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 Post subject: Tutorial: events handling with the Form Designer
PostPosted: Wed May 20, 2015 4:11 pm 
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The Basic Anatomy of a PureBasic Program

At its very basic, a PureBasic window-based program would look something like this (window-based and not Windows-based - referring to any program on any operating system that uses forms, dialogs, or windows):
Code:
OpenWindow(0, 100, 100, 300, 200, "My Window")

Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
There are two parts to this code.

The first part builds the interface, and simply instantiates a 300-pixel wide by 200-pixel high window at position 100, 100 on the screen, and gives it a title of My Window. In order to be referenced later, PureBasic also assigns the window an identifier of 0 - the first parameter.

The second part is known as the event loop, and is the backbone of any window-based PureBasic program. Although the example uses a Repeat-Until loop, any type of loop could be used in its place. The ultimate purpose is to listen for events that the operating system passes to the program, using the WaitWindowEvent() function, and to process those received events by executing any relevant code associated with the said event. This is known as an event-driven paradigm, and is the architecture that PureBasic is built upon.

It should be noted that the event loop is not running in a mad frenzy, like a normal endless loop. The WaitWindowEvent() function actually pauses program execution until it receives an event, at which time the event is passed into the loop to be processed. Then the loop resumes, and pauses again at the WaitWindowEvent() function to await the next event. This process continues until the #PB_Event_CloseWindow event is received, and the program terminates.

In the above skeleton example, the loop simply waits for events, but does not process them in any way. The only event that is processed is the #PB_Event_CloseWindow event, which as you can see, breaks the loop, and essentially ends the program:
Code:
Until event = #PB_Event_CloseWindow

The code instantiates a fully functional window, which behaves almost like any window of the respective operating system. However, this window can only be moved around or closed. It can't be maximised, minimised, or resized. To do that, the proper directives should be added to the OpenWindow() command, like so:
Code:
OpenWindow(0, 100, 100, 300, 200, "My Window", #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget | #PB_Window_SizeGadget)

Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
As you can see, some flags have been added to the OpenWindow() command, which is quite self-explanatory. These are just a few of the many directives that could be added to this command to control the attributes of the resulting window. Another very useful one is the #PB_Window_ScreenCentered flag, which simply centres the window on the screen. With this directive, the x and y positions of the OpenWindow() would be ignored, and could just be assigned zero values:
Code:
OpenWindow(0, 0, 0, 300, 200, "My Window", #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget | #PB_Window_SizeGadget | #PB_Window_ScreenCentered)

Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
Another thing to note is the difference between the #PB_Window_MaximizeGadget & #PB_Window_MinimizeGadget flags and #PB_Window_Maximize & #PB_Window_Minimize. As we have seen, the first two implements the maximise and minimise controls on the window. On the other hand, the second two sets the state of the window when the program starts, to either maximised or minimised. Needless to say, only one should be used at a time.

Another thing you'll notice is that the constants of these window flags are pretty verbose, which could result in lengthy commands. One way to handle this clutter would be to make use of PureBasic's line continuation feature, and break the flags up into separate lines, like this:
Code:
OpenWindow(0, 0, 0, 300, 200, "My Window", #PB_Window_MaximizeGadget |
                                           #PB_Window_MinimizeGadget |
                                           #PB_Window_SizeGadget |
                                           #PB_Window_ScreenCentered)
Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
That looks better, and greatly improves readability as well. Another approach would be to assign these flags to a variable, and then use that variable in the OpenWindow() command, like this:
Code:
wFlags = #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget |
         #PB_Window_SizeGadget | #PB_Window_ScreenCentered

OpenWindow(0, 0, 0, 300, 200, "My Window", wFlags)

Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
Not functionally relevant, but simply good coding practices.

There are many other window functions and features, but we'll leave that to the manual.


Handling Gadgets and Events

Now, let's add some gadgets to the window, and see how they work in the scheme of things. To demonstrate this simply, we'll use a button, label, and text box. Here's the code:
Code:
wFlags = #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget |
         #PB_Window_SizeGadget | #PB_Window_ScreenCentered

OpenWindow(0, 0, 0, 300, 200, "My Window", wFlags)
TextGadget(1, 50, 30, 200, 30, "This is a label...")
StringGadget(2, 50, 70, 200, 30, "")
ButtonGadget(3, 50, 120, 200, 30, "Click Me")

Repeat
  event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow
The window now contains three gadgets; a TextGadget(), a StringGadget(), and a ButtonGadget(), positioned accordingly, and assigned identifiers of 1, 2 and 3 respectively. The label's caption has been set as "This is a label", and the button's caption has been set as "Click Me"; but the text box has been left blank. However, the window still does nothing besides displaying itself along with its contents. This is because the event loop is not processing any events yet. So, let's do that now.

