File Coverage

blib/lib/Geo/Google/MapObject.pm
Criterion Covered Total %
statement 130 135 96.3
branch 56 76 73.6
condition 31 59 52.5
subroutine 17 17 100.0
pod 8 8 100.0
total 242 295 82.0


line stmt bran cond sub pod time code
1             package Geo::Google::MapObject;
2              
3 4     4   138688 use warnings;
  4         9  
  4         154  
4 4     4   18 use strict;
  4         7  
  4         111  
5 4     4   19 use Carp;
  4         13  
  4         2814  
6              
7             =head1 NAME
8              
9             Geo::Google::MapObject - Code to help with managing the server side of the Google Maps API
10              
11             =head1 VERSION
12              
13             Version 0.06
14              
15             =cut
16              
17             our $VERSION = '0.06';
18              
19             =head1 SYNOPSIS
20              
21             use HTML::Template::Pluggable;
22             use HTML::Template::Plugin::Dot;
23             use Geo::Google::MapObject;
24             my $map = Geo::Google::MapObject->new(
25             key => 'ABQFbHAATHwok56Qe3MBtg0s7lgkHBS9HKneet7v0OIFhIwnBhTEGCHLTRRRBa_lUOCy1fDamS5PQt8qULYfYQ',
26             zoom => 13,
27             size => '512x400',
28             maptype => 'terrain',
29             markers=>
30             [
31             {
32             location=>'51.242844,0.011716',
33             color=>'green',
34             label=>'P',
35             title=>'Periapt Technologies',
36             href=>'http://www.periapt.co.uk'
37             },
38             {
39             location=>'51.243757,0.006051',
40             color=>'red',
41             label=>'C',
42             title=>'Crown Roast Butchers',
43             href=>'http://www.crownroast.co.uk/'
44             },
45             ]
46             );
47             my $template = HTML::Template::Pluggable->new(file=>'map.tmpl');
48             $template->param(map=>$map);
49             return $template->output;
50            
51             =head1 DESCRIPTION
52              
53             This module is intended to provide a server side solution to working with the Google Maps API.
54             In particular an object of this class encapsulates a "map" object that provides support
55             for the static maps API, the javascript maps API, AJAX calls and non-javascript fallback data;
56             but without making many assumptions about the surrounding framework.
57             We do assume that a template framework with support for a "dot" notation is being used, for example L.
58             An important commitment of the module is support for graceful and consistent fallback to a functional non-javascript web page.
59              
60             The javascript and static Google map APIs do not behave in quite the same way when zoom and center are not specified.
61             Specifically it works quite well with the static maps (L)
62             but not so well with the javascript API.
63             To compensate for this the module gives a choice between: specifying the center and zoom levels; allowing the APIs and client side code to
64             do whatever they think best; using a built in algorithm to calculate a sensible zoom and center; and finally supplying ones
65             own algorithm to calculate a sensible zoom and center.
66              
67             =head1 INTERFACE
68              
69             =head2 new
70              
71             Supported arguments are
72              
73             =over
74              
75             =item autozoom
76              
77             If no center and/or zoom is specified this parameter can be used to calculate suitable
78             values by a process of averaging the markers. If this parameter is an integer between 0
79             and 21 then that number is taken as a maximum zoom level and the builtin
80             algorithm, C<< calculate_zoom_and_center >>, is used with that maximum zoom level.
81             If the parameter is a CODE ref, then that function is used instead. The CODE ref must
82             take an ARRAY ref of marker specifications as an input, and must return a pair consisting of the zoom
83             level as an integer followed by a latitude-longitude string representing the center.
84             Finally if the argument is blessed and has a C<< calculate_zoom_and_center >> method,
85             that will be used. For AUTO calculation of the center or zoom all
86             the markers must be in the form "decimal,decimal". The C<< json >> method will delete this
87             as it has no meaning once the zoom level and center have been determined.
