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119 lines
6.0 KiB
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<HTML><HEAD><TITLE>Tk Built-In Commands - focus manual page</TITLE></HEAD><BODY>
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<DL>
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<DD><A HREF="focus.htm#M2" NAME="L468">NAME</A>
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<DL><DD>focus - Manage the input focus</DL>
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<DD><A HREF="focus.htm#M3" NAME="L469">SYNOPSIS</A>
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<DL>
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<DD><B>focus</B>
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<DD><B>focus </B><I>window</I>
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<DD><B>focus </B><I>option</I> ?<I>arg arg ...</I>?
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</DL>
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<DD><A HREF="focus.htm#M4" NAME="L470">DESCRIPTION</A>
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<DL>
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<DD><A HREF="focus.htm#M5" NAME="L471"><B>focus</B></A>
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<DD><A HREF="focus.htm#M6" NAME="L472"><B>focus </B><I>window</I></A>
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<DD><A HREF="focus.htm#M7" NAME="L473"><B>focus -displayof</B> <I>window</I></A>
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<DD><A HREF="focus.htm#M8" NAME="L474"><B>focus -force </B><I>window</I></A>
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<DD><A HREF="focus.htm#M9" NAME="L475"><B>focus -lastfor</B> <I>window</I></A>
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</DL>
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<DD><A HREF="focus.htm#M10" NAME="L476">QUIRKS</A>
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<DD><A HREF="focus.htm#M11" NAME="L477">KEYWORDS</A>
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</DL><HR>
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<H3><A NAME="M2">NAME</A></H3>
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focus - Manage the input focus
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>focus</B><BR>
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<B>focus </B><I>window</I><BR>
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<B>focus </B><I>option</I> ?<I>arg arg ...</I>?<BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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The <B>focus</B> command is used to manage the Tk input focus.
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At any given time, one window on each display is designated as
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the <I>focus window</I>; any key press or key release events for the
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display are sent to that window.
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It is normally up to the window manager to redirect the focus among the
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top-level windows of a display. For example, some window managers
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automatically set the input focus to a top-level window whenever
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the mouse enters it; others redirect the input focus only when
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the user clicks on a window.
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Usually the window manager will set the focus
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only to top-level windows, leaving it up to the application to
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redirect the focus among the children of the top-level.
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<P>
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Tk remembers one focus window for each top-level (the most recent
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descendant of that top-level to receive the focus); when the window
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manager gives the focus
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to a top-level, Tk automatically redirects it to the remembered
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window. Within a top-level Tk uses an <I>explicit</I> focus model
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by default. Moving the mouse within a top-level does not normally
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change the focus; the focus changes only when a widget
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decides explicitly to claim the focus (e.g., because of a button
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click), or when the user types a key such as Tab that moves the
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focus.
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<P>
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The Tcl procedure <B>tk_focusFollowsMouse</B> may be invoked to
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create an <I>implicit</I> focus model: it reconfigures Tk so that
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the focus is set to a window whenever the mouse enters it.
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The Tcl procedures <B>tk_focusNext</B> and <B>tk_focusPrev</B>
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implement a focus order among the windows of a top-level; they
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are used in the default bindings for Tab and Shift-Tab, among other
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things.
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<P>
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The <B>focus</B> command can take any of the following forms:
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<P>
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<DL>
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<P><DT><A NAME="M5"><B>focus</B></A><DD>
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Returns the path name of the focus window on the display containing
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the application's main window, or an empty string if no window in
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this application has the focus on that display. Note: it is
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better to specify the display explicitly using <B>-displayof</B>
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(see below) so that the code will work in applications using multiple
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displays.
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<P><DT><A NAME="M6"><B>focus </B><I>window</I></A><DD>
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If the application currently has the input focus on <I>window</I>'s
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display, this command resets the input focus for <I>window</I>'s display
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to <I>window</I> and returns an empty string.
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If the application doesn't currently have the input focus on
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<I>window</I>'s display, <I>window</I> will be remembered as the focus
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for its top-level; the next time the focus arrives at the top-level,
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Tk will redirect it to <I>window</I>.
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If <I>window</I> is an empty string then the command does nothing.
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<P><DT><A NAME="M7"><B>focus -displayof</B> <I>window</I></A><DD>
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Returns the name of the focus window on the display containing <I>window</I>.
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If the focus window for <I>window</I>'s display isn't in this
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application, the return value is an empty string.
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<P><DT><A NAME="M8"><B>focus -force </B><I>window</I></A><DD>
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Sets the focus of <I>window</I>'s display to <I>window</I>, even if
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the application doesn't currently have the input focus for the display.
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This command should be used sparingly, if at all.
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In normal usage, an application should not claim the focus for
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itself; instead, it should wait for the window manager to give it
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the focus.
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If <I>window</I> is an empty string then the command does nothing.
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<P><DT><A NAME="M9"><B>focus -lastfor</B> <I>window</I></A><DD>
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Returns the name of the most recent window to have the input focus
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among all the windows in the same top-level as <I>window</I>.
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If no window in that top-level has ever had the input focus, or
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if the most recent focus window has been deleted, then the name
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of the top-level is returned. The return value is the window that
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will receive the input focus the next time the window manager gives
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the focus to the top-level.
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<P></DL>
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<H3><A NAME="M10">QUIRKS</A></H3>
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When an internal window receives the input focus, Tk doesn't actually
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set the X focus to that window; as far as X is concerned, the focus
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will stay on the top-level window containing the window with the focus.
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However, Tk generates FocusIn and FocusOut events just as if the X
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focus were on the internal window. This approach gets around a
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number of problems that would occur if the X focus were actually moved;
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the fact that the X focus is on the top-level is invisible unless
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you use C code to query the X server directly.
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<H3><A NAME="M11">KEYWORDS</A></H3>
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<A href="../Keywords/E.htm#events">events</A>, <A href="../Keywords/F.htm#focus">focus</A>, <A href="../Keywords/K.htm#keyboard">keyboard</A>, <A href="../Keywords/T.htm#top-level">top-level</A>, <A href="../Keywords/W.htm#window manager">window manager</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1990-1994 The Regents of the University of California.
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<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
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<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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