Class View

View is the base class for all views on the screen and represents a visible element that can render itself and contains zero or more nested views.
Inheritance
System.Object
Responder
View
Button
CheckBox
ComboBox
FrameView
HexView
Label
ListView
MenuBar
ProgressBar
RadioGroup
ScrollBarView
ScrollView
StatusBar
TextField
TextView
Toplevel
Implements
System.Collections.IEnumerable
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
Namespace: Terminal.Gui
Assembly: Terminal.Gui.dll
Syntax
public class View : Responder, IEnumerable
Remarks

The View defines the base functionality for user interface elements in Terminal/gui.cs. Views can contain one or more subviews, can respond to user input and render themselves on the screen.

Views can either be created with an absolute position, by calling the constructor that takes a Rect parameter to specify the absolute position and size (the Frame of the View) or by setting the X, Y, Width and Height properties on the view. Both approaches use coordinates that are relative to the container they are being added to.

When you do not specify a Rect frame you can use the more flexible Dim and Pos objects that can dynamically update the position of a view. The X and Y properties are of type Pos and you can use either absolute positions, percentages or anchor points. The Width and Height properties are of type Dim and can use absolute position, percentages and anchors. These are useful as they will take care of repositioning your views if your view's frames are resized or if the terminal size changes.

When you specify the Rect parameter to a view, you are setting the LayoutStyle to Absolute, and the view will always stay in the position that you placed it. To change the position change the Frame property to the new position.

Subviews can be added to a View by calling the Add method. The container of a view is the Superview.

Developers can call the SetNeedsDisplay method on the view to flag a region or the entire view as requiring to be redrawn.

Views have a ColorScheme property that defines the default colors that subviews should use for rendering. This ensures that the views fit in the context where they are being used, and allows for themes to be plugged in. For example, the default colors for windows and toplevels uses a blue background, while it uses a white background for dialog boxes and a red background for errors.

If a ColorScheme is not set on a view, the result of the ColorScheme is the value of the SuperView and the value might only be valid once a view has been added to a SuperView, so your subclasses should not rely on ColorScheme being set at construction time.

Using ColorSchemes has the advantage that your application will work both in color as well as black and white displays.

Views that are focusable should implement the PositionCursor to make sure that the cursor is placed in a location that makes sense. Unix terminals do not have a way of hiding the cursor, so it can be distracting to have the cursor left at the last focused view. So views should make sure that they place the cursor in a visually sensible place.

The metnod LayoutSubviews is invoked when the size or layout of a view has changed. The default processing system will keep the size and dimensions for views that use the LayoutKind.Absolute, and will recompute the frames for the vies that use LayoutKind.Computed.

Constructors

View()

Initializes a new instance of the View class and sets the view up for Computed layout, which will use the values in X, Y, Width and Height to compute the View's Frame.
Declaration
public View()

View(Rect)

Initializes a new instance of the View class with the absolute dimensions specified in the frame. If you want to have Views that can be positioned with Pos and Dim properties on X, Y, Width and Height, use the empty constructor.
Declaration
public View(Rect frame)
Parameters
Type Name Description
Rect frame The region covered by this view.

Properties

Bounds

The bounds represent the View-relative rectangle used for this view. Updates to the Bounds update the Frame, and has the same side effects as updating the frame.
Declaration
public Rect Bounds { get; set; }
Property Value
Type Description
Rect The bounds.

ColorScheme

The color scheme for this view, if it is not defined, it returns the parent's color scheme.
Declaration
public ColorScheme ColorScheme { get; set; }
Property Value
Type Description
ColorScheme

Driver

Points to the current driver in use by the view, it is a convenience property for simplifying the development of new views.
Declaration
public static ConsoleDriver Driver { get; }
Property Value
Type Description
ConsoleDriver

Focused

Returns the currently focused view inside this view, or null if nothing is focused.
Declaration
public View Focused { get; }
Property Value
Type Description
View The focused.

Frame

Gets or sets the frame for the view.
Declaration
public virtual Rect Frame { get; set; }
Property Value
Type Description
Rect The frame.
Remarks
Altering the Frame of a view will trigger the redrawing of the view as well as the redrawing of the affected regions in the superview.