88              
89             =item center
90              
91             This must be a location that would be recognized by the Google maps API.
92             If absent, and if no autozoom has been set, the Google maps API and client side javascript code
93             must between them work out a center.
94              
95             =item zoom
96              
97             This represents the zoom level (L), which
98             is a number between 0 and 21 inclusive. If absent (with no autozoom set) the API and client will need to set it.
99              
100             =item size
101              
102             The size (L) must either be a string
103             consisting of two numbers joined by the symbol C, or a hash ref with width and height parameters. In either
104             case the first number is the width and the second the height. If absent the Google API will be allowed to set
105             the size as it sees fit.
106              
107             =item format
108              
109             The optional format (L) must be one of
110             'png8', 'png', 'png32', 'gif', 'jpg', 'jpg-baseline'. If absent the Google API will be allowed to set
111             the format as it sees fit. Note that although the C<< json >> method will pass this on, it seems to have no meaning
112             in the dynamic API.
113              
114             =item maptype
115              
116             This must be one of the following: 'roadmap', 'satellite', 'terrain', 'hybrid's described in L. The C<< json >> method will translate these into numerical codes roadmap => 0, satellite => 1, terrain => 2 and hybrid => 3
117             as this makes it easy for the javascript code (L) to translate this numerical code into the client side codes. For example:
118              
119             var mapping = new Array(G_NORMAL_MAP, G_SATELLITE_MAP, G_PHYSICAL_MAP, G_HYBRID_MAP);
120             var maptype = mapping[data.maptype];
121              
122             =item mobile
123              
124             This parameter should be either the string 'true' or 'false' and defaults to 'false'. The static API uses it to provide more
125             robust tiles as described in L. However it seems to have no meaning
126             for the dynamic API.
127              
128             =item key
129              
130             The mandatory API key. You can sign up for one at L.
131              
132             =item sensor
133              
134             This parameter should be either the string 'true' or 'false' and defaults to 'false'. Both versions of the Google API
135             require it (L) and this is reflected in this module
136             by it being used by the C<< static_map_url >> and C<< javascript_url >> methods.
137              
138             =item markers
139              
140             If present the markers should be an array ref of marker specifications so that it can be used in a TMPL_LOOP.
141             Each marker specification should be a hash ref and may contain whatever keys are required
142             by the javascript client side code. It must however have a C<< location >> field which must be interpretable
143             by the Google API as a location. In general this means the location must be a string of the form "decimal,decimal",
144             where the first decimal is the latitude and the second longitude.
145             Other fields might include for example: id, title, href, icon. Generally these just get passed through by the C<< json >>
146             method and should be used by the client side code as it sees fit.
147             Three fields that have a special meaning, C<< color >>, C<< size >>, C<< label >> are those described by the static maps API
148             (L).
149             The GIcon class (L) contains lots of ways of specialising
150             the look and feel of the markers in the dynamic API; but I can find no easy way of consistently replicating the
151             the static marker styles in the dynamic API. The only other field which gets special treatment is C<< title >>. The C<< json >>
152             method will encode the title field. So for example if a marker has a title field of C<< 'Scloß' >>, then
153             if the javascript code uses this as the title attribute when creating a GMarker, then hovering the mouse over that marker
154             will display the German word for castle.
155              
156             =item hl
157              
158             This parameter specifies the language to be used. If absent the API will select the language. Only the dynamic javascript API
159             seems to use this parameter as described in L. As such this
160             is used in the C<< javascript_url >> method.
