Changing default icons for folders and drives

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Introduction

This article explains a simple way to get and set icons for folders (open and closed), hard drives, floppies and CD drives. The default icons are stored in Shell32.dll as icon resources. To change the icons, we need to modify the registry by adding some values and to set them back to default icons, we simply remove the values we added. Of course simply changing the registry values won't change the icons because Windows will take the icons from the icon cache. Tweak UI has a feature to flush the icon cache and I ran Spy++ on it as well as monitored registry changes. I found that what they do is to change the icon size value in the WindowMetrics registry key, broadcast a WM_SETTINGCHANGE with SPI_SETNONCLIENTMETRICS, change the icon size  back to it's original value and again broadcast the WM_SETTINGCHANGE  message. I did the same and found that it works fine.

Demo project

I put together a simple demo project for making things clearer for you. It will let you get and set folder and drive icons as well as let you set it back to their default values. I've used some interesting techniques in the program which I'll explain below for the interested ones.

Getting default (or customized) icons

The default icons are stored in Shell32.dll and we simply read the hard coded indexed icons out of the DLL. But before that we first check to see if the icons have already been customized by reading the registry.

void CShellIconChangerDlg::OnCbnSelchangeCombo1()
{
    //First chk if customized


    CString val;
    HKEY hKey;

    LONG result = ::RegOpenKeyEx(HKEY_LOCAL_MACHINE,
        "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Shell Icons",
        0,KEY_READ,&hKey);
    BYTE buff[512];
    ZeroMemory(buff,511);
    DWORD sz = sizeof buff;
    DWORD typ = REG_SZ;
    CString indbuff;
    indbuff.Format("%d",m_combo.GetItemData(m_combo.GetCurSel()));
    result = RegQueryValueEx(hKey,indbuff,0,&typ,buff,&sz);
    RegCloseKey(hKey);

    if(result == ERROR_SUCCESS)
    {
        val = buff;
        int comma = val.ReverseFind(',');
        int cusindex = 0;
        if(comma != -1)
        {
            CString tmpstr = val.Mid(comma+1);
            cusindex = atoi(tmpstr);
            val = val.Left(comma); 
        }

        HICON hIcon = ::ExtractIcon(AfxGetApp()->m_hInstance,
            val,cusindex);
        m_curicon.SetIcon(hIcon);
    }
    else
    {
        char sysfolder[MAX_PATH];
        GetSystemDirectory(sysfolder,MAX_PATH);
        CString strIconPath = sysfolder;
        strIconPath += "\\Shell32.dll";
        HICON hIcon = ::ExtractIcon(AfxGetApp()->m_hInstance,
            strIconPath,m_combo.GetItemData(m_combo.GetCurSel()));
        m_curicon.SetIcon(hIcon);
    }
}

ExtractIcon is a rather unknown function which will extract an indexed icon resource from a DLL or EXE file. Of course I might be wrong as to it's being unknown, I was speaking personally here. I didn't know of such a function till today.

Setting custom icons

void CShellIconChangerDlg::OnBnClickedOk()
{
    HKEY hKey;
    DWORD dwDisposition;
    LONG result = ::RegCreateKeyEx(HKEY_LOCAL_MACHINE,
        "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Shell Icons",0,
        NULL,REG_OPTION_NON_VOLATILE,KEY_WRITE,NULL,&hKey,&dwDisposition);
    CString buff;
    buff.Format("%d",m_combo.GetItemData(m_combo.GetCurSel()));
    RegSetValueEx(hKey,buff,0,REG_SZ,
        (const BYTE*)m_strIconPath.GetBuffer(0),m_strIconPath.GetLength());
    m_strIconPath.ReleaseBuffer();

    RegCloseKey(hKey);

    RefreshIcons();
    OnCbnSelchangeCombo1();
}

Well, there is not anything very much special here and we simply add a new value to the registry key as shown above. I use RegCreateKeyEx instead of RegOpenKeyEx because by default the sub-key Shell Icons does not exist. As you can see I then call RefreshIcons which is the function that duplicates what Tweak UI does. I'll explain it later in this article.