HasFocus

Declaration
public override bool HasFocus { get; }
Property Value
Type Description
System.Boolean
Overrides

Height

Gets or sets the height for the view. This is only used when the LayoutStyle is Computed, if the LayoutStyle is set to Absolute, this value is ignored.
Declaration
public Dim Height { get; set; }
Property Value
Type Description
Dim The height.

Id

Gets or sets an identifier for the view;
Declaration
public ustring Id { get; set; }
Property Value
Type Description
NStack.ustring The identifier.

IsCurrentTop

Returns a value indicating if this View is currently on Top (Active)
Declaration
public bool IsCurrentTop { get; }
Property Value
Type Description
System.Boolean

LayoutStyle

Controls how the view's Frame is computed during the LayoutSubviews method, if Absolute, then LayoutSubviews does not change the Frame properties, otherwise the Frame is updated from the values in X, Y, Width and Height properties.
Declaration
public LayoutStyle LayoutStyle { get; set; }
Property Value
Type Description
LayoutStyle The layout style.

MostFocused

Returns the most focused view in the chain of subviews (the leaf view that has the focus).
Declaration
public View MostFocused { get; }
Property Value
Type Description
View The most focused.

Subviews

This returns a list of the subviews contained by this view.
Declaration
public IList<View> Subviews { get; }
Property Value
Type Description
System.Collections.Generic.IList<View> The subviews.

SuperView

Returns the container for this view, or null if this view has not been added to a container.
Declaration
public View SuperView { get; }
Property Value
Type Description
View The super view.

WantContinuousButtonPressed

Gets or sets a value indicating whether this View want continuous button pressed event.
Declaration
public virtual bool WantContinuousButtonPressed { get; set; }
Property Value
Type Description
System.Boolean

WantMousePositionReports

Gets or sets a value indicating whether this View want mouse position reports.
Declaration
public virtual bool WantMousePositionReports { get; set; }
Property Value
Type Description
System.Boolean true if want mouse position reports; otherwise, false.

Width

Gets or sets the width for the view. This is only used when the LayoutStyle is Computed, if the LayoutStyle is set to Absolute, this value is ignored.
Declaration
public Dim Width { get; set; }
Property Value
Type Description
Dim The width.

X

Gets or sets the X position for the view (the column). This is only used when the LayoutStyle is Computed, if the LayoutStyle is set to Absolute, this value is ignored.
Declaration
public Pos X { get; set; }
Property Value
Type Description
Pos The X Position.

Y

Gets or sets the Y position for the view (line). This is only used when the LayoutStyle is Computed, if the LayoutStyle is set to Absolute, this value is ignored.
Declaration
public Pos Y { get; set; }
Property Value
Type Description
Pos The y position (line).

Methods

Add(View)

Adds a subview to this view.
Declaration
public virtual void Add(View view)
Parameters
Type Name Description
View view
Remarks

Add(View[])

Adds the specified views to the view.
Declaration
public void Add(params View[] views)
Parameters
Type Name Description
View[] views Array of one or more views (can be optional parameter).

AddRune(Int32, Int32, Rune)

Displays the specified character in the specified column and row.
Declaration
public void AddRune(int col, int row, Rune ch)
Parameters
Type Name Description
System.Int32 col Col.
System.Int32 row Row.
System.Rune ch Ch.

BringSubviewForward(View)

Moves the subview backwards in the hierarchy, only one step
Declaration
public void BringSubviewForward(View subview)
Parameters
Type Name Description
View subview The subview to send backwards
Remarks
If you want to send the view all the way to the back use SendSubviewToBack.

BringSubviewToFront(View)

Brings the specified subview to the front so it is drawn on top of any other views.
Declaration
public void BringSubviewToFront(View subview)
Parameters
Type Name Description
View subview The subview to send to the front
Remarks
SendSubviewToBack(View).

ChildNeedsDisplay()

Flags this view for requiring the children views to be repainted.
Declaration
public void ChildNeedsDisplay()

Clear()

Clears the view region with the current color.
Declaration
public void Clear()
Remarks

This clears the entire region used by this view.

Clear(Rect)

Clears the specified rectangular region with the current color
Declaration
public void Clear(Rect r)
Parameters
Type Name Description
Rect r

ClearNeedsDisplay()

Removes the SetNeedsDisplay and the ChildNeedsDisplay setting on this view.
Declaration
protected void ClearNeedsDisplay()

ClipToBounds()

Sets the Console driver's clip region to the current View's Bounds.
Declaration
public Rect ClipToBounds()
Returns
Type Description
Rect The existing driver's Clip region, which can be then set by setting the Driver.Clip property.