Before we begin, here are a few points about how PureBasic manages the events that it receives. Every event carries with it the identifiers of its intended window and gadget. Accordingly, in the case of multi-window applications, we'd first have to determine which window the event is intended for. This is done with the EventWindow() function. Then, we'd check which gadget it's meant for, and process it accordingly. This simplified pseudo-flow might illustrate it better:
Code:
repeat
  event = WaitWindowEvent()
    window = EventWindow()
      if window = window1
        if event = #PB_Event_CloseWindow
          end the application
        gadget = EventGadget()
          if gadget = gadget1
             execute code for gadget1
          if gadget = gadget2
             execute code for gadget2
          if gadget = gadget3
             execute code for gadget3
      if window = window2
        if event = #PB_Event_CloseWindow
          close this window
        gadget = EventGadget()
          if gadget = gadget4
             execute code for gadget4
          if gadget = gadget5
             execute code for gadget5
          if gadget = gadget6
             execute code for gadget6
      if window = window3
        if event = #PB_Event_CloseWindow
          close this window
        gadget = EventGadget()
          if gadget = gadget7
             execute code for gadget7
          if gadget = gadget8
             execute code for gadget8
          if gadget = gadget9
             execute code for gadget9
forever
Notice how the loop structure has changed, from Repeat-Until to Repeat-Forever. In multi-window applications, closing any one window will trigger the #PB_Event_CloseWindow event, but that does not necessarily mean to end the program. Therefore, this event is processed within each window's sub-loop, so to speak, and the relevant code would be executed accordingly; which is to either simply close the window, or end the program.

On the other hand, in single-window applications, closing the window indicates an intention to terminate the program. So, the #PB_Event_CloseWindow event could be safely processed exclusively. Furthermore, in single-window applications, the EventWindow() function could also be omitted, as all events are logically meant for it.

That's what we'll be doing, and we'll start with the button:
Code:
wFlags = #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget |
         #PB_Window_SizeGadget | #PB_Window_ScreenCentered

OpenWindow(0, 0, 0, 300, 200, "My Window", wFlags)
TextGadget(1, 50, 30, 200, 30, "This is a label...")
StringGadget(2, 50, 70, 200, 30, "")
ButtonGadget(3, 50, 120, 200, 30, "Click Me")

Repeat
  event = WaitWindowEvent()
  If #PB_Event_Gadget
    gadget = EventGadget()
   
    ;if the button is pressed (identifier = 3)
    If gadget = 3
     
      ;whatever code is here will be executed
     
    EndIf
  EndIf
Until event = #PB_Event_CloseWindow
The first If/EndIf block added within the event loop simply checks any events that it receives, and determines if it is a gadget event, #PB_Event_Gadget. If it's not, it continues the loop, and waits for the next event. If it is a gadget event, it will look for the gadget identifier with the EventGadget() function. Then it checks if it is an event from the button (gadget identifier 3), and if it is, executes the code within that second If/EndIf block.

Of course, there's no code there now, so it still does nothing. So let's perform an action:
Code:
wFlags = #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget |
         #PB_Window_SizeGadget | #PB_Window_ScreenCentered

OpenWindow(0, 0, 0, 300, 200, "My Window", wFlags)
TextGadget(1, 50, 30, 200, 30, "This is a label...")
StringGadget(2, 50, 70, 200, 30, "")
ButtonGadget(3, 50, 120, 200, 30, "Click Me")

Repeat
  event = WaitWindowEvent()
  If #PB_Event_Gadget
    gadget = EventGadget()
   
    ;if the button is pressed (identifier = 3)
    If gadget = 3
     
      ;sets some new text in the label (identifier = 1)
      SetGadgetText(1, "Hello Barry!")
     
    EndIf
  EndIf
Until event = #PB_Event_CloseWindow
Now, when the button is clicked, the text in the label will change.

Just for the fun of it, let's make use of the text box as well:
Code:
wFlags = #PB_Window_MaximizeGadget | #PB_Window_MinimizeGadget |
         #PB_Window_SizeGadget | #PB_Window_ScreenCentered

OpenWindow(0, 0, 0, 300, 200, "My Window", wFlags)
TextGadget(1, 50, 30, 200, 30, "This is a label...")
StringGadget(2, 50, 70, 200, 30, "")
ButtonGadget(3, 50, 120, 200, 30, "Click Me")

Repeat
  event = WaitWindowEvent()
  If #PB_Event_Gadget
    gadget = EventGadget()
   
    ;if the button is pressed (identifier = 3)
    If gadget = 3
     
      ;get the text from the text box (identifier = 2)
      text$ = GetGadgetText(2)
     
      ;and place it in the label (identifier = 1)
      SetGadgetText(1, text$)
     
    EndIf
  EndIf
Until event = #PB_Event_CloseWindow
Now, when the button is clicked, the label will contain the text that has been typed into the text box.

