ITaskbarList3::ThumbBarUpdateButtons method (shobjidl_core.h)

Shows, enables, disables, or hides buttons in a thumbnail toolbar as required by the window's current state. A thumbnail toolbar is a toolbar embedded in a thumbnail image of a window in a taskbar button flyout.


HRESULT ThumbBarUpdateButtons(
  [in] HWND          hwnd,
  [in] UINT          cButtons,
  [in] LPTHUMBBUTTON pButton


[in] hwnd

Type: HWND

The handle of the window whose thumbnail representation contains the toolbar.

[in] cButtons

Type: UINT

The number of buttons defined in the array pointed to by pButton. The maximum number of buttons allowed is 7. This array contains only structures that represent existing buttons that are being updated.

[in] pButton


A pointer to an array of THUMBBUTTON structures. Each THUMBBUTTON defines an individual button. If the button already exists (the iId value is already defined), then that existing button is updated with the information provided in the structure.

Return value


If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.


Because there is a limited amount of space in which to display thumbnails, as well as a constantly changing number of thumbnails to display, applications are not guaranteed a specific toolbar size. If display space is low, buttons in the toolbar are truncated from right to left as needed. Therefore, an application should prioritize the commands associated with its buttons to ensure that those of highest priority are to the left and are therefore least likely to be truncated.

Thumbnail toolbars are displayed only when thumbnails are being displayed on the taskbar. For instance, if a taskbar button represents a group with more open windows than there is room to display thumbnails for, the UI reverts to a legacy menu rather than thumbnails.


The following example shows how to use ThumbBarUpdateButtons to change the text and image on an existing button in a thumbnail toolbar on the extended taskbar.

HRESULT UpdateThumbarButton(HWND hwnd)
    // Define a single structure for the button to update. The ID is that
    // of an existing button, so the other information (bitmap index and 
    // tooltip) overwrites the existing values, updating the button.
    THUMBBUTON thbButton;
    thbButton.dwMask = THB_BITMAP | THB_TOOLTIP;
    thbButtons[0].iId = 1;
    thbButton.iBitmap = 3;
    thbButton.pszTip = TEXT("Different Text");
    // Create an instance of ITaskbarList3
    ITaskBarList3 *ptbl;
    HRESULT hr = CoCreateInstance(CLSID_TaskbarList, 

    if (SUCCEEDED(hr))
        // Update the toolbar. In this case, only the single button is updated.
        hr = ptbl->ThumbBarUpdateButtons(hwnd, 1, &thbButton);
    return hr;


Requirement Value
Minimum supported client Windows 7 [desktop apps only]
Minimum supported server Windows Server 2008 R2 [desktop apps only]
Target Platform Windows
Header shobjidl_core.h (include Shobjidl.h)
Library Explorerframe.lib
DLL Explorerframe.dll

See also






Taskbar Extensions