161              
162             =back
163              
164             =cut
165              
166             my %MAPTYPE = (
167             roadmap=>0,
168             satellite=>1,
169             terrain=>2,
170             hybrid=>3,
171             );
172              
173             sub new {
174 27     27 1 14780 my $class = shift;
175 27         138 my %args = @_;
176 27 50 33     140 $args{mobile} = 'false' unless exists $args{mobile} && $args{mobile} eq 'true';
177 27 50 33     131 $args{sensor} = 'false' unless exists $args{sensor} && $args{sensor} eq 'true';
178 27 100       75 if (exists $args{markers}) {
179 12 50       50 croak "markers should be an ARRAY" unless ref($args{markers}) eq "ARRAY";
180             }
181 27 50       72 croak "no API key" unless exists $args{key};
182 27 100 100     134 if (exists $args{markers} && exists $args{autozoom}) {
183 7         31 my ($zoom, $center) = _autocalculate(%args);
184 7   33     44 $args{zoom} ||= $zoom;
185 7   33     39 $args{center} ||= $center;
186 7         21 delete $args{autozoom};
187             }
188 27 50       76 if (exists $args{zoom}) {
189 27 50 33     342 croak "zoom not a number: $args{zoom}" unless ($args{zoom} =~ /^\d{1,2}$/) && $args{zoom} < 22;
190             }
191 27 50       73 if (exists $args{maptype}) {
192 0 0       0 croak "maptype $args{maptype} not recognized" unless exists $MAPTYPE{$args{maptype}};
193             }
194 27 100       73 if (exists $args{size}) {
195 26         76 my ($width, $height) = _parse_size($args{size});
196 17         78 $args{size} = {width=>$width,height=>$height};
197             }
198 18         80 return bless \%args, $class;
199             }
200              
201             sub _parse_size {
202 26     26   39 my $size = shift;
203 26         36 my ($width, $height);
204 26 100       135 if (ref($size) eq "HASH") {
    100          
205 7   66     299 $width = $size->{width} || croak "no width";
206 6   66     170 $height = $size->{height} || croak "no height";
207             }
208             elsif($size =~ /^(\d{1,3})x(\d{1,3})$/) {
209 16         37 $width = $1;
210 16         29 $height = $2;
211             }
212             else {
213 3         469 croak "cannot recognize size";
214             }
215 21 100 100     516 croak "width should positive and be no more than 640" unless ($width > 0 && $width <= 640);
216 19 100 100     380 croak "height should positive and be no more than 640" unless ($height > 0 && $height <= 640);
217 17         51 return ($width, $height);
218             }
219              
220             sub _autocalculate {
221 7     7   25 my %args = @_;
222 7         12 my $autozoom = $args{autozoom};
223 7   33     27 my $markers = $args{markers} || croak "cannot calculate autozoom without markers";
224 4     4   25 use Scalar::Util qw(blessed looks_like_number);
  4         12  
  4         1110  
225 7 50 33     69 if (looks_like_number($autozoom) && $autozoom >= 0 && $autozoom <= 21) {
    0 33        
    0 0        
226 7         22 return calculate_zoom_and_center($markers, $autozoom);
227             }
228             elsif (ref($autozoom) eq "CODE") {
229 0         0 return &$autozoom($markers);
230             }
231             elsif (blessed($autozoom) && $autozoom->can('calculate_zoom_and_center')) {
232 0         0 return $autozoom->calculate_zoom_and_center($markers);
233             }
234 0         0 croak "$autozoom not recognized as autozoom";
235             }
236              
237             =head2 calculate_zoom_and_center
238              
239             This function tales a reference to an array of marker specifications
240             and a maximum zoom level and returns a pair consisting of a suggested zoom level
241             and a center.
242              
243             The algorithm works by iteratively building the following objects:
244              
245             =over
246              
247             =item A set of points, starting with the first element of the array and adding the next one at each iteration.
248              
249             Actually we don't actually have a variable for this, but without thinking about this set conceptually
250             I cannot state the algorithm. The set starts of consisting of just the first marker location.
251              
252             =item C<< ($ctheta, $cphi) >>
253              
254             These numbers represent a central point of the set of points represented as radians. The algorithm does not guarantee
255             that the point is the true centre but we treat it as the centre of a circle. This starts of by taking the first element
256             and converting its latitude and longitude to radians.
257              
258             =item C<< $radius >>
259              
260             This variable is initialised to 0.
261              
262             =item The contract
263              
264             The algorithm requires that at each iteration all the points in the set are at most $radius radians from
265             ($ctheta, $cphi).
