Question

I have a WPF 4.0 application written in C# and am currently using System.Windows.Forms.Help.ShowHelp() to show the Windows Help file for the application.

I’d like to be able to control the initial size of the help viewer when it opens. Currently it defaults to the most recently used size.

How can I achieve this?

Answer 1

It’s possible. Add a class to your project and paste this code:

using System;
using System.Text;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;

static class Utils {
    public static void MoveHelpWindow(Rectangle rc) {
        EnumThreadWndProc callback = (hWnd, lp) => {
            // Check if this is the help window
            StringBuilder sb = new StringBuilder(260);
            GetClassName(hWnd, sb, sb.Capacity);
            if (sb.ToString() != "HH Parent") return true;
            MoveWindow(hWnd, rc.Left, rc.Top, rc.Width, rc.Height, false);
            return false;
        };
        foreach (ProcessThread pth in Process.GetCurrentProcess().Threads) {
            EnumThreadWindows(pth.Id, callback, IntPtr.Zero);
        }
    }
    // P/Invoke declarations
    private delegate bool EnumThreadWndProc(IntPtr hWnd, IntPtr lp);
    [DllImport("user32.dll")]
    private static extern bool EnumThreadWindows(int tid, EnumThreadWndProc callback, IntPtr lp);
    [DllImport("user32.dll")]
    private static extern int GetClassName(IntPtr hWnd, StringBuilder buffer, int buflen);
    [DllImport("user32.dll")]
    private static extern bool MoveWindow(IntPtr hWnd, int x, int y, int w, int h, bool repaint);
}

You use it like this, the BeginInvoke call is important:

Help.ShowHelp(this, @"file://c:\windows\help\bcmwlhlp.chm");
this.BeginInvoke(new MethodInvoker(() => Utils.MoveHelpWindow(new Rectangle(0, 0, 300, 200))));