Display

• Engine
• ArcGIS for Desktop Basic
• ArcGIS for Desktop Standard
• ArcGIS for Desktop Advanced
• Server

• Display objects
• Display caching
• Dynamic display
• Colors
• Color ramps
• Symbols
• Display feedback
• Rubber bands
• Trackers
• Representations

Display objects

• ScreenDisplay - Display device associated with a normal application window. It implements scrolling, backing store (caches), and invalidation.
• SimpleDisplay - Allows for all other devices that can be rendered using a Windows device context.

• How to draw a point on the screen
• How to draw a polygon on the screen
• How to draw a polyline on the screen
• How to draw a rectangle on the screen

Display caching

• Use the recording cache to redraw when the application is moved or exposed or when drawing, editing, or rubberbanding. This is very efficient since only one bitmap is needed.
• Select a new set of features, and invalidate only the selection cache. Features draw from cache. Graphics and annotation draw from cache. Only the feature selection draws from scratch.
• Move a graphic element or annotation over some features. Invalidate the annotation cache only. Features draw from cache. Feature selection draws from cache. Only the annotation draws from scratch.
• Create a new kind of layer called a tracking layer. Always return true for its cached property. To show vehicle movement when new Global Positioning System (GPS) signals are received, move the markers in the layer and invalidate the tracking layer only. All other layers draw from cache. Only the vehicle layer draws from scratch. This makes it possible to animate a layer.
• Create a base map by moving several layers into a group layer and setting the group layer's Cached property to true. Now you can edit and interact with layers that draw on top of the base map without redrawing the base map from scratch.

• Transforming envelopes in the display
• Sample: Triangle graphic element

• Create a feature class and add and remove features as necessary. Use standard renderers or custom symbols to draw features. Draw above or below any other layers. Wrap with the feature layer that has its own display cache for best performance (that is, set ILayer.Cached to true).
• Create a custom layer. Use either a proprietary database or a feature class to store features. Implement custom rendering in layer, that is, use the GDI directly. Draw above or below any other layers. Give feature layer its own display cache for best performance.
• Create a graphics layer. Store data as graphic elements. Render using standard or custom symbols. Draw above all other layers.
• Draw in response to IActiveViewEvents.AfterDraw. Store data in proprietary database. Draw directly using either GDI or IDisplay. Draw on top of everything else quickly. GPS extension uses this approach.

• As features in a geodatabase
• As elements in a graphics layer
• As proprietary data structure

• Text anti-aliasing is temporarily disabled. This prevents labels from being redrawn each time the animation layer is invalidated. Anti-aliased text uses the background as part of its rendering so typically, when anything below it changes, the text must draw from scratch.
• Transparent layers above the animation layer are not automatically invalidated with the animation layer. This speeds up the redraw with the following limitation: Features in the animation layer will no longer show through the transparent layer above it.
• All drawing is directed to the recording cache HDC rather than the window. This causes drawing to occur behind the scenes. When drawing is complete, the window is updated once from the completed recording cache. The result is less flashing.

• How to set the animation environment
• Sample: Move a graphic along a path in ArcMap

For further information see:

Dynamic display

Colors

• If all RGB values are equal, the color is a gray tone.
• If all RGB values are 0, the color is black (an absence of light).
• If all RGB values are 255, the color is white.

• If value=0, the color is black.
• If saturation=0, the color is a shade of gray.
• If value=255 and saturation=0, the color is white.

