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Exontrol Software - ExComboBox FAQ page

Frequently Asked Questions - ExComboBox Component

Listed below are the questions that we are asked quite often. Before you write us, be sure to check here. 

Are you looking for something?

Just press CTRL+F ( or select Edit\Find menu item ) and you have a dialog that will help you to locate the string that are you looking for.

Where can I find the control's release notes?

The control's release notes can be found on our web site, looking for the Release Notes column in the control's main page. Click here for direct link. 

How do I find the component's help file?

By default, the setup installs a chm file in your system folder. You can access the help file by pressing F1 key when in VB and the control is selected. You can also access the help file by typing ControlName.chm in the START menu RUN box. For instance, type excombobox.chm and the help file for ExComboBox component will be opened. 

How can I type normal text in ExComboBox like a simple combo box control?

By default, the control contains no columns so at least one column should be added before using it as in the following sample:
With ComboBox1
    .BeginUpdate
        .AutoComplete = False
        .ColumnAutoResize = True
        .Columns.Add "Default"
    .EndUpdate
End With

The AutoComplete property specifies that the control does complete the control's label area based on the selected item. Setting this property on False, will let you type any character inside.

Does your control support prompt feature?

Yes. A prompt is a label or short instruction placed inside an editable drop-down list as its default value. Unlike static text, prompts disappear from the screen once users type something into the combo box or it gets input focus. The Prompt property of the column provides this functionality. The following snippet of code displays a prompt for the control:
With ComboBox1
	.BeginUpdate 
	.ColumnAutoResize = True
	.AutoComplete = False
	.Columns.Add("Default").Prompt = "<i><fgcolor=808080>prompt</fgcolor></i>"
	.EndUpdate 
End With

I'm having a problem with the FilterBar. In the FilterBar sample project I have it selected to filter by ContactTitle = 'Owner'.  But it still shows other records in the list.

That's nothing strange in that sample. The sample shows data hierarchical. When the component applies the filter it looks for all items that match the criteria and includes the parent items as well, else the filtered items will be hidden. You can comment the code that uses SetParent method to let control displays data as a simple list. 

Is there any way to display a tool tip when cell's caption doesn't fit the cell's client area?

The CellTooltip property of Items object specifies the cell's tool tip. The cell's tool tip appears when the cursor is over the cell. If you set the CellTooltip ="..." ( three dots ), the control displays the cell's caption in a tool tip when it doesn't fit the cell's client area.  

How can I add new columns to the control?

The control provides a Columns property that helps you to add, remove or changes the columns of the control. By default, the control has no columns. The following code shows you how to add two columns to the control:

With ComboBox1
    .BeginUpdate
        With .Columns
            With .Add("Column 1")
                .Width = 164
            End With
            With .Add("Column 2")
                .HeaderImage = 1
            End With
        End With
    .EndUpdate
End With
When many changes are made to the control , you should invoke the BeginUpdate method to temporarily freeze the drawing of the control. This results in less distraction to the user, and a performance gain. After all updates have been made, invoke the EndUpdate method to resume drawing of the control.

How can I add new items to the control?

The control provides an Items property that helps you to add, remove or changes the items in the control. Before adding any new item to the control make sure that your control has at least one column. There are 4 methods to load items to the control. 

Because control can load a list as well as a hierarchy each item is specified by a handle HITEM not by index. Each property that refers a cell requires a handle and an index to a column.

By default, the control has no columns, so before adding new items you need to add columns like in the following sample 

With ComboBox1.Columns
        .Add "Column 1"
        With .Add("Column 2")
            .HTMLCaption = "Column <b>2</b>"
        End With
End With

The following sample uses the first method to add few items to the Items collection.

With ComboBox1.Items
    Dim h As HITEM, hChild As HITEM
    h = .AddItem("Group 1")
    .CellCaption(h, 1) = "Information about Group 1"
    hChild = .InsertItem(h, , "Child 1")
    .CellCaption(hChild, 1) = "Information about Child 1"
    hChild = .InsertItem(h, , "Child 2")
    .CellCaption(hChild, 1) = "Information about Child 2"
    
    h = .AddItem("Group 2")
    .CellCaption(h, 1) = "Information about Group 2"
    hChild = .InsertItem(h, , "Child 1")
    .CellCaption(hChild, 1) = "Information about Child 1"
    hChild = .InsertItem(h, , "Child 2")
    .CellCaption(hChild, 1) = "Information about Child 2"    
End With

When many changes are made to the control , you should invoke the BeginUpdate method to temporarily freeze the drawing of the control. This results in less distraction to the user, and a performance gain. After all updates have been made, invoke the EndUpdate method to resume drawing of the control.

The following sample uses the VB Array function to insert items to a multiple columns control: 

Private Sub Form_Load()
With ComboBox1
    .BeginUpdate
    
    .Columns.Add "Column 1"
    .Columns.Add "Column 2"
    .Columns.Add "Column 3"
    
    With .Items
        Dim h As HITEM
        h = .AddItem(Array("Item 1", "Item 2", "Item 3"))
        .InsertItem h, , Array("Item 1.1", "Item 2.1", "Item 3.1")
        .InsertItem h, , Array("Item 1.2", "Item 2.2", "Item 3.2")
        .ExpandItem(h) = True
    End With
    
    .EndUpdate
End With

The following sample insert items to a multiple columns controls:

Private Sub Form_Load()
With ComboBox1
    .BeginUpdate
    
    .Columns.Add "Column 1"
    .Columns.Add "Column 2"
    .Columns.Add "Column 3"
    
    With .Items
        Dim h As HITEM, h2 As HITEM
        h = .AddItem("Item 1")
        .CellCaption(h, 1) = "Item 2"
        .CellCaption(h, 2) = "Item 3"
        h2 = .InsertItem(h, , "Item 1.1")
        .CellCaption(h2, 1) = "Item 1.2"
        .CellCaption(h2, 2) = "Item 1.3"
        h2 = .InsertItem(h, , "Item 2.1")
        .CellCaption(h2, 1) = "Item 2.2"
        .CellCaption(h2, 2) = "Item 2.3"
        .ExpandItem(h) = True
    End With
    
    .EndUpdate
End With

I was able to add a new item, but now how can I insert it at the top of the list?

Once that you have the handle of the added item you have to sue the ItemPosition property to specify the item's position.

How can I get ride of the images panel at design time?