266              
267             =item The iteration
268              
269             We look at the next point. We look at the distance (C<< $distance >>) between the new point and C<< ($ctheta, $cphi) >>. If this is less than or
270             equal to C<< $radius >> the iteration is over. Otherwise the following happens:
271              
272             ($ctheta, $cphi) = mid point of ($ctheta, $cphi) and the new point
273             $radius = $radius + 0.5 * distance between ($ctheta, $cphi) and the new point
274              
275             =item At the end
276              
277             We convert C<< ($ctheta, $cphi) >> back to latitude and longitude and logarithmically convert the radius to a zoom level.
278              
279             =back
280              
281             I doubt that this algorithm is optimal but it seems quick, uses only one pass through the markers and can be seen in action
282             at L. Also if you have a better one you can specify it by passing a suitable CODE ref or blessed
283             scalar to the C<< autozoom >> parameter of the constructor.
284              
285             =cut
286              
287             sub calculate_zoom_and_center {
288 7     7 1 11 my $markers = shift;
289 7         11 my $maxautozoom = shift;
290              
291 4     4   4413 use Math::Trig qw(deg2rad great_circle_distance great_circle_midpoint rad2deg);
  4         80236  
  4         3980  
292             # At the end we guarantee that any two points are less than $distance apart
293             # and that ($ctheta, $cphi) is (more or less) in the middle.
294 7         11 my ($ctheta, $cphi);
295 7         8 my $distance = 0; # 2*$radius
296 7         12 my $firstpoint = 1;
297              
298 7         11 foreach my $l (@{$markers}) {
  7         14  
299 18 50       50 croak "location missing" unless exists $l->{location};
300 18 50       104 if ($l->{location} =~ /^(\-?\d+\.?\d*),(\-?\d+\.?\d*)$/) {
301 18         84 my $phi = deg2rad(90-$1);
302 18         204 my $theta = deg2rad($2);
303              
304 18 100       146 if ($firstpoint) {
305 7         10 $cphi = $phi;
306 7         9 $ctheta = $theta;
307 7         15 $firstpoint = 0;
308             }
309             else {
310 11         33 my $new_distance = great_circle_distance($theta, $phi, $ctheta, $cphi);
311 11 100       291 if ($new_distance > $distance) {
312 8         14 $distance = $new_distance + $distance/2;
313 8         26 my ($mtheta, $mphi) = great_circle_midpoint($theta, $phi, $ctheta, $cphi);
314 8 50 33     469 if (defined $mtheta && defined $mphi ) {
315 8         12 $ctheta = $mtheta;
316 8         19 $cphi = $mphi;
317             }
318             else {
319 0         0 return (0, "0,0");
320             }
321             }
322             }
323             }
324             }
325 7         15 my $zoom = $maxautozoom;
326 7 100       42 $zoom = int -(log $distance)/(log 2) if $distance > 0; ## no cr itic
327 7 50       20 $zoom = 0 if $zoom < 0;
328 7 100       16 $zoom = $maxautozoom if $zoom > $maxautozoom;
329 7         24 my $longitude = rad2deg($ctheta);
330 7         165 my $latitude = 90-rad2deg($cphi);
331 7         192 return ($zoom, "$latitude,$longitude");
332             }
333              
334             =head2 static_map_url
335              
336             Returns a URL suitable for use with the static maps API based upon the arguments passed to the constructor.
