如何访问Windows shell上下文菜单项？

Question

In Windows Explorer, you right click on a file, a context menu shows up which contains built-in items like 'Send to...' and/or 3rd party actions such as 'zip file with Winzip'. My question are:

• How to obtain the full list of available menu items for a specific file?
• For each menu item, how to get the caption?
• How to invoke a specific menu item action for a specific disk file?

Thank you in advance!

[EDIT]: While other info is absolutely useful, Delphi solution will be much appreciated!

Answer 1

The key to obtain the Shell Context menu is use the IContextMenu interface.

check this great article Shell context menu support for more details.

UPDATE

for delphi examples you can see the JclShell unit from the JEDI JCL (check the DisplayContextMenu function) and the ShellCtrls unit included in the samples folder of Delphi.

Answer 2

Short answer

Try the ShellBrowser Components from JAM Software. They have a component that will let you show Explorer's context menu with your own commands mixed in from a TPopupMenu.

---

Long answer

Getting the Explorer menu, querying all of its properties, and hosting them in your own menu is possible, but you really should be comfortable reading/writing low-level Win32 code and a working knowledge of C will help. You'll also need to watch out for some gotchas (covered below). I strongly recommend reading Raymond Chen's How to host an IContextMenu series for a lot of the technical details.

The easier approach is to query for the IContextMenu interface, then the HMENU, then use TrackPopupMenu to let have Windows show the menu, then call InvokeCommand at the end.

Some of the code below is untested or has been modified from what we're using, so proceed at your own risk.

Here's how you get the IContextMenu , for a group of files within a base folder:

function GetExplorerMenu(AHandle: HWND; const APath: string;
  AFilenames: TStrings): IContextMenu;
var
  Desktop, Parent: IShellFolder;
  FolderPidl: PItemIDList;
  FilePidls: array of PItemIDList;
  PathW: WideString;
  i: Integer;
begin
  // Retrieve the Desktop's IShellFolder interface
  OleCheck(SHGetDesktopFolder(Desktop));
  // Retrieve the parent folder's PItemIDList and then it's IShellFolder interface
  PathW := WideString(IncludeTrailingPathDelimiter(APath));
  OleCheck(Desktop.ParseDisplayName(AHandle, nil, PWideChar(PathW),
    Cardinal(nil^), FolderPidl, Cardinal(nil^)));
  try
    OleCheck(Desktop.BindToObject(FolderPidl, nil, IID_IShellFolder, Parent));
  finally
    SHFree(FolderPidl);
  end;
  // Retrieve PIDLs for each file, relative the the parent folder
  SetLength(FilePidls, AFilenames.Count);
  try
    FillChar(FilePidls[0], SizeOf(PItemIDList) * AFilenames.Count, 0);
    for i := 0 to AFilenames.Count-1 do begin
      PathW := WideString(AFilenames[i]);
      OleCheck(Parent.ParseDisplayName(AHandle, nil, PWideChar(PathW),
        Cardinal(nil^), FilePidls[i], Cardinal(nil^)));
    end;
    // Get the context menu for the files from the parent's IShellFolder
    OleCheck(Parent.GetUIObjectOf(AHandle, AFilenames.Count, FilePidls[0],
      IID_IContextMenu, nil, Result));
  finally
    for i := 0 to Length(FilePidls) - 1 do
      SHFree(FilePidls[i]);
  end;
end;

To get the actual menu items you need to call IContextMenu.QueryContextMenu . You can destroy the returned HMENU using DestroyMenu .

function GetExplorerHMenu(const AContextMenu: IContextMenu): HMENU;
const
  MENUID_FIRST = 1;
  MENUID_LAST = $7FFF;
var
  OldMode: UINT;
begin
  OldMode := SetErrorMode(SEM_FAILCRITICALERRORS or SEM_NOOPENFILEERRORBOX);
  try
    Result := CreatePopupMenu;
    AContextMenu.QueryContextMenu(Result, 0, MENUID_FIRST, MENUID_LAST, CMF_NORMAL);
  finally
    SetErrorMode(OldMode);
  end;
end;

Here's how you actually call the command that the user has selected from the menu:

procedure InvokeCommand(const AContextMenu: IContextMenu; AVerb: PChar);
const
  CMIC_MASK_SHIFT_DOWN   = $10000000;
  CMIC_MASK_CONTROL_DOWN = $20000000;
var
  CI: TCMInvokeCommandInfoEx;
begin
  FillChar(CI, SizeOf(TCMInvokeCommandInfoEx), 0);
  CI.cbSize := SizeOf(TCMInvokeCommandInfo);
  CI.hwnd := GetOwnerHandle(Owner);
  CI.lpVerb := AVerb;
  CI.nShow := SW_SHOWNORMAL;
  // Ignore return value for InvokeCommand.  Some shell extensions return errors
  // from it even if the command worked.
  try
    AContextMenu.InvokeCommand(PCMInvokeCommandInfo(@CI)^)
  except on E: Exception do
    MessageDlg(Owner, E.Message, mtError, [mbOk], 0);
  end;
end;

procedure InvokeCommand(const AContextMenu: IContextMenu; ACommandID: UINT);
begin
  InvokeCommand(AContextMenu, MakeIntResource(Word(ACommandID)));
end;

Now you can use the GetMenuItemInfo function to get the caption, bitmap, etc, but a much easier approach is to call TrackPopupMenu and let Windows show the popup menu. That would look something like this:

procedure ShowExplorerMenu(AForm: TForm; AMousePos: TPoint; 
  const APath: string; AFilenames: TStrings; );
var
  ShellMenu: IContextMenu;
  Menu: HMENU;
  MenuID: LongInt;
begin
  ShellMenu := GetExplorerMenu(AForm.Handle, APath, AFilenames);
  Menu := GetExplorerHMenu(ShellMenu);
  try
    MenuID := TrackPopupMenu(Menu, TPM_LEFTALIGN or TPM_TOPALIGN or TPM_RETURNCMD, 
      AMousePos.X, AMousePos.Y, 0, AForm.Handle, nil);
    InvokeCommand(ShellMenu, MenuID - MENUID_FIRST);
  finally
    DestroyMenu(Menu);
  end;
end;

If you actually want to extract the menu items/captions and add them to your own popup menu (we use Toolbar 2000 and do exactly that), here are the other big issues you'll run into:

• The "Send To" menu, and any others that are built on-demand won't work unless you handle messages and pass them to the IContextMenu2/IContextMenu3 interfaces.
• Menu bitmaps are in a couple of different formats. Delphi doesn't handle Vista high-color ones without coaxing, and the older ones are blended onto the background color using an XOR.
• Some menu items are owner-drawn, so you have to capture paint messages and have them paint to your own canvas.
• Hint strings won't work unless you manually query for them.
• You'll need to manage the lifetime of the IContextMenu and HMENU and only release them once the popup menu has been closed.

Answer 3

Here is an exmple how the operating system logic behind the "Send To ... | Mail recipient" context menu item can be used from a Delphi application to open the default mail client, displaying a new mail with the passed (selected) files attached:

How can I simulate 'Send To…' with Delphi?