The control provides a property ShowImageList that shows or hides that images list. By default, the property is True, to let new customers know that they can drag images without using an ImageList control. If you are going to add icons at runtime the control provides Images and ReplaceIcon methods. The Images method takes the handle to an ImageList control. The ReplaceIcon method works like follows:

  • ( Icon, -1) method. Adds a new icon to control's image list, and retrieves the index of the image. Sample: .ReplaceIcon Image1.Picture.Handle, adds a new icon to the end of the control's image list, .ReplaceIcon LoadPicture("D:\Icons\help.ico").Handle adds a new icon, loads the icon from a file, and adds it to control's image list
  • ReplaceIcon( Icon, n ) ( where n >= 0 ) method. Replaces an icon to control's image list. Sample: .ReplaceIcon Image1.Picture.Handle, 0 replaces the first icon in the control's image list
  • ReplaceIcon( 0, n ) (where n>= 0 ) method. Removes an icon given its index. Sample: .ReplaceIcon 0, 0 removes the first icon in the control's image list 
  • ReplaceIcon( 0, -1) method. Clears the images collection. Sample: .ReplaceIcon, clears the entire image list.

How can I delete an icon from the images list window, shown at design time?

You can delete an icon from the images list window in design mode by selecting the icon and pressing the BackSpace key. You can delete the icon using the Delete key but some containers delete the object when Delete key is used. 

How can I select an item?

The control provides several options to select an item or a value. The Select and Value properties selects a value on a specified column. 

For instance, the following sample looks for an item that has in the column "Column 1" the "Child 2", and selects it, if the value is found:

ComboBox1.Select(0) = "Child 2"

or

ComboBox1.Select("Column 1") = "Child 2"

Also, the Items object provides properties like: Items.SelectCount, Items.SelectItem, Items.SelectedItem that helps you to access the selected items. The control fires SelectionChanged event when user changes the selection. The following sample uses the FindItem method to looks for an item that contains in the column "Column 1" the value "Child 2"

ComboBox1.Items.SelectItem(ComboBox1.Items.FindItem("Child 2", "Column 1")) = True

or

ComboBox1.Items.SelectItem(ComboBox1.Items.FindItem("Child 2", 0)) = True

The following sample selects the first visible item:

ComboBox1.Items.SelectItem(ComboBox1.Items.FirstVisibleItem) = True
The following sample displays the selected items. Only the caption on the first column are displayed. If you want to display more columns you have to change the 0 with index of column being displayed.
With ComboBox1.Items
        Dim i As Long
        For i = 0 To .SelectCount - 1
            Debug.Print .CellCaption(.SelectedItem(i), 0)
        Next
End With

How can I find an item and how can I make sure that's visible?

There Items object provides few methods like FindItem, FindPath in order to find an item. The FindItem method looks for the first item that has in a column the giving value. For instance the following sample gets the handle of the item that contains in the first column ( "Column 1"  ) the value "Child 2":

Debug.Print ComboBox1.Items.FindItem("Child 2", "Column 1")

If the FindItem method fails to locate the item the 0 is returned. If a non 0 value is returned that means that the control was able to locate the item. 

The FindPath method looks for a path in the control's hierarchy using the SearchColumnIndex property as being the searching column . The method requires the full path separated by the "/".

Debug.Print ComboBox1.Items.FindPath("Group 2\Child 2")

Once that we have found the searched item all that we need to call EnsureVisibleItem method in order to ensure that the item is visible. If the item was a child of an item that was collapsed the EnsureVisibleItem method expands that item too.

How do I color an item or a cell?

The control provides multiple ways to do that. If you only need to alternate the background color for items you should use the BackColorAlternate property. If only a particular item needs to be colorized, you have to use properties like: ItemForeColor, ItemBackColor, CellForeColor or CellBackColor. Remember that control fires the InsertItem event when a new item is inserted to the Items collection. You can use the InsertItem event to apply different colors for the newly added items and cells.  

How do I color a column?

The InsertItem event is called each time when a new item is inserted to the Items collection. We can use this event to color a column like in the following sample:

Private Sub ComboBox1_InsertItem(ByVal Item As EXCOMBOBOXLibCtl.HITEM)
    With ComboBox1.Items
        .CellBackColor(Item, 1) = vbRed
    End With
End Sub
Another option that you have to color a column is if you are using the CountLockedColumns property. The CountLockedColumn property specifies the number of visible columns that are frozen on the left side. A frozen column is not scrollable. The control provides in that case a property called BackColorLock that specifies the background color for frozen area of the control. The same thing is for ForeColorLock property except that it specifies the foreground color for the frozen area. In case that CountLockedColumn > 0 the BackColor and ForeColor properties are applicable to the scrollable area of the control.

How do I bold a cell?

The control provides a plenty of properties like: CellBold, CellItalic, CellUnderline, CellStrikeout, ItemBold, ItemStrikeout,  and so on to help you set font attributes for a cell or for an item. As well as cells the column's header can have its own font attribute using the HeaderBold, HeaderItalic, and so on properties. Another alternative is using built-in HTML format.

Is there a way for the control resize its drop down window to the number of elements in it?

The IntegralHeight property helps you to do that. If the control's Style property is DropDown or DropDownList the IntegralHeight property resizes the drop down window to avoid displaying partial items. The control uses the DefaultItemHeight , Items.ItemCount and the HeightList properties to to compute the size of the drop down window. If the AllowSizeGrip property is True, the end user can resizes the drop down window at runtime. If the IntegralHeight property is True no partial items are displayed. You can use AllowHResize and AllowVResize to allow user resizes only the width or the height of the control by dragging the control's size grip.

How do I sort the list of items at runtime?

By default, the control automatically sort a column when the user clicks the column's header. If the SortOnClick property is exNoSort the control doesn't sort the items when user clicks the column's header. There are two methods to get items sorted like follows:

  • Using the SortOrder property of the Column object. The SortOrder property displays the sorting icon in the column's header if the DisplaySortIcon property is True: 

    ComboBox1.Columns(ColIndex).SortOrder = SortAscending
  • Using the SortChildren method of the Items object. The SortChildren sorts the items. The SortChildren method sorts the child items of the given parent item in the control. SortChildren will not recourse through the tree, only the immediate children of Item will be sorted. The following sample sort descending the list of root items on the "Column 1"( if your control displays a list, all items are considered being root items ).

    ComboBox1.Items.SortChildren 0, "Column 1", False

Can I loop through the items collection?

