Using winapi to change text on color dialog but 2 static controls have the same control id

Question

Let me start by saying that I am no stranger to using winapi calls to manipulate other windows, but this is the first time I have seen a window that has two identical control IDs. It seems that the color dialog hasn't changed much between windows versions and I can confirm that this behavior exists on all color dialogs from Windows Vista through to Windows 10 (possibly exists in win xp and lower as well but I can't be bothered to check).

What I am attempting to do is use winapi calls to localize the text in a color dialog control in C#. The best way I have found to do this is to use GetDlgItem() to get a handle to the control I wish to change and then use SetWindowText() to actually change the text. This works great for all controls on the color dialog except for the 'Basic colors:' and 'Custom colors:' labels, which both have a control ID of 0xFFFF (decimal value: 65535).

I use an app called WinID to do this type of work (I find it much easier than using Spy++) and you can see from the screenshots below that the ID of the two text labels do in-fact register as the same ID.

NOTE: I have tested this using Spy++ and of course I get the same values as shown below:

I would like to know 2 things:

1. How is it possible for 2 controls to have the same control id?
2. Is there a 'better way' to get a handle to a control from an external dialog/app using winapi calls? Please keep in mind that using something like FindWindowEx(nColorDialogHandle, IntPtr.Zero, "Static", "&custom colors:"); works, but is not useful to me because I must be able to find the handle without relying on the text in English since this must also work on color dialogs from a non-English version of Windows.

Below is some sample code to demonstrate how I am currently able to change the text on a color dialog. I am happy with the code except that I am unable to get a direct handle to the 'Custom colors:' label since using GetDlgItem() with the control id of 0xFFFF seems to return a handle to the first instance of the control with that ID (in this case it always returns a handle to the 'Basic colors:' label). The only way I am able to get the 'Custom colors:' handle is by using an indirect method of looping through all controls on the color dialog until I find one with text that has not already been changed. This works fine but I would like to know if there is a more direct way to get this handle without looping through controls:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Open the color dialog before the form actually loads

            ColorDialogEx oColorDialog = new ColorDialogEx(this.CreateGraphics());

            oColorDialog.FullOpen = true;
            oColorDialog.ShowDialog();
        }
    }

    public class ColorDialogEx : ColorDialog
    {
        private const Int32 WM_INITDIALOG = 0x0110; // Windows Message Constant
        private Graphics oGraphics;
        private const uint GW_HWNDLAST = 1;
        private const uint GW_HWNDPREV = 3;

        private string sColorPickerText = "1-Color Picker";
        private string sBasicColorsText = "2-Basic colors:";
        private string sDefineCustomColorsButtonText = "3-Define Custom Colors >>";
        private string sOKButtonText = "4-OK";
        private string sCancelButtonText = "5-Cancel";
        private string sAddToCustomColorsButtonText = "6-Add to Custom Colors";
        private string sColorText = "7-Color";
        private string sSolidText = "|8-Solid";
        private string sHueText = "9-Hue:";
        private string sSatText = "10-Sat:";
        private string sLumText = "11-Lum:";
        private string sRedText = "12-Red:";
        private string sGreenText = "13-Green:";
        private string sBlueText = "14-Blue:";
        private string sCustomColorsText = "15-Custom colors:";

        // WinAPI definitions

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern bool SetWindowText(IntPtr hWnd, string text);

        [DllImport("user32.dll", SetLastError = true)]
        internal static extern bool MoveWindow(IntPtr hWnd, int X, int Y, int nWidth, int nHeight, bool bRepaint);

        [DllImport("user32.dll")]
        public static extern long GetWindowRect(int hWnd, ref Rectangle lpRect);

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool GetTitleBarInfo(IntPtr hwnd, ref TITLEBARINFO pti);

        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        [DllImport("user32.dll")]
        private static extern IntPtr GetDlgItem(IntPtr hDlg, int nIDDlgItem);

        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);

