TK(2)                                                       TK(2)

          Tk: toplevel, namechan, cmd, pointer, keyboard, imageget,
          imageput, quote, rect - graphics toolkit

          include "draw.m";
          include "tk.m";
          tk := load Tk Tk->PATH;
          Image:    import Draw;

          Toplevel: adt
              display:    ref Draw->Display;
              wreq:       chan of string;
              image:      ref Image;
              ctxt:       ref Draw->Wmcontext;
              screenr:    Draw->Rect;

          toplevel: fn(display: ref Draw->Display, arg: string): ref Toplevel;
          namechan: fn(top: ref Toplevel, c: chan of string, n: string): string;
          cmd:      fn(top: ref Toplevel, arg: string): string;
          pointer:    fn(top: ref Toplevel, p: Draw->Pointer);
          keyboard: fn(top: ref Toplevel, key: int);
          getimage: fn(top: ref Toplevel, name: string):
                       (ref Image, ref Image, string);
          putimage: fn(top: ref Toplevel, name: string, i, m: ref Image): string;
          rect:     fn(top: ref Toplevel, name: string, flags: int): Draw->Rect;
          quote:    fn(s: string): string;
          color:    fn(s: string): int;

          The Tk module provides primitives for building user inter-
          faces, based on Ousterhout's Tcl/TK.  The interface to the
          toolkit itself is primarily the passing of strings to and
          from the elements of the toolkit using the cmd function; see
          section 9 of this manual for more information about the syn-
          tax of those strings.  Tkclient(2) is conventionally used to
          create tk windows that interact correctly with a running
          window manager.

          Toplevel creates a new window called a Toplevel, which is
          under the control of the Tk toolkit, on an existing display,
          usually one inherited from the graphics Context (see draw-
          context(2)). The Toplevel is passed to cmd and namechan
          (q.v.)  to drive the widgets in the window.  Arg is a string
          containing creation options (such as -borderwidth 2) that
          are applied when creating the toplevel window.

          Cmd passes command strings to the widgets in the Toplevel t

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     TK(2)                                                       TK(2)

          and returns the string resulting from their execution.  For
          example, given a canvas .c in the Toplevel t,
              x := int tk->cmd(t, ".c cget -actx");
          returns the integer x coordinate of the canvas.

          Bindings can be created in a Toplevel that trigger strings
          to be sent on Limbo channels.  Such channels must be
          declared to the Tk module using namechan.  For example, to
          create a button that sends the word Ouch when it is pressed:
              hitchannel := chan of string;
              tk->namechan(t, hitchannel, "channel");
                   "button .b.Hit -text Hit -command {send channel Ouch}");
              expl := <-hitchannel;     # will see Ouch when button pressed

          Pointer and keyboard pass mouse and keyboard events to a Tk
          window for delivery to widgets; they must be called by each
          application, which usually receives them via a Wmcontext
          structure (see draw-context(2)) obtained from the window
          manager, often via tkclient(2).

          Putimage passes an image and a mask into Tk.  If name is the
          name of a Tk widget, it must be either a panel(9) widget, or
          a top level widget (ie, ``.'')   or a menu widget, in which
          case the associated image or window image is set to i. (m is
          ignored for menu and top-level widgets.)  Otherwise, name
          must be the name of an existing image(9) which has its image
          and mask set to copies of i and m respectively.

          Initially, a Tk toplevel has no image to draw on.  Tk uses
          wreq to request new images of an external authority, and to
          inform said authority when the images are to be deleted.
          The requests are formatted as per quoted in string(2), and
          hold one of the following:

          !reshape name reqid minx miny maxx
               A new image for name is requested (name is either the
               toplevel widget or a menu).  The desired rectangle for
               the new image is given by [minx miny maxx maxy], and
               the application should respond by creating a new image
               and using putimage to pass it to Tk.  Reqid is used by
               Tk to filter out responses to out-of-date requests;
               when responding to a reshape request, the name passed
               to putimage should have a space and reqid appended.
               Tkclient(2) usually deals with the details of this.

          delete name
               The image name has been deleted. This is generated for
               menu(9) widgets when they are unmapped.

          raise name
               Tk widget name should be raised above other windows on

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     TK(2)                                                       TK(2)

               the same screen.

          lower name
               Tk widget name should be lowered beneath other windows
               on the same screen.

          Wreq may be set to nil if an application is not prepared to
          read requests sent on this channel.

          Rect returns the bounding rectangle of widget name in top.
          Flags determines the form of rectangle returned.  If flags
          is zero, the actual rectangle of name in screen coordinates,
          not including its border, is returned. The bitmask flags
          that can change this are:

               Include the widget's border.

               Return the rectangle required by the widget, rather
               than the rectangle that has been actually allocated to

               Return the rectangle in coordinates relative to the
               logical origin of the actual top level image.

          Quote returns a string that is the same as its arguments,
          but enclosed in curly braces and with internal curly braces
          escaped.  This can be used to make an arbitrary string into
          a word suitable as an argument to a Tk function.

          Color returns a colour in 32-bit RGBA format corresponding
          to the tk colour name s. (see types(9) for details).

          Screenr gives the rectangle of the screen containing the
          toplevel window.  Tk has no a priori way of knowing what
          this is; it is initially set to the rectangle of the display
          image, and may be set by the application if it knows better
          (e.g. from the wmrect file served by wm(1)).


          intro(9), image(9), panel(9), tkcmd(1), sh-tk(1), draw-
          context(2), tkclient(2), wmlib(2)
          `An Overview of Limbo/Tk', this manual, Volume 2.

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