DrawFrame(Rect, Int32, Boolean)

Draws a frame in the current view, clipped by the boundary of this view
Declaration
public void DrawFrame(Rect rect, int padding = 0, bool fill = false)
Parameters
Type Name Description
Rect rect Rectangular region for the frame to be drawn.
System.Int32 padding The padding to add to the drawn frame.
System.Boolean fill If set to true it fill will the contents.

DrawHotString(ustring, Boolean, ColorScheme)

Utility function to draw strings that contains a hotkey using a colorscheme and the "focused" state.
Declaration
public void DrawHotString(ustring text, bool focused, ColorScheme scheme)
Parameters
Type Name Description
NStack.ustring text String to display, the underscoore before a letter flags the next letter as the hotkey.
System.Boolean focused If set to true this uses the focused colors from the color scheme, otherwise the regular ones.
ColorScheme scheme The color scheme to use.

DrawHotString(ustring, Attribute, Attribute)

Utility function to draw strings that contain a hotkey
Declaration
public void DrawHotString(ustring text, Attribute hotColor, Attribute normalColor)
Parameters
Type Name Description
NStack.ustring text String to display, the underscoore before a letter flags the next letter as the hotkey.
Attribute hotColor Hot color.
Attribute normalColor Normal color.

EnsureFocus()

Finds the first view in the hierarchy that wants to get the focus if nothing is currently focused, otherwise, it does nothing.
Declaration
public void EnsureFocus()

FocusFirst()

Focuses the first focusable subview if one exists.
Declaration
public void FocusFirst()

FocusLast()

Focuses the last focusable subview if one exists.
Declaration
public void FocusLast()

FocusNext()

Focuses the next view.
Declaration
public bool FocusNext()
Returns
Type Description
System.Boolean true, if next was focused, false otherwise.

FocusPrev()

Focuses the previous view.
Declaration
public bool FocusPrev()
Returns
Type Description
System.Boolean true, if previous was focused, false otherwise.

GetEnumerator()

Gets an enumerator that enumerates the subviews in this view.
Declaration
public IEnumerator GetEnumerator()
Returns
Type Description
System.Collections.IEnumerator The enumerator.

LayoutSubviews()

This virtual method is invoked when a view starts executing or when the dimensions of the view have changed, for example in response to the container view or terminal resizing.
Declaration
public virtual void LayoutSubviews()

Move(Int32, Int32)

This moves the cursor to the specified column and row in the view.
Declaration
public void Move(int col, int row)
Parameters
Type Name Description
System.Int32 col Col.
System.Int32 row Row.

OnEnter()

Declaration
public override bool OnEnter()
Returns
Type Description
System.Boolean
Overrides

OnKeyDown(KeyEvent)

Declaration
public override bool OnKeyDown(KeyEvent keyEvent)
Parameters
Type Name Description
KeyEvent keyEvent Contains the details about the key that produced the event.
Returns
Type Description
System.Boolean
Overrides

OnKeyUp(KeyEvent)

Declaration
public override bool OnKeyUp(KeyEvent keyEvent)
Parameters
Type Name Description
KeyEvent keyEvent Contains the details about the key that produced the event.
Returns
Type Description
System.Boolean
Overrides

OnLeave()

Declaration
public override bool OnLeave()
Returns
Type Description
System.Boolean
Overrides

OnMouseEnter(MouseEvent)

Declaration
public override bool OnMouseEnter(MouseEvent mouseEvent)
Parameters
Type Name Description
MouseEvent mouseEvent
Returns
Type Description
System.Boolean
Overrides

OnMouseLeave(MouseEvent)

Declaration
public override bool OnMouseLeave(MouseEvent mouseEvent)
Parameters
Type Name Description
MouseEvent mouseEvent
Returns
Type Description
System.Boolean
Overrides

PositionCursor()

Positions the cursor in the right position based on the currently focused view in the chain.
Declaration
public virtual void PositionCursor()

ProcessColdKey(KeyEvent)

Declaration
public override bool ProcessColdKey(KeyEvent keyEvent)
Parameters
Type Name Description
KeyEvent keyEvent
Returns
Type Description
System.Boolean
Overrides

