Forms unit

forms.pp contains classes, types, and routines used to implement forms, which are the basis for the graphical user interface in the Lazarus Component Library ( LCL).

The following components are added to the Lazarus IDE component palette:

Standard Tab

• TFrame

Additional Tab

• TScrollBox
• TApplicationProperties

The unit also includes the TApplication and TScreen classes used in the Application and Screen singletons.

Classes and records

EScrollBar	class	Exception class raised in .
TApplication	class	Application management and configuration for a GUI application.
TApplicationProperties	class	A component that provides access to the properties for the current application.
TAsyncCallQueue	record	Represents an asynchronous callback queue.
TAsyncCallQueueItem	record	Record used for a queued asynchronous callback request.
TAsyncCallQueues	record	Management information for asynchronous callbacks.
TCMHintShow	record	Provides access to members in a CM_HINTSHOW control message.
TCMHintShowPause	record	Not used in the current LCL implementation.
TControlScrollBar	class	Scroll bar type used in TScrollingWinControl.
TCursorRec	record	Contains information about a cursor shape.
TCustomDesignControl	class	Provides a designer surface for scaling and layout of its child controls.
TCustomDockForm	class	A floating DockSite used to make TControls float.
TCustomForm	class	The base type for TForm classes.
TCustomFrame	class	The base type for TFrame.
TCustomHintAction	class	Represents a standard action used to get a Hint value.
TForm	class	Implements a form used in an LCL application.
TFormPropertyStorage	class	TFormPropertyStorage - class for storage of a Form's properties.
TFrame	class	Frames can be designed like Forms and used like custom controls, without much coding or installation in the IDE.
THintInfoAtMouse	record	Stores control and mouse position information for a hint display.
THintWindow	class	The pop-up box containing helpful information that appears when the mouse pointer hovers over an object.
THintWindowRendered	class	For a rendered hint with a child control added by an external provider.
TIDesigner	class	The abstract base class for visual Form designers.
TMonitor	class	Provides information about a physical monitor.
TMonitorList	class	A list of monitors available on the system.
TScreen	class	Provides information about screen displays in an application.
TScrollBox	class	Implements a windowed control with scroll bars.
TScrollingWinControl	class	Implements a windowed control with scroll bars.
TWindowMagnetManager	class	Implements a manager for form and screen snapping behavior in an application.
TWindowMagnetOptions	class	Implements options which control magnetic window behavior in form instances.

Procedures and functions

CreateWidgetset	procedure	Creates the widgetset singleton.
dbgs	function	Formats debugger messages for various types by converting their values into readable text.
FindRootDesigner	function	Gets the designer object for the specified persistent object (or its parent).
FreeWidgetSet	procedure	Destroys singletons for the Screen, Application, and WidgetSet.
GetDesignerForm	function	Gets the Form with the designer object for the specified control or persistent object.
GetFirstParentForm	function	Performs a recursive search for the first Parent of type TCustomForm.
GetLongHint	function	Returns the long version of a Hint string.
GetParentDesignControl	function	Gets the control which is the top-most TCustomDesignControl instance for the specified control, or Nil when not a TCustomDesignControl instance.
GetParentForm	function	Gets the form instance for the specified Control.
GetShortHint	function	Returns the short version of a Hint string.
GetTopFormSkipNonDocked	function	Gets the top-most form which hosts the specified control docksite form instances.
IsAccel	function	Determines whether the specified virtual key is used as an accelerator (short cut) in the given caption string.
KeyboardStateToShiftState	function	Converts virtual key state codes to TShiftState values.
KeyDataToShiftState	function	Converts modifier keys from the LParam in a keyboard message (WM_KEYUP for example) to a TShiftState value.
KeysToShiftState	function	Converts modifier keys in the LParam for a mouse message to a TShiftState value.
NeedParentDesignControl	function	Ensures that a TCustomDesignControl instance is found for the specified control.
NotifyApplicationUserInput	procedure	Signals all user input handlers for the application using the specified message.
Register	procedure	Registers components declared in this unit.
RestoreFocusState	procedure	Restores the previous focus state for an application to the specified value.
SaveFocusState	function	Saves the last focus state (focused control) in an application.
ShiftStateToKeys	function	Converts a shift state into a key state value compatible with the key state of a Windows API LParam.
StrToWindowState	function	Converts a string to a TWindowState enumeration value.
ValidParentForm	function	Gets a valid parent form for the specified control.
WindowStateToStr	function	Converts a TWindowState enumeration value to its String representation.

