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Dialog Events
Volume Number:3
Issue Number:1
Column Tag:Basic School

Dialog Events in ZBasic

By Dave Kelly


The word 'mania' as used in the title of this month's Basic column has a kind of dual meaning. My dictionary says that 'mania' means: 1. wild or violent mental disorder 2. an excessive enthusiasm; obsession. I find both definitions express what it is like to program with ZBasic. Many of you have been following the 'Basic Wars' as they have been progressing. MS Basic 3.0 has been announced as of the writing of this column, although I have not seen it yet. This is supposed to be a $25 upgrade. The MS Basic compiler is also supposed to be out, at least Microsoft is marketing it by direct mail. (Note: The MS Basic compiler and version 3.0 of the MS Basic interpreter are two different products, both of which you need to compile programs!) Pterodactyl Software's PCMacBasic has not come back off the drawing board and True Basic is no better off than when I reviewed it back in August. But there has still been some hope. Zedcor has been scrambling to fix bugs in ZBasic and release version 3.02. They are to be commended for their dedication to making their product a success.

Why do I say that both definitions of 'mania' describe programming with ZBasic? The second definition comes to mind first. I'm excited to see the big improvements that have been incorporated into ZBasic. In fact, the BOMB is a much less frequent sight. In fact, the BOMBs that appear from time to time now are more obscure. In fact, some of the BOMBs are 'self inflicted'. In other words, sometimes things that I am not doing correctly turn out to be the problem. But there have been a few problems that demonstrate that not all the problems have been removed from the compiler.

One such example of what I am talking about was brought to my attention by one of our subscribers from Switzerland. He summed up ZBasic nicely when he said "...ZBasic is really a great Basic if only it worked!" He described to me a problem he was having when working with DIALOGs and ZBasic. He stated that he could not "flush the value of the DIALOG(1) function". The answer to his problem turns out to not be too hard, however, it reveals to us some other difficulties that ZBasic has 'built in' to it.

First, the solution to the DIALOG(1) problem is that it is not a problem. It will be helpful to understand how the DIALOG functions operate. The DIALOG function originates with MS Basic. The excitement comes when I see all the enhancements that have been added to the ZBasic implementation of DIALOGs. The purpose of the DIALOG function is to inform us when events (such as BUTTON, EDIT FIELD and WINDOWs) that occur between the DIALOG ON and DIALOG OFF statements.

It is important, when using DIALOG functions, to know when the function data is valid. The DIALOG(0) function is the key to it all. When an event occurs, the DIALOG functions are stored up in a 64 event queue. The ON DIALOG GOSUB statement is supposed to cause an interrupt to occur when some kind of event has happened. I say it is 'supposed to' because when writing the sample program included here I found that some of the items in the queue were not automatically read until another event occurred. Of course the new event was then pushed onto the queue and would not automatically interrupt via ON DIALOG. My solution was to poll the event queue continuously unless it was empty by accessing the DIALOG(0) function. Anyway, ideally the ON DIALOG should notify the program whenever any DIALOG events occur. The are seven events that are common to ZBasic and MS Basic. ZBasic now has 16 DIALOG functions including functions which support the Zoom windows and keyboard events. The DIALOG(0) function will return a number 1-16 (1-7 in MS BASIC) which will indicate to you what kind of event occurred. At the same time, the function that coresponds to the DIALOG(0) result will be updated. The functions ( DIALOG (1-16) ) are ONLY valid just after the DIALOG(0) function returns an event of that type. Otherwise the last event of that type remains on, stored up in the DIALOG functions. The figure shows a flow chart of what happens when DIALOG(0) has an event to be processed. Just remember to poll DIALOG(0) first to find out which of the other functions you will need to poll next.

Figure 2.

Another phenomenon that was observed was that when events are active ( the lines between DIALOG ON, MENU ON, BREAK ON, MOUSE ON and DIALOG OFF, MENU OFF, BREAK OFF, MOUSE OFF) the program seems to run much slower than without events on. I tried to turn off events wherever possible with some increase in speed, but there seems to be some delay between polling the time an event occurs and when it is finally processed. Has anyone done any benchmarks to compare speed when events are turned on? It is a difficult thing to compare as the implementation varies so much from one language to another.

Look out here comes another bug... As it turns out, the DIALOG(8) and DIALOG(9) statements work great. The problem is that Zoom windows still don't work quite right. In ZBasic 3.02 the demo program below will BOMB if Zoom windows are made active. I have set it up to demonstrate how it should work. The PEEK (&28E) AND 128 statement towards the beginning of the program checks to see if the Mac has old 64K ROMS or the new 128K ROMS installed. If the new ROMS are available then the window type should be set to 9 when the windows are created.

