Class

DesktopUIControl


Description

DesktopUIControl is the base class for most other visual control classes.

Methods

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

Refresh

immediately As Boolean = False

x As Integer, y As Integer, width As Integer, height As Integer, immediately As Boolean = False

SetFocus

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


DesktopUIControl.Active

Active As Boolean

Indicates whether the DesktopUIControl is active.

This property is read-only.

Active is False when the control's window is not in the foreground. When a DesktopWindow is deactivated, its controls are automatically deactivated unless AllowAutoDeactivate is set to False.


DesktopUIControl.AllowAutoDeactivate

AllowAutoDeactivate As Boolean

Determines whether the control should be deactivated (on macOS) when the parent window is deactivated. The default is True.


DesktopUIControl.AllowTabStop

AllowTabStop As Boolean

If True, the control 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 control 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:

Me.AllowTabStop = False

DesktopUIControl.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.

Me.Enabled = False

DesktopUIControl.Handle

Handle As Ptr

Returns a handle to the control.

This property is read-only.

For interfacing with Mac APIs using Declares, DesktopControl.Handle returns NSViews (except for DesktopToolbar).

On Windows returns the HWND of the control.

On Linux it returns a GtkWidget.

The following gets a handle to the control.

Var p As Ptr = Me.Handle

DesktopUIControl.Height

Height As Integer

The height (in points) of the control.

This example sets the height of the control to 100:

Me.Height = 100

DesktopUIControl.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.


DesktopUIControl.Left

Left As Integer

The distance from the left side of the control to the left side of its containing window or container.

The following example moves the control 100 points from the left side of the window:

Me.Left = 150

DesktopUIControl.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.

Me.LockBottom = True

DesktopUIControl.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.

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.

Me.LockLeft = True

DesktopUIControl.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.

Me.LockRight = True

DesktopUIControl.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.

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.

Me.LockTop = True

DesktopUIControl.MouseCursor

MouseCursor As MouseCursor

The cursor to be displayed while the mouse is within the control and both the DesktopApplication and DesktopWindow class's MouseCursor properties are Nil.

If the DesktopApplication class's MouseCursor property is not Nil or the DesktopWindow'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 Opening event of the control sets the default cursor to the finger pointer.

Me.MouseCursor = System.Cursors.FingerPointer

DesktopUIControl.Name

Name As String

The name of the control. Set the name of the control in the Inspector.

This property is read-only.


DesktopUIControl.PanelIndex

PanelIndex As Integer

If the control has been placed on a DesktopTabPanel or DesktopPagePanel 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 DesktopTabPanel or DesktopPagePanel control, it returns the panel number. If the control is not on a DesktopPagePanel or DesktopTabPanel, 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 DesktopPagePanel.

This code displays the panel index of the control that is on the page.

MessageBox(Me.SelectedPanelIndex.ToString)

DesktopUIControl.Parent

Parent As Object

Used to get and set the control's parent control or window.

If the control is on the window, the Parent will be the Window. If the control is on the container, the Parent will be the container. If the control is completed enclosed by another control, the Parent will be that DesktopUIControl.

If you do not want the enclosing control to be the parent, set the Parent property of that control to Nil to make it the Window.

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.

Me.Parent = Nil

DesktopUIControl.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.

Note

This is a designtime-only property and thus can only be set in the Inspector and is not accessible via code.

If the Scope of a control is set to Private, it cannot be accessed from outside its parent window.


DesktopUIControl.TabIndex

TabIndex As Integer

The control's position in the Tab Order. The control with whose TabIndex is 0 will get the focus first.

On macOS, only controls where you enter data from the keyboard typically get the focus. In order to manually set focus to controls that don't allow keyboard entry, go to System Preferences, click on the Keyboard icon then on the Shortcuts tab and then check the Use keyboard navigation to move focus between controls checkbox.

This example sets the control's TabIndex.

Me.TabIndex = 2

DesktopUIControl.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 control:

Me.Tooltip = "Click to bark."

DesktopUIControl.Top

Top As Integer

The distance from the top of the control to the top of its containing window or container.

This example sets the top of the control to 140 points from the top of the window:

Me.Top = 140

DesktopUIControl.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.


DesktopUIControl.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 makes the control invisible:

Me.Visible = False

DesktopUIControl.Width

Width As Integer

The width (in points) of the control.

The following example resizes the control:

Me.Width = 200

DesktopUIControl.Window

Window As DesktopWindow

The control's parent window.

This property is read-only.

This code gets the parent window's Title property.

MessageBox(Me.Window.Title)

Method descriptions


DesktopUIControl.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 Opening event 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.

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:

If Not obj.FolderItem.IsFolder Then Return True

DesktopUIControl.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 Opening event of the control itself. For example, the line:

Me.AcceptPictureDrop

in the Opening 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.