Yes, you can. The following method uses a for each statement.. In the sample h variable specifies a handle to an item.

With ComboBox1
        Dim h As Variant
        For Each h In .Items
            Debug.Print .Items.CellCaption(h, 0)
        Next
End With
The second method to iterate the items can be the following:
With ComboBox1
	Dim i As Long
	For i = 0 To .Items.ItemCount - 1
		Debug.Print .Items.CellCaption(.Items.ItemByIndex(i), 0)
	Next
End With

Can I loop through the items collection recursively?

Yes. The following function displays all child items ( recursively )

Sub RecItem(ByVal c As EXCOMBOBOXLibCtl.ComboBox, ByVal h As HITEM)
    If Not (h = 0) Then
        Dim hChild As HITEM
        With c.Items
            Debug.Print .CellCaption(h, 0)
            hChild = .ItemChild(h)
            While Not (hChild = 0)
                RecItem c, hChild
                hChild = .NextSiblingItem(hChild)
            Wend
        End With
    End If
end sub

Is there anyway to implement an MS Access-like NotInList event with this control?

The NotInList event occurs when the user enters a value in the text box portion of a combo box that isn't in the combo box list. The control doesn't fire this event if the FireNotInList property is False, so make sure that the property is set to True. The following sample shows how to add a new entry to the items list when NotInList event is fired:

Private Sub ComboBox1_NotInList()
    If MsgBox("Do you want to add it?", vbYesNo) = vbYes Then
        With ComboBox1
            Debug.Print .EditText(.SearchColumnIndex)
            Dim h As HITEM
            h = .Items.AddItem(.EditText(0))
            .Items.CellCaption(h, 1) = .EditText(1)
            .Items.SelectItem(h) = True
            .Items.EnsureVisibleItem h
        End With
    End If
End Sub

My control has multiple columns and I want the label displays only one column. Is this possible? 

Yes, the control provides a property called SingleEdit. The SingleEdit property specifies whether the control's label display one or all visible columns in the control. If the SingleEdit property is True, the SearchColumnIndex property determines the column being displayed on the control's label. The control uses the TAB key to navigate through the visible columns. Actually when TAB key ( or SHIFT + TAB combination ) , the control changes the SearchColumnIndex property to point to next visible column. If you want to avoid changing the searching column you have to use the UseTabKey property.

In our VB code we need to somehow differentiate between your control and a standard combobox control. How should we do?

If TypeOf ComboBox1 Is EXCOMBOBOXLibCtl.ComboBox Then
	Debug.Print "ExComboBox"
End If

My control displays multiple columns but no horizontal scroll is displayed. How can I show the horizontal scroll bar ?

The ColumnAutoResize property is what you are looking for. If the control's ColumnAutoResize property is True, the control arranges all visible columns to fit the control's client area. In this case no horizontal scroll bar is displayed. If the ColumnAutoResize property if False, control displays a horizontal scroll bar if the width of visible columns doesn't fit the width of the client area. 

Is there anyway to programmatically drop down the combo box list?

To programmatically drop down the window you can use the following trick:

Private Sub Command1_Click()
	ComboBox1.SetFocus
	SendKeys "{F4}"
End Sub

or the following ( it is recommended using this one ):

Private Sub Command1_Click()
	ComboBox1.DropDown() = True
End Sub
The AutoDropDown property allows control to drop down automatically it's window when user start typing characters.

I'm building an application where I have to load 50,000 records from a MS Access table using stored procedures.  Can I use your control this way?

Yes. You need to implement a simple interface called IUnboundHandler. The setup program installs few samples about implementing the unbound handler. Using notification interface it's easy and quicker than using events.

 The HeightList & WidthList properties don’t appear to be in twips. Could you tell me what the HeightList & WidthList properties are measured in?

All control properties that specifies a size or a coordinate are measured in pixels. Uses TwipsPerPixelX and TwipsPerPixelY properties to convert twips coordinates to pixel coordinates. The control's mouse events receive coordinates in twips, and they need to be converted if they are passed to one of the control's properties or methods. See ItemFromPoint method.  

Is there a special download for the UNICODE version?

Yes. You can find UNICODE versions here.

Does the control acts the same like a combobox in access2000?

Actually, the control does more than access2000 combobox does. You can see nice features in the control like: colors, font, pictures, hierarchy, filters and so on.

I want to change the font at runtime, and it seems that doesn't working?

Changing the Name property of the Font object doesn't notify the control that the used font has been changed, so calling ComboBox1.Font.Name = "Arial Unicode MS" has effect only for the control's drop-down window, but it doesn't change the font for control inside text editors. Remember that Font is a system object, and it is not implemented by the control, so that's the reason why the control is not notified that the user has changed the font's name. The following sample changes the font used by inside text editors as well for the drop-down window :

Dim f As New StdFont
f.Name = "Arial Unicode MS"
ComboBox1.Font = f

Is there any way I can set the selection to an empty string if the empty string is not one of the values in the combobox?

You have to use the SelectItem property. If the control's Style is DropDown, you have to reset the text in the label using the EditText property. 

With ComboBox1.Items
	if .SelectCount > 0 then 
		.SelectItem(.SelectedItem(0)) = False
	end if
End With

The functionality I am looking for is when you click an item in a tree it selects it, but does not close the tree. Can I do this with your product?

Yes. please set the CloseOnDblClk property. The CloseOnDblClk property specifies whether the user closes the drop down window by dbl click.

Just wondering if it is possible to place an excombox on a toolbar?

Yes. Place the control to your toolbar and then call:

Private Sub Form_Load()
    ComboBox1.Height = 128 * Screen.TwipsPerPixelY
End Sub

 I have run across a problem, the drop down portion of the control is very narrow and I can't figure out how to make it higher?

If you are going to resize the control at runtime, the HeightList property can be used to set the height of the dropdown window. The LabelHeight property helps you to specify the control's label height. You can resize the size of the drop down portion of the control at design time by doing the followings:

  • select the control ( the focused rectangle shows that the control is selected )
  • resize the control to the desired height and width
  • save the project 

Another way to resize your control at design mode is:

  • set the control's Style property to Simple ( by default, the control's Style is DropDown )
  • select the control and resize its list until you have the desired width and height for the list portion.
  • set the control's Style property to DropDown or DropDownList.
  • save the project 

If your control requires the size greater than the size of the form, you can resize the form, resize the control, and then resize back the form.