337              
338             =cut
339              
340             sub static_map_url {
341 18     18 1 6872 my $self = shift;
342 18         35 my $url = "http://maps.google.com/maps/api/staticmap?";
343 18         25 my @params;
344              
345             # First the easy parameters
346 18         45 foreach my $i (qw(center zoom format mobile key sensor)) {
347 108 100       387 push @params, "$i=$self->{$i}" if exists $self->{$i};
348             }
349 18 100       117 push @params, "size=$self->{size}->{width}x$self->{size}->{height}" if exists $self->{size};
350              
351 18 100       54 if (exists $self->{markers}) {
352             # Now sort the markers
353 12         20 my %markers;
354 12         14 foreach my $m (@{$self->{markers}}) {
  12         27  
355 34         34 my @style;
356 34 100 66     149 push @style, "color:$m->{color}" if exists $m->{color} && $m->{color} =~
357             /^0x[A-F0-9]{6}|black|brown|green|purple|yellow|blue|gray|orange|red|white$/;
358 34 100 66     110 push @style, "size:$m->{size}" if exists $m->{size} && $m->{size} =~ /^tiny|mid|small$/;
359 34 100 66     100 push @style, "label:$m->{label}" if exists $m->{label} && $m->{label} =~ /^[A-Z0-9]$/;
360 34         55 my $style = join "|", @style;
361 34   33     33 push @{$markers{$style}}, $m->{location} || croak "no location for $style";
  34         172  
362             }
363 12         49 foreach my $m (sort keys %markers) {
364 19         30 my $param = "markers=";
365 19 100       47 $param .= "$m|" if $m;
366 19         22 $param .= join '|', @{$markers{$m}};
  19         50  
367 19         64 push @params, $param;
368             }
369             }
370              
371 18         103 $url .= join "&", @params;
372 18         113 return $url;
373             }
374              
375             =head2 javascript_url
376              
377             Returns a URL suitable for use in loading the dynamic map API.
378              
379             =cut
380              
381             sub javascript_url {
382 18     18 1 1491 my $self = shift;
383 18         66 my $url = "http://maps.google.com/maps?file=api&v=2&key=$self->{key}&sensor=$self->{sensor}";
384 18 100       60 $url .= "&hl=$self->{hl}" if exists $self->{hl};
385 18         102 return $url;
386             }
387              
388             =head2 markers
389              
390             This returns the marker array ref.
391              
392             =cut
393              
394             sub markers {
395 6     6 1 8470 my $self = shift;
396 6   100     41 return $self->{markers} || [];
397             }
398              
399             =head2 json
400              
401             This function uses the L module to return a JSON representation of the object.
402             It removes the API key as that should not be required by any javascript client side code.
403             If any marker object has a title attribute, then that attribute is encoded so it will display
404             correctly during mouse overs.
405              
406             =cut
407              
408             sub json {
409 17     17 1 11379 my $self = shift;
410 4     4   5012 use JSON;
  4         55188  
  4         22  
411 17         112 my %args = %$self;
412 17         47 delete $args{key};
413 4     4   5125 use HTML::Entities;
  4         28746  
  4         1612  
414 17 50       58 $args{maptype} = $MAPTYPE{$args{maptype}} if exists $args{maptype};
415 17         27 foreach my $i (0..$#{$args{markers}}) {
  17         70  
416 34 50       104 $args{markers}[$i]->{title} = decode_entities($args{markers}[$i]->{title}) if exists $args{markers}[$i]->{title};
417             }
418 17         139 return to_json(\%args, {utf8 => 1, allow_blessed => 1});
419             }
420              
421             =head2 width
422              
423             This returns the width of the image or undef if none has been set.
424              
425             =cut
426              
427             sub width {
428 18     18 1 71139 my $self = shift;
429 18 100       83 return undef unless exists $self->{size};
430 17         104 return $self->{size}->{width};
431             }
432              
433             =head2 height
434              
435             This returns the height of the image or undef if none has been set.
436              
437             =cut
438              
439             sub height {
440 18     18 1 1501 my $self = shift;
441 18 100       69 return undef unless exists $self->{size};
442 17         80 return $self->{size}->{height};
443             }
444              
445             =head1 TUTORIAL
446              
447             This module only covers the server side of a two way conversation between server and a talkative client.
448             As such the tutorial must also consider HTML and javascript.
449             Also to understand this tutorial we assume at least passing familiarity with the following:
450              
451             =over
452              
453             =item L or some other templating framework using the "dot" notation.
454              
455             =item The Google maps API: L.
