Class # RectControl ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Warning

This item was deprecated in version 2021r3. Please use `DesktopUIControl` as a replacement.

## Description RectControl is the base class for most other control classes. This means that all controls inherit the properties of the RectControl. A RectControl cannot be created or modified directly. Instead, you create and modify the RectControl subclasses like `PushButtons`, `TextFields`, `ListBoxes`, etc. ## Properties

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| Name | Type | Read-Only | Shared | |--------------------------------------------------------|--------------------------------------------------------|-----------|--------| | `Active` | `Boolean` | ✓ | | | `AllowAutoDeactivate` | `Boolean` | | | | `AllowTabStop` | `Boolean` | | | | `Enabled` | `Boolean` | | | | `Handle` | `Integer` | ✓ | | | `Height` | `Integer` | | | | `Index` | `Integer` | ✓ | | | `Left` | `Integer` | | | | `LockBottom` | `Boolean` | | | | `LockLeft` | `Boolean` | | | | `LockRight` | `Boolean` | | | | `LockTop` | `Boolean` | | | | `MouseCursor` | `MouseCursor` | | | | `MouseX` | `Integer` | ✓ | | | `MouseY` | `Integer` | ✓ | | | `Name` | `String` | ✓ | | | `PanelIndex` | `Integer` | | | | `Parent` | `Control` | | | | `Scope` | `Integer` | ✓ | | | `TabIndex` | `Integer` | | | | `Tooltip` | `String` | | | | `Top` | `Integer` | | | | `Transparent` | `Boolean` | | | | `TrueWindow` | `Window` | ✓ | | | `Visible` | `Boolean` | | | | `Width` | `Integer` | | | | `Window` | `Window` | ✓ | | ## Methods

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| Name | Parameters | Returns | Shared | |----------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------|--------| | `AcceptFileDrop` | FileType As `String` | | | | `AcceptPictureDrop` | | | | | `AcceptRawDataDrop` | Type As `String` | | | | `AcceptTextDrop` | | | | | `Close` | | | | | `DrawInto` | g As `Graphics`, x As `Integer`, y As `Integer` | | | | `Invalidate` | \[EraseBackground As `Boolean`\] | | | | `Refresh` | eraseBackground As `Boolean` | | | | | x As `Integer`, y As `Integer`, width As `Integer`, height As `Integer`, eraseBackground As `Boolean` | | | | `SetFocus` | | | | ## Events

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| Name | Parameters | Returns | |----------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------| | `Close` | | | | `ConstructContextualMenu` | Base As `MenuItem`, x As `Integer`, y As `Integer` | `Boolean` | | `ContextualMenuAction` | HitItem As `MenuItem` | `Boolean` | | `DragEnter` | obj As `DragItem`, Action As `Integer` | `Boolean` | | `DragExit` | obj As `DragItem`, Action As `Integer` | | | `DragOver` | x As `Integer`, y As `Integer`, obj As `DragItem`, Action As `Integer` | `Boolean` | | `DropObject` | Obj As `DragItem` Action As `Integer` | | | `KeyDown` | Key As `String` | `Boolean` | | `KeyUp` | Key As `String` | | | `MouseEnter` | | | | `MouseExit` | | | | `MouseMove` | X As `Integer`, Y As `Integer` | | | `MouseWheel` | X As `Integer`, Y As `Integer`, DeltaX As `Integer`, DeltaY As `Integer` | `Boolean` | | `Open` | | | ## Constants The following class constants of the `DragItem` class can be used to specify the value of the *Action* parameter with the `DragEnter`, `DragExit`, and `DragOver` events. | Class Constant | Description | |-------------------|------------------------| | DragActionDefault | Default action. | | DragActionCopy | Copy the dragged item. | | DragActionMove | Move the dragged item. | | DragActionLink | Link the dragged item. | ## Property descriptions

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RectControl.Active **Active** As `Boolean` Indicates whether the RectControl is active. This property is read-only. Active is `False` when the RectControl's window is not in the foreground. When a `Window` is deactivated, its controls are automatically deactivated unless `AllowAutoDeactivate` is set to `False`.

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RectControl.AllowAutoDeactivate **AllowAutoDeactivate** As `Boolean` Determines whether the control should be deactivated (on macOS) when the parent window is deactivated. The default is `True`.