Does the excombobox control allow for checkboxes that look different from the default one shown in the demo?

The control provides properties like CheckImage and RadioImage properties that help you to set your desired icons for check or radio buttons.

I have problems with the performances of the control.

When you expect performance you have to be carefully to each line of code in your project. Here's few hints about improving performance when you are using the control:

  • The Items property performs a QueryInterface each time when it is called. It is recommended using a variable that holds the Items  property instead calling the property itself. For instance call set its = ComboBox1.Items when form is loaded, and use 'its' variable each time when you need to access the Items collection.
  • Use With .. End With statements each time you can. It avoids calling too many times a QueryInterface by the control. 
  • Holds an column to a variable instead calling Item property. For instance, the Item property of the Columns object looks for a column. The Add method of Columns object retrieves the added Column object. For instance use code like follows to add and initialize a column:
With ComboBox1.Columns
    With .Add("Column 1")
        .Width = 128
        .AllowSizing = False
        .AllowDragging = False
        .DisplaySortIcon = False
    End With
End With
or
With ComboBox1.Columns
    Dim c As EXCOMBOBOXLibCtl.Column
    Set c = .Add("Column 1")
    c.Width = 128
    c.AllowSizing = False
    c.AllowDragging = False
    c.DisplaySortIcon = False
End With
  • Use BeginUpdate and EndUpdate methods when multiple operations require changing the control.

  • Whenever you want to access an column use its index instead its name. For instance if the "Column 1" is the first column in the control use the .Items.CellCaption( Handle, 0 ) instead .Items.CellCaption( Handle, "Column 1"). or .Columns(0) instead .Columns("Column 1")
  • If you are using the control using the unbound mode make sure that the ReadItem method is light and easy. The ReadItem method is called each time when the control requires an item. Obviously, once that an item was retrieved when control requires the same item, it was already cached so no ReadItem method is called. Also an improvement to ReadItem method could be using a variable its ( that holds the control's Items property ) instead Source.Items. 
  • If you are using the unbound mode, but you still get data from a recordset make sure that you are using an index on the table instead using FindItem method. You can use also hash tables. The Select property uses the FindItem method that does a linear search.

Is there a way to change the tooltip and the first three captions in the drop down filter window?

The control's Description property helps you to change descriptions used by the control. For instance: the .Description( exFilterBarAll ) = "(Alle)" changes the description for the first item in the drop down filter list, or the Description( exFilterBarPatternTooltip ) = "Geben Sie hier das Muster nach dem Sie filtern wollen an. Als Platzhalter können *,? oder # benutzt werden. Zum Filtern drücken Sie ENTER Durch drücken der Strg – Taste können Sie mehrere Begriffe aus der Liste selektieren und danach filtern " changes the tooltip when the cursor is over the drop down list. 

You can run the following code to see the identifiers for the control's descriptions that you might want to change:

Private Sub Form_Load()
    With ComboBox1
        For i = 0 To 15
            .Description(i) = i
        Next
    End With
End Sub

If I have a value in the combobox like ' Cash & Pay! ' it appears as ' Cash _Pay! ' in the dropdown list?

Changes the UseMnemonic property to False.

Does control support merging cells?

The Items object provides properties like ItemDivider, ItemDividerLine helps you to merge cells of the row into a single cell. The setup installs a sample VB\Divider that helps you to understand how ItemDivider works. Also, the ItemDivider property helps you to group items in the control. The divider items are not scrolled when the user drags the horizontal scroll bar so the groups titles will be visible most of the time. The ItemDivider property specifies the index of cell being displayed instead displaying the entire item.

Can I add a picture to a cell?

The CellPicture property of the Items object helps you to attach a picture file ( bmp, gif, whatever ) to a cell. The following sample shows how to attach a picture to the first visible cell of the control:

With ComboBox1.Items
	.CellPicture(.FirstVisibleItem, 0) = LoadPicture("c:\winnt\Zapotec.bmp")
End With

or you can use the following way as well:

Dim p As IPictureDisp
Set p = LoadPicture("c:\winnt\Zapotec.bmp")
With ComboBox1.Items
	.CellPicture(.FirstVisibleItem, 0) = p
End With 

If the picture's height is larger than item's height you can use the ItemHeight property to let picture fits the item's client area. The .CellPicture accepts objects of IPictureDisp type. The LoadPicture function retrieves an IPictureDisp object.

Any plans to introduce simple HTML formatting inside cell?

The version 1.0.4.2 includes the built-in HTML format inside cells. The CellCaptionFormat property specifies how the cell's caption ( CellCaption property ) is displayed. If the CellCaptionFormat property is exText no HTML formatting is applied. Else, if the CellCaptionFormat property is exHTML the CellCaption is formatted using HTML tags. The list of valid tags are:
  • <b> tag - draws a text bolded until </b> is reached.
  • <br> tag - breaks the line.
  • <i> tag - draws the text using italic font attribute until </i> is reached.
  • <s> tag - draws the text using strikeout font attribute until </s> is reached.
  • <u> tag - draws the text using underline font attribute until </u> is reached.
  • <fgcolor=RRGGBB> tag - draws the text using the RGB(RR,GG,BB) foreground color. </u>, until </fgcolor> is reached. RR, GG and BB should be hexa values.
  • <bgcolor=RRGGBB> tag - draws the text using the RGB(RR,GG,BB) background color. </u>, until </bgcolor> is reached. RR, GG and BB should be hexa values.
  • < dotline > - draws a dotted line. 
  • < solidline > - draws a dotted line
  • < upline > - draws up the line
  • < r > - right aligns the line

For instance: the HTML formatting "<b>Inbox</b> <fgcolor=0000FF>(78)</fgcolor>" draws the Inbox using bold font attributes, and (78) using the blue color, like: Inbox (78)

It seems that I am not able to move the focus to the next control on the form if I press TAB key. Am I doing something wrong?

Usually, it's happen if the control's UseTabKey property is True. If the UseTabKey property is True, the control uses the TAB key to navigate through visible columns. If the UseTabKey is False, the control doesn't handle the TAB key, and so you will be able to move the focus to next control in the form, by pressing the TAB key.

When dynamically creating columns and settings their width the column's width is not what I've specified in the Width property?

You have to put ColumnAutoResize property on False. By default, the control's ColumnAutoResize property is True. If the ControlAutoResize is True, the sum of visible columns widths is equal with the width of the client area.

