even on rather old systems with only a minimal |
| | 121 | set of libraries installed – using a single application binary. |
| | 122 | This was possible since most of the relevant functionality was either |
| | 123 | located in the only required library (GTK+) or was implemented within |
| | 124 | wxWidgets. Recent development outside the actual GTK+ project has |
| | 125 | made it necessary to rethink this design and make use of other |
| | 126 | projects' features in order to stay uptodate with current |
| | 127 | techological trends. Therefore, a system was implemented within |
| | 128 | wxWidgets that queries the system at runtime about various libraries |
| | 129 | and makes use of their features whenever possible, but falls back to |
| | 130 | a reasonable solution if not. The result is that you can create and |
| | 131 | distribute application binaries that run on old Linux systems and |
| | 132 | integrate fully with modern desktops, if they are available. This is |
| | 133 | not currently possible with any other software.</P> |
| | 134 | <P>Copyright 2004 © Robert Roebling, MD. No reprint permitted |
| | 135 | without written prior authorisation.<BR>Last modified 14/11/04</P> |
| | 136 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>About |
| | 137 | the author</FONT></FONT></P> |
| | 138 | <P>Robert Roebling works as a medical doctor in the Department of |
| | 139 | Neurology at the University clinic of Ulm in Germany. He has studied |
| | 140 | Computer Sciences for a few semesters and is involved in the |
| | 141 | wxWidgets projects since about 1996. He has started and written most |
| | 142 | of wxGTK port (beginning with GTK+ around 0.9) and has contributed to |
| | 143 | quite a number projects within wxWidgets, ranging from the image |
| | 144 | classes to Unicode support to making both the Windows and the GTK+ |
| | 145 | ports work on embedded platform (mostly PDAs). He is happily married, |
| | 146 | has two children and never has time.</P> |
| | 147 | <P STYLE="margin-top: 0.42cm; page-break-after: avoid"><FONT FACE="Albany, sans-serif"><FONT SIZE=4>Links |
| | 148 | and citations</FONT></FONT></P> |
| | 149 | <P>[1] See the wxWidgets homepage at <A HREF="http://www.wxwidgets.org/">www.wxwidgets.org</A>.<BR>[2] |
| | 150 | See the GTK+ homepage at <A HREF="http://www.gtk.org/">www.gtk.org</A>.<BR>[3] |
| | 151 | See more about GNOME at <A HREF="http://www.gnome.org/">www.gnome.org</A>, |
| | 152 | <A HREF="http://www.gnomedesktop.org/">www.gnomedesktop.org</A>, |
| | 153 | <A HREF="http://www.gnomejournal.org/">www.gnomejournal.org</A>, |
| | 154 | <A HREF="http://www.gnomefiles.org/">www.gnomefiles.org</A>.<BR>[4] |
| | 155 | See the Pango homepage at <A HREF="http://www.pango.org/">www.pango.org</A>.<BR>[5] |
| | 156 | See the Qt homepage at <A HREF="http://www.trolltech.com/">www.trolltech.com</A>.<BR>[6] |
| | 157 | See the KDE homepage at <A HREF="http://www.kde.org/">www.kde.org</A>.<BR>[7] |
| | 158 | See Gstreamer homepage at <A HREF="http://gstreamer.freedesktop.org/">gstreamer.freedesktop.org</A>.<BR>[8] |
| | 159 | See GNOME's Human Interface Guidelines at |
| | 160 | <A HREF="http://developer.gnome.org/projects/gup/hig">developer.gnome.org/projects/gup/hig</A>.<BR>[9] |
| | 161 | See FreeDesktop's homepage at <A HREF="http://www.freedesktop.org/">www.freedesktop.org</A>.<BR><BR><BR> |
| | 162 | </P> |
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