Integration with other file managers

[m1l]

I'm developing a file manager and one of users asked about supporting QuickLook. I have tried passing the path to .exe as parameter but that does not work. Is it possible to already pass a file to be previewed in some way?

[xupefei]

Passing a path to QuickLook.exe should work -- but only when the user is using MSI or ZIP version of QuickLook (does not work for Windows Store version).

The best option is to send a message to a named pipe (code):

string PipeName = "QuickLook.App.Pipe." + WindowsIdentity.GetCurrent().User?.Value;
string Toggle = "QuickLook.App.PipeMessages.Toggle";

public static void SendMessage(string pipeMessage, string path = null)
{
    if (path == null)
        path = "";

    try
    {
        using (var client = new NamedPipeClientStream(".", PipeName, PipeDirection.Out))
        {
            client.Connect();

            using (var writer = new StreamWriter(client))
            {
                writer.WriteLine($"{pipeMessage}|{path}");
                writer.Flush();
            }
        }
    }
    catch (Exception e)
    {
        Debug.WriteLine(e.ToString());
    }
}

The code above can be used like this:

SendMessage(Toggle, "C:\path\to\file.txt");

The preview window will be closed when the same message is sent for the second time.
If the second message is still PipeMessages.Toggle but with a different path, QuickLook will switch to preview the new path.

---

If sending a message is too complicated to your application, you can instead provide something e.g. WM_COPYDATA so I can get the selected file from QuickLook's side, like what I have done for Directory Opus (code).

[m1l]

Thank you! With the provided code it was 5 minute to integrate. The only place I have trouble with now is how to check if preview window is already open (in case user selects another file, to show preview only if preview window is already opened). I have tried the MainWindowHandle of the "QuickLook" process but it is 0. Is there a proper way to check?

[xupefei]

No, there isn't any direct method to ask QuickLook for that, but it is possible with Windows APIs. I would suggest the following steps:

1. Use EnumWindows and GetClassName to check if any window is having a class name starting HwndWrapper[QuickLook.exe;; (full class name looks like HwndWrapper[QuickLook.exe;;8a9110c8-bad4-4b12-b2f7-fb06c505b290]).

2. On your side, Send Toggle message when Spacebar is pressed. Additionally, if a preview window is visible, send Switch message when the selection changes. Although the Switch message does nothing when no preview is visible, it is good to avoid wasting CPU time by checking for any window before sending the message.

The Switch message has the same format with Toggle: SendMessage("QuickLook.App.PipeMessages.Switch", "C:\path\to\file.txt");

[m1l]

Great. I did have to additionally use IsWindowVisible from user32.dll or it finds that class even when the window is closed. Total of <6 ms per check. Thank you!

[LunarLanding]

I tried using it from the command line and it stops working.
Steps:

• verify it works normally.
• verify pipe works and exists with get-childitem \\.\pipe\ | out-string -stream | Select-String -Pattern "QuickLook" on powershell
• execute on command prompt echo "QuickLook.App.PipeMessages.Toggle|[absolute path to document.pdf]" > \\.\pipe\QuickLook.App.Pipe.[SID]
• expected preview to open, but nothing happens, the pipe is gone and the normal spacebar shortcut on windows explorer does not work.

[xupefei]

@LunarLanding Any exception log?