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RectControl.AllowTabStop **AllowTabStop** As `Boolean` If `True`, the RectControl is in the Tab Order and accepts the focus when the user tabs into it. The default is `True`. If `False`, the user cannot tab into it to give it the focus. However, the RectControl can gain the focus by other means, such as the user's clicking on it or by setting the focus in code. This example removes the control from the Tab Order: ``` xojo Me.AllowTabStop = False ```

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RectControl.Enabled **Enabled** As `Boolean` Determines if the control should be enabled when the owning window is opened. A disabled control cannot be clicked and cannot receive the focus. This example disables the control. Its caption is grayed out. ``` xojo Me.Enabled = False ```

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RectControl.Handle **Handle** As `Integer` Returns a handle to the control. This property is read-only. For interfacing with Mac APIs using `` Declare`s, `RectControl ``.Handle returns NSViews (except for `Toolbar`). On Windows returns the HWND of the control. On Linux it returns a GtkWidget. The following gets a handle to the control. ``` xojo Var i As Integer = Me.Handle ```

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RectControl.Height **Height** As `Integer` The height (in points) of the control. This example sets the height of the control to 100: ``` xojo Me.Height = 100 ```

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RectControl.Index **Index** As `Integer` If the control is used in a control set, this specifies the control's index in the set. This property is read-only. The *control set* is often used to manage a group of RadioButtons since a single RadioButton in a window doesn't make much sense. Most typically, you create an instance of the RadioButton, assign 0 to its Index property, and then duplicate it. This increments the value of Index for each new instance but retain the original control's name. To determine which RadioButton the user clicked, use the Action event handler of the control set. The parameter *Index* contains the value of Index for the RadioButton that was clicked. The event handler is this: ``` xojo Sub Action(Index As Integer) Label1.Text = "You chose radio button " + index.ToString + "." End Sub ``` To set a RadioButton in a control set, you use its *Index* property to refer to the RadioButton whose value you want to set. For example, the following line selects the second RadioButton from code: ``` xojo RadioButton1(1).Value = True ' 0-based ```

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RectControl.Left **Left** As `Integer` The left side of the control in local coordinates (relative to the window). The following example moves the control 100 points from the left side of the window: ``` xojo Me.Left = 150 ```

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RectControl.LockBottom **LockBottom** As `Boolean` Determines whether the bottom edge of the control should stay at a set distance from the bottom edge of the parent control, if there is one, or the owning window. This property can be set in the control's Inspector. The following example sets it in code. ``` xojo Me.LockBottom = True ```

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RectControl.LockLeft **LockLeft** As `Boolean` Determines whether the left edge of the control should stay at a set distance from the left edge of the parent control, if there is one, or the owning window. Beginning with version 2009r5, LockLeft and Locktop default to `True` when you add a new control to a window. Existing controls will be altered only if LockRight and/or LockBottom are not set. *LockLeft* has no effect unless *LockRight* is `True`. This property can be set in the control's Inspector. The following example sets it in code. ``` xojo Me.LockLeft = True ```

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RectControl.LockRight **LockRight** As `Boolean` Determines whether the right edge of the control should stay at a set distance from the right edge of the parent control, if there is one, or the owning window. This property can be set in the control's Inspector. The following example sets it in code. ``` xojo Me.LockRight = True ```

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RectControl.LockTop **LockTop** As `Boolean` Determines whether the top edge of the control should stay at a set distance from the top edge of the parent control, if there is one, or the owning window. Beginning with version 2009r5, LockTop and LockLeft default to `True` when you add a control to a window. Existing controls will be altered only if LockRight and/or LockBottom are not set. *LockTop* has no effect unless *LockBottom* is `True`. This property can be set in the control's Inspector. The following example sets it in code. ``` xojo Me.LockTop = True ```

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RectControl.MouseCursor **MouseCursor** As `MouseCursor` The cursor to be displayed while the mouse is within the control and both the `DesktopApplication` and `Window` class's MouseCursor properties are `Nil`. If the `DesktopApplication` class's MouseCursor property is not `Nil` or the `Window`'s MouseCursor property is not `Nil`, then any control's MouseCursor property is ignored. You can use a cursor stored in the `Cursors` module. On Macintosh, you can also obtain a `MouseCursor` from a resource file. This line in the Open event of the control sets the default cursor to the finger pointer. ``` xojo Me.MouseCursor = System.Cursors.FingerPointer ```

