Class

DesktopOpenGLSurface


Description

Sets up OpenGL on all platforms and provides basic functionality. It does the basic setup of OpenGL on each platform. It's up to you to clear buffers and do all the OpenGL drawing.

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

MakeCurrent

Refresh

immediately As Boolean = False

SetFocus

Property descriptions


DesktopOpenGLSurface.Active

Active As Boolean

Indicates whether the control 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.


DesktopOpenGLSurface.AllowAutoDeactivate

AllowAutoDeactivate As Boolean

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


DesktopOpenGLSurface.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

DesktopOpenGLSurface.ColorBits

ColorBits As Integer

The depth of the color buffer. The default is 24.


DesktopOpenGLSurface.Composited

Composited As Boolean

Whether or not the surface is composited. The default is True.


DesktopOpenGLSurface.ContextHandle

ContextHandle As Integer

Returns a handle to the underlying OpenGL context.

This property is read-only.

The following gets a handle to the OpenGLSurface:

Var i As Integer
i = Me.ContextHandle

DesktopOpenGLSurface.DepthBits

DepthBits As Integer

The depth of the depth buffer. The default is 24.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.Height

Height As Integer

The height (in points) of the control.

This example sets the height of the control to 100:

Me.Height = 100

DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.Name

Name As String

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

This property is read-only.


DesktopOpenGLSurface.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.SelectedPanelIndex.

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

MessageBox(Me.SelectedPanelIndex.ToString)

DesktopOpenGLSurface.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 control.

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

DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.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."

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.Width

Width As Integer

The width (in points) of the control.

The following example resizes the control:

Me.Width = 200

DesktopOpenGLSurface.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


DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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("????")

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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.

Warning

Although the DesktopOpenGLSurface has this method, it's not supported.


DesktopOpenGLSurface.MakeCurrent

MakeCurrent

Sets the DesktopOpenGLSurface as the current thread's OpenGL context.


DesktopOpenGLSurface.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.

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)

DesktopOpenGLSurface.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


DesktopOpenGLSurface.Closing

Closing

The control is closing.


DesktopOpenGLSurface.Configure

Configure(MemoryBlock)

For advanced configuration of the OpenGL context. On Mac and Linux, returns an attributes array list (an array of 32-bit integers). On Windows, return a PIXELFORMATDESCRIPTOR structure.

This event is called before the Opening event.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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

DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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.


DesktopOpenGLSurface.Error

Error(Boolean)

If OpenGLSurface cannot set up the OpenGL context properly, it will fire this event.


DesktopOpenGLSurface.KeyDown

KeyDown(Key As String) As Boolean

The user has pressed the Key passed while the control has the focus.

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.


DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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 control.

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

DesktopOpenGLSurface.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.


DesktopOpenGLSurface.MouseEnter

MouseEnter

The mouse has entered the area of the control.


DesktopOpenGLSurface.MouseExit

MouseExit

The mouse has left the area of the control.


DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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 control. Mouse clicks that are released to the left or above a control are negative.


DesktopOpenGLSurface.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.


DesktopOpenGLSurface.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

DesktopOpenGLSurface.Render

Render

Fires when you call the Render method. You can perform OpenGL drawing here and when this event exits, it will swap the image buffers for double-buffered OpenGL contexts.


DesktopOpenGLSurface.Resized

Resized

The surface has been resized by the user or by code that changes the surface's Width or Height properties.

Notes

The DesktopOpenGLSurface control and the OpenGL module are based on the OpenGLSurface plug-in from Tinrocket, LLC at http://2002-2010.tinrocket.com/software/openglsurface/index.html.

The OpenGL module contains all the OpenGL calls, functions, and constants that you will need. See http://www.opengl.org/ for the OpenGL documentation. The online version of the Red Book for OpenGL 1.1 is available at http://www.glprogramming.com/red.

Additional information: * OpenGL uses a per-thread context. * All of the functions in the OpenGL module affect the current context. * The current OpenGL context is undefined outside of an DesktopOpenGLSurface Opening, Resized or Render event. * MakeCurrent can be used to make a specific OpenGLCanvas the current context.

Compatibility

Desktop projects on all supported operating systems.

See also

DesktopUIControl parent class; OpenGL module.