Color ramps

• Working with symbols and colors
• Sample: Use an AlgorithmicColorRamp to color a ClassBreaksRenderer

For further information see:

Symbols

Arrow marker symbol examples are shown in the following illustration:

Character marker symbol examples are shown in the following illustration:

Picture marker symbol examples are shown in the following illustration:

Multilayer marker symbol examples are shown in the following illustration:

• How to make a character marker symbol
• How to make a picture marker symbol

The width of a line symbol is in printer's points - about 1/72 of an inch. An example of line symbol width is shown in the following illustration:

• How to make a line fill symbol
• How to make a gradient fill symbol

• Creating other kinds of custom symbols
• How to make a line callout

For further information see:

Display feedback

• Feedback objects that return a new geometry. The interfaces for these objects have a Stop method that returns the new geometry. These objects are as follows:
  • NewEnvelopeFeedback
  • NewBezierCurveFeedback
  • NewDimensionFeedback
  • NewLineFeedback
  • NewPolygonFeedback
  • MoveEnvelopeFeedback
  • MoveLineFeedback
  • MovePointFeedback
  • MovePolygonFeedback
  • BezierMovePointFeedback
  • LineMovePointFeedback
  • PolygonMovePointFeedback
  • ReshapeFeedback
  • ResizeEnvelopeFeedback
  • StretchLineFeedback
• Feedback objects that are for display purposes only. You must calculate the new geometry. For example, you can use the start and end mouse locations to calculate the delta x and delta y shifts, then you can update or create the geometry from this information. These feedback objects are as follows:
  • MoveGeometryFeedback
  • MoveImageFeedback
  • NewMultiPointFeedback
  • VertexFeedback
  The objects are used in applications to allow graphic elements to be digitized and modified within the map (data view) and layout (layout view) and are also used by the ArcMap feature editing tools. Some of the feedback objects have a Constraint property that determines how the feedback behaves. These constraints can specify, for example, that ResizeEnvelopeFeedback maintains the aspect ratio of the input envelope. The details of these constraints are given with the individual feedbacks. The display feedback objects also provide some of the base functionality for the rubber band objects. Use the rubber band objects first if they suit your requirements; select the display feedback objects for greater control over the user interface (UI) when modifying graphics or features. This greater control comes at the cost of additional code.
  IDisplayFeedback is used to define the common operations on the display feedback objects. These include moving, symbolizing, and refreshing the display feedback objects as well as setting the Display property (for example, setting it to IActiveView.ScreenDisplay). IDisplayFeedback is useful only in combination with one of the display feedback objects and its derived interfaces - for example, the NewPolygonFeedback object and its INewPolygonFeedback interface. Nearly all of the display feedback interfaces employ interface inheritance from IDisplayFeedback; hence, there is no need to use caching to access its methods and properties.
  Typically, the Display and Symbol properties would be set when a display feedback object is initialized, while the MoveTo method would be called in a mouse move event. Setting the Symbol property is optional. If not set, a default symbol is used. The Refresh method is used to redraw the feedback after the window has been refreshed (for example, when it is reactivated), and it should be called in response to the tool's refresh event. The hDC parameter, which is required by the Refresh method, is actually passed into the subroutine for you.
  For additional information, see: Sample: Display feedback.
  
  

  Rubber bands

  The rubber band objects are shown in the following diagram:
  
