Developer's Guide - MapGuide Open Source - OSGeo

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Overview of Layers Layers represent vector data, raster data, and drawing data in a map. Each type of layer has unique characteristics. NOTE The word layer has different meanings in different contexts. A layer can refer to the layer definition in the resource repository, and it can also refer to the map layer. For the purposes of the Web Tier, a layer refers to a map layer, and a layer definition refers to the layer definition in the resource repository. Basic Layer Properties Layer Groups A map contains one or more layers (MgLayer objects) that are rendered to create a composite image. Each layer has properties that determine how it displays in the map and map legend. Some of the properties are: ■ Layer name: A unique identifier ■ Legend label: The label for the layer as it appears in the map legend. ■ Visibility: whether the layer should be displayed in the map. Note that actual visibility is dependent on more than just the visibility setting for a layer. See Layer Visibility (page 26) for further details. ■ Selectable: Whether features in the layer are selectable. This only applies to layers containing feature data. The MgMap::GetLayers() method returns an MgLayerCollection object that contains all the layers in the map. The MgLayerCollection::GetItem() method returns an individual MgLayer object, by either index number in the collection or layer name. Layers in the collection are sorted by drawing order, with the top layers at the beginning of the collection. For example, using PHP syntax, if $layers is a collection containing the layers in a map, then $layers->GetItem(0) returns the top-most layer. Layers can be optionally grouped into layer groups. Layers in the same group are displayed together in the legend. 24 | Chapter 2 Interacting With Layers
The visibility for all layers in a group can be set at the group level. If the group visibility is turned off then none of the layers in the group will be visible, regardless of their individual visibility settings. If the group visibility is turned on, then individual layers within the group can be made visible or not visible separately. Layer groups can be nested so a group can contain other groups. This provides a finer level of control for handling layer visibility or legend groups. The MgMap::GetLayerGroups() method returns an MgLayerGroupCollection object that contains all the layer groups in the map. Each layer group in a map must have a unique name, even if it is nested within another group. Base Layer Groups The AJAX viewer can use base layer groups to optimize image rendering times. Layers in a base layer group are rendered together to generate a single raster image that can be sent to the viewer. The image is divided into tiles so only the required tiles need to be rendered and sent, instead of the entire image. Tiles are cached on the server; if a tile already exists in the cache it does not need to be rendered before being sent. Each base layer group has a series of pre-defined scales that are used for rendering. When a request is made to view a portion of the map at a given scale, the AJAX viewer renders the tiles at the pre-defined scale that is closest to the requested map view scale. Layers within a base layer group are rendered together. Visibility settings for individual layers are ignored and the visibility setting for the group is used instead. Layers above the base layers will generally be vector layers with transparent backgrounds. This makes the images small and relatively quick to load in the viewer. You may have more than one base layer group. Lower layers will be hidden by higher layers unless the higher layers have transparent areas or have their visibility turned off. NOTE A layer can only belong to one group at a time. It cannot be part of both a base layer group and a regular group. Layer Groups | 25
Page 1 and 2: MapGuide Open Source Developer’s
Page 3 and 4: Contents Chapter 1 Introduction . .
Page 5: Another Way To Create Layers . . .
Page 8 and 9: What This Guide Covers This guide d
Page 11 and 12: This next sample MapGuide page disp
Page 13 and 14: Example Code This sample illustrate
Page 15 and 16: echo 'Map ' . $map->GetName() . ' u
Page 17 and 18: displays the spatial reference syst
Page 19 and 20: Viewer Frames Most custom MSPs disp
Page 21 and 22: Viewer Sample Application - Zoom
Page 23 and 24: Embedding a Viewer in Your Own Page
Page 25 and 26: Resources and Repositories A MapGui
Page 27: $mapDefId = new MgResourceIdentifie
Page 32 and 33: Layer Style Layer Visibility The da
Page 34 and 35: function OnPageLoad() { parent.Zoom
Page 36 and 37: MgInitializeWebTier ($webconfigFile
Page 39 and 40: Working With Feature Data 3 In this
Page 41 and 42: Querying Feature Data In order to w
Page 43 and 44: Examples These examples assume that
Page 45 and 46: $districtQuery = new MgFeatureQuery
Page 47 and 48: $districtQuery = new MgFeatureQuery
Page 49 and 50: There are different selection tools
Page 51 and 52: Script command. See Example: Listin
Page 53 and 54: 4 Initialize the MgSelection object
Page 55 and 56: the $layerClassName = $layer->GetFe
Page 57 and 58: The PHP code in this example create
Page 59 and 60: $resourceService = $siteConnection-
Page 61 and 62: Modifying Maps and Layers In this c
Page 63 and 64: This example ■ loads a layer that
Page 65 and 66: } // ... The page then goes on to s
Page 67 and 68: Function CreateScaleRange() CreateA
Page 69 and 70: Function CreateLineTypeStyle() Crea
Page 71 and 72: ... //-----------------------------
Page 73 and 74: Adding Layers To A Map The precedin
Page 75 and 76: function add_layer_resource_to_map(
Page 77 and 78: Analyzing Features In this chapter
Page 79 and 80: ■ MgLineString — a series of co
Page 81 and 82:
To create an MgCoordinateSystem obj
Page 83 and 84:
■ Determine the SRS for the featu
Page 85 and 86:
Inserting, Deleting, and Updating F
Page 87 and 88:
Example $queryOptions = new MgFeatu
Page 89 and 90:
} The geometries for the selected f
Page 91 and 92:
$map->Save($resourceService); The f
Page 93 and 94:
} 'ResourceId')->item(0); $featureS
Page 95 and 96:
Digitizing and Redlining In this ch
Page 97 and 98:
For example, see task_pane_redlinin
Page 99 and 100:
Create a temporary feature source t
Page 101 and 102:
Custom Output In this chapter ■ I
Page 103 and 104:
■ Images can be copied to the Win
Page 105:
$dwfVersion = new MgDwfVersion("6.0
Page 108 and 109:
G geographic coordinates 74 geometr
Page 110:
Viewer, embedded in HTML page 17 Vi
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