Change browser size using C#

Question

Can I change the browser width from C#?

I want to do something similar to this:

var window = window.open("page.html");
window.resize(100,100);

but in C#, something like this:

Process p = Process.GetProcessesByName("page.html")[0];
p.resize(100,100);

Is it possible?

Answer 1

Once you have obtained the handle to the main window of an application such as a browser, you can use the Windows API SetWindowPos() to change its size.

You would get the window handle from somewhere like Process.MainWindowHandle or by calling some Windows API method such as FindWindow().

Here's an example. To test it, first open Notepad without opening a file, so that its title is exactly "Untitled - Notepad". This is needed so the FindWindow() in the sample code will find it.

If you run the code, it should move and resize the Notepad window. It will probably wind up behind Visual Studio because that will be the active window, so you'll need to mimimise Visual Studio to see where Notepad went.

The P/Invoke declarations were obtained from PInvoke.Net.

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Security;


namespace Demo
{
    class Program
    {
        [Flags]
        public enum SetWindowPosFlags: uint
        {
            // ReSharper disable InconsistentNaming

            /// <summary>
            ///     If the calling thread and the thread that owns the window are attached to different input queues, the system posts the request to the thread that owns the window. This prevents the calling thread from blocking its execution while other threads process the request.
            /// </summary>
            SWP_ASYNCWINDOWPOS = 0x4000,

            /// <summary>
            ///     Prevents generation of the WM_SYNCPAINT message.
            /// </summary>
            SWP_DEFERERASE = 0x2000,

            /// <summary>
            ///     Draws a frame (defined in the window's class description) around the window.
            /// </summary>
            SWP_DRAWFRAME = 0x0020,

            /// <summary>
            ///     Applies new frame styles set using the SetWindowLong function. Sends a WM_NCCALCSIZE message to the window, even if the window's size is not being changed. If this flag is not specified, WM_NCCALCSIZE is sent only when the window's size is being changed.
            /// </summary>
            SWP_FRAMECHANGED = 0x0020,

            /// <summary>
            ///     Hides the window.
            /// </summary>
            SWP_HIDEWINDOW = 0x0080,

            /// <summary>
            ///     Does not activate the window. If this flag is not set, the window is activated and moved to the top of either the topmost or non-topmost group (depending on the setting of the hWndInsertAfter parameter).
            /// </summary>
            SWP_NOACTIVATE = 0x0010,

            /// <summary>
            ///     Discards the entire contents of the client area. If this flag is not specified, the valid contents of the client area are saved and copied back into the client area after the window is sized or repositioned.
            /// </summary>
            SWP_NOCOPYBITS = 0x0100,

            /// <summary>
            ///     Retains the current position (ignores X and Y parameters).
            /// </summary>
            SWP_NOMOVE = 0x0002,

            /// <summary>
            ///     Does not change the owner window's position in the Z order.
            /// </summary>
            SWP_NOOWNERZORDER = 0x0200,

            /// <summary>
            ///     Does not redraw changes. If this flag is set, no repainting of any kind occurs. This applies to the client area, the nonclient area (including the title bar and scroll bars), and any part of the parent window uncovered as a result of the window being moved. When this flag is set, the application must explicitly invalidate or redraw any parts of the window and parent window that need redrawing.
            /// </summary>
            SWP_NOREDRAW = 0x0008,

            /// <summary>
            ///     Same as the SWP_NOOWNERZORDER flag.
            /// </summary>
            SWP_NOREPOSITION = 0x0200,

            /// <summary>
            ///     Prevents the window from receiving the WM_WINDOWPOSCHANGING message.
            /// </summary>
            SWP_NOSENDCHANGING = 0x0400,

            /// <summary>
            ///     Retains the current size (ignores the cx and cy parameters).
            /// </summary>
            SWP_NOSIZE = 0x0001,

            /// <summary>
            ///     Retains the current Z order (ignores the hWndInsertAfter parameter).
            /// </summary>
            SWP_NOZORDER = 0x0004,

            /// <summary>
            ///     Displays the window.
            /// </summary>
            SWP_SHOWWINDOW = 0x0040,

            // ReSharper restore InconsistentNaming
        }

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int x, int y, int cx, int cy, SetWindowPosFlags uFlags);

        [SuppressMessage("Microsoft.Security", "CA2118:ReviewSuppressUnmanagedCodeSecurityUsage"), SuppressUnmanagedCodeSecurity]
        [DllImport("User32", CharSet=CharSet.Auto, SetLastError=true)]
        public static extern IntPtr FindWindow
        (
            [MarshalAs(UnmanagedType.LPTStr)] string lpClassName,  // class name
            [MarshalAs(UnmanagedType.LPTStr)] string lpWindowName  // window name
        );

        void run()
        {
            IntPtr notepadWindow = FindWindow(null, "Untitled - Notepad");

            if (notepadWindow != IntPtr.Zero)
                SetWindowPos(notepadWindow, IntPtr.Zero, 0, 0, 400, 400, SetWindowPosFlags.SWP_SHOWWINDOW);
        }

        static void Main()
        {
            new Program().run();
        }
    }
}