What controls scroll handle size?

[qwert]

I have a scrollable control that contains an image. When the image is twice a big as the scrollable area can display, I would like the scroll handle to be half the height of the scroll area. Instead, it's maybe 1/20th -- too small to easily grab. The childGUI is defined with this statement:

_GUIScrollBars_SetScrollInfoMax($hChildGUI, $SB_VERT, $Height-300)

where $height is the height if the image and 300 is the height of the scrollable area on the window.

So far, I haven't found any setting that affects the handle's height.

Thanks in advance for any help.

Edited July 29, 2009 by qwert

[Authenticity]

#include <GUIScrollBars.au3>
#include <ScrollBarConstants.au3>

Global $hGUI = GUICreate('Test', 200, 200)
_GUIScrollBars_Init($hGUI, 500, 500)

GUISetState()
AdlibEnable('_Randomness', 1000)

Do
Until GUIGetMsg() = -3
GUIDelete()
Exit

Func _Randomness()
    _GUIScrollBars_SetScrollInfoPage($hGUI, $SB_HORZ, Random(20, 100, 1))
    _GUIScrollBars_SetScrollInfoPage($hGUI, $SB_VERT, Random(20, 100, 1))
EndFunc

[qwert]

Thanks for the nice example. I was able to add this line and get the result I wanted:

_GUIScrollBars_SetScrollInfoPage($hChildGUI, $SB_VERT, 400)

From MSDN:

nPage Specifies the page size. A scroll bar uses this value to determine the appropriate size of the proportional scroll box.

"determine the appropriate size" sounds like a calculation. Too bad they don't say what it is. I'll have to experiment.

Thanks again for your help.