        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        private static extern int GetClassName(IntPtr hWnd, System.Text.StringBuilder lpClassName, int nMaxCount);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

        [StructLayout(LayoutKind.Sequential)]
        struct TITLEBARINFO
        {
            public const int CCHILDREN_TITLEBAR = 5;
            public uint cbSize;
            public RECT rcTitleBar;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = CCHILDREN_TITLEBAR + 1)]
            public uint[] rgstate;
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left, Top, Right, Bottom;

            public RECT(int left, int top, int right, int bottom)
            {
                Left = left;
                Top = top;
                Right = right;
                Bottom = bottom;
            }

            public RECT(System.Drawing.Rectangle r) : this(r.Left, r.Top, r.Right, r.Bottom) { }

            public int X
            {
                get { return Left; }
                set { Right -= (Left - value); Left = value; }
            }

            public int Y
            {
                get { return Top; }
                set { Bottom -= (Top - value); Top = value; }
            }

            public int Height
            {
                get { return Bottom - Top; }
                set { Bottom = value + Top; }
            }

            public int Width
            {
                get { return Right - Left; }
                set { Right = value + Left; }
            }

            public System.Drawing.Point Location
            {
                get { return new System.Drawing.Point(Left, Top); }
                set { X = value.X; Y = value.Y; }
            }

            public System.Drawing.Size Size
            {
                get { return new System.Drawing.Size(Width, Height); }
                set { Width = value.Width; Height = value.Height; }
            }

            public static implicit operator System.Drawing.Rectangle(RECT r)
            {
                return new System.Drawing.Rectangle(r.Left, r.Top, r.Width, r.Height);
            }

            public static implicit operator RECT(System.Drawing.Rectangle r)
            {
                return new RECT(r);
            }

            public static bool operator ==(RECT r1, RECT r2)
            {
                return r1.Equals(r2);
            }

            public static bool operator !=(RECT r1, RECT r2)
            {
                return !r1.Equals(r2);
            }

            public bool Equals(RECT r)
            {
                return r.Left == Left && r.Top == Top && r.Right == Right && r.Bottom == Bottom;
            }

            public override bool Equals(object obj)
            {
                if (obj is RECT)
                    return Equals((RECT)obj);
                else if (obj is System.Drawing.Rectangle)
                    return Equals(new RECT((System.Drawing.Rectangle)obj));
                return false;
            }

            public override int GetHashCode()
            {
                return ((System.Drawing.Rectangle)this).GetHashCode();
            }

            public override string ToString()
            {
                return string.Format(System.Globalization.CultureInfo.CurrentCulture, "{{Left={0},Top={1},Right={2},Bottom={3}}}", Left, Top, Right, Bottom);
            }
        }

        public ColorDialogEx(Graphics g)
        {
            oGraphics = g;
        }

        protected override IntPtr HookProc(IntPtr nColorDialogHandle, int msg, IntPtr wparam, IntPtr lparam)
        {
            IntPtr returnValue = base.HookProc(nColorDialogHandle, msg, wparam, lparam);

            if (msg == WM_INITDIALOG)
            {
                IntPtr[] oStaticHandleArray = new IntPtr[9];

                // Change the window title

                SetWindowText(nColorDialogHandle, sColorPickerText);

                // Get titlebar info for calculations later

                TITLEBARINFO oTITLEBARINFO = new TITLEBARINFO();
                oTITLEBARINFO.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(oTITLEBARINFO);
                GetTitleBarInfo(nColorDialogHandle, ref oTITLEBARINFO);

                // Change the text of the "Basic colors:" label

                oStaticHandleArray[0] = GetDlgItem(nColorDialogHandle, 0xFFFF);

                SetWindowText(oStaticHandleArray[0], sBasicColorsText);

                // Change the text of the "Define Custom Colors >>" button

                SetWindowText(GetDlgItem(nColorDialogHandle, 0x2CF), sDefineCustomColorsButtonText);

