ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/PROG/PASCAL/TOTDOC.ZIP/CHAPT8.TXT

Text File | 1991-02-10 | 16.5 KB | 396 lines

                                                                      Displaying
                                                                        Messages
                                                                               &
                                                                         Prompts



         "As Miss America, my goal is to bring peace to the entire world and
         then to get my own apartment."

                                                                        Jay Leno



Introduction
         The totMSG unit includes a variety of easy-to-use objects for display-
         ing messages and prompts. A message is simply a pop-up window which is
         displayed until the user presses [KEYCAP], [KEYCAP], or clicks the
         mouse on the close icon/button. Similarly, a prompt is a pop-up window,
         but the user must select one of the options displayed at the bottom of
         the window. A prompt window can have two or three buttons. The buttons
         come in two varieties: strip-buttons like the ones used in the Turbo
         Pascal IDE, and box-buttons like the ones used by PC Tools and the
         Norton Utilities.



The Object Hierarchy
         Figure 8.1 illustrates the object hierarchy for the totMSG unit. The
         base (or primitive) object is BaseMessageOBJ, and all the other messag-
         ing objects descend from it. You should never declare an instance of
         type BaseMessageOBJ, as it is an abstract object. Use one of the
         following four descendant objects:

         MessageOBJ         This is the basic message displaying object. Between
                            one and twenty lines of text can be displayed in a
                            moveable window. At the bottom of the window is a
                            single strip-button, which defaults to the text
                            "OK".  The user removes the window by clicking the
                            mouse on the button or close icon, or by pressing
                            [KEYCAP] or [KEYCAP].
         ButtonMessageOBJ   This object is a descendant of MessageOBJ and
                            operates in the same way. The only difference is
                            that the button is a box-button.

         PromptOBJ          The PromptOBJ object is descendant from the BaseMes-
                            sageOBJ, and should be used when you want to prompt
                            the user to choose a specific option. A message is
                            displayed in a moveable window, and two or three
                            strip-buttons are displayed. The user removes the
                            window by clicking on one of the buttons or the
                            close icon, or by pressing [KEYCAP]. The buttons can

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                            be selected in one of three ways: clicking on the
                            button, tabbing to a button and pressing [KEYCAP],
                            or pressing a button hotkey.

         ButtonPromptOBJ    This objects displays box-buttons, but in all other
                            aspects it operates like PromptOBJ.


Figure 8.1                                                             [PICTURE]
Message
Object Hierarchy
         This combination of objects provides you with ways of displaying
         single, double and triple button messages, using strip- or box-buttons.
         The decision to use strip- or box-buttons is solely cosmetic. The
         strip-buttons are more "elegant", but the box-buttons are larger and
         easier to select with the mouse.

Common Methods

         Since all the objects are derived from the BaseMessageOBJ, they share a
         set of common methods. The following three methods can (and should) be
         used with any of the messaging objects:

         Init(Style:byte;Tit:string);

         The Init method is passed two parameters. The first is the window box
         style, and the second, the window title. Refer to 5-7 for a discussion
         of box styles and titles. As always, this method must be called before
         any other.

         AddLine(Str:string);

         Call this method to add a line of text to the method. For example, if
         you want to display five lines of text, call AddLine five times. Up to
         twenty lines of text can be displayed in a message. The text should be
         no more than seventy characters long. The first line of text is always
         displayed on the first line of the window, i.e. immediately below the
         title. To force a space between the title and the text, call AddLine
         with an empty string, e.g. AddLine('');.  Similarly, the buttons are
         positioned directly below the last line of text. Just call Addline with
         an empty string to force a gap between the text and the buttons. The
         Toolkit automatically computes the size of the message window based on
         the number of lines added, the width of the longest line, and the style
         of button selected.

         WinForm: WinFormPtr;



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         This function method returns a pointer to the Toolkit WinFormOBJ object
         which is used to manage user input while the message is being dis-
         played. You can use this function method to directly access the WinFor-
         mOBJ methods with the following syntax: WinForm^.method. Refer to
         chapter 11: Controlling User Input for a full discussion of WinFormOBJ.



