Apply changes made in registry regarding window metrics

Did you try with SPIF_UPDATEINIFILE | SPIF_SENDCHANGE and without SendNotifyMessage ?

@David Lowndes Yes, I can .

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace MyConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Hi, press Enter to change borders");

            Console.ReadKey();

            Helper helper = new Helper();

            helper.SetExpectedWindowParameters();

            Console.Write("Press Enter to change borders back");
            Console.ReadKey();

            helper.ReloadWindowParameters();

            Console.Write("Press Enter to end");
            Console.ReadKey();
        }
    }

    class Helper
    {
        private const int LF_FACESIZE = 32;

        // A "logical font" used by old-school windows
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        private struct LOGFONT
        {
            public int lfHeight;
            public int lfWidth;
            public int lfEscapement;
            public int lfOrientation;
            public int lfWeight;
            public byte lfItalic;
            public byte lfUnderline;
            public byte lfStrikeOut;
            public byte lfCharSet;
            public byte lfOutPrecision;
            public byte lfClipPrecision;
            public byte lfQuality;
            public byte lfPitchAndFamily;

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = LF_FACESIZE)]
            public string lfFaceName;

            // to shut it up about the warnings
            public LOGFONT(string lfFaceName)
            {
                this.lfFaceName = lfFaceName;
                lfHeight = lfWidth = lfEscapement = lfOrientation = lfWeight = 0;
                lfItalic = lfUnderline = lfStrikeOut = lfCharSet = lfOutPrecision
                = lfClipPrecision = lfQuality = lfPitchAndFamily = 0;
            }

        }

        private struct NONCLIENTMETRICS
        {
            public int cbSize;
            public int iBorderWidth;
            public int iScrollWidth;
            public int iScrollHeight;
            public int iCaptionWidth;
            public int iCaptionHeight;
            public LOGFONT lfCaptionFont;
            public int iSMCaptionWidth;
            public int iSMCaptionHeight;
            public LOGFONT lfSMCaptionFont;
            public int iMenuWidth;
            public int iMenuHeight;
            public LOGFONT lfMenuFont;
            public LOGFONT lfStatusFont;
            public LOGFONT lfMessageFont;
            public int iPaddedBorderWidth;
        }

        private const int SPIF_SENDCHANGE = 0x02;
        private const int SPI_GETNONCLIENTMETRICS = 0x29;
        private const int SPI_SETNONCLIENTMETRICS = 0x2A;
        private NONCLIENTMETRICS metrics;
        private NONCLIENTMETRICS backupMetrics;
        private IntPtr setMetricsThread;
        private uint setMetricsThreadID = 0;
        private bool gotMetrics = true;
        private int HWND_BROADCAST = 0xFFFF;
        private uint WM_SETTINGCHANGE = 0x1A;

        // NONCLIENTMETRICS IMPORTS

        [DllImport("user32", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool SystemParametersInfo(int Action, int Param, ref NONCLIENTMETRICS lpParam, int WinIni);

        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern bool SendNotifyMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

        public void SetExpectedWindowParameters()
        {
            metrics = new NONCLIENTMETRICS();
            backupMetrics = new NONCLIENTMETRICS();
            metrics.cbSize = Marshal.SizeOf(metrics);
            backupMetrics.cbSize = Marshal.SizeOf(backupMetrics);

            Console.Write("Getting NONCLIENTMETRICS");
            if (!SystemParametersInfo(SPI_GETNONCLIENTMETRICS, metrics.cbSize, ref metrics, 0) ||
                !SystemParametersInfo(SPI_GETNONCLIENTMETRICS, backupMetrics.cbSize, ref backupMetrics, 0))
            {
                gotMetrics = false;
                Console.Write("Failed to get NONCLIENTMETRICS, error code: " + Marshal.GetLastWin32Error());
                return;
            }

            metrics.iPaddedBorderWidth = 0x11;
            metrics.iBorderWidth = 0x21;

            Console.Write("Setting NONCLIENTMETRICS");
            if (!SystemParametersInfo(SPI_SETNONCLIENTMETRICS, metrics.cbSize, ref metrics, 0))
            {
                Console.Write("Failed to set NONCLIENTMETRICS at startup, error code: " + Marshal.GetLastWin32Error());
                return;
            }

