State of Play

• Currently, ListViewGroup only supports Header and HeaderAlignment (although this is buggy, see #2555)
• Our definition of LVGROUPW is actually too small: LVGROUP actually exposes a lot more functionality (https://docs.microsoft.com/en-us/windows/win32/api/commctrl/ns-commctrl-lvgroup)

Missing Feature Parity

• See http://www.componentowl.com/better-listview.html
• See https://www.codeproject.com/Articles/16009/A-Much-Easier-to-Use-ListView-2
• See https://msdn.microsoft.com/en-gb/msdnmag/issues/07/08/WindowsCPP/default.aspx

Support For Images

• You can set the LVSIL_GROUPHEADER list view image list
• You can set the LVGF_TITLEIMAGE flag on mask and set iTitleImage to a valid index into the LVSIL_GROUPHEADER image list

This would add the following APIs to ListView and ListViewGroup:

public class ListView
{
    ...
    public ImageList GroupHeaderImageList { get; set; }
    ...
}

public class ListViewGroup
{
    ...
    public int TitleImageIndex { get; set; }
    ...
}

E.g.

Collapsible

• Can set the LVGF_STATE flag on uMask and set stateMask to LVGS_COLLAPSIBLE and state to LVGS_COLLAPSIBLE
• https://www.codeproject.com/Articles/31276/Add-Group-Collapse-Behavior-on-a-Listview-Control

This would add the following APIs to ListViewGroup:

public class ListViewGroup
{
    ...
    public bool Collapsible { get; set; }
    ...
}

E.g.

Discussion

• The rightmost collapse/expand icon doesn't work: to fix this we need to call base.WndProc in WM_LBUTTONUP handler

Collapsed

• Can set the LVGF_STATE flag on uMask and set stateMask to LVGS_COLLAPSED and state to LVGS_COLLAPSED

This would add the following APIs to ListViewGroup:

public class ListViewGroup
{
    ...
    public bool Collapsed { get; set; }
    ...
}

E.g.

HeaderVisible

• Can set the LVGF_STATE flag on uMask and set stateMask to LVGS_NOHEADER and state to LVGS_NOHEADER

This would add the following APIs to ListViewGroup:

public class ListViewGroup
{
    ...
    public bool HeaderVisible { get; set; } = true;
    ...
}

E.g.

Description Top/Bottom

• You can set the LVGF_DESCRIPTIONTOP flag on mask and set pszDescriptionTop to a valid string and cchDescriptionTop to the length of the string
• You can set the LVGF_DESCRIPTIONBOTTOM flag on mask and set pszDescriptionBottom to a valid string and cchDescriptionBottom to the length of the string

This would add the following APIs to ListViewGroup:

public class ListViewGroup
{
    ...
    public string TopDescription { get; set; }
    public string BottomDescription { get; set; }
    ...
}

E.g.

/cc @weltkante @RussKie