Layers in a GISDK Application

The Maptitude platform keeps a running list of all the different layers that are being used anywhere in a GISDK application. It also keeps track of where each layer is being used. For example, the States layer could be part of two different map windows, and one editor window. Each layer is identified by name, and the names are unique.

Sometimes, different geographic files contain layers with the same name. For example, the ccstreet.cdf file contains a layer named Streets. If you create a small extract of this file, the name of the layer in this new file is also called Streets. If you include both of these layers in a GISDK application (in a single map, or in two different maps), Maptitude renames the second one Streets:1.

Here is a short example that adds layers from a selected geographic file to an existing map.

Macro "add layers to the current map"

curr_map = GetMap() // get the name of the current map

on escape do Return() end // If user clicks escape, skip it

// Ask the user to choose a geographic file...

db = ChooseFile({{"Standard","*.dbd"},{"Compact", "*.cdf"}},

"Choose file to add...", )

on escape default

lyrs = GetDBLayers(db) // get a list of layers in the geographic file...

for i = 1 to lyrs.length do

// Add the layer to the map

lyr_name = AddLayer(curr_map, lyrs[i], db, lyrs[i])

// Set the style for the layer, or you won't see anything!!!

RunMacro("set a style for the layer", lyr_name)

// Check to see if the layer name has changed...

if lyr_name <> lyrs[i] then

ShowMessage("The name of layer " + lyrs[i] + " has been changed to "

+ lyr_name + "!")

end

endMacro

Macro "set a style for the layer" (layer_name)

solid_linestyle = LineStyle({{{1, -1, 0}}})

line_width = 0.25

color_black = ColorRGB(0,0,0)

color_gray = ColorRGB(32768,32768,32768)

color_green = ColorRGB (0,49152,0)

fillstyle_none = FillStyle({

" ",

" "})

inf = GetLayerInfo(layer_name)

if inf = null then Return()

if inf[9] = null then do

// The layer doesn't have a style set up yet.

t = GetLayerType(layer_name)

layer_bar = layer_name + "|"

if t = "Point" then do

SetIcon (layer_bar, "Font Character", "Caliper Cartographic|4", 36)

SetIconColor(layer_bar, color_black)

end

else if t = "Line" then do

SetLineStyle(layer_bar, solid_linestyle)

SetLineWidth(layer_bar, line_width)

SetLineColor(layer_bar, color_gray)

end

else if t = "Area" then do

SetLineStyle(layer_bar, solid_linestyle)

SetLineWidth(layer_bar, line_width)

SetLineColor(layer_bar, color_green)

SetFillStyle(layer_bar, fillstyle_none)

SetFillColor(layer_bar, color_black)

end

endMacro

When you drop a layer from a map using DropLayer(), Maptitude automatically checks the master layer list to see if the layer is currently used in any other maps, editors, or layouts. If not, the layer is dropped from the master layer list.

GISDK has several functions to tell you what layers exist in an application, which layers are in which maps, and other information about each layer. Here is a quick summary:

GISDK Function	Summary
GetLayer()	Gets the name of the current layer, if any
GetLayerDB()	Gets the name of the location where a layer is stored
GetLayerDBPos()	Gets the layer "position" within a geographic file
GetLayerInfo()	Gets summary information about a layer
GetLayerNames()	Gets a list of all layers in the system
GetLayers()	Gets information on layers in the system and the current layer
GetLayerScope()	Gets the scope of a map layer
GetLayerType()	Gets the type of a map layer (Point, Line, Area, Image)
GetMapCurrentLayer()	Gets the name of the current layer in a map
GetMapLayers()	Gets a list of the layers in a map
IsLayer()	Determines whether a layer is any of the given types
RenameLayer()	Changes the name of a map layer

Here is a sample macro that opens two map files, and compares the list of layers in each map.

Macro "compare two maps"
map1 = OpenMap("map1.map", option_array)
map2 = OpenMap("map2.map", option_array)

lyrs_all = GetLayerNames("All")	// Get a list of all layers in the system

tmp = GetMapLayers(map1, "All")	// Get a list of all the layers in map1
lyrs1 = tmp[1]

tmp = GetMapLayers(map2, "All")	// ...and do the same for map2
lyrs2 = tmp[1]

// Now loop over all the layers...
for i = 1 to lyrs_all.length do
pos = ArrayPosition(lyrs1, {lyrs_all[i]}, )	// find the position of this
// layer in map 1
if pos = 0 then	// If it's not there...

ShowMessage(lyrs_all[i]+" is not in map " + map1)


pos = ArrayPosition(lyrs2, {lyrs_all[i]}, )	// do the same test on the 2nd map
if pos = 0 then

ShowMessage(lyrs_all[i]+" is not in map " + map2)

end
endMacro