coordinate system for graphic

I would like to know what are the use of ScaleHeight, ScaleLeft, ScaleTop, ScaleWidth, ScaleX, ScaleY). I don't have basic in coordinate system in visual basic. Need some explaination. Why the default coordinate system on the upper-left corner?

Why don't you take a look in here: http://msdn.microsoft.com/en-us/libr...(v=vs.60).aspx

It gets even more bizarre, but we accept what we cannot change.

When specifying a point as (x, y) the cartesian coordinates are mirrored on the Y axis from what might feel conventional. I.e. Y grows down rather than up.

However radial coordinates, by which I mean angles as used in drawing circles and arcs via the Circle method, still grow counter-clockwise... instead of the clockwise you'd expect given the mirrored cartesian plane.

And negative angle values are not negative angle values, but positive angles where the "sign" indicates you want a line drawn from the arc's endpoint to the center.

Just for grins:

Code:

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Option Explicit
'upperleft: (-,+)
'upperright: (+,+)
'lowerleft: (-,-)
'lowerright: (+,-)

Private Sub Form_Load()
 AutoRedraw = True
 ScaleMode = vbPixels
 Me.Scale (-ScaleWidth, ScaleHeight)-(ScaleWidth, -ScaleHeight)
 Line (-ScaleWidth, 0)-(ScaleWidth, 0)
 Line (0, -ScaleHeight)-(0, ScaleHeight)
End Sub
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
 Caption = "X: " & X & " Y: " & Y
End Sub

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