How do you suggest handling properties and methods for an exComboBox control into my VC project?

We recommend using #import directive to import the control's type library into your VC project. You don't need the control's TLB file. The dll file installed in your system folder exports the control's type library as well. For instance,  the #import "c:\winnt\system32\excombobox.dll" imports the control's type library to your project. By default, the #import directive creates a namespace EXCOMBOBOXLib.

How do I select a blank value?

The following snippet unselects the selected item:

With ComboBox1.Items
        If .SelectCount > 0 Then
            .SelectItem(.SelectedItem(0)) = False
        End If
End With

The AutoSearch behavior is case sensitive by special characters?

The control provides the ASCIILower and ASCIIUpper properties that helps you to specify the set of characters that are converted by the auto search feature. For instance if you have the set Ä/ä Ü/ü Ā/ā Ă/ă Ą/ą Ć/ć Ĉ/ĉ Ċ/ċ Č/č Ď/ď Ē/ē Ĕ/ĕ Ė/ė Ę/ę Ě/ě Ĝ/ĝ Ğ/ğ Ġ/ġ Ģ/ģ Ĥ/ĥ Ō/ō Ŏ/ŏ Ŕ/ŕ Ŗ/ŗ Ř/ř Ś/ś, you have to call something like: ASCIILower like "abcdefghijklmnopqrstuvwxyzäüā....", and ASCIIUpper like  "ABCDEFGHIJKLMNOPQRSTUVWXYZÄÜA...."

I'm having problems with selection events and functions. Could be that it's a demo control?

The DEMO version disables the SelectionChanged event, SelectItem, SelectCount and SelectedItem properties. If you require a fully functional version please contact us. We will send you an updated version.

Is there any way to associate an extra data to a column? As I know there is CellData for cells, and ItemData for items, but I couldn't find for column.

The Data property of the column holds an extra data. The Data value is not used by the control, it is of Variant type, and it can be used to store extra values for your columns.

I use your control into an ATL dialog and I cannot get GetDlgControl working as I expect. What do you suggest?

Can I determine what shows the edit control?

The EditText property gets the text in the edit control. If you have multiple columns the EditText( ColIndex ) gives the edit's text at the specified column.

Can I associate a key to a column?

The Key property of the Column object associates a key to a column. The Key and Caption properties are used by functions like Items.CellCaption, Items.CellBold, ... and so on. For instance,  the CellCaption( hItem, "ABC" ) gets the cell's caption for the item hItem on the column that has the caption "ABC" or it has the key = "ABC".

How can I assign multiple icons to a cell?

The CellImage property assign a single icon to the cell. Instead if multiple icons need to be assigned to a single cell you have to use the CellImages property. The CellImages property takes a list of additional icons and display them in the cell. The list is separated by ','  and should contain numbers that represent indexes to Images list collection. The following sample assign first and third icon to a cell:

With ComboBox.Items
        .CellImages(.ItemByIndex(0), 1) = "1,3"
End With

Is there any print and print preview support?

Yes, the Exontrol ExPrint component ( exprint.dll ) provides Print and Print Preview capabilities for the exComboBox component. Once that you can have the exPrint component in your Components list, insert a new instance of "ExPrint 1.0 Control Library" to your form and add the following code:

Private Sub Command1_Click()
    With Print1
        Set .PrintExt = ComboBox1.Object
        .Preview
    End With
End Sub

The Exontrol Print Preview mainframe looks like follows:

I want to handle myself how the columns get sorted when user clicks the column's caption. Is it possible?

The control provides the SortOnClick property that helps you to handle how the control sorts the columns when user clicks the column's header. The following sample shows how to sort a column using SortOrder property.

Private Sub Form_Load()
    ComboBox1.SortOnClick = exNoSort
End Sub

Private Sub ComboBox1_ColumnClick(ByVal Column As EXCOMBOBOXLibCtl.IColumn)
    Column.SortOrder = (Column.SortOrder + 1) Mod 3
End Sub

In this case if an user clicks a column, the column gets sorted like follows:

  • if the column was unsorted, it is sorted ascending
  • if the column was sorted ascendant, the control sorts the column descendent
  • if the column is descendent, the column becomes unsorted ( no sorting icon displayed on the column's header bar )   

You can simulate the exDefaultSort by using the following handler:

Private Sub ComboBox1_ColumnClick(ByVal Column As EXCOMBOBOXLibCtl.IColumn)
    Column.SortOrder = (Column.SortOrder + 1) Mod 3 + 1
End Sub

How can I determine if an item has child items?

You can use Items.ChildCount or Items.ItemChild property like follows:

If (ComboBox1.Items.ChildCount(h) <> 0) Then
End If

or

If (ComboBox1.Items.ItemChild(h) <> 0) Then
End If

The Items.ItemHasChildren property adds an expand button to the left side of the cell, no matter if the item contains child items. It is useful to build your virtual tree. 

I was wondering if it is possible to modify the Style property at runtime?

The Style property can be changed at runtime, starting with the version 1.0.5.7. If you are creating and removing the control dynamically and you need to set the appropriate Style property at runtime make sure that you are loading data after setting the Style property. The Style property clears the columns and items collections.

Is it possible to disable PageUp and PageDown keys?

The Key property replaces a virtual key that's used by the control.

The following sample disables the PageUp and PageDown keys:

ComboBox1.Key(vbKeyPageUp) = 0
ComboBox1.Key(vbKeyPageDown) = 0

The following sample shows how to open the drop down window when user hits the F2 key: ( by default, the control opens the drop down window if the user presses the F4 key )

ComboBox1.Key(vbKeyF4) = 0
ComboBox1.Key(vbKeyF2) = vbKeyF4

If I use the EditText property to clear the control's label, it doesn't work. What can I do?

The EditText property has effect only if the control's Style property is DropDown or Simple. The following sample shows how to change the control's label. 

With ComboBox1
        Dim bAutoSelect As Boolean
        Dim bAutoSearch As Boolean
        
        bAutoSelect = .AutoSelect
        bAutoSearch = .AutoSearch
        .AutoSelect = False
        .AutoSearch = False
        
        .EditText(0) = "new label"
        
        .AutoSelect = bAutoSelect
        .AutoSearch = bAutoSearch
End With

How do I remove the selected item?