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RectControl.MouseX **MouseX** As `Integer` The X coordinate of the mouse (points). Measured from the top-left corner of the control. This property is read-only. This code is in the MouseDown event of a `TextField` and displays the X-coordinate at the point of the MouseDown event. ``` xojo Me.Value = Str(Me.MouseX) ```

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RectControl.MouseY **MouseY** As `Integer` The Y coordinate of the mouse (points). Measured from the top-left corner of the control. This property is read-only. This code is in the MouseDown event of a `TextField` and displays the Y-coordinate at the point of the MouseDown event. ``` xojo Me.Value = Str(Me.MouseY) ```

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RectControl.Name **Name** As `String` The name of the control. Set the name of the control in the Inspector. This property is read-only.

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RectControl.PanelIndex **PanelIndex** As `Integer` If the control has been placed on a `TabPanel` or `PagePanel` control, this is the panel (page/tab) that the control is on. If the control is not on a panel, it returns -1. The first panel is numbered zero. If the control has been placed on a panel of a `TabPanel` or `PagePanel` control, it returns the panel number. If the control is not on a `PagePanel` or `TabPanel`, it returns -1. If you change the PanelIndex to a nonexistent panel, the control will disappear until you give it a PanelIndex value that corresponds to a panel that exists. If you are looking to change the currently selected panel (page/tab), use `PagePanel.SelectedPanelIndex`. This code displays the panel index of the control that is on the page. ``` xojo Label3.Value = Str(Me.PanelIndex) ```

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RectControl.Parent **Parent** As `Control` Used to get and set the control's parent control or window. Returns `Nil` if the parent is the window. Assign `Nil` to make the control's parent the window, even if it is enclosed by another control. The child control's behavior in the IDE will reflect the parent's state. If the parent control is somehow in another window, an `InvalidParentException` will occur. The following example sets the parent of the control to the window. ``` xojo Me.Parent = Nil ```

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RectControl.Scope **Scope** As `Integer` Used to determine whether access to the control is Public (0) or Private (2). The default is Public. This property is read-only. If the Scope of a control is set to Private, it cannot be accessed from outside its parent window.

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RectControl.TabIndex **TabIndex** As `Integer` The **RectControl's** position in the Tab Order. It is 0-based. A TabIndex of 0 is the first RectControl to get the focus. On the Mac you need Full Keyboard Access turned on in System Preferences (Keyboard-\>Shortcuts) in order to manually set focus to non-text controls. This example sets the control's TabIndex. ``` xojo Me.TabIndex = 2 ```

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RectControl.Tooltip **Tooltip** As `String` Text of help message displayed as a Windows or Linux "tooltip" or macOS help tag. The tip/tag is displayed when the user hovers the mouse cursor over the control. This example adds a tooltip to a `BevelButton` that has an icon. ``` xojo Me.CaptionAlignment = 0 ' left Me.CaptionDelta = 10 Me.Tooltip = "Click to bark." Me.Icon = Woof ' added to the project Me.CaptionPosition = 2 ```

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RectControl.Top **Top** As `Integer` The top of the control in local coordinates (relative to the window). This example sets the top of the control to 140 points from the top of the window: ``` xojo Me.Top = 140 ```

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RectControl.Transparent **Transparent** As `Boolean` Determines whether the control is transparent on Windows. The default is `False`. Has no effect on macOS or Linux. Transparent controls draw more slowly and use more memory in order to cache the background. Unless you absolutely require transparency, leave this set to False. For projects that were created prior to 2018r1, this property defaults to True to emulate previous behavior. Consider changing it to False to improve performance if you do not require transparency.

