Form/Ocx Form Object

Purpose

A Form object is a window or dialog box that makes up part of an application's user interface.

Syntax

Form

Description

Forms are the foundation for creating the interface of an application. You can use forms to add windows and dialog boxes to your application. You can also use them as containers for items that are not a visible part of the application's interface. For example, you might have a form in your application that serves as a container for graphics that you plan to display in other forms.

You can design a form using the Form Editor or create them in code. A form designed with the Form Editor is brought into the program using the LoadForm command. In code, forms are created by Form, OpenW, Ocx Form, ParentW, ChildW, and Dialog .

To close and destroy a Form, the appropriate method or command must be used; Forms can not be closed/destroyed using Nothing as other objects can.

Forms have properties that determine aspects of their appearance, such as position, size, and color; and aspects of their behavior, such as whether or not they are resizable.

Forms can also respond to events initiated by a user or triggered by the system. For example, you could write code in a form's Click event procedure that would enable the user to change the color of a form by clicking it.

In addition to properties and events, you can use methods to manipulate forms using code. For example, you can use the Move method to change a form's location and size.

When designing forms, set the BorderStyle property to define a form's border, and set the Caption property to put text in the title bar. In code, you can use the Hide and Show methods to make forms invisible or visible at run-time.

Properties

The PictureMode property determinates how the Form picture is displayed (0 = default, 1 = Tile, 2 = stretched).

Methods

Events

Some properties are only valid for an Ocx Form, a form used as a control. For instance, a non-Ocx form cannot have a Parent, but an Ocx can and does (more accurately, interrogating Parent for a non-Ocx Form is returns a reference to itself - if youi need to find it's Parent, use the GetParent(hWnd) API function).

Remarks

Note Setting the BorderStyle to 0 removes the border. If you want your form to have a border without the title bar or Control-menu box, delete any text from the form's Caption property and set the form's ControlBox properties to False.

Positional and size propeties (Top, Left, Width, Height, etc) use different unit types, dependant upon the type of Form being set/read: Ocx Forms use pixels and non-Ocx Forms/Windows twips. There is no definitive way to tell the difference programmatically between the different Form types (the relevant values are stored in the internal GB32 Form Value Tables which can not be directly referenced) and the functions IsObject and IsControl return True for all types; all forms return "Form" when interrogated with TypeName and if you interrogate the control, the class names are all the same. The FormType function in the example below is the closest one can come to differentiating, but be warned that there will be rare instances where it will not work correctly:

OpenW 1

OpenW Owner Win_1, 2

OpenW MdiParent 4

OpenW MdiChild Owner Win_4, 3

Form frm1

Ocx Form frx = "", 10, 10, 100, 100

Ocx ComboBox cbx

Trace FormType(Win_1) // 1 (Window/Form)

Trace FormType(Win_2) // 1 (Window/Form) - There is no way of telling if a Window is owned in code

Trace FormType(Win_3) // 3 (MdiChild Window)

Trace FormType(Win_4) // 2 (MdiParent Window)

Trace FormType(frm1) // 1 (Window/Form)

Trace FormType(frx) // 4 (Ocx Form)

Trace FormType(cbx) // -3 (Not a Form)

CloseW 2

Trace FormType(Win_2) // -1 (Object is Nothing)

Debug.Show

Function FormType(ctrl As Control)

If IsNothing(ctrl) Then Return -1 // Control does not exist

If Not IsObject(ctrl) Then Return -2 // Value passed not an Object

If TypeName(ctrl) <> "Form" Then Return -3 // Control passed not a form

If GetParent(ctrl.hwnd) <> 0

If ctrl.MdiChild Then Return 3 // Form is MdiChild window

Return 4 // Form is OCX Form

EndIf

If ctrl.MdiParent Then Return 2 // Form is MdiParent

Return 1 // Form is Form/Window

EndFunction

Known Issues

[Solved in OCX version 2.38] Using Ocx Forms in windows created using OpenW can cause Memory Access issues. Once again, closing the IDE and reloading solves this for a short while but the problem usually reappears. The reason for this is unknown; the workaround is to open the window using the Form Command instead.
[Reported by James Gaite, 25/05/2020]

The DDEWndProc, Message and MessageProc events do not work for OCX Forms if they are part of an array; it appears that the code was never written to handle these message routines.
[Reported by James Gaite, 03/05/2022]