Setting to default

void CShellIconChangerDlg::OnBnClickedButton2()
{
    HKEY hKey;
    DWORD dwDisposition;
    LONG result = ::RegCreateKeyEx(HKEY_LOCAL_MACHINE,
        "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Shell Icons",0,
        NULL,REG_OPTION_NON_VOLATILE,KEY_WRITE,NULL,&hKey,&dwDisposition);
    CString buff;
    buff.Format("%d",m_combo.GetItemData(m_combo.GetCurSel()));
    RegDeleteValue(hKey,buff);
    RegCloseKey(hKey);

    RefreshIcons();
    OnCbnSelchangeCombo1();
}

Setting to default is a simple matter of deleting the values we added to the registry and calling RefreshIcons.

Browse for icons dialog

void CShellIconChangerDlg::OnBnClickedButton1()
{
    WCHAR szIconPath[MAX_PATH]={0};
    int index = 0;
    if(PickIconDlg(m_hWnd,(WCHAR*)&szIconPath,MAX_PATH,&index))
    {
        CString str;
        str.Format("%S,%d",szIconPath,index);
        m_strIconPath = str;
        HICON hIcon = ::ExtractIcon(AfxGetApp()->m_hInstance,
            CString(szIconPath),index);
        m_iconpreview.SetIcon(hIcon);
    }
}

I have used the PickIconDlg shell function to show the user the standard shell browser dialog. It will let you browse icon files as well as DLLs and other files containing icons. It's only available in Shell32.dll version 5.0 and above, which means this is not available for pre-Windows 2000 users.

RefreshIcons similaire � Tweak UI

void CShellIconChangerDlg::RefreshIcons()
{
    CString val;
    HKEY hKey;

    LONG result = ::RegOpenKeyEx(HKEY_CURRENT_USER,
        "Control Panel\\Desktop\\WindowMetrics",
        0,KEY_READ,&hKey);
    BYTE buff[256];
    ZeroMemory(buff,255);
    DWORD sz = sizeof buff;
    DWORD typ = REG_SZ;
    RegQueryValueEx(hKey,"Shell Icon Size",0,&typ,buff,&sz);
    RegCloseKey(hKey);

    val = buff;

    int i = atoi(val);
    i++;
    val.Format("%d",i);

    result = ::RegOpenKeyEx(HKEY_CURRENT_USER,
        "Control Panel\\Desktop\\WindowMetrics",
        0,KEY_WRITE,&hKey);
    RegSetValueEx(hKey,"Shell Icon Size",0,REG_SZ,
        (const BYTE*)val.GetBuffer(0),val.GetLength());
    val.ReleaseBuffer();
    RegCloseKey(hKey);

    ::SendMessage(HWND_BROADCAST ,
        WM_SETTINGCHANGE,SPI_SETNONCLIENTMETRICS,NULL);


    i = atoi(val);
    i--;
    val.Format("%d",i);

    result = ::RegOpenKeyEx(HKEY_CURRENT_USER,
        "Control Panel\\Desktop\\WindowMetrics",
        0,KEY_WRITE,&hKey);
    RegSetValueEx(hKey,"Shell Icon Size",0,REG_SZ,
        (const BYTE*)val.GetBuffer(0),val.GetLength());
    val.ReleaseBuffer();
    RegCloseKey(hKey);

    ::SendMessage(HWND_BROADCAST ,
        WM_SETTINGCHANGE,SPI_SETNONCLIENTMETRICS,NULL);
}

Basically the whole purpose of this function is to flush the icon cache and force Windows to redraw the icons. By changing the shell icon size value in the registry and then broadcasting WM_SETTINGCHANGE with SPI_SETNONCLIENTMETRICS, we manage to flush the icon cache. Of course we then need to set the shell icon size back to  normal. I know it sounds like a rather round about way to do it, but till they add a "ShFlushIconCache" to the shell API, this is the only solution we have.

The index numbers

Conclusion

Please note that the CDROM index is not valid when you have a CD-RW drive. I haven't figured out the index for CD-RW drives. Or perhaps it did not work in my case because mine is a DVD/CD-RW combo drive. Anyway as usual please send in the feedback through the really cool forum found at the bottom of this article. Thomas Freudenberg has written an article on the same topic here; though in his case, while he does not demonstrate the Tweak UI simulation, he does include a more complete list of icon indices.