Opening Event:

Me.AcceptPictureDrop

DropObject Event:

If obj.PictureAvailable Then
  Me.Backdrop = obj.Picture
End If

DesktopUIControl.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.

Me.AcceptRawDataDrop("????")

DesktopUIControl.AcceptTextDrop

AcceptTextDrop

Permits text to be dropped on the control.

This line in the Opening event of a control that can accept dragged text.

Me.AcceptTextDrop

DesktopUIControl.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.

Me.Close

DesktopUIControl.DrawInto

DrawInto(g As Graphics, x As Integer, y As Integer)

Draws the contents of the control into the specified Graphics context. The parameters x and y are the coordinates of the top, left corner.

This example draws the current control into the Graphics of a Picture and then displays it as the Backdrop of a Canvas:

Var p As New Picture(Me.Width, Me.Height)
Me.DrawInto(p.Graphics, 0, 0)
Canvas1.Backdrop = p

DesktopUIControl.Refresh

Refresh(immediately As Boolean = False)

Redraws the portion specified of the contents of the control the next time the OS redraws the control or immediately if True is passed.


DesktopUIControl.Refresh

Refresh(x As Integer, y As Integer, width As Integer, height As Integer, immediately As Boolean = False)

Redraws the portion specified of the contents of the control the next time the OS redraws the control or immediately if True is passed.

If you are calling this so frequently that you experience a slowdown in your code, pass True for the immediately parameter.

Calling this method causes the Render event to fire.

Refresh the entire area immediately:

Me.Refresh(True)

Refresh a portion of the area the next time the OS redraws the control:

Me.Refresh(100, 150, 200, 300)

DesktopUIControl.SetFocus

SetFocus

If applicable, sets the focus to the DesktopUIControl. 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 DesktopWindow 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.

Note

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 in the Opening event sets the focus to the that control. If another control has the focus when this line is executed, then the user sees this control gets the focus.

Me.SetFocus

Event descriptions


DesktopUIControl.Closing

Closing

The control is closing.


DesktopUIControl.ConstructContextualMenu

ConstructContextualMenu(Base As DesktopMenuItem, 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.

// Add some items
base.AddMenu(New DesktopMenuItem("Test 1"))
base.AddMenu(New DesktopMenuItem("Test 2"))
base.AddMenu(New DesktopMenuItem("Test 3"))

// Add a Separator
base.AddMenu(New DesktopMenuItem(DesktopMenuItem.TextSeparator))

// Add a sub menu
Var submenu As New DesktopMenuItem("SubMenu")
submenu.AddMenu(New DesktopMenuItem("SubMenu Test 1"))
submenu.AddMenu(New DesktopMenuItem("SubMenu Test 2"))
submenu.AddMenu(New DesktopMenuItem("SubMenu Test 3"))
base.AddMenu(submenu)

// Add a Separator
base.AddMenu(New DesktopMenuItem(DesktopMenuItem.TextSeparator))

Return True

DesktopUIControl.ContextualMenuItemSelected

ContextualMenuItemSelected(HitItem As DesktopMenuItem) As Boolean

Fires when a contextual menuitem selectedItem was selected but the MenuItemSelected event and the MenuHandler for the DesktopMenuItem 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 MenuItemSelected event or the Menu Handler for the items on the contextual menu. See the example of a contextual menu in the examples for the DesktopUIControl 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.

If selectedItem <> Nil Then MessageBox(selectedItem.Text)
Return True

DesktopUIControl.DragEnter

DragEnter(obj As DragItem, Action As DragItem.Types) As Boolean

Fires when the passed DragItem enters the DesktopUIControl.

Returns a Boolean. Return True from this event to prevent the drop from occurring.

The Action parameter specifies the type of drag action.

To restrict file drops to just folders (and not files), you can put this code in the DragEnter event:

If Not obj.FolderItem.IsFolder Then Return True

DesktopUIControl.DragExit

DragExit(obj As DragItem, Action As DragItem.Types)

Fires when the passed DragItem exits the DesktopUIControl.

The Obj parameter is the item being dragged. The Action parameter specifies the type of drag action.


DesktopUIControl.DragOver

DragOver(x As Integer, y As Integer, obj As DragItem, Action As DragItem.Types) As Boolean

Fires when the DragItem is over the DesktopUIControl.

The Obj parameter is the object being dragged. The coordinates x and y are relative to the DesktopUIControl. Returns a Boolean. Return True from this event to prevent the drop from occurring.

The Action parameter specifies the type of drag action, which is typically done by holding down a modifier key (Shift, Alt, Option, Command, etc.) while doing the drag.


DesktopUIControl.DropObject

DropObject(Obj As DragItem Action As DragItem.Types)

The item represented by Obj has been dropped on the control.

The Obj parameter is the object being dragged. The Action parameter specifies the type of drag action.

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 Opening event.