                // Save the "OK" button size and new width

                Rectangle oOKButtonRect = new Rectangle();
                int nOKButtonWidth = (int)oGraphics.MeasureString(sOKButtonText, new Font("Microsoft Sans Serif", 8, FontStyle.Regular)).Width + 20;  // +20 accounts for extra +10 padding on either side

                // Find the "OK" Button

                IntPtr nChildHandle = GetDlgItem(nColorDialogHandle, 0x1);

                if (nChildHandle.ToInt32() > 0)
                {
                    // The "OK" button was found
                    // Now save the current size and position

                    GetWindowRect(nChildHandle.ToInt32(), ref oOKButtonRect);

                    // We have to subtract oOKButtonRect.X value from oOKButtonRect.Width to obtain the "real" button width (same thing with subtracting Y value from Height)

                    oOKButtonRect.Width = oOKButtonRect.Width - oOKButtonRect.X;
                    oOKButtonRect.Height = oOKButtonRect.Height - oOKButtonRect.Y;

                    // Resize the "OK" button so that the new text fits properly
                    // NOTE: I cannot be sure 100% if it is correct to use the titlebar to find the position of the button or not but the math works out in all of my tests

                    MoveWindow(nChildHandle, oOKButtonRect.X - oTITLEBARINFO.rcTitleBar.X, oOKButtonRect.Y - oTITLEBARINFO.rcTitleBar.Y - oTITLEBARINFO.rcTitleBar.Height, nOKButtonWidth, oOKButtonRect.Height, true);

                    // Finally, change the button text

                    SetWindowText(nChildHandle, sOKButtonText);
                }

                // Find the "Cancel" Button

                nChildHandle = GetDlgItem(nColorDialogHandle, 0x2);

                if (nChildHandle.ToInt32() > 0)
                {
                    // The "Cancel" button was found
                    // Now get the current size and position

                    Rectangle oCancelButtonRect = new Rectangle();
                    GetWindowRect(nChildHandle.ToInt32(), ref oCancelButtonRect);

                    // We have to subtract oCancelButtonRect.X value from oCancelButtonRect.Width to obtain the "real" button width (same thing with subtracting Y value from Height)

                    oCancelButtonRect.Width = oCancelButtonRect.Width - oCancelButtonRect.X;
                    oCancelButtonRect.Height = oCancelButtonRect.Height - oCancelButtonRect.Y;

                    // Resize the "Cancel" button so that the new text fits properly
                    // NOTE: I cannot be sure 100% if it correct to use the titlebar to find the position of the button or not but the math works out in all of my tests

                    MoveWindow(nChildHandle, oOKButtonRect.X + nOKButtonWidth - oTITLEBARINFO.rcTitleBar.X + 6, oCancelButtonRect.Y - oTITLEBARINFO.rcTitleBar.Y - oTITLEBARINFO.rcTitleBar.Height, (int)oGraphics.MeasureString(sCancelButtonText, new Font("Microsoft Sans Serif", 8, FontStyle.Regular)).Width + 20, oCancelButtonRect.Height, true);

                    // Finally, change the button text

                    SetWindowText(nChildHandle, sCancelButtonText);
                }

                // Change the text of the "Add to Custom Colors" button

                SetWindowText(GetDlgItem(nColorDialogHandle, 0x2C8), sAddToCustomColorsButtonText);

                // Change the text of the "Color" label text

                oStaticHandleArray[1] = GetDlgItem(nColorDialogHandle, 0x2DA);

                SetWindowText(oStaticHandleArray[1], sColorText);

                // Change the text of the "Solid" label text

                oStaticHandleArray[2] = GetDlgItem(nColorDialogHandle, 0x2DB);

                SetWindowText(oStaticHandleArray[2], sSolidText);

                // Change the text of the "Hue:" label

                oStaticHandleArray[3] = GetDlgItem(nColorDialogHandle, 0x2D3);

                SetWindowText(oStaticHandleArray[3], sHueText);