  The following classes implement the IRubberBand interface, allowing you to digitize geometries on the display using the mouse - either to create whole new geometry objects or to update existing ones. As such, they can be viewed as simple versions of the feedback objects. Examples of uses for the rubber band objects include dragging an envelope, forming a new polyline, or moving a point. Each class supports the IRubberBand interface, but the behavior is distinct to the individual class.
  • RubberCircle
  • RubberEnvelope
  • RubberLine
  • RubberPoint
  • RubberPolygon
  • RubberRectangularPolygon
  The IRubberBand interface has two methods, TrackExisting and TrackNew, that are used to move existing geometries and create new geometries, respectively. These methods are typically called from within the code for a tool's OnMouseDown event, and they handle all subsequent mouse events. They capture subsequent mouse and keyboard events, such as OnMouseMove, OnMouseUp, and OnKeyDown events, and complete when they receive an OnMouseUp event or abort if the Esc key is pressed. This means that little code is required to use them, although this comes at the expense of flexibility.
  Typically, these objects are used for simple tasks such as dragging a rectangle or creating a new line. Operations that involve moving the vertices of existing geometries require the feedback objects to be used instead. The TrackNew method takes two parameters: an IScreenDisplay object representing the ScreenDisplay to draw the rubber band and an ISymbol object for drawing the rubber band. If no symbol is given, the default symbol is used. The method returns a new geometry object - the type of geometry returned depends on the class that was used. RubberPolygon returns a polygon object. If the method fails to complete, that is, if you press the Esc key, then nothing is returned. The types of geometry that are returned for TrackNew by each rubber band object are as follows:
  • RubberCircle - ICircularArc
  • RubberEnvelope - IEnvelope
  • RubberLine - IPolyline
  • RubberPoint - IPoint
  • RubberPolygon - IPolygon
  • RubberRectangularPolygon - IPolygon
  The TrackExisting method also takes ScreenDisplay and Symbol parameters as well as IGeometry representing the input geometry. This last parameter represents the geometry to move on the screen and is passed by reference so that it can be altered by the rubberband operation. The method returns a Boolean, which will be true unless the operation was interrupted by the Esc key being pressed. The method will do nothing if the geometry that is passed in does not intersect the current mouse location. The types of geometry that are expected by TrackExisting for each rubber band object are as follows:
  • RubberCircle - Not implemented
  • RubberEnvelope - IEnvelope
  • RubberLine - IPolyline
  • RubberPoint - IPoint
  • RubberPolygon - IPolygon
  • RubberRectangularPolygon - IPolygon
  For additional information, see Sample: RubberBand zoom.
  
  

  Trackers

  The selection tracker objects are shown in the following diagram:
  
  The three types of selection tracker objects are as follows:
  • An envelope tracker allows you to move and resize the element. This functionality is implemented by the EnvelopeTracker object for all element types, including point, line, polygon, and group elements.
  • A vertex edit tracker allows you to move vertices of lines, polygons, curves, and curved text. This functionality is implemented by the LineTracker and PolygonTracker objects.
  • A callout tracker allows you to move a text callout. This functionality is implemented by the CalloutTracker object.
  The CancelTracker object is used by ArcObjects to monitor the Esc key (optionally, the space bar and mouse clicks as well) and terminate processes at your request.
  For additional information, see Selection trackers.
  
  

  Representations

  A representation class is also called a feature class representation. It is associated with a collection of representation rules to symbolize features and store that information in the geodatabase. It allows the geometry and properties of features to be altered from the rule without disrupting the associated spatial data. Representations are representations of individual features participating in a representation class. RepresentationClass, RepresentationRules, and Representation are objects in the Geodatabase library.
  RepresentationRules is a collection of one or more individual RepresentationRule objects that are used to categorize features in a geodatabase into groups. A regular representation rule consists of multiple layers of basic symbols such as BasicMarkerSymbol, BasicLineSymbol, or BasicFillSymbol for drawing markers, line strokes, and fill patterns, respectively. All basic symbol classes implement the IBasicSymbol interface.
  More complex symbology can be achieved by including one or more geometric effects in a representation rule. A geometric effect is a dynamic process that alters geometry at draw time. It can even change geometry type. For example, point, line, or polygon geometries can be processed through GeometricEffectBuffer to produce buffer polygons around them.
  All representation rule objects support the IRepresentationRule interface. Use the LayerCount and Layer properties to get the total number of symbol layers and to retrieve individual symbol layers at a given index. The InsertLayer method can be used to insert a symbol layer into a representation rule. You can specify the index and basic symbol as input values. Use the RemoveLayer method to remove a specific symbol layer present in the representation rule given its index.
  RepresentationRule also implements IRepresentationRuleInit, which is useful for transforming a regular ArcGIS symbol to a basic symbol. Since only basic symbols are used to construct a representation rule, it is important to transform a regular symbol to a basic symbol to use it with representations.
  For additional information, see Cartographic representations.
  BasicMarkerSymbol
  A basic marker symbol is used to draw marker symbols and has marker, size, and angle as its graphic attributes. These attributes can be managed using the IGraphicAttributes interface. The attributes are listed in the esriGraphicAttribute enumeration and are prefixed with esriGAMarker - for example, esriGAMarkerSize. All basic marker symbol classes implement IBasicMarkerSymbol, which has a single MarkerPlacement property. 
  Marker placement objects are marker placement styles for placing markers. You can place single or multiple markers depending on the marker placement you choose. For example, MarkerPlacementOnPoint places a single marker over a point, while MarkerPlacementAlongLine places multiple markers along a line. The default marker placement for any basic marker symbol is MarkerPlacementOnPoint. Use IMarkerPlacement to create and manipulate the properties of placement styles.
  The esriMarkerPlacementAttributes enumeration lists graphic attributes for all marker placements where each attribute is prefixed with esriGA(name)(attribute), such as esriGAInsidePolygonGridAngle, where MarkerPlacementInsidePolygon is the marker placement style and GridAngle is its graphic attribute.
  Examples of basic marker symbols are shown in the following graphic:
  
