Getting the width of Win32 TreeView control - winapi

Question

The Win32 TreeView control does not have a built-in message/macro to get its (scrollable) width, e.g. if want to set the TreeView's width so it won't need to have a scrollbar.
How can this be done?

Answer 1

Here's a C function to do this:
int TreeView_GetWidth(HWND hTreeWnd)
{
SCROLLINFO scrollInfo;
SCROLLBARINFO scrollBarInfo;
scrollInfo.cbSize = sizeof(scrollInfo);
scrollInfo.fMask = SIF_RANGE;
scrollBarInfo.cbSize = sizeof(scrollBarInfo);
// To find the whole (scrollable) width of the tree control,
// we determine the range of the scrollbar.
// Unfortunately when a scrollbar isn't needed (and is invisible),
// its range isn't zero (but rather 0 to 100),
// so we need to specifically ignore it then.
if (GetScrollInfo(hTreeWnd, SB_HORZ, &scrollInfo) &&
GetScrollBarInfo(hTreeWnd, OBJID_HSCROLL, &scrollBarInfo))
{
// Only if the scrollbar is displayed
if ((scrollBarInfo.rgstate[0] & STATE_SYSTEM_INVISIBLE) == 0)
{
int scrollBarWidth = GetSystemMetrics(SM_CXVSCROLL);
// This is a hardcoded value to accomodate some extra pixels.
// If you can find a cleaner way to account for them (e.g. through
// some extra calls to GetSystemMetrics), please do so.
// (Maybe less than 10 is also enough.)
const int extra = 10;
return (scrollInfo.nMax - scrollInfo.nMin) + scrollBarWidth + extra;
}
}
return 0;
}