1XNEST(1) General Commands Manual XNEST(1)
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6 Xnest - a nested X server
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9 Xnest [-options]
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12 Xnest is a client and a server. Xnest is a client of the real server
13 which manages windows and graphics requests on its behalf. Xnest is a
14 server to its own clients. Xnest manages windows and graphics requests
15 on their behalf. To these clients Xnest appears to be a conventional
16 server.
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19 Xnest supports all standard options of the sample server implementa‐
20 tion. For more details, please see the manual page on your system for
21 Xserver. The following additional arguments are supported as well.
22 -display string
24 This option specifies the display name of the real server that
25 Xnest should try to connect with. If it is not provided on the
26 command line Xnest will read the DISPLAY environment variable in
27 order to find out the same information.
28 -sync
30 This option tells Xnest to synchronize its window and graphics
31 operations with the real server. This is a useful option for
32 debugging, but it will slow down the performance considerably. It
33 should not be used unless absolutely necessary.
34 -full
36 This option tells Xnest to utilize full regeneration of real server
37 objects and reopen a new connection to the real server each time
38 the nested server regenerates. The sample server implementation
39 regenerates all objects in the server when the last client of this
40 server terminates. When this happens, Xnest by default maintains
41 the same top level window and the same real server connection in
42 each new generation. If the user selects full regeneration, even
43 the top level window and the connection to the real server will be
44 regenerated for each server generation.
45 -class string
47 This option specifies the default visual class of the nested
48 server. It is similar to the -cc option from the set of standard
49 options except that it will accept a string rather than a number
50 for the visual class specification. The string must be one of the
51 following six values: StaticGray, GrayScale, StaticColor, Pseudo‐
52 Color, TrueColor, or DirectColor. If both, -class and -cc options
53 are specified, the last instance of either option assumes prece‐
54 dence. The class of the default visual of the nested server need
55 not be the same as the class of the default visual of the real
56 server; although, it has to be supported by the real server. See
57 xdpyinfo for a list of supported visual classes on the real server
58 before starting Xnest. If the user chooses a static class, all the
59 colors in the default colormap will be preallocated. If the user
60 chooses a dynamic class, colors in the default colormap will be
61 available to individual clients for allocation.
62 -depth int
64 This option specifies the default visual depth of the nested
65 server. The depth of the default visual of the nested server need
66 not be the same as the depth of the default visual of the real
67 server; although, it has to be supported by the real server. See
68 xdpyinfo for a list of supported visual depths on the real server
69 before starting Xnest.
70 -sss
72 This option tells Xnest to use the software screen saver. By
73 default Xnest will use the screen saver that corresponds to the
74 hardware screen saver in the real server. Of course, even this
75 screen saver is software generated since Xnest does not control any
76 actual hardware. However, it is treated as a hardware screen saver
77 within the sample server code.
78 -geometry WxH+X+Y
80 This option specifies geometry parameters for the top level Xnest
81 windows. These windows corresponds to the root windows of the
82 nested server. The width and height specified with this option
83 will be the maximum width and height of each top level Xnest win‐
84 dow. Xnest will allow the user to make any top level window
85 smaller, but it will not actually change the size of the nested
86 server root window. As of yet, there is no mechanism within the
87 sample server implementation to change the size of the root window
88 after screen initialization. In order to do so, one would probably
89 need to extend the X protocol. Therefore, it is not likely that
90 this will be available any time soon. If this option is not speci‐
91 fied Xnest will choose width and height to be 3/4 of the dimensions
92 of the root window of the real server.
93 -bw int
95 This option specifies the border width of the top level Xnest win‐
96 dow. The integer parameter must be a positive number. The default
97 border width is 1.
98 -name string
100 This option specifies the name of the top level Xnest window. The
101 default value is the program name.
102 -scrns int
104 This option specifies the number of screens to create in the nested
105 server. For each screen, Xnest will create a separate top level
106 window. Each screen is referenced by the number after the dot in
107 the client display name specification. For example, xterm -display
108 :1.1 will open an xterm client in the nested server with the dis‐
109 play number :1 on the second screen. The number of screens is lim‐
110 ited by the hard coded constant in the server sample code which is
111 usually 3.
112 -install
114 This option tells Xnest to do its own colormap installation by
115 bypassing the real window manager. For it to work properly the
116 user will probably have to temporarily quit the real window man‐
117 ager. By default Xnest will keep the nested client window whose
118 colormap should be installed in the real server in the WM_COL‐
119 ORMAP_WINDOWS property of the top level Xnest window. If this col‐
120 ormap is of the same visual type as the root window of the nested
121 server, Xnest will associate this colormap with the top level Xnest
122 window as well. Since this does not have to be the case, window
123 managers should look primarily at the WM_COLORMAP_WINDOWS property
124 rather than the colormap associated with the top level Xnest win‐
125 dow. Unfortunately, window managers are not very good at doing
126 that yet so this option might come in handy.
127 -parent window_id
129 This option tells Xnest to use the window_id as the root window
130 instead of creating a window. This option is used by the xrx xnest‐
131 plugin.
