## NAME

Tk_CreateMainWindow, Tk_CreateWindow, Tk_CreateWindowFromPath, Tk_DestroyWindow, Tk_MakeWindowExist - create or delete window

## SYNOPSIS

#include <tk.h>

Tk_Window Tk_CreateMainWindow(interp, screenName, baseName, className)

Tk_Window Tk_CreateWindow(interp, parent, name, topLevScreen)

Tk_Window Tk_CreateWindowFromPath(interp, tkwin, pathName, topLevScreen)

Tk_DestroyWindow(tkwin)

Tk_MakeWindowExist(tkwin)

## ARGUMENTS

`Tcl_Interp *interp` (out)
  Tcl interpreter to use for error reporting. If no error occurs, then *interp isn't modified. For Tk_CreateMainWindow, this interpreter is associated permanently with the created window, and Tk-related commands are bound into the interpreter.
`char *screenName` (in)
  String name of screen on which to create window. Has the form displayName.screenNum, where displayName is the name of a display and screenNum is a screen number. If the dot and screenNum are omitted, the screen number defaults to 0. If screenName is NULL or empty string, defaults to contents of DISPLAY environment variable.
`char *baseName` (in)
  Name to use for this main window. See below for details.
`char *className` (in)
  Class to use for application and for main window.
`Tk_Window parent` (in)
  Token for the window that is to serve as the logical parent of the new window.
`char *name` (in)
  Name to use for this window. Must be unique among all children of the same parent.
`char *topLevScreen` (in)
  Has same format as screenName. If NULL, then new window is created as an internal window. If non-NULL, new window is created as a top-level window on screen topLevScreen. If topLevScreen is an empty string (``'') then new window is created as top-level window of parent's screen.
`Tk_Window tkwin` (in)
  Token for window.
`char *pathName` (in)
  Name of new window, specified as path name within application (e.g. .a.b.c).

## DESCRIPTION

The three procedures Tk_CreateMainWindow, Tk_CreateWindow, and Tk_CreateWindowFromPath are used to create new windows for use in Tk-based applications. Each of the procedures returns a token that can be used to manipulate the window in other calls to the Tk library. If the window couldn't be created successfully, then NULL is returned and interp->result is modified to hold an error message.

Tk supports three different kinds of windows: main windows, internal windows, and top-level windows. A main window is the outermost window corresponding to an application. Main windows correspond to the independent units of an application, such as a view on a file that is part of an editor, or a clock, or a terminal emulator. A main window is created as a child of the root window of the screen indicated by the screenName. Each main window, and all its descendants, are typically associated with a single Tcl command interpreter. An internal window is an interior window of a Tk application, such as a scrollbar or menu bar or button. A top-level window is one that is created as a child of a screen's root window, rather than as an interior window, but which is logically part of some existing main window. Examples of top-level windows are pop-up menus and dialog boxes.

Tk_CreateMainWindow creates a new main window and associates its interp argument with that window and all its eventual descendants. Tk_CreateMainWindow also carries out several other actions to set up the new application. First, it adds all the Tk commands to those already defined for interp. Second, it turns the new window into a toplevel widget, which will cause the X window to be created and mapped as soon as the application goes idle. Third, Tk_CreateMainWindow registers interp so that it can be accessed remotely by other Tk applications using the send command and the name baseName. Normally, baseName consists of the name of the application followed by a space and an identifier for this particular main window (if such an identifier is relevant). For example, an editor named mx displaying the file foo.c would use ``mx foo.c'' as the basename. An application that doesn't usually have multiple instances, such as a clock program, would just use the name of the application, e.g. ``xclock''. If baseName is already in use by some other registered interpreter, then Tk_CreateMainWindow extends baseName with a number to produce a unique name like ``mx foo.c #2'' or ``xclock #12''. This name is used both as the name of the window (returned by Tk_Name) and as the registered name of the interpreter. Fourth, Tk_CreateMainWindow sets className as the class of the application (among other things, this is used for lookups in the option database), and also as the class of the main widget.

Either internal or top-level windows may be created by calling Tk_CreateWindow. If the topLevScreen argument is NULL, then the new window will be an internal window. If topLevScreen is non-NULL, then the new window will be a top-level window: topLevScreen indicates the name of a screen and the new window will be created as a child of the root window of topLevScreen. In either case Tk will consider the new window to be the logical child of parent: the new window's path name will reflect this fact, options may be specified for the new window under this assumption, and so on. The only difference is that new X window for a top-level window will not be a child of parent's X window. For example, a pull-down menu's parent would be the button-like window used to invoke it, which would in turn be a child of the menu bar window. A dialog box might have the application's main window as its parent. This approach means that all the windows of an application fall into a hierarchical arrangement with a single logical root: the application's main window.

Tk_CreateWindowFromPath offers an alternate way of specifying new windows. In Tk_CreateWindowFromPath the new window is specified with a token for any window in the target application (tkwin), plus a path name for the new window. It produces the same effect as Tk_CreateWindow and allows both top-level and internal windows to be created, depending on the value of topLevScreen. In calls to Tk_CreateWindowFromPath, as in calls to Tk_CreateWindow, the parent of the new window must exist at the time of the call, but the new window must not already exist.

In truth, the window-creation procedures don't actually issue the command to X to create a window. Instead, they create a local data structure associated with the window and defer the creation of the X window. The window will actually be created by the first call to Tk_MapWindow. Deferred window creation allows various aspects of the window (such as its size, background color, etc.) to be modified after its creation without incurring any overhead in the X server. When the window is finally mapped all of the window attributes can be set while creating the window.

The value returned by a window-creation procedure is not the X token for the window (it can't be, since X hasn't been asked to create the window yet). Instead, it is a token for Tk's local data structure for the window. Most of the Tk library procedures take Tk_Window tokens, rather than X identifiers. The actual X window identifier can be retrieved from the local data structure using the Tk_WindowId macro; See the Tk_WindowId manual entry for details.

Tk_DestroyWindow deletes a window and all the data structures associated with it, including any event handlers created with Tk_CreateEventHandler. In addition, Tk_DestroyWindow will delete any children of tkwin recursively (where children are defined in the Tk sense, consisting of all windows that were created with the given window as parent). If tkwin was created by Tk_CreateInternalWindow then event handlers interested in destroy events are invoked immediately. If tkwin is a top-level or main window, then the event handlers will be invoked later, after X has seen the request and returned an event for it.

If a window has been created but hasn't been mapped, so no X window exists, it is possible to force the creation of the X window by calling Tk_MakeWindowExist. This procedure issues the X commands to instantiate the window given by tkwin.

## KEYWORDS

create, deferred creation, destroy, display, internal window, main window, register, screen, top-level window, window