If Obj.PictureAvailable Then
  Me.Image = obj.Picture
ElseIf Obj.FolderItemAvailable Then
  Me.Image = Picture.Open(obj.FolderItem)
End If

DesktopUIControl.FocusLost

FocusLost

The DesktopUIControl has lost the focus.

This property must be set to True for the DesktopUIControl to be capable of getting then losing the focus.

Note

On macOS, controls other than text fields and lists will accept and lose focus only if the full keyboard access option is enabled in System Preferences/Keyboard.


DesktopUIControl.FocusReceived

FocusReceived

The DesktopUIControl has received the focus and has a selection rectangle around it.

This property must be set to True for the DesktopUIControl to be capable of getting the focus.

Note

On macOS, controls other than text fields and lists will accept focus only if the full keyboard access option is enabled in System Preferences/Keyboard.


DesktopUIControl.KeyDown

KeyDown(Key As String) As Boolean

The user has pressed the Key passed while the control 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.


DesktopUIControl.KeyUp

KeyUp(Key As String)

Fires when the passed Key is released in the control that has the focus.

It is not guaranteed to be the same key that received the KeyDown event.


DesktopUIControl.MouseDown

MouseDown(X As Integer, Y As Integer) As Boolean

The mouse button was pressed inside the control's region at the location passed in to x, y.

This event fires repeatedly while the mouse button is being held down.

The coordinates x and y are local to the control, i.e. they represent the position of the mouse click relative to the upper-left corner or the DesktopUIControl.

Return True if you are going to handle the MouseDown. In such a case:

  • The Pressed event, if any, will not execute and the state of the object will not change.

  • You will receive the MouseUp event.

If you return False, the system handles the MouseDown so the MouseUp event handler do not get called.

The MouseDown event uses the DragItem constructor when the user drags the contents of the control. It is:

Var d As DragItem
d = New DragItem(Self, Me.Left, Me.Top, Me.Width, Me.Height)
d.Picture = Me.Image
d.Drag // Allow the drag

DesktopUIControl.MouseDrag

MouseDrag(X As Integer, Y As Integer)

The mouse button was pressed inside the control and moved (dragged) at the location local to the control passed in to x, y.

This event fires repeatedly while the mouse button is down regardless of whether or not the mouse coordinates are changing.

This event will not occur unless you return True in the MouseDown event.


DesktopUIControl.MouseEnter

MouseEnter

The mouse has entered the area of the control.


DesktopUIControl.MouseExit

MouseExit

The mouse has left the area of the control.


DesktopUIControl.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.


DesktopUIControl.MouseUp

MouseUp(X As Integer, Y As Integer)

The mouse button was released. Use the x and y parameters to determine if the mouse button was released within the control's boundaries.

Note

This event will not occur unless you return True in the MouseDown event. The return value is ignored.

The parameters x and y are local coordinates, i.e. they represent the position of the mouse click relative to the upper-left corner or the DesktopUIControl. Mouse clicks that are released to the left or above a control are negative.


DesktopUIControl.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.


DesktopUIControl.Opening

Opening

The control is about to be displayed. Use this event to initialize a control.

The Opening event is called after the Constructor.

Be warned that initializing control property values using the Constructor instead of the Opening event may result in those property values being overwritten by what is set in the Inspector. For best results, use the Opening 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.

Sub Opening()
  Me.AcceptPictureDrop
  Me.AcceptFileDrop("JPEG")
End Sub

Notes

Most visual controls inherit the properties of the DesktopUIControl. A DesktopUIControl cannot be created or modified directly. Instead, you create and modify the DesktopUIControl subclasses like DesktopButtons, DesktopTextFields, DesktkopListBoxes, etc.


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 RadioGroup 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 DesktopUIControl 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 a RadioGroup within the GroupBox. In this case, the GroupBox is the parent of the RadioGroup and the 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 RadioGroup.

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.

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 will cause the control's Parent to become the window.


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. It is no longer a child.

../../../_images/desktopuicontrol_parented_control.png ../../../_images/desktopuicontrol_unparented_control.png

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.

../../../_images/desktopuicontrol_moving_parented_controls.png
  • 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.

  • Disabling the TabPanel 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 DesktopCanvas 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 Opening 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 DesktopMenuItem is passed in as a parameter.

base.AddMenu(New DesktopMenuItem("Import"))
base.AddMenu(New DesktopMenuItem("Export"))
Return True  //display the contextual menu

The following Select Case statement in the ContextualMenuItemSelected event handler inspects the selected menu item, which is passed in as the HitItem as DesktopMenuItem parameter.

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 DesktopWindow 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.

Me.MouseCursor = Pen

Sample code

This example shows how the DropObject event handler of a DesktopTextArea (named TextArea1 in this example) would be coded to handle one or more text documents or some text being dropped on it:

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

Desktop projects on all supported operating systems.

See also

DesktopControl parent class