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RectControl.TrueWindow **TrueWindow** As `Window` Returns a reference to the actual enclosing `Window`. This property is read-only. TrueWindow walks up the window hierarchy and finds the actual enclosing window regardless of how deeply nested the RectControl or `DesktopContainer` hierarchy is. `Window` also has a TrueWindow property. This example accesses the TrueWindow and displays its Title property in a `TextField`. ``` xojo TextField1.Text = Me.TrueWindow.Title ```

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RectControl.Visible **Visible** As `Boolean` Determines whether the control is visible when its owning window is opened. The default is `True`: the control is visible. The following code in the DisclosureTriangle Action event handler displays or hides a ListBox on the window: ``` xojo ListBox1.Value = Me.Visible ```

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RectControl.Width **Width** As `Integer` The width (in points) of the control. The following example resizes the control: ``` xojo Me.Width = 200 ```

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RectControl.Window **Window** As `Window` The control's parent window. This property is read-only. This code gets the parent window's Title property. ``` xojo TextField1.Text = Me.Window.Title ``` ## Method descriptions

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RectControl.AcceptFileDrop **AcceptFileDrop**(FileType As `String`) Permits documents of type *FileType* to be dropped on the control. *FileType* must be a file type that you defined in via the `FileType` class or the File Type Sets Editor. This code in the Open event of an `ImageWell` makes it possible for the user to drop either a picture or a file that is a jpeg image. The File Type Sets editor was used to define the “image/jpeg” file type. It is one of the “Common File Types” that is available in the editor. ``` xojo Me.AcceptPictureDrop Me.AcceptFileDrop("image/jpeg") ``` To restrict file drops to just folders (and not files), you can put this code in the `DragEnter` event: ``` xojo If Not obj.FolderItem.IsFolder Then Return True ```

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RectControl.AcceptPictureDrop **AcceptPictureDrop** Permits pictures to be dropped on the control. If a control should accept pictures in a drag and drop, then AcceptPictureDrop needs to be called prior to the drop. Typically, it is in the Open event of the control itself. For example, the line: ``` xojo Me.AcceptPictureDrop ``` in the Open event of the control that will receive the dragged pictures is needed. When the picture is dropped, the `DropObject` event is called and this is where you will put your code to handle the drop. Canvas.Open: ``` xojo Me.AcceptPictureDrop ``` Canvas.DropObject: ``` xojo If obj.PictureAvailable Then Me.Backdrop = obj.Picture End If ```

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RectControl.AcceptRawDataDrop **AcceptRawDataDrop**(Type As `String`) Permits data (of the Type specified) to be dropped on the control. The following specfies a generic file type defined in the File Type Sets editor. ``` xojo Me.AcceptRawDataDrop("????") ```

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RectControl.AcceptTextDrop **AcceptTextDrop** Permits text to be dropped on the control. This line in the Open event of a control that can accept dragged text. ``` xojo Me.AcceptTextDrop ```

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RectControl.Close **Close** Closes a control. Closing a control permanently removes the control from memory, making it impossible to access. You can close both non-indexed controls and indexed controls. When you close an indexed control, the indexes for the remaining controls will shift downward so that the indexes start with zero and are consecutive. The following code closes the control. When this is executed from a visible control, the control disappears from the window. ``` xojo Me.Close ```

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RectControl.DrawInto **DrawInto**(g As `Graphics`, x As `Integer`, y As `Integer`) Draws the contents of the RectControl into the specified `Graphics` context. The parameters *x* and *y* are the coordinates of the top, left corner. This method does not work with `HTMLViewer` and `OpenGLSurface`. This example draws the current control into the Graphics of a Picture and then displays it as the Backdrop of a Canvas: ``` xojo Var p As New Picture(Me.Width, Me.Height) Me.DrawInto(p.Graphics, 0, 0) Canvas1.Backdrop = p ```

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RectControl.Invalidate **Invalidate**(\[EraseBackground As `Boolean`\]) Similar to RefreshRect, but causes the specified region of the RectControl to be marked dirty and to be redrawn when the window contents need to be redrawn. The region to be redrawn is specified by the *X*, *Y*, *Width*, and *Height* parameters. This form of Invalidate was formerly called InvalidateRect. The following code refreshes the control. EraseBackground defaults to `True`. ``` xojo Me.Invalidate(False) ```

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RectControl.Refresh **Refresh**(eraseBackground As `Boolean`) Repaints the portion specified of the contents of the control immediately. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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RectControl.Refresh **Refresh**(x As `Integer`, y As `Integer`, width As `Integer`, height As `Integer`, eraseBackground As `Boolean`) Repaints the portion specified of the contents of the control immediately. Calling this frequently can cause the code executing to slow down. It is often preferable to call `Invalidate` instead. Refresh the entire area: ``` xojo Me.Refresh(False) ``` Refresh a portion of the area: ``` xojo Me.Refresh(100, 150, 200, 300) ```