ProcessHotKey(KeyEvent)

Declaration
public override bool ProcessHotKey(KeyEvent keyEvent)
Parameters
Type Name Description
KeyEvent keyEvent
Returns
Type Description
System.Boolean
Overrides

ProcessKey(KeyEvent)

Declaration
public override bool ProcessKey(KeyEvent keyEvent)
Parameters
Type Name Description
KeyEvent keyEvent
Returns
Type Description
System.Boolean
Overrides

Redraw(Rect)

Performs a redraw of this view and its subviews, only redraws the views that have been flagged for a re-display.
Declaration
public virtual void Redraw(Rect region)
Parameters
Type Name Description
Rect region The region to redraw, this is relative to the view itself.
Remarks

Views should set the color that they want to use on entry, as otherwise this will inherit the last color that was set globaly on the driver.

Remove(View)

Removes a widget from this container.
Declaration
public virtual void Remove(View view)
Parameters
Type Name Description
View view
Remarks

RemoveAll()

Removes all the widgets from this container.
Declaration
public virtual void RemoveAll()
Remarks

ScreenToView(Int32, Int32)

Converts a point from screen coordinates into the view coordinate space.
Declaration
public Point ScreenToView(int x, int y)
Parameters
Type Name Description
System.Int32 x X screen-coordinate point.
System.Int32 y Y screen-coordinate point.
Returns
Type Description
Point The mapped point.

SendSubviewBackwards(View)

Moves the subview backwards in the hierarchy, only one step
Declaration
public void SendSubviewBackwards(View subview)
Parameters
Type Name Description
View subview The subview to send backwards
Remarks
If you want to send the view all the way to the back use SendSubviewToBack.

SendSubviewToBack(View)

Sends the specified subview to the front so it is the first view drawn
Declaration
public void SendSubviewToBack(View subview)
Parameters
Type Name Description
View subview The subview to send to the front
Remarks
BringSubviewToFront(View).

SetClip(Rect)

Sets the clipping region to the specified region, the region is view-relative
Declaration
public Rect SetClip(Rect rect)
Parameters
Type Name Description
Rect rect Rectangle region to clip into, the region is view-relative.
Returns
Type Description
Rect The previous clip region.

SetFocus(View)

Focuses the specified sub-view.
Declaration
public void SetFocus(View view)
Parameters
Type Name Description
View view View.

SetNeedsDisplay()

Invoke to flag that this view needs to be redisplayed, by any code that alters the state of the view.
Declaration
public void SetNeedsDisplay()

SetNeedsDisplay(Rect)

Flags the specified rectangle region on this view as needing to be repainted.
Declaration
public void SetNeedsDisplay(Rect region)
Parameters
Type Name Description
Rect region The region that must be flagged for repaint.

ToString()

Declaration
public override string ToString()
Returns
Type Description
System.String
Overrides
System.Object.ToString()

Events

Enter

Event fired when the view get focus.
Declaration
public event EventHandler Enter
Event Type
Type Description
System.EventHandler

KeyDown

Invoked when a key is pressed
Declaration
public event EventHandler<View.KeyEventEventArgs> KeyDown
Event Type
Type Description
System.EventHandler<View.KeyEventEventArgs>

KeyPress

Invoked when a character key is pressed and occurs after the key up event.
Declaration
public event EventHandler<View.KeyEventEventArgs> KeyPress
Event Type
Type Description
System.EventHandler<View.KeyEventEventArgs>

KeyUp

Invoked when a key is released
Declaration
public event EventHandler<View.KeyEventEventArgs> KeyUp
Event Type
Type Description
System.EventHandler<View.KeyEventEventArgs>

Leave

Event fired when the view lost focus.
Declaration
public event EventHandler Leave
Event Type
Type Description
System.EventHandler

MouseEnter

Event fired when the view receives the mouse event for the first time.
Declaration
public event EventHandler<MouseEvent> MouseEnter
Event Type
Type Description
System.EventHandler<MouseEvent>

MouseLeave

Event fired when the view loses mouse event for the last time.
Declaration
public event EventHandler<MouseEvent> MouseLeave
Event Type
Type Description
System.EventHandler<MouseEvent>

Implements

System.Collections.IEnumerable