The following sample shows how you can remove the selected item when user hits the Delete key:

Private Sub ComboBox1_KeyDown(KeyCode As Integer, Shift As Integer)
    If (KeyCode = vbKeyDelete) Then
        With ComboBox1
            If .Items.SelectCount() > 0 Then
            
                ' Removes the selected item, if there is one
                .Items.RemoveItem .Items.SelectedItem(0)
                
                If (.Style <> DropDownList) Then
                    ' Clears the control's label if it is required
                    Dim i As Long
                    For i = 0 To .Columns.Count - 1
                        .EditText(i) = vbNullString
                    Next
                End If
                
            End If
        End With
    End If
End Sub

I need to be able to insert an image in the edit part of the combo box, is that possible?

Yes. The EditImage property assign an icon to the column's edit box. If the icon doesn't exist no icon is displayed. The AssignEditImageOnSelect property automatically assigns the icon for the column's edit when the selection is changed.

How can I get the column that's sorted?

The SortOrder property of the Column object specifies the column's sort order. The following function retrieves the index of column that's sorted, or-1 if there is no sorted column:
Private Function getSortingColumn(ByVal g As EXCOMBOBOXLibCtl.ComboBox) As Long
    Dim c As EXCOMBOBOXLibCtl.Column
    For Each c In g.Columns
        If Not c.SortOrder = EXCOMBOBOXLibCtl.SortNone Then
            getSortingColumn = c.Index
            Exit Function
        End If
    Next
    getSortingColumn = -1
End Function

Does your control support incremental search?

Yes. The control supports 'start with' and 'contains' incremental search feature. The AutoSearch property specifies whether the incremental search is supported. The AutoSearch property of the Column object defines the type of incremental searching.

When using the incremental searching feature, how do you clear the search criteria that has been typed in?

The SearchColumnIndex property resets the searching string, so you can use a sample like follows:
Private Sub ComboBox1_LostFocus()
    Dim i As Long
    With ComboBox1
        i = .SearchColumnIndex
        .SearchColumnIndex = -1
        .SearchColumnIndex = i
    End With
End Sub

How can I show the drop down portion of the control as soon as it becomes active?

Call the DropDown property to show the drop down portion of the control. Use the DropDown property to show the drop down portion of the control when it gains the focus like in the following sample:
Private Declare Function SetCursorPos Lib "user32" (ByVal x As Long, ByVal y As Long) As Long
Private Declare Function GetCursorPos Lib "user32" (lpPoint As POINTAPI) As Long
Private Type POINTAPI
        x As Long
        y As Long
End Type
Dim p As POINTAPI

Private Sub ComboBox1_GotFocus()
    ComboBox1.DropDown() = True
    GetCursorPos p
    SetCursorPos p.x - 16, p.y
End Sub

Is there any option to show the drop down portion of the control when user presses the arrow down key? 

You can use a code like follows:
Private Sub ComboBox1_DropDown()
    ComboBox1.Key(vbKeyDown) = vbKeyDown
End Sub

Private Sub ComboBox1_DropUp()
  ComboBox1.Key(vbKeyDown) = vbKeyF4
End Sub

Private Sub ComboBox1_GotFocus()
    ComboBox1.Key(vbKeyDown) = vbKeyF4
End Sub

Thanks to Calvin Shields, who shared the note.

Can I make an item being not selectable?

Starting with the version 2.0.0.6, the control provides the SelectableItem property. The SelectableItem property specifies whether an item is selectable. A not selectable item is not focusable item. Use the EnableItem property to enable or disable an item.

Can I display a hidden column into the control's label?

Yes. It is possible. The AdjustSearchColumn property specifies whether the SearchColumnIndex property could refer a hidden column. Use the SingleEdit property to display a single column in the control's label. So, you need to set the AdjustSearchColumn property on False, and to specify the index of column being displayed on the control's label using the SearchColumnIndex property. For instance, let's say that the drop down window contains some information and we need to display other information when selecting an item. You can do it by drawing your self the control's label, or you can have a hidden column with the information that should be displayed on the control's label. Another case, could be if you would like to display single line item in the control's label even if the drop down portion of the control contains items using multiple lines.

Is there any option to drop down the control when user clicks the control?

The Click event is not fired when user the control's label, so you might want to check one of the following methods. If the Style property is DropDownList and the AutoDropDown property is True, the control shows the drop down portion of the control when user clicks the control's label area. The following samples use the DropDown method to programmatically show the drop down portion of the control.

The following samples uses different methods to drop down the control when user clicks the control's label area. In order to run any of the following sample, please insert the control to a form/dialog, and apply its default template ( so we have loaded columns and items ).

The following VB sample drops down the control when it receives the focus by clicking:

Private Declare Function GetMessagePos Lib "user32" () As Long
Private Declare Function WindowFromPoint Lib "user32" (ByVal xPoint As Long, ByVal yPoint As Long) As Long
Private Declare Function IsChild Lib "user32" (ByVal hWndParent As Long, ByVal hwnd As Long) As Long

Private Sub ComboBox1_GotFocus()
    With ComboBox1
        If (IsChild(.hwnd, WindowFromPoint(GetMessagePos() And &HFFF, GetMessagePos() / 65536))) Then
            .DropDown("") = True
        End If
    End With
End Sub

The sample calls the DropDown method when the control gains the focus. 

The following VC sample shows the drop down portion of the control when the user clicks the control's label area ( WM_PARENTNOTIFY method ):

void OnParentNotify(UINT message, LPARAM lParam) 
{
	CDialog::OnParentNotify(message, lParam);

	if ( LOWORD( message ) == WM_LBUTTONDOWN )
	{
		CRect rtClient;
		m_combobox.GetClientRect( &rtClient );
		m_combobox.ClientToScreen( &rtClient );
		ScreenToClient( &rtClient );
		POINT ptCursor = { ((long)(short)LOWORD(lParam)), ((long)(short)HIWORD(lParam)) };
		if ( PtInRect( &rtClient, ptCursor ) )
		{
			COleVariant vtMissing; V_VT( &vtMissing )= VT_ERROR;
			m_combobox.SetDropDown( vtMissing, TRUE );
		}
	}
	
}

The OnParentNotify method handles the WM_PARENTNOTIFY message of the Dialog class. A parent's OnParentNotify member function is called by the framework when its child window is created or destroyed, or when the user clicks a mouse button while the cursor is over the child window. The m_combobox wraps the control, and it is a member of the dialog class. The sample calls the DropDown method only if the user clicks the control's label area.