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RectControl.SetFocus **SetFocus** If applicable, sets the focus to the RectControl. KeyDown events are directed to the control. If the control cannot get the focus on the platform on which the application is running, SetFocus does nothing. The SetFocus method of the `Window` class or the `ClearFocus` method can be used to remove the focus from the control that currently has the focus, leaving no control with the focus. On the Mac you need Full Keyboard Access turned on in System Preferences (Keyboard-\>Shortcuts) in order to manually set focus to non-text controls. The following example sets the focus to TextField1. If another control has the focus when this line is executed, then the user sees that TextField1 gets the focus. ``` xojo TextField1.SetFocus ``` ## Event descriptions

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RectControl.Close **Close** The control is about to close.

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RectControl.ConstructContextualMenu **ConstructContextualMenu**(Base As `MenuItem`, x As `Integer`, y As `Integer`) As `Boolean` This event is called when it is appropriate to display a contextual menu for the control. This event handler is the recommended way to handle contextual menus because this event figures out whether the user has requested the contextual menu, regardless of how they did it. Depending on platform, it might be in the MouseUp or MouseDown event and it might be a right+click or by pressing the contextual menu key on the keyboard, for example. *Base* is analogous to the menu bar for the contextual menu. Any items you add to *Base* will be shown as menu items. If you return `False`, the event is passed up the parent hierarchy. If you return `True`, the contextual menu is displayed. The parameters *x* and *y* are the mouse locations. If the event was fired because of a non-mouse event, then *x* and *y* are both set to -1. See the example of a contextual menu in the following section. The following ConstructContextualMenu event handler builds a menu with three menu items plus a submenu with three additional menu items. ``` xojo ' Add some items base.AddMenu(New MenuItem("Test 1")) base.AddMenu(New MenuItem("Test 2")) base.AddMenu(New MenuItem("Test 3")) ' Add a Separator base.AddMenu(New MenuItem(MenuItem.TextSeparator)) ' Add a sub menu Var submenu As New MenuItem("SubMenu") submenu.AddMenu(New MenuItem("SubMenu Test 1")) submenu.AddMenu(New MenuItem("SubMenu Test 2")) submenu.AddMenu(New MenuItem("SubMenu Test 3")) base.AddMenu(submenu) ' Add a Separator base.AddMenu(New MenuItem(MenuItem.TextSeparator)) Return True ```

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RectControl.ContextualMenuAction **ContextualMenuAction**(HitItem As `MenuItem`) As `Boolean` Fires when a contextual menuitem *hitItem* was selected but the Action event and the MenuHandler for the menuitem did not handle the menu selection. This event gives you a chance to handle the menu selection by inspecting the menuitem's Text or Tag properties to see which item was selected. Use this in conjunction with ConstructContextualMenu if you have not specified the Action event or the Menu Handler for the items on the contextual menu. See the example of a contextual menu in the examples for the RectControl class. `Return` `True` if this event has handled the item the user chose from the contextual menu. Returning `False` will cause the control's parent to execute its ContextualMenuAction event. This can be handy if you have the same contextual menu for several controls who share the same `Parent` (several on the same window for example). By returning `False` you can handle them all in a single event. This simple event handler displays the value of the selected menu item. ``` xojo If hitItem <> Nil Then MessageBox(hitItem.Value) Return True ```

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RectControl.DragEnter **DragEnter**(obj As `DragItem`, Action As `Integer`) As `Boolean` Fires when the passed `DragItem` enters the RectControl. Returns a `Boolean`. Return `True` from this event to prevent the drop from occurring. The Action parameter specifies the drag action. It can take the following class constants of the `DragItem` class: | Value | Class Constant | |-------|--------------------------------------------------------------------| | 0 | `DragItem`.DragActionDefault | | 1 | `DragItem`.DragActionCopy | | 2 | `DragItem`.DragActionMove | | 3 | `DragItem`.DragActionLink | To restrict file drops to just folders (and not files), you can put this code in the DragEnter event: ``` xojo If Not obj.FolderItem.IsFolder Then Return True ```

