XTipComboBox - Display tooltips for combobox

• Download demo project - 31 Kb

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Introduction

XTipComboBox displays tooltips for a combobox, just like tooltips are displayed for a tree control whose items are too long to fit in tree control's client area. When a listbox item in combobox is too long to fit in the listbox, a tooltip will be displayed that allows viewing of complete text. Similarly, a tooltip is displayed when text in combo's edit box is too wide for edit box.

Here is how the tooltips look - note that the tooltip colors will match what is being tooltipped:

        

        

        

Implementation Notes

CXTipComboBox is derived from CComboBox, and implements one virtual function and four message handlers:

• PreSubclassWindow() - this virtual function allows us to create tooltip window, add combobox as its tool, and perform other initialization. Note use of TTF_TRANSPARENT. This flag tells tooltip control to forward mouse messages (including mouse clicks) to the parent window. In the case of the listbox, this will prevent two CBN_SELENDOK messages from being sent to the parent dialog.
  
  
• OnCtlColor() - This is not what you think. According to MSDN article HOWTO: Subclass CListBox and CEdit Inside of CComboBox (Q174667), this is actually recommended way of subclassing listbox of a combobox. We use this to subclass listbox only - for edit box, it is simpler to handle inside CXTipComboBox.
  
  
• OnMouseMove() - This message handler catches mouse moves, and when mouse is inside combo client rect, tooltip will be activated.
  
  
• OnTimer() - A timer is used only when a tooltip is being displayed. When code in OnTimer() detects that mouse is no longer inside client rect, tooltip is removed.
  
  
• OnDestroy() - Unsubclasses the listbox.
  
  

Note that nearly identical code is implemented for first four functions in XTipComboBox.cpp and XTipListBox.cpp.

Tooltip Notes

As mentioned above, tooltip is created in PreSubclassWindow():

    // create tooltip
    m_hWndToolTip = ::CreateWindowEx(WS_EX_TOPMOST,
                              TOOLTIPS_CLASS,
                              NULL,
                              TTS_NOPREFIX | TTS_ALWAYSTIP,
                              CW_USEDEFAULT,
                              CW_USEDEFAULT,
                              CW_USEDEFAULT,
                              CW_USEDEFAULT,
                              m_hWnd,
                              NULL,
                              NULL,
                              NULL);
    ASSERT(m_hWndToolTip);

    // initialize toolinfo struct
    memset(&m_ToolInfo, 0, sizeof(m_ToolInfo));
    m_ToolInfo.cbSize = sizeof(m_ToolInfo);
    m_ToolInfo.uFlags = TTF_TRACK | TTF_TRANSPARENT;
    m_ToolInfo.hwnd = m_hWnd;

    // add combo box
    ::SendMessage(m_hWndToolTip, TTM_SETMAXTIPWIDTH, 0, SHRT_MAX);
    ::SendMessage(m_hWndToolTip, TTM_ADDTOOL, 0, 
                                          (LPARAM) (LPTOOLINFO) &m_ToolInfo);
    ::SendMessage(m_hWndToolTip, TTM_SETTIPBKCOLOR, 
                                          ::GetSysColor(COLOR_HIGHLIGHT), 0);
    ::SendMessage(m_hWndToolTip, TTM_SETTIPTEXTCOLOR, 
                                      ::GetSysColor(COLOR_HIGHLIGHTTEXT), 0);

    // reduce top & bottom margins
    CRect rectMargins(0,-1,0,-1);
    ::SendMessage(m_hWndToolTip, TTM_SETMARGIN, 0, (LPARAM)&rectMargins);

    // set font
    CFont *pFont = GetFont();
    ::SendMessage(m_hWndToolTip, WM_SETFONT, (WPARAM)(HFONT)*pFont, FALSE); 

In typical dialog box situations, you would need to use RelayEvent() along with LPSTR_TEXTCALLBACK to pass tooltip text to tooltip control. Since we are dealing with two separate controls (edit box and list box) wrapped in one combobox control, it is easier to intercept mouse moves and position the tooltip ourselves. Inside OnMouseMove(), we determine position of the mouse, get text underneath, and calculate whether text will fit inside client rect. If it won't fit, we display tooltip, using TTM_TRACKACTIVATE message. Here we also set text and background colors for tooltip, depending on what is being tooltipped. Finally, a timer is used to keep track of when mouse moves outside client rect, so that tooltip will be removed.

How To Use

To integrate CXTipComboBox into your app, you first need to add following files to your project:

• XTipComboBox.cpp
• XTipComboBox.h
• XTipListBox.cpp
• XTipListBox.h

Next, include header file XTipComboBox.h in appropriate project files (usually, dialog header files). Now you are ready to start using CXTipComboBox. If you already have a dialog box with combobox controls, just replace CComboBox with CXTipComboBox in the dialog header file. There is no extra initialization you need to do.

Demo App

The XTipComboBoxTest.exe demo shows how to use CXTipComboBox.

Revision History

Version 1.0 - 2003 June 30

• Initial public release.

Usage

This software is released into the public domain. You are free to use it in any way you like. If you modify it or extend it, please to consider posting new code here for everyone to share. This software is provided "as is" with no expressed or implied warranty. I accept no liability for any damage or loss of business that this software may cause.