Not exactly Flappy Birds, but I hope that it explains PureBasic's programming structure adequately.


Using PureBasic Forms

The PureBasic form designer simply automates the coding of the user interface. However, the form files that are generated can't be modified, and should thus be called from another module. Furthermore, the structure of these self-generated form files are quite different, in that most of the code are encapsulated within procedures.

However, the program logic remains the same, and the implementation is quite easy.

Let's try to recreate the above example in a form project:

1. From the PureBasic IDE, click on the File menu, and select Preferences.... In the left panel of the dialog that appears, select Form, then in the dialog window, make sure that the Generate event procedure and Generate event loop options are selected. Click Apply then Ok.

2. Again, from the PureBasic IDE, click on the Form menu, and select New Form.

3. Resize the model window to 300 pixels by 200 pixels either by dragging the drag-handle located at its bottom-right corner, or by changing the width and height values in the properties window.

4. Also in the properties window, set the window caption to My Window and select the following constants:
#PB_Window_MaximizeGadget
#PB_Window_MinimizeGadget
#PB_Window_SizeGadget
#PB_Window_ScreenCentered


5. Now, from the Toolbox panel, select the Button gadget by clicking on it once (click and release). Then move the mouse over to the model window and click-hold-down-and-drag the mouse to draw the button at the desired location; release when done. In the properties window, enter the caption for the button as Click Me, and in the Event procedure field, enter buttonEvent.

6. Repeat step number 4 for a String and Text gadget, and enter the caption for the Text gadget as This is a label..., but leave the caption for the String gadget blank. For these two gadgets, leave the Event procedure field blank.

7. Click Ctrl-S (or select Save from the File menu), and save the form under the file name MyForm.pbf.

8. From the Form menu, select Switch Code/Design View, and you should be able to see the auto-generated code, which should look something like this:
Code:
;
; This code is automatically generated by the FormDesigner.
; Manual modification is possible to adjust existing commands, but anything else will be dropped when the code is compiled.
; Event procedures needs to be put in another source file.
;

Global Window_0

Global Button_0, Text_0, String_0

Declare buttonEvent(EventType)

Procedure OpenWindow_0(x = 0, y = 0, width = 300, height = 200)
  Window_0 = OpenWindow(#PB_Any, x, y, width, height, "My Window", #PB_Window_SystemMenu | #PB_Window_MinimizeGadget | #PB_Window_MaximizeGadget | #PB_Window_SizeGadget | #PB_Window_ScreenCentered)
  Button_0 = ButtonGadget(#PB_Any, 50, 120, 200, 30, "Click Me")
  Text_0 = TextGadget(#PB_Any, 50, 30, 200, 30, "This is a label...")
  String_0 = StringGadget(#PB_Any, 50, 70, 200, 30, "")
EndProcedure

Procedure Window_0_Events(event)
  Select event
    Case #PB_Event_CloseWindow
      ProcedureReturn #False

    Case #PB_Event_Menu
      Select EventMenu()
      EndSelect

    Case #PB_Event_Gadget
      Select EventGadget()
        Case Button_0
          buttonEvent(EventType())         
      EndSelect
  EndSelect
  ProcedureReturn #True
EndProcedure

OpenWindow_0()

Repeat
  event = WaitWindowEvent()
Until Window_0_Events(event) = #False

End

9. That's it for the form designer. Now to create the external module that will handle the button procedure, buttonEvent().

10. Click Ctrl-N (or select New from the File menu), for a new PureBasic file, and enter the following code:
Code:
XIncludeFile "MyForm.pbf"

Procedure buttonEvent(eventType.i)
  ;get the text from the text box (identifier = String_0)
  text$ = GetGadgetText(String_0)
 
  ;and place it in the label (identifier = Text_0)
  SetGadgetText(Text_0, text$) 
EndProcedure

11. Click Ctrl-S (or select Save from the File menu), and save this file as MyFormEvents.pb, in the same folder as MyForm.pbf. If it's not in the same folder, you'd have to include the proper file paths to locate the form file:
Code:
XIncludeFile "C:\...relevant file paths...\MyForm.pbf"

12. You're done! Click F5 (or select Compile/Run from the Compiler menu) to run the code, and you should see the same results as the earlier manually-coded example.