Types

PAsyncCallQueueItem	type	A queued asynchronous callback request node.
PCursorRec	type	Contains information about a cursor shape.
PModalResult	type	Dummy type for the values that can be returned as a modal result.
TAppHintTimerType	enumeration	Represents TApplication hint timer states.
TApplicationDoubleBuffered	enumeration	Enumeration with values used in the DoubleBuffered property in TApplication.
TApplicationExceptionDlg	enumeration	Enumeration with dialog types for an application.
TApplicationFlag	enumeration	Application state flags.
TApplicationFlags	set	Set type used to store values from the TApplicationFlag enumeration.
TApplicationGlyphDrawEffectsEnabled	enumeration	Controls glyph drawing effects for mouse-over and mouse-down events in an application.
TApplicationHandlerType	enumeration	Types of Application notification handlers.
TApplicationNavigationOption	enumeration	Which keys can be used for the navigation within a form.
TApplicationNavigationOptions	set	Which keys can be used for the navigation within a form.
TApplicationShowGlyphs	enumeration	Indicates the application policy for displaying glyphs on menus and buttons.
TApplicationType	enumeration	Identifies the kind of device where the application currently runs.
TBorderIcon	enumeration	Represents a visual element in a window title bar; depends on window manager support.
TBorderIcons	set	Represents a visual element in a window title bar; depends on window manager support.
TCloseAction	enumeration	Represents actions that can occur when a form is closed.
TCloseEvent	procedure type	Type used for an OnClose event handler in a form.
TCloseQueryEvent	procedure type	Specifies an OnCloseQuery handler event handler.
TCustomFormClass	type	Class reference for the TCustomForm class.
TCustomFrameClass	type	Class type used to create new instances of TCustomFrame.
TDataEvent	procedure type	Specifies the type used for an asynchronous callback method.
TDefaultMonitor	enumeration	The preferred monitor for showing a form.
TDropFilesEvent	procedure type	Type used for an OnDropFiles event handler.
TExceptionEvent	procedure type	Defines an event handler signalled to perform exception handling in an application.
TFocusState	type	Pointer to focus state information for the last active control in an application.
TFormClass	type	Class type used to create new TForm instances.
TFormHandlerType	enumeration	TForm Notification handler types.
TFormState	set	Set type used to store values from the TFormState enumeration.
TFormStateType	enumeration	Form state flags.
TGetDesignerFormEvent	procedure type	Specifies an event handler signalled to get the form with the designer for a persistent object.
TGetHandleEvent	procedure type	Specifies an event handler used to get the handle for the main form in an application.
THelpEvent	procedure type	Type used for an OnHelp event handler.
THintWindowClass	type	Class of THintWindow.
TIdleEvent	procedure type	Specifies an event handler signalled when an application becomes idle.
TIsFormDesignFunction	procedure type	Specifies a Boolean function type used to implement the routine assigned to the IsFormDesign variable.
TLogMessageEvent	procedure type	Defines an event handler signalled to handle log messages written using the TApplication.Log method.
TMessageBoxFunction	procedure type	The type used for the MessageBox variable.
TModalDialogFinished	procedure type	Specifies an event handler signalled when a modal message dialog is completed.
TModalResult	type	Dummy type for the values that can be returned as a modal result.
TMonitorDefaultTo	enumeration	The monitor to use when screen coordinates are outside of the physical bounds for the screens.
TOnUserInputEvent	procedure type	Specifies an event handler signalled to respond to user input messages in an application.
TPopupMode	enumeration	Defines the handling performed for a parent window in forms and dialogs.
TPosition	enumeration	Represents the Position and Size of a Form on Screen.
TProcedure	procedure type	Type used for a procedure that takes no arguments.
TProcedureOfObject	procedure type	Type used for an object procedure that takes no arguments.
TQueryEndSessionEvent	procedure type	Specifies an event type used to handle a WM_QUERYENDSESSION window message in an application.
TScreenControlEvent	procedure type	Type for a screen notification handler used for control-related events.
TScreenFormEvent	procedure type	Type used for a screen notification handler for form-related events.
TScreenNotification	enumeration	Screen notification events and handler types.
TScrollBarInc	type	The range for scroll bar increments.
TScrollBarKind	enumeration	The orientation of a scroll bar.
TScrollBarStyle	enumeration	Scroll bar style flags.
TShortCutEvent	procedure type	Type used for an OnShortcut event handler.
TShowHintEvent	procedure type	Defines an event handler signalled to perform hint display.
TShowInTaskbar	enumeration	Identifies the display preference for a form on the TaskBar.
TTaskBarBehavior	enumeration	How forms are represented in the TaskBar.
TTileMode	enumeration	Values representing the arrangement order for tiled MDI child windows.
TWindowState	enumeration	Represents the actual State of the window on the screen.

Constants

DefaultApplicationBiDiMode	constant	Contains the default BiDiMode value used for the current LCL version.
DefaultBorderIcons	constant	Maps form border styles to their border icons.
DefHintColor	constant	The default hint window background color.
DefHintHidePause	constant	The default pause (in milliseconds) before a hint is hidden.
DefHintHidePausePerChar	constant	The default pause (in milliseconds) added to DefHintHidePause.
DefHintPause	constant	The default pause before the hint window is displayed (in milliseconds).
DefHintShortPause	constant	The default pause (in milliseconds) before a Hint is re-displayed.

Variables

Application	variable	The TApplication singleton.
ExceptionObject	variable	Variable representing the current exception object in an application.
HintWindowClass	variable	The class type used to create hint window instances for an application.
IsFormDesign	variable	Address of the function used to determine if a specified control is a form designer.
MessageBoxFunction	variable	Provides the routine used to display a message dialog in widgetset implementations.
OnGetDesignerForm	variable	Event handler signalled to get the designer form for the specified form or control.
RequireDerivedFormResource	variable	When True every form must have a resource (e.g. a .res file). An exception is raised if the resource is missing when creating a form.
Screen	variable	The TScreen singleton for the application.

Uses

• Classes
• SysUtils
• Types
• TypInfo
• Math
• CustApp
• System.UITypes
• LCLStrConsts
• LCLType
• LCLProc
• LCLIntf
• LCLVersion
• LCLClasses
• InterfaceBase
• LResources
• Graphics
• Menus
• LMessages
• CustomTimer
• ActnList
• Clipbrd
• HelpIntfs
• Controls
• ImgList
• Themes
• LazFileUtils
• LazUTF8
• Maps
• IntegerList
• LazMethodList
• LazLoggerBase
• Laztracer
• LazUtilities
• GraphType