Map Service GetDefaultLayerDrawingDescriptions method

Returns information about layer renderers, symbols, and labels.

GetDefaultLayerDrawingDescriptions(String MapName, int[] LayerIDs, ServerSymbolOutputOptions OutputOptions)

Return Value
 

An array of LayerDrawingDescription for layers which IDs were passed in. The result contains drawing descriptions only for feature layers. Therefore the count of input LayerIDs may not match with the count of returned array of LayerDrawingDescription. If any ID is passed in that is neither of a FeatureLayer nor of an existing layer, no LayerDrawingDescription will be returned for that ID.

Remarks

You may want to use MapLayerInfo.HasLayerDrawingDescription to check whether a map service will return a LayerDrawingDescription for a layer.
 

The OutputOptions parameter can be null, in that case a map service returns images in PNG format. In absence of an output directory images are returned as PNG mime.
 

A LayerDrawingDescription object contains information on the symbology and labels specified by the author. FeatureRenderer describes how the layer is symbolized while LabelingDescription contains all label classes defined in the source map by the author.

Please note that ArcGIS Server map services only return the following:
 

Types of renderers:

• SimpleRenderer

• UniqueValueRenderer

• ClassBreaksRenderer
   

Data exclusion from renderer is not currently supported
 

Types of symbols

• Point features

• SimpleMarkerSymbol

• PictureMarkerSymbol

• Line features

• SimpleLineSymbol

• Polygon features

• SimpleFillSymbol

• PictureFillSymbol
   

If a layer’s renderer is not one of those supported one, nothing will be returned. Symbols that are not the supported are downgraded a supported one. Please see the rules below.

A layer's symbols are downgraded as follows:

Point symbols

• Simple marker symbols are returned using the following types:
  
  
   

• Any other types such as picture marker symbol, character marker symbol, multi layer symbol, etc. are returned as picture marker symbols with a url pointing to an image file.
   

Line symbols

• Simple line symbols are returned as is. The following are supported:
  
  
  
   

• All other symbols, such as cartographic line symbol, marker line symbol, multilayer line symbol etc., are returned as simple solid line symbol. In case of multi layer symbol, a simple line symbol with the properties from the first symbol’s layer of layer’s geometry type is returned.
   

Polygon symbols

• Simple fill symbols are always returned as solid fills. Other types of simple fill symbols such as crossed, horizontal etc. are returned as solid fill symbol type. The outline symbol may be downgraded following above mentioned rules.

• A picture fill symbol is returned as picture fill symbol with a URI pointing to an image file. The server applies transparent, background & foreground colors, if any specified, to the output image.

• All other fill symbols including multi-layer symbols are returned as simple fill symbols with the properties from the first symbol’s layer of layer’s geometry type is returned.
   

Labels

• LabelingDescription is returned as a part of the FeatureLayerDrawingDescriptions. This property is empty if:

• any of the label classes have a “WhereClause” (in ArcMap, it termed a SQL Query).

• an advanced label expression is used.

• any of the label classes contain unsupported keywords when conversion is requested.
  
  
   

• The label expressions in a LabelClassDescription can be converted to a Label Expression by setting the ServerSymbolOutputOptions.ConvertLabelExpressions to true. Only label expressions that conform to the following keywords are converted:

• ServerSymbolOutputOptions.ConvertLabelExpressions can be set to false if the clients want the original label expressions set in the map service whether it is VBScript or JScript.

• TextSymbol’s background is ignored by the server. For example, only the properties of text placed inside a highway shield will be returned and shield (background of the text symbol) itself will be ignored.
  
  

• Label Placement

• Point label’s position could be one of 8 positions around a point. When a weight is set for each position in ArcMap, ArcGIS Server returns the position that has the highest priority. For example, when the label position is set to “Prefer Top Right, all allowed”, the server will return esriServerPointLabelPlacementAboveRight.
  
  
   

• Line label placements are simplified into those listed in the esriServerLineLabelPlacementType enumerators.  In ArcMap label positions are constrained by 2 different options listed below. The list also shows what are they converted to by a map service.

• Vertical position of the label

• Above/Top - esriServerLinePlacementAbove

• On the line - esriServerLinePlacementCenter

• Below/Right - esriServerLinePlacementBelow.  When more than one options are checked in ArcMap, A map service gives priority in the order they are listed above unless “Start Point Priorities” are blocked for that position.

• Position along the line

• At Best - esriServerLinePlacementAlong

• At Start - when “Before” has higher priority in “Start Point Priorities”, a map service returns esriServerLinePlacement*Before, or esriServerLinePlacement*Start is returned.

• At End - when “After” has higher priority in “Start Point Priorities”, a map service returns esriServerLinePlacement*After, or esriServerLinePlacement*End is returned
  
   

Here are few examples:
 

Example #1: See the screen shot below where in ArcMap (a) “Above” is checked, (b) “Location along the line” is “At Start” and (c) “Before” in “Start Point Priorities” has higher priority, the map service returns esriServerLinePlacementAboveBefore.

Example #2: See the screen shot below where in ArcMap (a) both “On the line” and “Below” positions are checked, (b) “Location along the line” is “At Start” and (c) “At” and “After” in “Start Point Priorities” have same higher priority than “Before”, the map service returns esriServerLinePlacementCenterStart.

Polygon labels are always converted to horizontal labels.

Examples