           Note: the colors used by the message objects are derived from two
           sources. The display of the window border and the message text is
           controlled by the window settings used by the WinForm object.
           Although this object is not discussed until chapter 11, it is
           worthwhile noting that you can modify the window colors with the
           following method call: WinForm^.Win^.SetColors. For example:
                    MyMsg.WinForm^.Win^.SetColors(23,31,30,28);
           The display color of the message buttons are controlled by the
           default colors set in the global instance IOTOT. The following
           method can be used to change the button colors: IOTOT^.SetColBut-
           ton. For example:
                    IOTOT^.SetColButton(32,46,47,46);
           Refer to chapter 11 for further information.



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         Done;

         This method disposes of all the memory used by the object instance, and
         should always be called.



Simple Messages

         The MessageOBJ and ButtonMessageOBJ objects are used for displaying
         simple messages, i.e. an informational message where you don't want the
         user to make a selection. The user just reads the message and removes
         it.
         Both these objects include the following method:


         Show;
         This method instructs the Toolkit to display the message window.


         Listed below is the (by now familiar) example DEMMS1.PAS, followed by
         figure 8.2 which illustrates the generated display.
         program DemoMessageOne;
         {demms1 - simple message}

         Uses DOS, CRT,
              totFAST, totMSG;
         Var
            MsgWin : MessageOBJ;

         begin
            Screen.Clear(white,'░'); {paint the screen}
            with MsgWin do
            begin
               Init(1,' Message ');
               AddLine('');
               AddLine('The message unit provides a');
               AddLine('very easy way of displaying');
               AddLine('pop-up messages in a move-');
               AddLine('able window.');
               AddLine('');
               Show;
               Done;
            end;
         end.

Figure 8.2                                                              [SCREEN]
A Simple Message



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         By simply changing the instance declaration to MsgWin: ButtonMessa-
         geOBJ; the message will be displayed using a box-button. The example
         DEMMS2.PAS contains this simple modification, and the output is shown
         in figure 8.3.


Figure 8.3                                                              [SCREEN]
A Simple Message
with a Box-Button


         By default, the button text is "OK", and the button has a hotkey of
         "O", i.e. the user can select the button, and thereby clear the mes-
         sage, by pressing [KEYCAP]. The following method provides a way of
         changing the button text and hotkey:


         SetOption(Str:string;Hotkey:word);
         This method changes the button settings. The first parameter identifies
         the text to be displayed, and the second is the keycode of the hotkey
         used to select the button. A code of 0 (zero) signifies no hotkey.



           Note: the totIO1 unit includes a constant MaxButtonWidth which
           sets the maximum button string length. By default, the maximum
           string length is 30. However, it can be modified. This subject is
           fully addressed in chapter 11: Controlling User Input.



         Listed below is the example file DEMMS3, which is similar to
         DEMMS1.PAS. The only difference is that the SetOption method was used
         to change the default button settings. Notice that the "~" symbol is
         used to highlight specific letters in the button text. This concept was
         discussed in chapter 5: Writing to the Screen on page 5-3 (WriteHi).


         program DemoMessageThree;
         {demms3 - using SetOption to change button text}

         Uses DOS, CRT,
              totFAST, totMSG;
         Var
            MsgWin : MessageOBJ;



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         begin
            Screen.Clear(white,'░'); {paint the screen}
            with MsgWin do
            begin
               Init(1,' Message ');
               AddLine('');
               AddLine('The message unit provides a');
               AddLine('very easy way of displaying');
               AddLine('pop-up messages in a move-');
               AddLine('able window.');
               AddLine('');
               SetOption(' A very ~l~ong button ',76);
               Show;
               Done;
            end;
         end.


