App/SB/Windows hang using Shapes.Move on TextBox in LDEvents.Resized w/ GraphicsWindow

[sjsepan3]

When resizing GraphicsWindow and moving controls with Shapes.Move, App locks up, and must restart windows.

What follows is a series of tests (5), where 1-4 are ok, and 5 exhibits error:
=====1========
Minimal app, LitDev Extensions libs not enabled in lib folder (renamed)

no error

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint 
BackgroundColor better
GraphicsWindow.Height = 600

'-------Controls---------

'LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  'resize client area and controls 
  'Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
EndSub

=====2==========
Minimal app, LitDev Extensions libs enabled in lib folder (not renamed)

no error

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint 
BackgroundColor better
GraphicsWindow.Height = 600

'-------Controls---------

'LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  'resize client area and controls 
  'Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
EndSub

=====3==========
Minimal app, LitDev Extensions libs enabled in lib folder (not renamed), resize event wired

no error

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint 
BackgroundColor better
GraphicsWindow.Height = 600

'-------Controls---------

LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  'resize client area and controls 
  'Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
EndSub

=====4==========
Minimal app, LitDev Extensions libs enabled in lib folder (not renamed), resize event wired, control added

no error

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint 
BackgroundColor better
GraphicsWindow.Height = 600

'-------Controls---------

txtStatusMessage = Controls.AddTextBox(0, GraphicsWindow.Height-25)

'-------Events---------

LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  'resize client area and controls 
  'Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
EndSub

=====5================
Minimal app, LitDev Extensions libs enabled in lib folder (not renamed), resize event wired, control added, and
control moved

error

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint 
BackgroundColor better
GraphicsWindow.Height = 600

'-------Controls---------

txtStatusMessage = Controls.AddTextBox(0, GraphicsWindow.Height-25)

'-------Events---------

LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  'resize client area and controls 
  Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
EndSub

===============

[sjsepan3]

Windows 7 SP1, in VirtualBox 6.1.38.153438 on Linux Mint 21.2
SmallBasic 1.2
LitDev Extensions 1.2.24.0

[sjsepan3]

In summary, tests seem to indicate that:

• there is no error while dragging resize handles on GraphicWindow while LitDev not enabled,
• nor when LitDev enabled,
• nor when resize event wired to handler (no control),
• nor when control exists (not moved);
• only when control finally moved in event handler.

[litdev1]

Hi,

Hard to to trace the exact issue, but clearly related to the window size and shape move update on the event thread - these are all actually performed on the UI thread that is called after the event ends.

For me, when it crashes I can kill the SB program with task manager using Ctrl+Alt+Del.

Small Basic does suffer from this and many similar thread event issues and the solution I have always suggested is based on setting flags in events and doing the UI work on the main UI thread in a game or event handler loop, which is closer to how more advanced languages (C# etc) do it, using a dispatcher that would send it to an queue on the UI main thread.

See here, nearly 10 years old now, but still how I would do it, ZWDZ741.000

Could ask this kind of question here, trying to get some content going!

[sjsepan3]

Reading through the TechNet article now, to see what they are recommending...Looks like non re-entrancy plus multiple Resize events could be at play...

I was hoping that the following might work...

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint BackgroundColor better
GraphicsWindow.Height = 600
onResizeActive = "False"

'-------Controls---------

txtStatusMessage = Controls.AddTextBox(0, GraphicsWindow.Height-25)

'-------Events---------

LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  If onResizeActive = "False" Then
    onResizeActive = "True"
    'resize client area and controls 
    Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
    onResizeActive = "False"
  EndIf
EndSub

...but it does not -- probably because the events come in too fast for the first one to get the flag set in time.

I will have to try the loop...

[sjsepan3]

@litdev1 Using the loop example in the TechNet article, I modified the test code as follows:

GraphicsWindow.Width = 800 'set before adding controls w/ positions based on size; also seems to paint BackgroundColor better
GraphicsWindow.Height = 600
onResizeActive = "False"

'-------Controls---------

txtStatusMessage = Controls.AddTextBox(0, GraphicsWindow.Height-25)

'-------Events---------

LDEvents.Resized = GraphicsWindow_OnResized

'-----------Init----------

GraphicsWindow.Show()

While ("True")
  If onResizeActive = "True" Then
    onResizeActive = "False"
    'resize client area and controls 
    Shapes.Move(txtStatusMessage, 0, GraphicsWindow.Height-25)
  EndIf
  Program.Delay(20)
EndWhile
'------------Event Handlers---------------

Sub GraphicsWindow_OnResized
  onResizeActive = "True"
EndSub
  

This is working so far...

[litdev1]

@sjsepan3
Great, that is what I would do, similar to the SB import link I gave (ZWDZ741.000).
The event loop idea solves many SB issues, especially with interactive games.
If you google for 'game event loop' you will see it is a totally standard way of handling events.

[sjsepan3]

@litdev1
I was wondering what that code was -- hadn't used that feature.
I also applied the event-loop approach to the project from which this test version was distilled, and it worked there too, so I think we can close this issue, as that seems to be the right method.
Thanks for steering me in the right direction!