Circle Method failure

[Guest_imported]

Hi,
I've got a strange problem with drawing circles.
Details are in the souce code shown below.
(Using VB Pro 6 on a win98 second edition box)

Any help would be very much appreciated.

Cheers,

David


*Source Code to reproduce problem*

Private Sub Form_Load()

ScaleMode = vbPixels
Circle (4226, 1383), 4087 ' succeeds
Circle (4226, 1383), 4088 ' fails silently


' coordinates of bounding box (of failing method) are
' as follows:
' left = 138
' right = 8314
' top = -2705
' bottom = 5471

' according to MS platform SDK documentation on
' ellipse() and arc() functions
' these limitations exist under Win95/98:
' left + right <= 32767
' top + bottom <= 32767
' left + right + top + bottom <= 32767

' the above bounding box clearly fits within these
' limitations
' so what is the problem?
' NB this also fails directly calling the arc() api
' function from vb as well

' I need to be able to know exactly what causes this,
' so I can trap for it. since occasionally a GPF occurs
' in GDI.EXE when this happens.

End Sub

 

[sunaj]

Hi dcpurton,

I tried your code in my VB60 (winNT), and with the forms autoredraw property set to true both circles works fine.

Sunaj

 

[Guest_imported]

That makes sense, as I'm fairly sure that this is a 16bit win95/98 thing. NT uses a 32bit coordinate system so these coords should be nowhere near its limits.

For now I'm just not letting it draw circles any bigger than this radius - but this is dodgy since I can't say for certain *why* this fails (under at least two boxen running win95 and 98). I can also reproduce the problem in C, so either the SDK documentation is up the creek or I'm missing something important.

Can't be helped