132
134 Starting up Xnest is as simple as starting up xclock from a terminal
135 emulator. If a user wishes to run Xnest on the same workstation as the
136 real server, it is important that the nested server is given its own
137 listening socket address. Therefore, if there is a server already run‐
138 ning on the user's workstation, Xnest will have to be started up with a
139 new display number. Since there is usually no more than one server
140 running on a workstation, specifying Xnest :1 on the command line will
141 be sufficient for most users. For each server running on the worksta‐
142 tion the display number needs to be incremented by one. Thus, if you
143 wish to start another Xnest, you will need to type Xnest :2 on the com‐
144 mand line.
145 To run clients in the nested server each client needs to be given the
147 same display number as the nested server. For example, xterm -display
148 :1 will start up an xterm in the first nested server and xterm -display
149 :2 will start an xterm in the second nested server from the example
150 above. Additional clients can be started from these xterms in each
151 nested server.
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154 Xnest behaves and looks to the real server and other real clients as
155 another real client. It is a rather demanding client, however, since
156 almost any window or graphics request from a nested client will result
157 in a window or graphics request from Xnest to the real server. There‐
158 fore, it is desirable that Xnest and the real server are on a local
159 network, or even better, on the same machine. As of now, Xnest assumes
160 that the real server supports the shape extension. There is no way to
161 turn off this assumption dynamically. Xnest can be compiled without
162 the shape extension built in, and in that case the real server need not
163 support it. The dynamic shape extension selection support should be
164 considered in further development of Xnest.
165 Since Xnest need not use the same default visual as the the real
167 server, the top level window of the Xnest client always has its own
168 colormap. This implies that other windows' colors will not be dis‐
169 played properly while the keyboard or pointer focus is in the Xnest
170 window, unless the real server has support for more than one installed
171 colormap at any time. The colormap associated with the top window of
172 the Xnest client need not be the appropriate colormap that the nested
173 server wants installed in the real server. In the case that a nested
174 client attempts to install a colormap of a different visual from the
175 default visual of the nested server, Xnest will put the top window of
176 this nested client and all other top windows of the nested clients that
177 use the same colormap into the WM_COLORMAP_WINDOWS property of the top
178 level Xnest window on the real server. Thus, it is important that the
179 real window manager that manages the Xnest top level window looks at
180 the WM_COLORMAP_WINDOWS property rather than the colormap associated
181 with the top level Xnest window. Since most window managers appear to
182 not implement this convention properly as of yet, Xnest can optionally
183 do direct installation of colormaps into the real server bypassing the
184 real window manager. If the user chooses this option, it is usually
185 necessary to temporarily disable the real window manager since it will
186 interfere with the Xnest scheme of colormap installation.
187 Keyboard and pointer control procedures of the nested server change the
189 keyboard and pointer control parameters of the real server. Therefore,
190 after Xnest is started up, it will change the keyboard and pointer con‐
191 trols of the real server to its own internal defaults. Perhaps there
192 should be a command line option to tell Xnest to inherit the keyboard
193 and pointer control parameters from the real server rather than impos‐
194 ing its own. This is a future consideration.
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197 Xnest as a server looks exactly like a real server to its own clients.
198 For the clients there is no way of telling if they are running on a
199 real or a nested server.
200 As already mentioned, Xnest is a very user friendly server when it
202 comes to customization. Xnest will pick up a number of command line
203 arguments that can configure its default visual class and depth, number
204 of screens, etc. In the future, Xnest should read a customization
205 input file to provide even greater freedom and simplicity in selecting
206 the desired layout. Unfortunately, there is no support for backing
207 store and save under as of yet, but this should also be considered in
208 the future development of Xnest.
209 The only apparent intricacy from the users' perspective about using
211 Xnest as a server is the selection of fonts. Xnest manages fonts by
212 loading them locally and then passing the font name to the real server
213 and asking it to load that font remotely. This approach avoids the
214 overload of sending the glyph bits across the network for every text
215 operation, although it is really a bug. The proper implementation of
216 fonts should be moved into the os layer. The consequence of this
217 approach is that the user will have to worry about two different font
218 paths - a local one for the nested server and a remote one for the real
219 server - since Xnest does not propagate its font path to the real
220 server. The reason for this is because real and nested servers need
221 not run on the same file system which makes the two font paths mutually
222 incompatible. Thus, if there is a font in the local font path of the
223 nested server, there is no guarantee that this font exists in the
224 remote font path of the real server. Xlsfonts client, if run on the
225 nested server will list fonts in the local font path and if run on the
226 real server will list fonts in the remote font path. Before a font can
227 be successfully opened by the nested server it has to exist in local
228 and remote font paths. It is the users' responsibility to make sure
229 that this is the case.
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232 Won't run well on servers supporting different visual depths. Still
233 crashes randomly. Probably has some memory leaks.
234
236 Davor Matic, MIT X Consortium
237X Version 11 xorg-server 1.3.0.0 XNEST(1)