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RectControl.DragExit **DragExit**(obj As `DragItem`, Action As `Integer`) Fires when the passed `DragItem` exits the RectControl. The *Obj* parameter is the item being dragged. The *Action* parameter specifies the drag action. It can take the following class constants of the `DragItem` class: | Value | Constant | |-------|--------------------------------------------------------------------| | 0 | `DragItem`.DragActionDefault | | 1 | `DragItem`.DragActionCopy | | 2 | `DragItem`.DragActionMove | | 3 | `DragItem`.DragActionLink |

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RectControl.DragOver **DragOver**(x As `Integer`, y As `Integer`, obj As `DragItem`, Action As `Integer`) As `Boolean` Fires when the `DragItem` is over the RectControl. The *Obj* parameter is the object being dragged. The coordinates x and y are relative to the RectControl. Returns a `Boolean`. Return `True` from this event to prevent the drop from occurring. The *Action* parameter specifies the drag action, which is typically done by holding down a modifier key (Shift, Alt, Option, Command, etc.) while doing the drag. It can take the following class constants of the `DragItem` class: | Value | Constant | |-------|--------------------------------------------------------------------| | 0 | `DragItem`.DragActionDefault | | 1 | `DragItem`.DragActionCopy | | 2 | `DragItem`.DragActionMove | | 3 | `DragItem`.DragActionLink |

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RectControl.DropObject **DropObject**(Obj As `DragItem` Action As `Integer`) The item represented by *Obj* has been dropped on the control. The *Obj* parameter is the object being dragged. The *Action* parameter specifies the drag action. It can take the following class constants of the `DragItem` class: {\| class="genericTable" ! width=10% Class Constant 0 \| `DragItem`.DragActionDefault 1 \| `DragItem`.DragActionCopy 2 \| `DragItem`.DragActionMove 3 \| `DragItem`.DragActionLink } The following DropObject event handler can handle either a dropped picture or a dropped file. The type of file that it can handle needs to have been specified in a call to AcceptFileDrop prior to the drop, for example, in the Open event. ``` xojo If Obj.PictureAvailable Then Me.Image = obj.Picture ElseIf Obj.FolderItemAvailable Then Me.Image = Picture.Open(obj.FolderItem) End If ```

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RectControl.KeyDown **KeyDown**(Key As `String`) As `Boolean` The user has pressed the *Key* passed while the RectControl has the focus. How KeyDown works depends on the type of control. **TextField and TextArea** Returning `True` means the key is intercepted, preventing the key from actually reaching the control at all. This would be useful if you want to override the behavior of the tab key for example. Returning `False` means the key reaches the control. **All Other Controls** Returning `True` prevents the KeyDown event on the parent control (usually the window) from executing. Returning `False` results in the execution of the KeyDown event of the parent control.

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RectControl.KeyUp **KeyUp**(Key As `String`) Fires when the passed *Key* is released in the RectControl that has the focus. It is not guaranteed to be the same key that received the KeyDown event.

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RectControl.MouseEnter **MouseEnter** The mouse has entered the area of the control.

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RectControl.MouseExit **MouseExit** The mouse has left the area of the control.

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RectControl.MouseMove **MouseMove**(X As `Integer`, Y As `Integer`) The mouse has moved within the control to the coordinates passed. The coordinates are local to the control, not to the window.

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RectControl.MouseWheel **MouseWheel**(X As `Integer`, Y As `Integer`, DeltaX As `Integer`, DeltaY As `Integer`) As `Boolean` The mouse wheel has been moved. The parameters *X* and *Y* are the mouse coordinates relative to the control that has received the event. The parameters *DeltaX* and *DeltaY* hold the number of scroll lines the wheel has been moved horizontally and vertically, as defined by the operating system. *DeltaX* is positive when the user scrolls right and negative when scrolling to the left. *DeltaY* is positive when the user scrolls down and negative when scrolling up. Returns a `Boolean`. Return `True` to prevent the event from propagating further.

