GraphicsWindow.GetPixel generates an exception

Question

Hello everyone,

I'm trying to run a Small Basic program on a "Windows 10 Home Single Language" (a computer of one of my Thai students).

I get the following error: "Exception has been thrown by the target of an invocation".

On other systems (Windows 7, Windows 10...), the same program doesn't generate any error.

Would anyone have an idea on the cause of this problem and, maybe, on a way to fix it?

Thanks. :-)

J.

Answer 1

You should post some code behind (or the special part), which causes the exception !

Answer 2

Following article may help you.

https://social.technet.microsoft.com/wiki/contents/articles/29200.small-basic-errors.aspx#Exception_has_been_thrown_by_the_target_of_an_invocation

---

Nonki Takahashi

Answer 3

Thanks.

I worked on the problem for a few hours and here is what I can tell you.

My program is the following:

GraphicsWindow.Width = 0.8 * Desktop.Width
GraphicsWindow.Height = 0.8 * Desktop.Height

GraphicsWindow.DrawRectangle(1,1,GraphicsWindow.Width-1,GraphicsWindow.Height-1)
GraphicsWindow.DrawText(0,0,"GraphicsWindow.Width = " + GraphicsWindow.Width) ' = 1440
GraphicsWindow.DrawText(0,20,"GraphicsWindow.Height = " + GraphicsWindow.Height) ' = 897

For i = 1 To GraphicsWindow.Width
  GraphicsWindow.SetPixel(i,100,"black")
EndFor

For i = 1 To 759 ' Changing 759 into 760 will generate an exception.
  GraphicsWindow.GetPixel(i,50)
EndFor

When I run it, I get this (knowing that the screen resolution of the tablet is 2160x1440):

And the error message is:

   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at Microsoft.SmallBasic.Library.Internal.SmallBasicApplication.<>c__DisplayClass1.<.cctor>b__0()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Any idea?

Thanks in advance for any help you are able to provide. :-)

J.

Answer 4

I guess it's about your screen resolution. Similar problem there was some time ago, look here if this thread can help you:

mouse-object-bug

small-basic-mouse-position

related to 'LitDev' commands:

LDGraphicsWindow.MouseXOffset
LDGraphicsWindow.MouseXScale
LDGraphicsWindow.MouseYOffset
LDGraphicsWindow.MouseYScale

LDUtilities.DPIX
LDUtilities.DPIY

Also found 1 usage example with these commands from Tryhest (ID: FKF800-0) on challenge-of-the-month-may-2017

Answer 5

Thanks for your answer.

I tried all of the 22 possible screen resolutions proposed by that tablet:
2160x1440
2048x1152
1920x1440
1620x1200
1920x1080
1856x1392
1792x1344
1680x1050
1600x1200
1600x900
1440x900
1400x1050
1366x768
1280x1024
1280x960
1280x800
1280x768
1280x720
1280x600
1152x864
1024x768
800x600

My program generated the same error message ("Exception has been thrown by the target of an invocation") each time.

So... any other idea on how to fix the problem?

J.

Answer 6

Please ensure:

* All systems (Win7, Win10) esp. the one 'Win10 Home Single Language' are running the same SmallBasic version?? (eg. SB 1.2)

* The used decimal separator (like in  0.8 * Desktop.Width)  is your system default  (point vs. comma) ??

* Ensure about your GraphicsWindow.Width!  You can show it by eg.

GraphicsWindow.Title = "W = "+ GraphicsWindow.Width +" | DtW = "+ Desktop.Width     ' before the 'For'  loops

* Note that x/y coordinates in the GraphicsWindow range from:

x ..  0 to GraphicsWindow.Width-1

y ..  0 to GraphicsWindow.Height-1

 ... like used in GetPixel(x,y)  and  SetPixel(x,y, color)

* ?? Something unclear about dimensions:

you say: screen resolution (Desktop.Width x .Height) of the tablet = 2160x1440

GraphicsWindow.Width = 0.8 * Desktop.Width  =  0.8 * 2160  = 1728  (NOT 1440)

GraphicsWindow.Height = 0.8 * Desktop.Height  = 0.8 * 1440 =  1152  (NOT 897)

Generally it would be better (and shorter) to use variables, like this:

gw = 0.8 * Desktop.Width
gh = 0.8 * Desktop.Height
GraphicsWindow.Width = gw
GraphicsWindow.Height = gh

GraphicsWindow.DrawRectangle(1,1, gw-1,gh-1)
GraphicsWindow.DrawText(0,0, "GraphicsWindow.Width = "+ gw)
GraphicsWindow.DrawText(0,20, "GraphicsWindow.Height = "+ gh)
GraphicsWindow.Title = "W = "+ gw +" | DtW = "+ Desktop.Width

For i = 1 To gw-1
  GraphicsWindow.SetPixel(i,100, "Black")
EndFor

For i = 1 To Math.Min(gw-1, 760) ' To ??  Changing 759 into 760 will generate an exception.
  GraphicsWindow.GetPixel(i,50)
EndFor

Answer 7

Thank you very much for your help.

Yes, I'm running Small Basic 1.2 on all systems.

Here is what I get with your program:

J.