  The following table lists the available marker placement styles along with their valid input geometry types and graphic attributes:

  Marker placement	Valid input geometry	Graphic attributes
  AlongLine	Line Polygon	Step Endings Control points Angle to line
  AtExtremities	Line	Type Offset Angle to line
  Decoration	Line Polygon	Number of positions Begin gap End gap Flip all Flip first Angle to line
  InsidePolygon	Polygon	X step Y step Grid angle Shift odd rows X offset Y offset Clipping
  OnLine	Line Polygon	Position Relative to Angle to line
  OnPoint	Point	X offset Y offset
  OnVertices	Line Polygon	On end points On control points On regular vertices Angle to line
  PolygonCenter	Polygon	X offset Y offset Center method Center clipping
  RandomAlongLine	Line Polygon	Step Endings Control points Random Skew effect
  RandomInPolygon	Polygon	X offset Y offset Clipping
  VariableAlongLine	Line Polygon	Step Endings Control points Min zoom Max zoom Zoom number Method Offset

  For additional information, see Create a custom marker placement for placing markers around a point.
  BasicLineSymbol
  A basic line symbol is used to draw stroke symbols. All basic line symbol classes implement IBasicLineSymbol, which has a single Stroke property. LineStroke has width, caps, joins, and color as its graphic attributes. These attributes can be manipulated using the IGraphicAttributes interface. The attributes are listed in the esriGraphicAttribute enumeration and are prefixed with esriGAStroke, such as esriGAStrokeWidth. Use ILineStroke to create and manipulate the properties of a new stroke symbol.
  BasicFillSymbol
  A basic fill symbol is used to draw fill symbols. All basic fill symbol classes implement IBasicFillSymbol, which has a single FillPattern property. The three fill patterns and their graphic attributes are shown in the following table:

  Fill pattern	Graphic attributes
  SolidColorPattern	Color
  GradientPattern	Color1 Color2 Pattern style Interval Percent Algorithm Angle
  LinePattern	Color Width Angle Step Offset

  These attributes can be manipulated using the IGraphicAttributes interface. The attributes are listed in the esriGraphicAttribute enumeration and are prefixed with esriGA(fill pattern type), such as esriGASolidColorPatternColor. Use IFillPattern to create and manipulate the properties of a new Fill Pattern symbol.
  Fill patterns of BasicFillSymbol are shown in the following graphic from left to right: solid, hatch, and gradient:
  
  GeometricEffect and GeometricEffects
  Geometric effects are dynamic processes that alter the geometry of features. A single representation rule can contain multiple geometric effects, functioning in sequence to create complex symbols. When a single RepresentationRule object is applied with a chain of geometric effects, the end result of applying the chain of effects can be considered and managed as a single geometric effect. For this reason, the RepresentationRule class inherits both the IGeometricEffect and IGeometricEffects interfaces. The result of geometric effects applied on a rule are directly passed to all basic symbol layers present in the rule for drawing features. While IGeometricEffects is useful to browse through individual geometric effects participating in the rule, IGeometricEffect is useful to manage the chain of multiple geometric effects as a single geometric effect.
  For example, as shown in the following illustration, if there are two geometric effects - GeometricEffectDash and GeometricEffectOffset - applied on line strokes in sequential order, you can use IGeometricEffects to get the results for individual dash or offset effects but not both. However, you can use IGeometricEffect to get the result of applying a combination of dash and offset effects as a single effect.
  
