TTreeView thumb size

How can I get height of thumb on the vertical scroll bar on the TTreeView?
Dmitry_Asked:
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fvaConnect With a Mentor Commented:
Oh, take a look in WinAPI help at GetScrollInfo call. Maybe you will understand better my intention.

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fvaCommented:
GetSystemMetrics(SM_CYVTHUMB)

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Dmitry_Author Commented:
The thumb height depends by specific window (window size), how can I get thumb height for specific window?
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fvaCommented:
Oh, sorry. You are right. I guess that the best you can do is to get the scroll-bar page size and deduce from that the size of the thumb. Something like:

var asi:TScrollInfo;

...
asi.cbSize:=sizeof(TScrollInfo);
asi.fMask:=SIF_ALL;
GetScrollInfo(MyTreeView.Handle,SB_VERT,asi);
ThumbSize:=(MyTreeView.Height-2*GetSystemMetrics(SM_CYVSCROLL))/(asi.nMax-asi.nMin)*asi.nPage;

After some adjustments you might get it as you want.

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Dmitry_Author Commented:
It's not working, ThumbSize always zero
I'm not understanding how it should work, can you explain, please
Dmitry
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fvaCommented:
Well, it was only a suggestion, not code I have tested or used for myself. The idea is that the thumb size is said (in WinAPI help) to be deduced from the page size. So I was thinking that if you get the page size and relate it somehow to the Min-Max interval then you will get some approximation.

Scrollbar size (without arrows) .......... nMax - nMin
ThumbSize (unknown)....................... nPage

You could step into the code and try to see what does asi contain after the GetScrollInfo call. Maybe nPage is zero and then the idea does not work.

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