CGGOOGLEMAPWIDGET

CGGOOGLEMAPWIDGET
This is the driver for the cgGoggleMapWidget object, which is a compound widget
object that obtains a Google static map from Google Maps and displays it in the
program's draw widget window. It can be used either as a stand-alone program or
to create a map image in draw widget in a larger widget program.
This program implements a subset of the Google Static Map API, which can be found in
more detail here: https://developers.google.com/maps/documentation/staticmaps/. The
program works by building a URL for a map image. A connection to the Internet is
required to then request a map image (in GIF, JPEG or PNG format) to be returned from
Goggle Maps. The returned image is then read and loaded into a draw widget window
of the right size for the returned map image. The default is to delete the image file
that is created, but the user can also set keywords to retain the image that is downloaded
from Google Maps. Users are able to control button and motion events in the resulting
draw widget with their own event handler module. A cgMap coordinate object is created
to establish a map reference coordinate system on top of the returned map image, allowing
other map information to be drawn on top of the returned map image.

Params

parent: in, optional, type=long
The identifier of the parent widget of the draw widget that is going to be
created by the program. If not provided, the program will create its own
top-level base widget as the parent.

Keywords

box_axes: in, optional, type=boolean, default=0
Set this keyword to draw box axes around the Google Map.
button_events: in, optional, type=boolean, default=0
Set this keyword to turn button events on for the draw widget in the program.
center_latitude: in, optional, type=float, default=40.60
The center latitude of the requested Google map. If not provided, the latitude of
Fort Collins, Colorado, home of Coyote. Latitudes are only recognized to four
decimals values of precision.
center_longitude: in, optional, type=float, default=-105.10
The center longitude of the requested Google map. If not provided, the longitude of
Fort Collins, Colorado, home of Coyote. Longitude are only recognized to four
decimals values of precision.
event_method: in, optional, type='string'
The name of the event handler method for the draw widget. If you use this keyword,
you will also need to write this event handler module. It gets sent one positional
parameter, the event structure created by the draw widget.
event_pro: in, optional, type='string'
The name of an external event handler procedure for the draw widget. The event handler
procedure gets sent one positional parameter, the event structure created by the draw widget.
imagetype: in, optional, type=string, default='png32'
The type of image format the Google map should be returned in. The default is
a 32-bit full color PNG file. The image types are given in the Google Static Map
API documentation and are as follows: png or png8, png32, gif, jpg, and jpg-baseline.
keep_image: in, optional, type=boolean, default=0
Set this keyword if you wish to save the Google map as an image when the object
is destroyed.
maptype: in, optional, type=string, default='terrain'
Set this keyword to the type of map you wish to retrieve from Google Maps. The
choices are listed in the Google Static Map API documentation and are: "roadmap",
"terrain", "satellite", and "hybrid".
markers: in, optional, type=structure
A scalar or array of cgGoogleMapMarker structures. If present, the markers will
be requested with the map from Google. The cgGoogleMapMarker structure is defined
like this::
struct = { cgGOOGLEMAPMARKER, $
size: "", $ ; The marker size ("tiny", "small", "mid" or "normal")
color: "", $ ; A color name as provided by cgColor.
label: "", $ ; A single uppercase character label from the set {A-Z,0-9}.
lats: Ptr_New(), $ ; A pointer to one or more latitude values.
lons: Ptr_New() } ; A pointer to one or more longitude values.
Note that the user will be responsible for freeing the pointers in the MARKERS
structure. This program will not do that.
motion_events: in, optional, type=boolean, default=0
Set this keyword to turn motion events on for the draw widget in the program.
tempDir: in, optional, type=string
The directory where the image containing the Google map is written. By default,
it is obtained from the environment like this: tempdir = GetEnv('IDL_TMPDIR').
visiblemarkers: in, optional, type=boolean, default=1
Set this keyword to 0 to temporarily turn off the display of the markers. Normally,
markers are drawn (if present), unless this flag is set to 0.
xsize: in, optional, type=int, default=600
The X size of the program's draw widget. A maximum of 690 if box axes are requested
and a maximum of 640 if no box axes are requested. Box axes require a 25 pixel border
and the maximum size of a Google Map is 640 pixels.
ysize: in, optional, type=int, default=600
The Y size of the program's draw widget. A maximum of 690 if box axes are requested
and a maximum of 640 if no box axes are requested. Box axes require a 25 pixel border
and the maximum size of a Google Map is 640 pixels.
zoomlevel: in, optional, type=integer, default=12
The zoom level of the requested Google map. Should be an integer between 0 and 21.

Returns

The return value is an instance of a cgGoggleMapWidget object.

Examples

Used to put two markers on a map of Fort Collins, Colorado, in a stand-alone window::
PRO cgGoggleMapWidget_Test
marker1 = {cgGOOGLEMAPMARKER, 'normal', 'dodger blue', 'A', Ptr_New(40.600), Ptr_New(-105.100)}
marker2 = {cgGOOGLEMAPMARKER, 'normal', 'purple', 'B', Ptr_New(40.605), Ptr_New(-105.105)}
googleObject = cgGoggleMapWidget(MARKERS=[marker1, marker2], MAPTYPE='Terrain')
END

Author

FANNING SOFTWARE CONSULTING::
David W. Fanning
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: david@idlcoyote.com
Coyote's Guide to IDL Programming: http://www.idlcoyote.com

History

Change History::
Written, 25 June 2012. DWF.