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RectControl.Open **Open** The control is about to be displayed. Use this event to initialize a control. The Open event is called after the Constructor. Be warned that initializing control property values using the Constructor instead of the Open event may result in those property values being overwritten by what is set in the Inspector. For best results, use the Open event for control initialization rather than the control Constructor. If the control is supposed to handle drag and drop, you need to tell it which type of item it needs to be able to handle. The following example informs the control that pictures and files can be dropped on it. The type of the file it needs to support is specified via the File Types Editor. ``` xojo Sub Open() Me.AcceptPictureDrop Me.AcceptFileDrop("JPEG") End Sub ``` ## Notes ### The control hierarchy In some cases you build portions of your interface by placing some controls within another control. For example, you use the `GroupBox` control to organize other controls, usually `RadioButtons` or possibly `Checkboxes`. The `TabPanel` and `PagePanel` controls also designed to enclose other controls. The control that encloses the others is known as the parent control and the controls that are entirely within its borders are the child controls. This works automatically if you create the controls in the order of: parent-child. That is, create the control that encloses the others first, then create the child controls or duplicate existing child controls and keep them inside the parent control. You can use the `Parent` property of the RectControl class to either get or set the parent of an existing control. If you create a child control before its parent, you can set its parent using its `Parent` property. If a control is not completely enclosed by another control then it doesn't automatically become a child; it overlaps the other control. If you move a child outside its parent, it is no longer a child of that control. If you move it completely inside another control, it becomes the child of that control. When you copy a parent control, you copy all its child controls as well. You can create more than one level of nesting. For example, you can place a `GroupBox` within a `TabPanel` and then place several `` RadioButton`s within the :doc:`GroupBox ``. In this case, the `GroupBox` is the parent of the `` RadioButton`s and the :doc:`TabPanel `` is the parent of the `GroupBox`. To make this work automatically, you must create them in the order that respects the hierarchy: first create the `TabPanel`, then the `GroupBox`, and then the `RadioButtons`. Obviously, the parent control must be in the same window as its child controls. If you attempt to get the parent of a control whose parent is in another window, you will get an `InvalidParentException` error. If a control is not enclosed by another control, then its “parent” is its window. But, since the `Parent` property of a control is a `Control`, the `Parent` property will be `Nil`-since a `Window` is not subclassed from the `Control` class. Before trying to access the Parent property of a control, be sure to first test whether it is `Nil`. If you don't, you will get a `NilObjectException` error if the control's "parent" is the parent window. If a control is enclosed by another control, but you don't want it to behave as a child, then set its `Parent` property to `Nil`. This breaks the default Parent-Child relationship that is normally maintained by the control hierarchy. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Control hierarchy features To take advantage of the features of the control hierarchy automatically, create the parent control first and then add the child controls by dragging fully into the interior of the parent control. When you add a child to a parent in this manner, a marquee surrounds the parent. A marquee also surrounds the parent control whenever you select an existing child control. You can disable the marquee in Preferences/Options. If you duplicate a child control and leave the duplicate within the parent, then it is automatically a child. However, if you move the duplicate outside the parent, it is no longer a child. A control must be fully enclosed by the parent to be considered a child. In the following example, both `` TextField`s report the identity of their parents. The bottom one was duplicated from the top one but has been moved out of the :doc:`TabPanel ``. It is no longer a child. > ![image](images/rectcontrol_pic1.jpg) > > ![image](images/rectcontrol_pic2.jpg) When you move a child out of the'scope' of the parent, the marquee surrounding the parent is turned off, indicating that the child is not under parental control anymore. If you move the bottom `TextField` back within the `TabPanel`, it becomes a child of the `TabPanel` once again. Moving a parent control moves its child controls as well. In the following example, the `TabPanel` shown above was moved down. It takes the top `TextField` with it, but leaves the bottom one orphaned. > ![image](images/rectcontrol_pic3.jpg) - Deleting a parent control deletes all child controls. - Hiding a parent hides all child controls, but retains the previous visibility status of all children. - Showing a parent control shows only the child controls whose visibility is set. - Disabling a parent control disables all its child controls, but retains the previous visibility status of all children. In the IDE, disabling a container visually disables all the child controls, but does not update the Enabled property. Here is a disabled `GroupBox` in the IDE in which two RadioButtons and two TextFields are children. When the `GroupBox` is disabled, all four children are disabled. Since all children are disabled when a parent is disabled, the TextFields are not enterable. > ![image](images/rectcontrol_pic4_ide.jpg) > > ![image](images/rectcontrol_pic4.jpg) - Enabling a parent control enables only the child controls whose Enabled property is set. In the following example, only the bottom row of child controls have the Enabled property set. When the GroupBox is enabled the top row of controls remains disabled. > ![image](images/rectcontrol_gb_half_enabled.jpg) - Disabling the `GroupBox` disables all child controls, as expected. