125 lines
5.8 KiB
HTML
125 lines
5.8 KiB
HTML
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<html>
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<head>
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<title>The Official FVWM Homepage - Interface and Initialization Mechanism</title>
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</head>
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<body BACKGROUND="black-stone1.jpg"
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bgcolor="#000000" text="#ffffff"
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link="#FFFF88" vlink="#EEDDDD" alink="#ff0000">
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<center>
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<h1><font color="pink">The Official FVWM Homepage - Interface and Initialization Mechanism</font></h1>
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</center>
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<H2> <font color="turquoise">Module Invocation</font></h2>
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Modules MUST be launched by Fvwm. Fvwm will first open a pair of pipes
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for communication with the module. One pipe is for messages to Fvwm
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from the module, and the other is for messages to the module from
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Fvwm. Each module has its own pair of pipes. After the pipes are open,
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Fvwm will fork and spawn the module. Modules must be located in the
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ModulePath, as specified in the user's .fvwm2rc file. Modules can be
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initiated as fvwm starts up, or can be launched part way through an X
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session.
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<H2> <font color="turquoise">Module Arguments</font></h2>
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<h3>Args 0</h3>
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Like any UNIX program, arg 0 is the full pathname of the module.
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Most modules acquire this for use in error message, parsing their
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own configuration commands, some other possible uses.
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Arg 0 is related to the optional arg 6 described under "Module Aliases".
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<h3>Args 1 and 2</h3>
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The pipes are open when the module starts execution. The
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integer file descriptors are passed to the module as the first and
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second command line arguments.
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<h3>Arg 3</h3>
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The third command line argument is a character pointer pointing to the
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full path name of the last configuration file that fvwm read in.
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If there was no configuration file this arg points as to a string
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containing "none".
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In fvwm2, there is little reason for a module to use this argument.
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<h3>Arg 4</h3>
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The next command line argument is the application
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window in whose context the module was launched. This is 0 if the
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module is launched without an application window context.
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<h3>Arg 5</h3>
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The next
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argument is the context of the window decoration in which the module
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was launched. Contexts are listed below:
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<FONT COLOR="YELLOW"><PRE>#define C_NO_CONTEXT 0 - launched during initialization
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#define C_WINDOW 1 - launched from an application window
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#define C_TITLE 2 - launched from a title bar
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#define C_ICON 4 - launched from an icon window
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#define C_ROOT 8 - launched from the root window
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#define C_FRAME 16 - launched from a corner piece
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#define C_SIDEBAR 32 - launched from a side-bar
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#define C_L1 64 - launched from left button #1
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#define C_L2 128 - launched from left button #2
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#define C_L3 256 - launched from left button #3
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#define C_L4 512 - launched from left button #4
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#define C_L5 1024 - launched from left button #5
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#define C_R1 2048 - launched from right button #1
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#define C_R2 4096 - launched from right button #2
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#define C_R3 8192 - launched from right button #3
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#define C_R4 16384 - launched from right button #4
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#define C_R5 32768 - launched from right button #5</FONT></PRE>
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<h3>Arg 6 and above</h3>
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A number of user specified command line arguments may be present
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(optional). Up to 35 arguments may be passed. For example, in:
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<FONT COLOR="YELLOW"><PRE>
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Module "FvwmIdentify" FvwmIdentify Hello rob! ``-fg purple''
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</FONT></PRE>
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we would get argv[6] = ``Hello'', argv[7] = ``rob!'', argv[8] = ``-fg purple''.
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<P>
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<H2> <font color="turquoise">Module Aliases</font></h2>
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In the original fvwm, if you wanted to run 2 copies of a module, you
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where advised to copy or soft-link the module executable to another name.
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For example, you might have had to copies of FvwmButtons running.
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Some of the modules now accept arg 6 as an Alias of the module name.
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<p>
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This alias is used in module generated messages, in recognizing configuration
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commands, and possibly other uses. FvwmAnimate makes full use of this
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and might provide a good model to follow.
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<H2> <font color="turquoise">Acquiring the read/write pipes</font></h2>
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The following mechanism is recommended to acquire the pipe
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descriptors:
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<FONT COLOR="YELLOW"><PRE>
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int fd[2];
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void main(int argc, char **argv) {
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if((argc < 6)) {
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fprintf(stderr,
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"%s: Should only be executed by fvwm!\n", argv[0]);
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exit(1);
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}
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fd[0] = atoi(argv[1]);
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fd[1] = atoi(argv[2]);</FONT></PRE>
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<P>
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The descriptor fd[0] is available for the module to send messages to
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fvwm, while the descriptor fd[1] is available to read messages from
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fvwm.
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Since "int fd[2]" is an array, you will often see modules send commands
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to fvwm with the construct "SendText(fd,"Command",0);".
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Of course, they really mean "SendText(&fd[0],"Command",0);".
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<H2> <font color="turquoise">Pipe Status</font></h2>
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Special attention is paid to the status of the pipe. If Fvwm gets a
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read error on a module-to-fvwm pipe, then it assumes that the module
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is terminating,
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and all communication with the module is terminated. Similarly, if a
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module gets a read error on an fvwm-to-module pipe, then it should
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assume that fvwm is terminating, and it should gracefully shut down.
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All modules should also allow themselves to be shut down via the
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Delete Window protocol for X-11.
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<H2> <font color="turquoise">Reading initial configuration information
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</font></h2>
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In previous implementations, the modules were expected to read and
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parse the .fvwmrc file by themselves. This caused some difficulty if a
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pre-processor was used on the .fvwmrc file. In fvwm-2.0 and later,
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fvwm retains the module command lines (those which start with a
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``*''), and passes them to any module on request. Modules can
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request the command list by sending a ``Send_ConfigInfo'' command to
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fvwm. Modules can request configuration commands interactively,
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see M_SENDCONFIG in
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<A href="mod_f2m_communication.html">Fvwm-to-Module Communication</a>
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and
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<A href="mod_m2f_communication.html">Module-to-Fvwm Communication</a>.
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<hr>
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</body>
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</html>
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