Figure 8.4                                                              [SCREEN]
Changing the
Button Text


Multi-Button Prompts

         The PromptOBJ and ButtonPromptOBJ objects are used for displaying mes-
         sages with two or three buttons. The user removes a message by select-
         ing one of the buttons.
         By default, Prompt objects have two buttons, with the text "OK" and
         "Cancel". The function method Show is used to instruct the Toolkit to
         display the message. This function returns a member of the enumerated
         type tAction to indicate which option the user selected. The enumerated
         type tAction is declared in the totIO1 unit as follows:

                  Type
                  tAction = (None,NextField,PrevField,Finished,Escaped,
                             Refresh,Signal,Enter,Help,Stop1,Stop2,
                             Stop3,Stop4,Stop5,Stop6,Stop7,Stop8,Stop9);
         The majority of these members are for use in full screen editing
         (discussed in chapter 11), and the only ones that should be used with
         messaging are: Finished, Escaped, or Stop1 through Stop9. By default,
         if the user selects the OK button, the member "Finished" is returned,
         and if the user selects the Cancel button or presses [KEYCAP], the
         member "Escaped" is returned. The syntax of the Show method is as
         follows:


         Show:tAction;



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         Displays the message window, and returns a member of the enumerated
         type tAction, to indicate which button the user selected.


         The on-disk example DEMMS4.PAS illustrates how to display a PromptOBJ
         using the default button settings. The following method, SetOption,
         provides a way of changing the button text and hotkeys:

         SetOption(ID:byte; Str:StringBut;Hotkey:word;Act:tAction);

         The first parameter indicates which button you want to define, and can
         have a value of 1, 2 or 3. The second parameter is the text to be
         displayed in the button. The third button is a key code identifying a
         hotkey which can be used to select the button. Finally, the fourth
         parameter is a member of the enumerated type tAction. This is the mem-
         ber which will be returned by the method Show if this button is
         selected. Only use the members Finished, Escaped, or Stop1 through
         Stop9, and assign a different value to each button!

         Remember that the objects also have the methods Init, Done and AddLine
         which were discussed previously. Listed below is the demo program
         DEMMS5.PAS which illustrates the use of the SetOption method. Figure
         8.5 illustrates the resultant display.

         program DemoMessageFive;
         {demms5 - two strip-buttons with specific text}
         Uses DOS, CRT,
              totFAST, totMSG, totIO1;

         Var
            MsgWin : PromptOBJ;
            ActionCode: tAction;
         begin
            Screen.Clear(white,'░'); {paint the screen}
            with MsgWin do
            begin
               Init(1,' Warning ');
               AddLine('');
               AddLine(' The file already exists on disk, and ');
               AddLine(' the contents will be over-written.');
               AddLine('');
               SetOption(1,' ~P~roceed ',80,Finished);
               SetOption(2,' ~A~bort ',65,Escaped);
               ActionCode := Show;
               Done;
            end;
         end.



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Figure 8.5                                                              [SCREEN]
Using PromptOBJ


         The message could have been generated with box-buttons simply by using
         the object ButtonPromptOBJ instead of PromptOBJ - see the on-disk exam-
         ple DEMMS6.PAS.


         The SetOption method is also the way to add a third button. Just pass a
         button ID of 3 and a third button will be displayed. The listing of
         DEMMS7.PAS followed by figure 8.6 illustrates this technique:

         program DemoMessageSeven;
         {demms7 - three buttons}
         Uses DOS, CRT,
              totFAST, totMSG, totIO1;

         Var
            MsgWin : PromptOBJ;
            ActionCode: tAction;
         begin
            Screen.Clear(white,'░'); {paint the screen}
            with MsgWin do
            begin
               Init(1,' Warning ');
               AddLine('');
               AddLine(' The file already exists on disk, and ');
               AddLine(' the contents will be over-written.');
               AddLine('');
               SetOption(1,' ~P~roceed ',80,Finished);
               SetOption(2,' ~A~bort ',65,Escaped);
               SetOption(3,' ~H~elp ',72,Stop1);
               ActionCode := Show;
               Done;
            end;
         end.




Figure 8.6                                                              [SCREEN]
Using Three
Buttons


         The on-disk example DEMMS8.PAS shows how to use ButtonPromptOBJ to dis-
         play three box-buttons.