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Inside Macintosh: Macintosh Toolbox Essentials /

Chapter 4 - Window Manager / Using the Window Manager

Hiding and Showing a Window

Whenever the user clicks a window's close box, you remove the window from the screen. Sometimes, however, you might find it's more efficient to merely hide the window, instead of removing its data structures.

If your application includes a Find modeless dialog box that searches for a string, for example, you might want to keep the structures in memory as long as the user is working. When the user closes the dialog box by clicking the close box, you simply hide the window by calling the HideWindow procedure. The next time the user chooses the Find command, your dialog box window is already available, in the same location and with the same text selected as when it was last used.

To reverse the HideWindow procedure, you must call both ShowWindow, which makes the window visible, and SelectWindow, which makes it the active window. Figure 4-22 illustrates how the three procedures affect the window's status on the screen.

Figure 4-22 The cumulative effects of HideWindow, ShowWindow, and SelectWindow

The application-defined procedure for closing a window--DoCloseCmd, described
on page 4-54--hides the Find and Spell Check dialog box windows when the
user closes them. Listing 4-18 illustrates a sample application-defined procedure, DoShowModelessFindDialogBox, for redisplaying the Find dialog box when the
user next chooses the Find command.

Listing 4-18 Showing a hidden dialog box

PROCEDURE DoShowModelessFindDialogBox;
BEGIN
   IF gFindDialog = NIL THEN     {no Find dialog box exists yet}
   BEGIN
      {create Find dialog box}
      gFindDialog := GetNewDialog(rFindModelessDialog, NIL,
                                  Pointer(-1));
      IF gFindDialog = NIL THEN        {creation failed}
         Exit(DoShowModelessFindDialogBox);     {exit}
      {store value that identifies dbox in window refCon field}
      SetWRefCon(gFindDialog, LongInt(kMyFindModelessDialog))
      ShowWindow(gFindDialog);         {make dialog box visible}
   END
   ELSE              {dialog box already exists}
   BEGIN
      ShowWindow(gFindDialog);         {make it visible}
      SelectWindow(gFindDialog);       {select it}
   END;
END;

The DoShowModelessFindDialogBox procedure first checks whether the Find
dialog box already exists. If it doesn't, then DoShowModelessFindDialogBox creates a new dialog box through the Dialog Manager. It stores the constant that represents
the Find dialog box in the refCon field of the new window record, makes the window visible, and draws the dialog box contents. If the Find dialog box already exists, DoShowModelessFindDialogBox makes the dialog box window visible and selects it. When the Window Manager then generates an activate event, the application calls its own procedure to draw the contents.