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Dragging There are three possible items a user can drag from a control: text, a picture, and/or a `FolderItem`. In order for the user to be able to drag, the control must create a `DragItem` object in the appropriate event handler. The appropriate event handler depends on the type of object. For example, the appropriate event handler for a `Canvas` control is the MouseDown event handler since the user must be holding down the mouse button to drag. The `DragItem` object represents the data that the user is dragging. `DragItem` objects have properties to hold text, pictures, and `folderItems`. One or more of these properties must be populated with the values the user wishes to drag. When you create a new `DragItem` object using the `DragItem` constructor, you specify the drag rectangle that will appear as the user drags from the control. `TextFields`, `TextAreas`, and `ListBoxes` have implicit dragging built in to them. This means that they will create a new `DragItem` and drag rectangle for you. `TextFields` and `TextAreas` automatically populate the Text property of the `DragItem` with the text the user is dragging. `ListBoxes` have a DragRow event handler where you can populate the `DragItem` with the data to be dragged. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Dropping Before a control will accept an item being dropped on it, you must call the `AcceptFileDrop`, `AcceptPictureDrop`, `AcceptRawDataDrop`, and/or `AcceptTextDrop` methods to indicate the drop types that will be allowed. This is usually done in the control's `Open` event handler. When an acceptable item is dropped on the control, the control's `DropObject` event handler will execute and will be passed the `DragItem` that has been dropped on the control. At that point you can use the `DragItem's` methods to determine what kind of data is available and access it. If you are only allowing a particular type of drag data (text for example) then there would be no need to test the type of data that is being dragged. You can get the text from the `Text` property of the `DragItem`. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Handling contextual menus The following code in a `ConstructContextualMenu` event builds a simple contextual menu. The parameter *Base* as `MenuItem` is passed in as a parameter. ``` xojo base.AddMenu(New MenuItem("Import")) base.AddMenu(New MenuItem("Export")) Return True //display the contextual menu ``` The following `Select` statement in the `ContextualMenuAction` event handler inspects the selected menu item, which is passed in as the *HitItem* as `MenuItem` parameter. ``` xojo Select Case hitItem.Text Case "Import" MessageBox("You chose Import") Case "Export" MessageBox("You chose export") End Select Return True ``` On macOS, standard controls no longer filter contextual clicks. This responsibility can always be overridden by you in the MouseDown event for the control. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Changing the cursor The MouseCursor property controls which cursor will be displayed while the mouse is within the control, assuming that the MouseCursor properties of the `DesktopApplication` and parent `Window` classes are `Nil`. You can, for example, assign different MouseCursors to different controls within a window and the shape of the pointer will change whenever it is over a particular control. The `Cursors` module contains a library of custom cursors that you access with the syntax `System.Cursors`.MouseCursorName. Please see the `MouseCursor` class for information about the library of custom cursors. If you also need custom cursors at the Window or Application levels, you need to manage them along the lines described in the section on the `MouseCursor` class. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Custom cursors in windows If you need to use custom cursors in the Windows build of your application, you can do so using a slightly modified version of this technique. 1. With a resource editor, create a CURS resource that contains only one cursor. Give the resource file a name that indicates the type of cursor contained in the resource file. 2. Repeat this process for each custom cursor. 3. Add all the resource files to the Project Editor. 4. You can then access each custom cursor by name, e.g. ``` xojo Me.MouseCursor = Pen ``` ## Sample code This example shows how the DropObject event handler of a `TextArea` (named TextArea1 in this example) would be coded to handle one or more text documents or some text being dropped on it: ``` xojo Sub DropObject(Obj As DragItem, action As Integer) If Obj.TextAvailable Then TextArea1.Text = Obj.Text ElseIf Obj.FolderItemAvailable Then Do ' Load the styled text from the document ' into TextArea1 If Not TextArea1.Open(Obj.FolderItem) Then MessageBox("Drag Failed") End If Loop Until Not Obj.NextItem End If ``` ## Compatibility All project types on all supported operating systems. ## See also `Control` parent class; `Control` class.