456              
457             =item The static Google maps API: L
458              
459             =item Javascript, AJAX. Specifically we are using the yui framework (L) though any other framework will do.
460              
461             =back
462              
463             =head2 The markup
464              
465             We probably have a template file, map.tmpl, some thing like the following:
466              
467            
468            
469            
470             Test Map Tutorial
471              
472            
473            
474              
475            
476            
477              
478            
479            
480            
481            
482              
483            
484            
485            
486            
487              
488            
489            
490              
491            
494            
495             alt="Test map"
496             src=""
497             width=""
498             height=""
499             />
500            
501              
502            
506            
507            
508            
509            
510             ">
511            
512            
513             ">
514            
515            
516            
517            
518            
519            
520            
521            
522            
523            
524              
525            
526              
527            
528            
529              
530             =head2 The perl
531              
532             The code to actually produce the web page must look something like this:
533              
534             use HTML::Template::Pluggable;
535             use HTML::Template::Plugin::Dot;
536             use Geo::Google::MapObject;
537             my $t = HTML::Template::Pluggable->new(filename => 'map.tmpl');
538             my $map = Geo::Google::MapObject->new(....);
539             $t->param(maps=>$map);
540             print $t->output;
541              
542             This is all that would be needed in a javascript free environment. With javascript
543             enabled the client is going to ask for the same data in a JSON format (at least
544             we are only supporting JSON). The code to service that request will look something like:
545              
546             use Geo::Google::MapObject;
547             my $map = Geo::Google::MapObject->new(....);
548             print $map->json;
549              
550             =head2 The javascript
551              
552             As indicated in the markup above we are expecting the javascript to be in a file called maps.js.
553             We expect it to look something like the following:
554              
555             function mapInitialize() {
556              
557             /* Read the "link" element that tells us how to contact the server. See markup above. */
558             var get_init_data = YAHOO.util.Dom.get('get_init_data').href;
559              
560             /* Build the AJAX callback object consisting of three parts. */
561             var callback =
562             {
563              
564             /* Part I: Function called in the event of a successful call. */
565             success: function(o) {
566              
567             /* Convert the JSON response into a javascript object.
568             This structure corresponds to the Geo::Google::MapObject in perl
569             as intermediated by its "json" method.
570             */
571             var data = YAHOO.lang.JSON.parse(o.responseText);
572              
573             if (GBrowserIsCompatible()) {
574              
575             /* Build up the Map object which will replace #map_canvas in the above markup. */
576             var mapopt = {};
577             if (data.size) {
578             mapopt.size = new GSize(parseInt(data.size.width), parseInt(data.size.height));
579             }
580             var markers = data.markers;
581             var map = new GMap2(YAHOO.util.Dom.get("map_canvas"), mapopt);
582             var maptype = null;
583             if (data.maptype) {
584             maptype = o.argument[parseInt(data.maptype)];
585             }
586             var zoom = null;
587             if (data.zoom) {
588             zoom = parseInt(data.zoom);
589             }
590             var center = markers[0].location;
591             if (data.center) {
592             center = data.center;
593             }
594             map.setCenter(GLatLng.fromUrlValue(center), zoom, maptype);
595             map.setUIToDefault();
596              
597             /* Now for each marker build and add a GMarker object */
598             for(var i = 0; i < markers.length; i++) {
599            
600             var opt = {title: markers[i].title};
601             if (!markers[i].href) {
602             opt.clickable = false;
603             }
604             if (markers[i].icon) {
605             opt.icon = new GIcon(G_DEFAULT_ICON, markers[i].icon);
606             if (markers[i].shadow) {
607             opt.icon.shadow = markers[i].shadow;
608             }
609             }
610             var mark = new GMarker(GLatLng.fromUrlValue(markers[i].location), opt);
611             if (markers[i].href) {
612             mark.href = markers[i].href;
613             GEvent.addListener(mark, "click", function(){window.location=this.href;});
614             }
615             map.addOverlay(mark);
616             }
617             }
618             }, /* End of Part I */
619              
620             /* Part II: Function called in the event of failure */
621             failure: function(o) {alert(o.statusText);},
622              
623             /* Part III: Data that is passed to the success function.