There are many different ways to implement the PureBasic form file, and this is just one of them. For example, for greater control of the event loop, it could be disabled in the form designer preferences, and implemented in an external module. And for absolute control, even the event procedure option could be disabled and implemented manually. This would mean that the form file is used purely as an interface builder with no higher function.

In any case, really hope it helps. :lol:

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 Post subject: Re: Help: Events handling with the Form Designer
PostPosted: Wed May 20, 2015 10:34 pm 
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Wow! Thank you!

I was hoping for a simple example so I could figure out how to organize it and how to make the variables visible between the two files. You gave me a full tutorial that you obviously put some time and thought into and I thank you. That really jumpstarted me. :)

They ought to include your post in the help as a getting started thing.

I do understand about event programming, at least somewhat. My background is as a procedural programmer. I retired before I had to get serious about event driven programs, about 20 years ago. This stuff really confuses me. I've just looked over and tried your examples and I think they're going to be a big help getting me going with Pure Basic.

Barry


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 Post subject: Re: Help: Events handling with the Form Designer
PostPosted: Thu May 21, 2015 6:31 am 
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barryem wrote:
I do understand about event programming, at least somewhat. My background is as a procedural programmer.
Hi Barry. I'm so glad that you found the post helpful; thank you for your kind words. :D

I meant no condescension in my approach; my apologies if it came across that way. I was almost certain from your earlier post that you have prior programming experience, but I just couldn't be sure how much. So, I thought that the best approach would be to start from the bottom; that way anyone who reads it could dive in at the point that suits them, without leaving out the basics.

Hopefully it would benefit others as well. :lol:

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 Post subject: Re: Help: Events handling with the Form Designer
PostPosted: Thu May 21, 2015 11:10 pm 
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I never thought you were condescending. You answered my questions and then some. You have no way to know my experience level and in fact with GUI programming it's fairly low. I did know about a few of the things you described but even those explanations were clarifying. You explained things I didn't understand and tied them in with things I did understand. It was exactly what I needed and far more than I expected.

I spent some time with your examples and they just made sense and, as often happens, I couldn't remember what I was so confused about before. Thank you.

Twenty years ago I was a very experienced programmer having begun in the punch card days long before computers had screens. But I retired 20 years ago and I've only done a bit of programming here and there since then. I've forgotten a lot and much of what I knew doesn't fit with today's computers anyway. In my final years of working I began to learn about GUI programming but it was never my focus and I found it confusing and really not very important to my work. Not long after that I retired. It was only after that that Windows began to become important so really this is largely new to me and probably always will be. I'm probably the most experienced newbie I know :)

Barry


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 Post subject: Re: Help: Events handling with the Form Designer
PostPosted: Fri May 22, 2015 4:54 am 
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Hello again Barry. That's good to know; thank you for saying so. :)

Twenty years away from anything would indeed cause the natural onset of amnesia. But I'm pretty sure that it'll all be flooding back in no time; just like riding a bike.

After all, the underlying logic will always be the same; it's only the syntax and paradigms that change. :wink:

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PostPosted: Sun May 24, 2015 3:03 am 
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TI-994A,

I bought PB a few months ago and have been working my way through these forums trying to learn the ins and outs of PB for my needs. I could have asked the very same question as Barry months ago (and should have!) Just goes to prove again the only dumb question is the one you don't ask. I am like Barry too, in that I have not done any interactive GUI programming in 15 years or more and the tools I used then are long orphaned. I just want to thank you for presenting such a complete and concise explanation for using the Form Designer and the basic flow of PB programming in general. I must also thank NetMaestro for posting good advice and examples for options available in creating and controlling multiple form/screen programs. Many Thanks!

John


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PostPosted: Sun May 24, 2015 5:52 am 
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jwrjrjwrjr wrote:
...the only dumb question is the one you don't ask.
Hi John, and welcome to the PureBasic forum. :)

You're absolutely correct. I'm especially happy when any of my answers are found helpful. Thank you kindly for saying so. :D

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PostPosted: Mon Dec 21, 2015 7:41 pm 
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TI-994A wrote:
...
Hopefully it would benefit others as well. :lol:


Absolutely! I'd just like to add my thanks as well - having come back to PB after a long break, your tutorial is extremely good, clear and easy to follow. Thank you indeed for taking the time to put it together. Perhaps it could be made into a sticky or added into the manual? It's truly first class! :D

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Cruster wrote:
...your tutorial is extremely good, clear and easy to follow.

So kind of you for saying so. Thank you; your words are truly appreciated. :D

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@TI-994A
I appreciated your explanation :)

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PostPosted: Mon Jan 25, 2016 1:49 pm 
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Splitted the topic and made it sticky, so this very good tutorial will be easier to find.