Answer 8

Hmmm,  same Exception message like above, and does'nt like the GraphicsWindow.GetPixel(760,50) ?!

col = GraphicsWindow.GetPixel(760,50)  ' should return #000000

Reduced to a minimum and only using integers:

gw = Math.Floor(0.8 * Desktop.Width)  ' 1024.0
gh = Math.Floor(0.8 * Desktop.Height) ' 614.4

GraphicsWindow.Top = 0
GraphicsWindow.Left = 0
GraphicsWindow.Width = gw
GraphicsWindow.Height = gh
GraphicsWindow.Title = "WxH = "+ gw +"x"+ gh +" | DtW = "+ Desktop.Width  ' 1024.0 ; 1280

'For i = 1 To Math.Min(gw - 1, 760)  ' To ??  Changing 759 into 760 will generate an exception.
'  col = GraphicsWindow.GetPixel(i, 50)
''  TextWindow.WriteLine(i +": "+ col)
'EndFor
TextWindow.WriteLine(GraphicsWindow.GetPixel(760, 50))

If this does'nt work either, i dont know ...

Answer 9

Thank you Pappa Lapub.

Unfortunately, it doesn't work either. Below 759, no problem. Above, it generates an exception.

I suppose the problem comes from Small Basic's GraphicsWindow. Whatever the numbers I feed GraphicsWindow.Width and GraphicsWindow.Height with are, the window will always occupy the totality of the screen.

For example, if I set the screen resolution of the tablet to 1280x768 and I explicitly ask Small Basic for a half-screen window...

GraphicsWindow.Width = 640
GraphicsWindow.Height = 384

...I will get a full screen window.

And if, just after this, I ask Small Basic to tell me the size of my window...

GraphicsWindow.DrawText(0,0,"GraphicsWindow.Width = " + GraphicsWindow.Width)
GraphicsWindow.DrawText(0,20,"GraphicsWindow.Height = " + GraphicsWindow.Height)

...the answer will be 1280 x 705.

Functions GraphicsWindow.Left and GraphicsWindow.Top don't work either. The window will always start from (0,0).

Any idea?

J.

PS: I've just uninstalled SB / rebooted the system / reinstalled SB (1.2). It doesn't change anything.

Answer 10

Hi ,

Try Upgrading Your Small Basic To 1.3, Its Available On The Window Store Here = https://www.microsoft.com/en-us/store/p/small-basic/9pfqkjljpb1r 

This Can Be Downloaded Only If You Have The Following System Requirements

Thanks,

Answer 11

Thanks. I can download it but nothing happens when I click the "Launch" button.
(In the Task Manager, I can see "SB.exe" appear and disappear immediately. "Run as administrator" doesn't help either.)

J.

Answer 12

Hi,

Try Reinstalling The Small Basic 1.2

Thanks,

Answer 13

It didn't work either. (See the "PS" in my previous message.)

J.

Answer 14

GraphicsWindow.Top =0.8* Desktop.Height 
GraphicsWindow.Width =0.8* Desktop.Width
TextWindow.WriteLine(GraphicsWindow.Top)
TextWindow.WriteLine(GraphicsWindow.Width)

Hi ,

Does The Following Code Causes Exception

Thanks,

Answer 15

No. Only

GraphicsWindow.GetPixel(x,y)

with x >= 760 causes an exception.

Answer 16

col = LDGraphicsWindow.GetPixel(x,y)    would use a different approach, plz try that.

I suppose, you did'nt change your Graphics settings (from default settings):

Here are my (default) settings for eg. 'Intel HD Graphics', but should be similar for others too:

RightClick Desktop background -> ContextMenu ->

-> 'Graphics Properties...' -> opens  'Display settings' (CtrlPanel applet) -> Default settings

or

-> Menu item 'Graphics Options' (with following Subnodes):

> Screen Adjustment:    Keep Display scaling ✓           !!!
> Shortcut Keys:           On/Off however
> Traysymbol:               On/Off  however
> Resolution/Dimensions:  your current Width x Height (eg. 1366 x 768) ✓
> Rotation:                   0 degrees ✓                              !!!
> Profile:                      some video options

The menu items (like 'Screen Adjustment' etc) are free translated from german, perhaps they are named different for your OS language.

TextWindow.WriteLine("dpiX: "+ LDUtilities.DPIX)  ' should be same as for Y below !
TextWindow.WriteLine("dpiY: "+ LDUtilities.DPIY)  ' should be same as for X above !
GraphicsWindow.Left = 0
GraphicsWindow.Top = 0
TextWindow.WriteLine("moffX: "+ LDGraphicsWindow.MouseXOffset)  ' x-Pos of the GW client area from left (8 for GW left border/frame)
TextWindow.WriteLine("moffY: "+ LDGraphicsWindow.MouseYOffset)  ' y-pos of the GW client area from top (30 for titlebar and GW border)

Answer 17

Hi

Try Downloading The LITDEV Extension Here = https://gallery.technet.microsoft.com/Small-Basic-LitDev-75827dc5

And Use 

colourofpixel = LDGraphicsWindow.GetPixel(x,y) 'This is to find the colour of pixel

Thanks,

Answer 18

To answer Pappa Lapub:

Even in Thai, the Graphics options seem to be normal.

I'm not sure I understood your explanations concerning DPIX, DPIY and LDGraphicsWindow.MouseX/YOffset, but here is what I get:

dpiX: 96
dpiY: 96
moffX: 0
moffY: 23

To answer Pappa Lapub and RoshanPriyaKumar:

LDGraphicsWindow.GetPixel does not generate an exception and my program works (almost) normally using it: http://tinyurl.com/yaz4vh5q. There is (still) a problem with the display moving suddenly to the right and down with no apparent reason... (Again, this problem only appears on the tablet of one of my students.)

So, if the problem of the exception generated by GraphicsWindow.GetPixel is not solved, at least I can now get around it.

Thanks a lot for your help.

J.