624             We are using this to map from numerical maptypes that Geo::Google::MapObject has passed us to the
625             forms used in Google maps API.
626             */
627             argument: [G_NORMAL_MAP, G_SATELLITE_MAP, G_PHYSICAL_MAP, G_HYBRID_MAP]
628              
629             }; /* End of constructing the AJAX callback object. */
630              
631             /* This calls the server which should hopefully kick off callback.success with lots of lovely data. */
632             var transaction = YAHOO.util.Connect.asyncRequest('GET', get_init_data, callback, null);
633              
634             } /* end of mapInitialize function */
635              
636             /* This will make sure that we call the above function at a good time. */
637             YAHOO.util.Event.onDOMReady(mapInitialize);
638              
639             /* We still have to do the memory cleanup ourselves. */
640             YAHOO.util.Event.addListener(window, 'unload', 'GUnload');
641              
642             =head2 Taking it further
643              
644             There are lots of variations that can be done with this. The Geo::Google::MapObject object will pass
645             on all fields it does not recognize via the C<< json >> function and these can be used by the javascript
646             in whatever way required. Similarly fields added to the marker specification will be passed by the C<< markers >>
647             function and can be used in the template in whatever way required.
648              
649             You can also make the markers draggable and have the act of dragging a marker update data on the server.
650             There is an example of where this has been done at L.
651             The details of how this is done depend intrinsically on the implementation of the data storage on the server.
652             I would suggest that in general the steps required to make the markers draggable might be as follows:
653              
654             =over
655              
656             =item Clean interface to the data storage.
657              
658             I think this is a clear case where an ORM (L) offers some advantages.
659             You could look at L or write your own interface using L.
660              
661             =item Derive a class from Geo::Google::MapObject.
662              
663             Your derived class constructor should get the data you need from the data storage interface layer, use it to
664             create a Geo::Google::MapObject and bless that into your derived class.
665              
666             =item Provide URLs that update the data underlying your map objects.
667              
668             These will probably be POST methods and need not return anything other than an "OK" string.
669             They should probably call the data storage interface layer directly to update the data.
670             There is no point creating a map object merely to update the underlying data.
671              
672             =item Add link elements to your markup indicating which URL is needed to update the marker data.
673              
674            
675              
676             An advantage of using these link elements is that you might have multiple maps to manage.
677             By using the link elements to communicate with the client side, a lot more code and templates can be reused.
678              
679             =item Get the javascript side to read your new link elements.
680              
681             var move_marker = YAHOO.util.Dom.get('move_marker').href;
682              
683             =item Add a C<< draggable >> flag to the GMarker constructor
684              
685             var opt = {title: markers[i].title, draggable: true};
686              
687             =item Make sure your GMarkers are labelled in a way that your server can understand
688              
689             Just after the GMarker object, mark, has been created add
690              
691             mark.label = markers[i].label;
692            
693             =item Make your GMarker object subscribe to the C<< dragend >> event.
694              
695             GEvent.addListener(mark,
696             "dragend",
697             function(latlng) {
698             var location = latlng.toUrlValue(12);
699             var postdata = "id="+this.label+"&location="+location;
700             YAHOO.util.Connect.asyncRequest('POST',
701             move_marker,
702             {
703             success: function(o){},
704             failure: function(o) {alert(o.statusText);},
705             argument: []
706             },
707             postdata);
708             });
709              
710             =back
711              
712             =head1 DIAGNOSTICS
713              
714             =over
715              
716             =item C<< markers should be an ARRAY >>
717              
718             The markers parameter of the constructor must be an ARRAY ref of marker configuration data.
719              
720             =item C<< no API key >>
721              
722             To use this module you must sign up for an API key (http://code.google.com/apis/maps/signup.html) and supply it as
723             the key parameter.