The following C# sample displays the drop down portion of the control when user clicks the control's label area:

protected override void DefWndProc( ref Message msg )
{
	base.DefWndProc( ref msg );

	if ( msg.Msg == 0x210 /*WM_PARENTNOTIFY*/ )
	{
		Point pt = new Point( msg.LParam.ToInt32() & 0xFFFF, msg.LParam.ToInt32() >> 16 );
		PointToScreen( pt );
		Control c = GetChildAtPoint(pt);
		if ( c != null )
			if ( c == axComboBox1 )
				axComboBox1.set_DropDown( "", true );
	}
}

The following VB.NET sample displays the drop down portion of the control when the user clicks the control's label area:

Protected Overrides Sub DefWndProc(ByRef m As Message)
    MyBase.DefWndProc(m)

    If (m.Msg = &H210) Then 'WM_PARENTNOTIFY
        Dim pt As Point
        pt.X = m.LParam.ToInt32() And &HFFFF
        pt.Y = m.LParam.ToInt32() / 65536
        Dim c As Control
        c = GetChildAtPoint(pt)
        If Not (c Is Nothing) Then
            If c Is AxComboBox1 Then
                AxComboBox1.set_DropDown("", True)
            End If
        End If
    End If
End Sub

The following VFP sample displays the drop down message when the control gains the focus by clicking the control's label area:

DECLARE LONG GetMessagePos IN user32

DECLARE LONG WindowFromPoint IN user32; 
	LONG   x,; 
	LONG   y
	
DECLARE LONG IsChild IN user32;
	LONG   hWndParent,; 
	LONG   hWnd

local x, y
x = Bitand(GetMessagePos(),4095)
y = Int(GetMessagePos() / 65536)
with thisform.ComboBox1
	if ( 0 # IsChild( .hWnd(), WindowFromPoint( x, y ) ) )
		.Object.DropDown("") = .t.
	endif
endwith  
  

I can't get the cursor when Style property is DropDown?

If the control has no columns, there is no edit control in the label area, so cursor can't show up. Use the Add method to insert new columns to the control.

How do I assign a new look for the selected item?

The component supports skinning parts of the control, including the selected item. Please check the control's help file for the Add method of the Appearance object. There you will find almost everything you need to change the visual appearance for most of the UI parts of the control. Shortly, the idea is that identifier of the skin being added to the Appearance collection is stored in the first significant byte of property of the color type. In our case, we know that the SelBackColor property changes the background color for the selected item. This is what we need to change. In other words, we need to change the visual appearance for the selected item, and that means changing the background color of the selected item. So, the following code ( blue code ) changes the appearance for the selected item:
With ComboBox1
    .VisualAppearance.Add &H34, App.Path + "\aqua.ebn"
    .SelBackColor = &H34000000
End With

Please notice that the 34 hexa value is arbitrary chosen, it is not a predefined value. Shortly, we have added a skin with the identifier 34, and we specified that the SelBackColor property should use that skin, in order to change the visual appearance for the selected item. Also, please notice that the 34 value is stored in the first significant byte, not in other position. For instance, the following sample doesn't use any skin when displaying the selected item:

With ComboBox1
    .VisualAppearance.Add &H34, App.Path + "\aqua.ebn"
    .SelBackColor = &H34
End With  

This code ( red code ) DOESN'T use any skin, because the 34 value is not stored in the higher byte of the color value. The sample just changes the background color for the selected item to some black color ( RGB(0,0,34 ) ). So, please pay attention when you want to use a skin and when to use a color. Simple, if you are calling &H34000000, you have 34 followed by 6 ( six ) zeros, and that means the first significant byte of the color expression. Now, back to the problem. The next step is how we are creating skins? or EBN files? The Exontrol's exbutton component includes a builder tool that saves skins to EBN files. So, if you want to create new skin files, you need to download and install the exbutton component from our web site. Once that the exbutton component is installed, please follow the steps.

Let's say that we have a BMP file, that we want to stretch on the selected item's background.

  1. Open the VB\Builder or VC\Builder sample
  2. Click the New File button ( on the left side in the toolbar ), an empty skin is created. 
  3. Locate the Background tool window and select the Picture\Add New item in the menu, the Open file dialog is opened.
  4. Select the picture file ( GIF, BMP, JPG, JPEG ). You will notice that the visual appearance of the focused object in the skin is changed, actually the picture you have selected is tiled on the object's background.
  5. Select the None item, in the Background tool window, so the focused object in the skin is not displaying anymore the picture being added.
  6. Select the Root item in the skin builder window ( in the left side you can find the hierarchy of the objects that composes the skin ), so the Root item is selected, and so focused.
  7. Select the picture file you have added at the step 4, so the Root object is filled with the picture you have chosen.
  8. Resize the picture in the Background tool window, until you reach the view you want to have, no black area, or change the CX and CY fields in the Background tool window, so no black area is displayed.
  9. Select Stretch button in the Background tool window, so the Root object stretches the picture you have selected.
  10. Click the Save a file button, and select a name for the new skin, click the Save button after you typed the name of the skin file. Add the .ebn extension.
  11. Close the builder

You can always open the skin with the builder and change it later, in case you want to change it.

Now, create a new project, and insert the component where you want to use the skin, and add the skin file to the Appearance collection of the object, using blue code, by changing the name of the file or the path where you have selected the skin. Once that you have added the skin file to the Appearance collection, you can change the visual appearance for parts of the controls that supports skinning. Usually the properties that changes the background color for a part of the control supports skinning as well.

How can I display a tooltip when user hovers an anchor element?

Use the ShowToolTip method and AnchorFromPoint property to display a tooltip when user hovers an anchor element.

How can I display currency format within the column?

There are several options in order to display a different content for the column. By default, the Items.CellCaption property indicates the value being shown in the cell.
  1. Column.FormatColumn property specifies a formula to display the column's new content, using predefined functions for numbers, strings, dates and so on.
  2. Change the Value parameter of the FormatColumn event which is fired if the Column.FireFormatColumn property is True. For instance the following sample displays  the second column using current currency format with 2 decimals. The Item parameter of the FormatColumn event indicates the item where the cell is hosted, the ColIndex indicates the column where the cell belongs, while the Value parameter indicates the cell's value before formatting and after. In case you need formatting multiple columns, you can distingue them using the ColIndex parameter.
    Private Sub ComboBox1_FormatColumn(ByVal Item As EXCOMBOBOXLibCtl.HITEM, ByVal ColIndex As Long, Value As Variant)
        Value = FormatCurrency(Value, 2, vbUseDefault)
    End Sub
    
    Private Sub Form_Load()
        With ComboBox1
            .BeginUpdate
            .Columns.Add "A"
            .Columns.Add("B").FireFormatColumn = True ' Index of it is 1
            With .Items
                .AddItem Array("One", 1)
                .AddItem Array("Two", 2)
            End With
            .EndUpdate
        End With
    End Sub
  3. Items.CellOwnerDraw property indicates an object that perform owner draw on cells.

