Release 10.1A: OpenEdge Development:
Progress 4GL Handbook

Using multiple windows

As you’ve already learned, there is no DEFINE WINDOW statement in Progress. Any windows you build for your application are dynamic windows. This section summarizes some of the window handles and attributes that can be useful to you in designing an application with multiple windows.

You create a window with the CREATE WINDOW statement, which has the same syntax as every other CREATE statement you’ve seen.

Window system handles

The simple examples in this book that don’t use a window you create (or that is created for you in code the AppBuilder generates) use the default window that is part of every session. This has a system handle called DEFAULT-WINDOW. This handle is not something you would ordinarily use in a real application.

You’ve seen the CURRENT-WINDOW system handle, which holds the handle of the window used by default for parenting frames, dialog boxes, and message alert boxes. The CURRENT-WINDOW attribute of a procedure overrides CURRENT-WINDOW for the context of that procedure only, without changing the value of the session-wide system handle. The statements in the standard AppBuilder window template that set both CURRENT-WINDOW and the CURRENT-WINDOW procedure attribute to the procedure’s window provide a good default for parenting of objects created and used in that procedure.

Another useful system handle is ACTIVE-WINDOW, which holds the handle of the window that has received the most recent input focus in the application. This handle can help you assure that a dialog box or message alert box appears parented to the window where the user is currently working, even if it is not the current window of the procedure that executes the code to display the dialog box or message.

Useful window attributes, methods, and events

Table 18–1 describes the numerous attributes, methods, and events that you can use to control the appearance and behavior of windows in your application.

Table 18–1: Window attributes, methods, and events

Type	Name	Description
Attribute	TITLE	Specifies the window title.
	HEIGHT-CHARS WIDTH-CHARS HEIGHT-PIXELS WIDTH-PIXELS	Specifies the standard height and width of the window.
	MIN-HEIGHT-CHARS MIN-WIDTH-CHARS MIN-HEIGHT-PIXELS MIN-WIDTH-PIXELS	Specifies the minimum height and width of the window.
	MAX-HEIGHT-CHARS MAX-WIDTH-CHARS MAX-HEIGHT-PIXELS MAX-WIDTH-PIXELS	Specifies the maximum height and width of the window.
	VIRTUAL-HEIGHT-CHARS VIRTUAL-WIDTH-CHARS VIRTUAL-HEIGHT-PIXELS VIRTUAL-WIDTH-PIXELS	Specifies the maximum display area of the window.
	MESSAGE-AREA MESSAGE-AREA-FONT	Defines a message area and its font at the bottom of the window, where messages that are not qualified with the VIEW-AS ALERT-BOX phrase are displayed.
	STATUS-AREA STATUS-AREA-FONT	Defines a status area and its font at the bottom of the window.
	SCROLL-BARS	Defines whether scroll bars appear when the window is resized.
	MENUBAR POPUP-MENU	Associates a menu or pop-up menu with a window.
	PARENT	Establishes parent-child relationships between windows.
Method	LOAD-ICON()	Takes the name of an image file with the .ico extension and displays the image in the title bar of the window, in the task bar when the window is minimized, and when the user selects the window using ALT+TAB.
	LOAD-SMALL-ICON()	Takes the name of an image file for an icon in the title bar or the task bar. The .ico file for either method can be an image of 16x16 or 32x32 pixels.
Event	WINDOW-MINIMIZED	Fires when a window is minimized.
	WINDOW-MAXIMIZED	Fires when a window is maximized.
	WINDOW-RESTORED	Fires when a window is restored after being minimized.
	WINDOW-RESIZED	Fires when a keyboard or mouse event starts to change the window’s size. The window’s RESIZE attribute must be true for this to occur.
	WINDOW-CLOSE	Fires when the user selects the standard icon used to close the window. In fact, Progress does not take any action automatically when the WINDOW-CLOSE event occurs—it does not even close the window! For this reason, you need to define a trigger for the WINDOW-CLOSE event, as described in the next section.

WINDOW-CLOSE event example

The simplest example of an action on the WINDOW-CLOSE event is this:

WAIT-FOR WINDOW-CLOSE OF CURRENT-WINDOW.

If the WAIT-FOR statement is the last executable statement in a nonpersistent procedure, the event satisfies the WAIT-FOR and the procedure terminates.

The AppBuilder window template uses indirection to direct the WINDOW-CLOSE event for the window to the procedure itself, using this standard ON WINDOW-CLOSE trigger:

DO:   /* This event will close the window and terminate the procedure. */   APPLY "CLOSE":U TO THIS-PROCEDURE.   RETURN NO-APPLY. END.

You’ve already seen the rest of the steps in this sequence, with the CLOSE event on the procedure running disable_UI and deleting the procedure itself.