724              
725             =item C<< zoom not a number: %s >>
726              
727             There must be a zoom parameter which is a number from 0 to 21.
728              
729             =item C<< maptype %s not recognized >>
730              
731             The maptype must be one of roadmap, satellite, terrain, hybrid.
732              
733             =item C<< no width >>
734              
735             =item C<< no height >>
736              
737             =item C<< width should be positive and no more than 640 >>
738              
739             =item C<< height should be positive and no more than 640 >>
740              
741             =item C<< cannot recognize size >>
742              
743             The size parameter must either be a string like "300x500" or a hash array like {width=>300,height=>500}.
744             And both width and height must be between 1 and 640 inclusive.
745              
746             =item C<< cannot calculate autozoom without markers >>
747              
748             If you pass an C<< autozoom >> parameter to the constructor you must also pass at least one marker.
749              
750             =item C<< % not recognized as autozoom >>
751              
752             An autozoom parameter was passed to the constructor that was not recognized as such.
753              
754             =item C<< location missing >>
755              
756             A marker specification was missing a location during autozoom calculation.
757              
758             =item C<< no location for %s >>
759              
760             Every marker object must have a location.
761              
762             =back
763              
764             =head1 CONFIGURATION AND ENVIRONMENT
765              
766             Geo::Google::MapObject requires no configuration files or environment variables.
767              
768             =head1 DEPENDENCIES
769              
770             =over
771              
772             =item Templating framework
773              
774             We assume the use of L and L
775             though other template frameworks may work.
776              
777             =item Google Maps API
778              
779             You need to have one of these which can be obtained from L.
780              
781             =item Javascript and AJAX
782              
783             We assume a degree of familiarity with javascript, AJAX and client side programming.
784             For the purposes of documentation we assume YUI: L, but this
785             choice of framework is not mandated.
786              
787             =item L
788              
789             The autozoom algorithm optionally used by this module depends upon the L for its mathematical
790             calculations. Since alternative algorithms or no algorithm at all can be used, I think it might be better to have this as a separate module.
791              
792             =back
793              
794             =head1 INCOMPATIBILITIES
795              
796             None reported.
797              
798             =head1 BUGS AND LIMITATIONS
799              
800             =over
801              
802             =item paths etc
803              
804             Currently there is no support for paths, polygons or viewports.
805              
806             =item version 3
807              
808             We are currently only supporting version 2 of the API.
809              
810             =item testing
811              
812             We encode the title attributes of markers in the C<< json >> function as this seems to be necessary.
813             However I have not yet managed to get a decent test script for this behaviour.
814             There are many other cases that should be tested though I think the most critical cases
815             have been tested.
816              
817             =item character encoding
818              
819             This module is only tested against UTF-8 web pages. I have no intention
820             of changing this as I cannot think of why anyone would consciously choose to encode
821             web pages in any other way. I am open to persuasion however.
822              
823             =back
824              
825             Please report any bugs or feature requests to
826             C, or through the web interface at
827             L.
828              
829              
830             =head1 ACKNOWLEDGEMENTS
831              
832             Thanks to Andreas Koenig for pointing out that this module had an issue with C<< Build.PL >>.
833              
834             =head1 AUTHOR
835              
836             Nicholas Bamber C<< >>
837              
838              
839             =head1 LICENCE AND COPYRIGHT
840              
841             Copyright (c) 2009, Nicholas Bamber C<< >>. All rights reserved.
842              
843             This module is free software; you can redistribute it and/or
844             modify it under the same terms as Perl itself. See L.
845              
846              
847             =head1 DISCLAIMER OF WARRANTY
848              
849             BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
850             FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
851             OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
852             PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
853             EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
854             WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
855             ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
856             YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
857             NECESSARY SERVICING, REPAIR, OR CORRECTION.
858              
859             IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
860             WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
861             REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE
862             LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL,
863             OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
864             THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
865             RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
866             FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
867             SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
868             SUCH DAMAGES.
869              
870             =cut
871              
872             1; # End of Geo::Google::MapObject