  The RepresentationRule class does not implement IGraphicAttributes. Thus, when IGeometricEffect is used to reference a RepresentationRule to retrieve the chain of effects on this rule as a single effect, IGraphicAttributes must not be used to get back the graphic attributes present for these effects.
  The following table lists the available geometric effects along with their valid input and output geometry types and graphic attributes:

  Geometric effect	Input geometry : Output geometry	Graphic attributes
  AddControlPoints	Line : Line, Polygon : Polygon	Tolerance
  Buffer	Point : Polygon, Line : Polygon, Polygon : Polygon	Size
  Cut	Line : Line, Polygon : Line	Begin, End, Invert
  Dashes	Line : Line, Polygon : Line	Pattern, Endings
  Donut	Polygon : Polygon	Width, Simple, Method
  EnclosingPolygon	Line : Polygon, Polygon : Polygon	Method
  Move	Line : Line, Polygon : Polygon	X Offset, Y Offset
  OffsetCurve	Line : Line, Polygon : Polygon	Offset, Method, Simple
  Radial	Point : Line	Angle, Length
  RegularPolygon	Point : Polygon	Radius, Edges, Angle
  Reverse	Line : Line	Reverse
  Rotate	Line : Line, Polygon : Polygon	Angle
  Simplify	Line : Line, Polygon : Polygon	Tolerance
  Scale	Line : Line, Polygon : Polygon	X Factor, Y Factor
  SmoothCurve	Line : Line, Polygon : Polygon	Tolerance
  TaperedPolygon	Line : Polygon	From width, To width, Length
  Wave	Line : Line, Polygon : Polygon	Period, Width, Style

  For more information, see Create custom move, rotate, and scale GeometricEffects within a single project.
  Graphic attributes and graphic attribute types
  Graphic attributes are attributes used to define graphical properties for marker placements and geometric effects, and BasicMarkerSymbol, LineStroke, GradientPattern, LinePattern, and SolidColorPattern objects. RepresentationClass also has a single graphic attribute for controlling its visibility property. All graphic attributes are enumerated into esriGraphicAttribute, esriGeometricEffectAttributes, and esriMarkerPlacementAttributes enumerations.
  IGraphicAttributes is the basic interface that a class must implement to have a list of its own graphic attributes. Use the ClassName property on this interface in conjunction with either IGeometricEffect or IMarkerPlacement to determine which geometric effect or marker placement object is currently used. The esriGraphicAttributeType enumeration has the following attribute types:
  • Boolean
  • Color
  • Dash
  • Double
  • Enum
  • Integer
  • Marker
  • Size
  • Text
  The BasicMarkerSymbol modifying graphic attributes, color, angle, size, and transparency are shown in the following illustration:
   
  MapContext and OutputContext
  The following reference frames are used for data translation among geographic, map, and output display contexts:
  • Geographic reference frame - A feature layer represents geographic data and can be reprojected prior to drawing the features on a map.
  • Map reference frame (MRF) - An intermediate frame introduced to define a clear context in which geometric effects and on-the-fly processing work. This frame is similar to the map sheet frame that is used with a 72 dpi graphic resolution centered at the geographic spatial reference. The advantage of having the MRF is to provide a stable context for geometric effects and marker placement properties as this is in a graphic frame but independent of zoom levels and pan positions. Linear attributes (distance and length) are relative to this frame. For example, a 12 point offset is a 12 unit displacement in MRF. Effects store these attributes in MRF units and use them without any transformation.
  • Output reference frame - Consists of an output device that displays the map with a zoom level that is not equal to the reference scale as well as a changed center position.
  Representation reference frames are shown in the following diagram:
  
  Use IMapContext and IOutputContext to get references to the MapContext and OutputContext objects.
  
  

  For further information see:
  

  Sample: Create a custom marker placement for placing markers around a point