The DDButton control allows developers to build custom drop-down and
auto-complete controls with literally few lines of code.
Architecture
Technically, the drop-down control you implement using DDButton has three
elements:
-
The DDButton control.
-
The parent control(s) that saves the user input. This can be the DDButton
control itself, or any other control (e.g., a text box, picture box, etc.).
-
The form to be dropped down.
The DDButton control may be used as a container (control property IsContainer=True)
or as a standalone control (IsContainer=False).
When you use DDButton as a container, it is automatically made a parent
control. And, in the most simple case you can use the DDButton control's Text
property to display the user input from the drop-down form.
The DDButton control supports automatic resizing based on the font size. So,
the control you create as described above will look just like a regular combo
box.
To allow users edit the text in the control, place a text box inside the
DDButton control. Since DDButton supports docking, your text box can resize
automatically when the DDButton control is resized.
To display anything else but the text (e.g., an icon next to a user name), you
can place any controls you need inside the DDButton control:
The control on the picture above is comprised of two image controls and two
edit boxes inside a DDButton control.
When DDButton is used as standalone control, you can bind a parent control from
the code:
Together with the possibility to programmatically drop (at custom location) and
hide the drop-down form this in fact allows developers to use any control as
"drop down button".
Standalone DDButton control can also be used to create auto-complete tools. For
details, see the Creating Auto-Complete Tools section later in this
topic.
Drop-Down Form Behavior
The dropped form behaves much like a common drop-down list. The form will be
automatically dropped in right direction if there is no space to drop it in
default direction, and will automatically hide in all cases when the typical
dropped window does.
The difference from the regular dropped windows is that the drop-down form
doesn't automatically hide if the focus belongs to the parent control (or to a
control inside the parent DDButton control) or to the form itself. This fact
makes it possible to create complicated drop-down forms, e.g. treeviews,
checklists, grids, etc.
Good news is that you can make the drop-down form resizable using the Alter
Sourcing's Grip control. For details, see the Grip Control chapter.
The drop-down direction can be customized:
If there is no space to show the entire form, its position and drop direction
will be adjusted.
Creating Auto-Complete Tools
DDButton also allows for easy implementation of auto-complete windows:
In this case the edit box is the parent control, and the drop-down form is
displayed and hidden programmatically in response to the keyboard input.
Control Appearance
The DDButton control appearance can be customized using four properties. Below
find some examples of control appearance:
The control size can be adjusted automatically when user changes the font size.
Windows XP Themes
DDButton fully supports the Windows XP themes. When user changes the theme, or
changes the appearance from Windows Classic to Windows XP and
back, appropriate event is raised and the DDButton control appearance is
changed automatically.
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