            Console.Write("Sending WM_SETTINGCHANGE");
            if (!SendNotifyMessage((IntPtr)HWND_BROADCAST, WM_SETTINGCHANGE, SPI_SETNONCLIENTMETRICS, 0))
            {
                Console.Write("Failed to broadcast after setting metrics, error code: " + Marshal.GetLastWin32Error());
            }
        }

        public void ReloadWindowParameters()
        {
            if (!gotMetrics)
                return;

            Console.Write("Setting NONCLIENTMETRICS back");
            if (!SystemParametersInfo(SPI_SETNONCLIENTMETRICS, Marshal.SizeOf(typeof(NONCLIENTMETRICS)), ref backupMetrics, 0))
            {
                Console.Write("Failed to set NONCLIENTMETRICS at exit, error code: " + Marshal.GetLastWin32Error());
                return;
            }

            Console.Write("Sending WM_SETTINGCHANGE");
            if (!SendNotifyMessage((IntPtr)HWND_BROADCAST, WM_SETTINGCHANGE, SPI_SETNONCLIENTMETRICS, 0))
            {
                Console.Write("Failed to broadcast after reloading metrics, error code: " + Marshal.GetLastWin32Error());
            }
        }
    }
}

@RLWA32 The issue is earlier - in the method SystemParametersInfo(), the code do not proceed to the SendNotifyMessage() method. That is the strange part...

@Castorix31 The issue is happening in SystemParametersInfo() method. The code do not proceed to the SendNotifyMessage() method. That is the strange part...

The issue is earlier - in the method SystemParametersInfo(), the code do not proceed to the SendNotifyMessage() method. That is the strange part...

I could understand a SystemParametersInfo hang if it was broadcasting WM_SETTINGCHANGE. But like you say, this does seems strange. Have you considered calling SystemParametersInfo from a worker thread so that the entire application doesn't hang if the function doesn't return?

Is your pinvoke definition of NONCLIENTMETRICS OK? I notice it doesn't have the StructLayout attribute like your LOGFONT definition has - but I'm not that familiar with pinvoking. It might be simpler to write the example as a C/C++ console program when you won't have such things to worry about.
Also, what happens if you just get/set the setting (i.e. don't change any settings)?

The code in C++ has same issue.

// MetricsTest.cpp : Defines the entry point for the console application.
//
 
#include "stdafx.h"
#include "windows.h"
#include <iostream>
 
int _tmain(int argc, _TCHAR* argv[])
{
	NONCLIENTMETRICS metrics = {0};
	metrics.cbSize = sizeof(metrics);
	std::cout << "Getting NONCLIENTMETRICS" << std::endl;
	if (!SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &metrics, 0))
	{
		std::cout << "Failed to set NONCLIENTMETRICS at startup" << std::endl;
		return 1;
	}
 
	metrics.iPaddedBorderWidth = 0x00;
	metrics.iBorderWidth = 0x01;
	metrics.cbSize = sizeof(metrics);
 
	std::cout << "Setting NONCLIENTMETRICS" << std::endl;
	if (!SystemParametersInfo(SPI_SETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &metrics, 0))
	{
		std::cout << "Failed to set NONCLIENTMETRICS at startup" << std::endl;
		return 1;
	}
 
 
	std::cout << "Sending WM_SETTINGCHANGE" << std::endl;
	if (!SendNotifyMessage(HWND_BROADCAST, WM_SETTINGCHANGE, SPI_SETNONCLIENTMETRICS, 0))
	{
		std::cout << "Failed to broadcast after setting metrics" << std::endl;
		return 1;
	}
 
 
	return 0;
}

@RLWA32 The solution with background threat is our current workaround. When we returning back origin user value at the end of the application it is necessary to display splash screen for few seconds so the returning can procced.

And what if you don't alter the metrics values between Get/Set ?

The issue is still there.

The docs for SPI_SETNONCLIENTMETRICS say "Also, the lfHeight member of the LOGFONT structure must be a negative value." I don't know if implementing this change will make a difference but it's worth a try.

OK, so are you aware of this happening in conjunction with any other application besides SharePoint, and have you tried different versions of SharePoint too (just in case the latest version doesn't exhibit the problem)?
I suspect the only course of action now is to raise it with paid MS support.