MyAtari magazine: 'C'ing through the window 'pains'

Issue 15: Jan 2002

Features
-	Foreword
-	Tip of the Day
-	My trip down the Champs-Elysées
-	'C'ing through the window 'pains'
-	Atari UK 2
-	Star Alliance - Battle for Earth
-	M: Interactive Composition

Reviews
-	Calamus from scratch
-	Porthos 1.28
-	Put a Little Bee Under the Bonnet of your TT

News

'C'ing through the window 'pains'

by Steve Ollett

Introduction
Back in the March 2001 issue of MyAtari, I wrote a tutorial covering the creation of menus in C, using Lattice C and WERCS.

In the meantime, there's been the birth of my daughter, extensive decorating of my house, and of course researching into window handling using C. This month I'm back with a short tutorial on how to interact with GEM windows and menus.

At the end of this article you will find a link to a ZIP archive that contains all the files you'll need to make the most of this tutorial, including the executable and source code.

So what does 'New Menu Program' do?
After double clicking the executable file, NEW_MENU.PRG, the following screen will be displayed.

From here the user can access the GEM menubar at the top of the screen which allows you to do the following;

$[Screen-shot: /|\ menu]$

'About NEW MENU...' displays a dialog box which provides details about the program.

'Open' opens a GEM window.
'Close' closes the open GEM window.
'Quit' exits the program.

'Dim Me' disables the menu item.
'Check Me' toggles a tick on/off.
'Notes...' displays another alert dialog.

Selecting the 'Open' menu item under the 'File' menu opens a GEM window similar to the one shown below.

The user is able to interact with the GEM window thanks to the DO...LOOP subroutine (detailed in the source code). Whenever the user interacts with the GEM window, a window event is triggered which results in the following;

Window Event	Action
CLOSE	Closes the GEM window
TITLE	Title bar
FULL	Toggles between full size and previous window size. When switching to full size, the contents of the GEM window is redrawn.
INFO	I have set the 'Information bar' to inform the user what the last function carried out on the window was.
SIZE	Resizes the window. As with correct conventions, a window will only redraw if increased in size, not when made smaller, although this feature can be added by modifying the DoSizer() Function.
MOVE	The window can be moved about the screen, although it is not constrained to be completely within the screen.
TOPPED	If you have XControl in the desk accessories slot, you can switch between it and our test window by clicking on the appropriate title bar.
LFARROW	Left Arrow (disabled)
RTARROW	Right Arrow (disabled)
HSLIDE	Horizontal Arrow (disabled)
UPARROW	Up Arrow (disabled)
DNARROW	Down Arrow (disabled)
VSLIDE	Vertical Arrow (disabled)

How does the 'New Menu Program' work
Below I have written a brief overview of how the 'New Menu Program' works. For a more detailed explanation, please read the source code provided which includes helpful comments above most of the C commands which explain what's going on.

A brief overview is...

Upon execution, load RSC file. If an error occurs then EXIT.
Initialise and display the menubar.
Open a virtual workstation (for window contents).
Loop until a window/menu event occurs. Upon a window/menu event, execute the appropriate code. If the user has not selected 'Quit', return to program loop.
Close any open windows, remove the menubar, close any virtual workstations and clears the resource file from memory.
Returns to the desktop.

Finally...
Well, this tutorial was a long time in happening. For next time I'll consider having a look at using the slider bars, or maybe a simple dialog box created using WERCS. Bye for now.

Files

New Menu Program archive
ZIP archive containing:
- NEW_MENU.PRG (Executable)
- NEW_MENU.RSC (Resource file for executable)
- NEW_MENU.C (Source code)
- NEW_MENU.H (Header file produced by resource editor)
- NEW_MENU.HRD (Header file produced by resource editor)
- NEW_MENU.O (Object code)
- NEW_MENU.PRJ (Project file for Lattice C Compiler)

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MyAtari magazine - Feature #4, January 2002