                // Change the text of the "Sat:" label

                oStaticHandleArray[4] = GetDlgItem(nColorDialogHandle, 0x2D4);

                SetWindowText(oStaticHandleArray[4], sSatText);

                // Change the text of the "Lum:" label

                oStaticHandleArray[5] = GetDlgItem(nColorDialogHandle, 0x2D5);

                SetWindowText(oStaticHandleArray[5], sLumText);

                // Change the text of the "Red:" label

                oStaticHandleArray[6] = GetDlgItem(nColorDialogHandle, 0x2D6);

                SetWindowText(oStaticHandleArray[6], sRedText);

                // Change the text of the "Green:" label

                oStaticHandleArray[7] = GetDlgItem(nColorDialogHandle, 0x2D7);

                SetWindowText(oStaticHandleArray[7], sGreenText);

                // Change the text of the "Blue:" label

                oStaticHandleArray[8] = GetDlgItem(nColorDialogHandle, 0x2D8);

                SetWindowText(oStaticHandleArray[8], sBlueText);

                // Change the text of the "Custom Colors:" label

                SetCustomColorsText(nColorDialogHandle, oStaticHandleArray);
            }

            return returnValue;
        }

        private static string GetClassName(IntPtr nHandle)
        {
            // Create the stringbuilder object that is used to get the window class name from the GetClassName win api function

            System.Text.StringBuilder sClassName = new System.Text.StringBuilder(100);
            GetClassName(nHandle, sClassName, sClassName.Capacity);
            return sClassName.ToString();
        }

        private static string GetWindowText(IntPtr nHandle)
        {
            // Create the stringbuilder object that is used to get the window text from the GetWindowText win api function

            System.Text.StringBuilder sWindowText = new System.Text.StringBuilder(100);
            GetWindowText(nHandle, sWindowText, sWindowText.Capacity);
            return sWindowText.ToString();
        }

        private void SetCustomColorsText(IntPtr nHandle, IntPtr[] oStaticHandleArray)
        {
            // Find the last control based on the handle to the main window

            IntPtr nWorkingHandle = GetWindow(FindWindowEx(nHandle, IntPtr.Zero, null, null), GW_HWNDLAST);
            bool bFound = false;

            do
            {
                // Look only for "Static" controls that we have not already changed

                if (GetClassName(nWorkingHandle) == "Static" && oStaticHandleArray.Contains(nWorkingHandle) == false)
                {
                    // Found a "Static" control
                    // Check to see if it is the one we are looking for

                    string sControlText = GetWindowText(nWorkingHandle);

                    if (sControlText != "")
                    {
                        // Found the "Custom Colors:" label
                        // Change the text of the "Custom Colors:" label

                        SetWindowText(nWorkingHandle, sCustomColorsText);
                        bFound = true;
                    }
                }

                // Working backwards we look for the previous control

                nWorkingHandle = GetWindow(nWorkingHandle, GW_HWNDPREV);

                // Jump out of the loop when the working handle doesn't find anymore controls

                if (nWorkingHandle == IntPtr.Zero)
                    break;
            } while (bFound == false);
        }
    }
}

Answer 1

This dialog is already localized. You can look at it with Visual Studio. Copy c:\windows\system32\en-US\comdlg32.dll.mui to, say, c:\temp\test.dll. Replace "en-US" with your local language tag. In VS use File > Open > File and pick test.dll. You'll see the resources in the MUI file, open the Dialog node and double-click the one named "CHOOSECOLOR". The resource editor opens, you can pick an item in the dialog template and look at its properties in the Property window.

Hopefully it is obvious why the STATIC control has the default IDSTATIC id (65535), there is no need for Windows to do anything to change its properties so no need to find it back. And not for you either, your user will have his own copy of the MUI file that contains the dialog with strings in his native language.

Do note that a machine usually only has MUI files for a single language. If you need to do this to, say, create screenshots for documentation then start here.