What is the best way to loop or enumerate through all the items in the control and extract cell data?

There are the several ways of enumerating the items/cells in the control. The following samples are in VB, but they can be easily converted to any other programming language. This samples shows you an idea how easily you can enumerate through the items.

A). Using the GetItems method of the control. The GetItems method gets the items as they are displayed, sorted and filtered to an array or vector. Also, the GetItems method collect the child items as well, no matter if the parent item is collapsed. The GetItems method returns an array. For instance, if your control contains 1 column, the GetItems will retrieves a one-dimensional array. A 2 columns will get a two-dimensional array, an so on. You can use the PutItems method to insert the array to the control.

B). Using the for each statement for Items property of the control. The Items property gets a collection of items as they were added. This method lists the items by index not by their positions. The items is represented by handles, so the handle can be used in the Cell properties to refer the cell. For instance, Items.CellCaption(Handle,Column) gets the cell from the Item with the specified handle on specified column. The following sample displays the cells in the first column as they were added:

With ComboBox1
        Dim h As Variant
        For Each h In .Items
            Debug.Print .Items.CellCaption(h, 0)
        Next
End With

If you need to access multiple columns add the Debug.Print .Items.CellCaption(h, 1), Debug.Print .Items.CellCaption(h, 2) ... for each column you require.

C). A similar approach to B is using the Items.ItemCount and Items.ItemByIndex properties. This method lists the items by index not by their positions.

With ComboBox1
    Dim i As Long
    With .Items
        For i = 0 To .ItemCount - 1
            Debug.Print .CellCaption(.ItemByIndex(i), 0)
        Next
    End With
End With

The Items. ItemByIndex retrieves the handle of the item giving its index. For instance, the first added item has the index 0, the second added item has the index 1, and so on.

D). Using the Items.NextVisibleItem property. This method gets the items as they are displayed, sorted and filtered.

With ComboBox1
    With .Items
        Dim h As Long
        h = .RootItem(0)
        While Not h = 0
            Debug.Print .CellCaption(h, 0)
            h = .NextVisibleItem(h)
        Wend
    End With
End With

E). Using the Items.ItemChild and Items.NextSiblingItem property. This method enumerates recursively the items and its children. This method gets the items as they are displayed, sorted and filtered, including the children items that are not visible aka parent item is collapsed.

With ComboBox1
    With .Items
        For i = 0 To .RootCount - 1
            RecItem ComboBox1, .RootItem(i)
        Next
    End With
End With
Sub RecItem(ByVal c As Object, ByVal h As Long)
    If Not (h = 0) Then
        Dim hChild As Long
        With c.Items
            Debug.Print .CellCaption(h, 0)
            hChild = .ItemChild(h)
            While Not (hChild = 0)
                RecItem c, hChild
                hChild = .NextSiblingItem(hChild)
            Wend
        End With
    End If
End Sub

Can I use arrays to load to your control?

Here's some ideas on how you can use arrays with the control.

A). Using the GetItems/PutItems to get or put the items/cells using arrays. The GetItems method gets the items/cells of the control to a safe array. The PutItems inserts the array of values to the control. For instance the following sample adds 3 columns and 1001 items from an array:

With ComboBox1
    .Columns.Add "C1"
    .Columns.Add "C2"
    .Columns.Add "C3"
    Dim v(2, 1000) As String
    v(1, 10) = "zece"
    .PutItems v
End With

In VB the arrays is zero-based, so 2 indicates actually 0, 1 and 2 ( 3 columns ).

B). You can use the PutItems method to insert a hierarchy, for single-column control. The following sample adds a hierarchy as Root\Child 1, Child 2\SubChild 1, SubChild 2

With ComboBox1
    .LinesAtRoot = exLinesAtRoot
    .Columns.Add "Nodes"
    .PutItems Array("Root", Array("Child 1", "Child 2", Array("SubChild 1", "SubChild 2")))
End With

C). You can use the arrays to fill a multiple-columns control in Items.AddItem/Items.InsertItem methods as in the following sample:

With ComboBox1
    .Columns.Add "C1"
    .Columns.Add "C2"
    .Columns.Add "C3"
    With .Items
        .AddItem Array("Cell 1.1", "Cell 1.2", "Cell 1.3")
        .AddItem Array("Cell 2.1", "Cell 2.2", "Cell 2.3")
    End With
End With

How do I jump to another control in the form if the user presses the ENTER key? 

The idea is to handle the KeyDown event, and to use the UseTabKey property on False like in the following VB6 sample:
Private Sub ComboBox1_KeyDown(KeyCode As Integer, Shift As Integer)
    If (KeyCode = vbKeyReturn) Then
        SendKeys "{TAB}"
        KeyCode = 0
    End If
End Sub

Private Sub Form_Load()
    ComboBox1.UseTabKey = False
End Sub

The sample sends the TAB key when user presses the ENTER key, so the form will jump to another control in the form. The sample uses the VB6's SendKeys method to send a key to the focused control ( as the KeyDown is called, the control has the focus, so also itself receives the new key being sent by the SendKeys method )

In VFP you can use the following alternative for KeyDown event of the control:

*** ActiveX Control Event ***
LPARAMETERS keycode, shift

IF ( keycode = 13 ) then
	keycode = 0
	KEYBOARD '{TAB}'
ENDIF

The equivalent of VB's SendKeys method in VFP is KEYBOARD method as used in the previously sample.

Can I scroll the control's content by touching the capacitive screen with fingers?

The AutoDrag property indicates what the control does when the user clicks an item and starts dragging it. For instance, using the AutoDrag feature you can automatically lets the user to drag and drop the data to OLE compliant applications like Microsoft Word, Excel and so on. In order to let user scrolls the control's content set the AutoDrag property on:
  • AutoDragEnum.exAutoDragScrollOnShortTouch + AutoDragEnum.exAutoDragScroll