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Fred wrote:
Splitted the topic and made it sticky, so this very good tutorial will be easier to find.
Thanks everyone, for all the kind words. And thank you, Fred; truly appreciated.

So glad it's been helpful. :D

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PostPosted: Sat Feb 13, 2016 9:28 pm 
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If i use the Form Designer, then i should not modify the resulting ".pbf"-File.
So i would need to have somewwhere an "Initilization Event" that is called once the Form "is ready" so i can fill the controls with default values.
I did not see this anywhere here. How is that done?
From else where i know some sort of "#WM_INITDIALOG" Message.

Code:
Procedure FRM_Main(event,num)
  Select event     
  Case #WM_INITDIALOG
    Debug "Here"
  EndSelect
EndProcedure

But seems not to work. Where can i call this message?

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newtheogott wrote:
...i would need to have somewwhere an "Initilization Event" that is called once the Form "is ready" so i can fill the controls with default values. ... How is that done? ...Where can i call this message?

This skeleton example might help clarify the fundamentals of implementing a PureBasic form file:

* myForm.pbf (a form with a text gadget and two buttons)
Code:
;
; This code is automatically generated by the FormDesigner.
; Manual modification is possible to adjust existing commands, but anything else will be dropped when the code is compiled.
; Event procedures needs to be put in another source file.
;

Global Window_0

Global Text_0, Button_0

Procedure OpenWindow_0(x = 0, y = 0, width = 600, height = 400)
  Window_0 = OpenWindow(#PB_Any, x, y, width, height, "Simple FD Example", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)
  Text_0 = TextGadget(#PB_Any, 120, 140, 360, 30, "This is a text gadget", #PB_Text_Center)
  SetGadgetColor(Text_0, #PB_Gadget_BackColor,RGB(255,128,255))
  Button_0 = ButtonGadget(#PB_Any, 120, 190, 360, 30, "This is a button")
EndProcedure

* myCode.pb
Code:
IncludeFile "myForm.pbf"

OpenWindow_0()   ;<-- no parameters indicated - defaults will be used

While WaitWindowEvent() ! #PB_Event_CloseWindow : Wend
Ensure that both files (myForm.pbf & myCode.pb) are in the same folder, and simply run the myCode.pb program.

You'd notice that the form is displayed, although at this point, it does nothing yet.

This second example (using the same form file, myForm.pbf) demonstrates the interaction between form and code, setting and changing element attributes, and reacting to element events:

* myCode_2.pb
Code:
;include the form file
IncludeFile "myForm.pbf"

;load some sample fonts
LoadFont(1, "Arial", 12)
LoadFont(2, "Arial", 14)

;initialise and instantiate the form
;no parameters given - default values used
OpenWindow_0()

;set & change attributes of form elements
;
;setting window and gadget colours
SetWindowColor(Window_0, RGB(200, 200, 255))
SetGadgetColor(Text_0, #PB_Gadget_FrontColor, RGB(255, 255, 0))

;setting gadget fonts
SetGadgetFont(Text_0, FontID(2))
SetGadgetFont(Button_0, FontID(1))
SetGadgetFont(Button_1, FontID(1))

;the main program loop
Repeat
  ;wait for event to occur
  Select WaitWindowEvent()
     
    ;if window close-button pressed 
    Case #PB_Event_CloseWindow
      ;breaks the event loop and ends the program
      appQuit = 1
     
    ;if any gadget event triggered 
    Case #PB_Event_Gadget
      ;determine which gadget
      Select EventGadget()
         
        ;code to run if first button clicked 
        Case Button_0
          count + 1
          ;setting text to the text gadget
          SetGadgetText(Text_0, "Clicks: " + Str(count))
         
        ;code to run if second button clicked   
        Case Button_1
          count = 0
          ;setting text to the text gadget
          SetGadgetText(Text_0, "Clicks: 0")
         
      EndSelect
  EndSelect
 
;repeats as long as variable, appQuit, is zero
Until appQuit = 1
Once again, ensure that this file (myCode_2.pb) is also saved in the same folder as the form file (myForm.pbf), and then run it.

The code has been fairly well-commented, and should be quite self-explanatory.

Hope it helps. :wink:


* make sure that all form and code files are saved in the same folder - otherwise make sure that the path to the form file is included in the IncludeFile() statements.

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 Post subject: Re: Tutorial: events handling with the Form Designer
PostPosted: Sun Feb 14, 2016 11:13 am 
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If i understand you right, i have to disable the "create Event Loop" in the Form Designer and do that manually in an include file, then i can write my Form-initialization just in front of that.

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