The example program outlines the basic flow which you will want to use when you implement your own ZBasic event loops. Notice that Menu events and Dialog events are mixed in the same event loop. This same structure also applies for MS BASIC. Any questions?

REM ZBasic V3.02 Dialog Example
REM ©MacTutor 1987
REM By Dave Kelly

WINDOW OFF:REM Always use this as first line of program to prevent default 
window from being created
COORDINATE WINDOW:REM Set window to  Macintosh coordinate system
False=0:True=NOT False
IF PEEK(&28E) AND 128 THEN Wtype=1 ELSE Wtype=9
Wtype=1:REM  Due to Bugs in ZBasic 3.02 Zoom window will not be used.

MENU 1,0,1,"File"
MENU 1,1,1,"Quit"
WINDOW 1,"Window 1",(10,50)-(250,200),Wtype
TEXT 4,9,0,0
BUTTON 1,1,"Button 1",(20,20)-(100,50)
BUTTON 2,1,"Button 2",(20,60)-(100,90)
WINDOW 2,"Window 2",(275,50)-(500,200),Wtype
TEXT 4,9,0,0
EDIT FIELD 1,"",(10,10)-(100,35),1,1
EDIT FIELD 2,"",(10,40)-(100,65),1,1
WINDOW 3,"Dialog Event (Window #3)", (10,250)-(500,340),28
TEXT 4,9,0,0
ON DIALOG   GOSUB "DialogEvent"
ON BREAK    GOSUB "BreakEvent"
GOTO "Mainloop"

IF Menunumber=1 AND Itemnumber=1 THEN END

D = DIALOG(0):REM check to see what event occured
Currentwindow = WINDOW(0)
Windowselection = WINDOW(1)
IF D = 1 GOSUB "Buttonevent"
IF D = 2 GOSUB "EditEvent"
IF D = 3 GOSUB "InactiveWindow"
IF D = 4 GOSUB "Closebox"
IF D = 5 GOSUB "Refresh"
IF D = 6 GOSUB "Returnkey"
IF D = 7 GOSUB "Tabkey"
IF D = 8 GOSUB "Zoomin"
IF D = 9 GOSUB "Zoomout"
IF D =10 GOSUB "Shifttab"
IF D =11 GOSUB "Clearkey"
IF D =12 GOSUB "LeftArrow"
IF D =13 GOSUB "RightArrow"
IF D =14 GOSUB "UpArrow"
IF D =15 GOSUB "DownArrow"
IF D =16 GOSUB "Keypress"
PRINT @(50,3) "DIALOG(0) :        ";D
PRINT @(50,4) "Active Window #";Currentwindow
PRINT @(50,5) "Output Window #";Windowselection
WINDOW OUTPUT Outwindow:WINDOW Windowselection

Bstatus=BUTTON(Buttonclicked):BUTTON Buttonclicked,3-Bstatus
PRINT@(1,1)   "Button clicked :   ";Buttonclicked

PRINT@(1,2)   "Edit Field :       ";EditField
PRINT@(1,3)   "Inactive Window :  ";Windowselection
IF ClosedWindow=3 THEN END
PRINT@(1,4)   "Closed Window :    ";ClosedWindow
PRINT @(1,5)  "Erased Window :    ";ErasedWindow
PRINT @(25,1) "Return press :     ";Returnpress
PRINT @(25,2) "Tab press :        ";Tabpress

PRINT@(1,1) "Thank you for zooming in window";Zin
PRINT @(25,3) "Zoom in window :   ";Zin
PRINT@(1,1)"Thank you for zooming out window";Zout
PRINT @(25,4) "Zoom out window :  ";Zout
PRINT @(25,5) "Current Edit Field:";CurrentEdit
PRINT @(25,5) "Current Edit Field:";CurrentEdit

PRINT @(25,5) "Current Edit Field:";CurrentEdit
PRINT @(25,5) "Current Edit Field:";CurrentEdit
PRINT @(25,5) "Current Edit Field:";CurrentEdit
PRINT @(25,5) "Current Edit Field:";CurrentEdit

PRINT @(50,1) "ASCII key pressed :";ASCIIkey;"  "
PRINT @(75,1) " ":PRINT @(75,1) CHR$(ASCIIkey)

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