[mapserver-users] querying in mode=tile

[Mr. Puneet Kishor]

On Sep 11, 2011, at 10:03 PM, Richard Greenwood wrote:

> On Sun, Sep 11, 2011 at 8:48 AM, Mr. Puneet Kishor <punk.kish at gmail.com> wrote:
>> 
>> On Sep 11, 2011, at 8:03 AM, Richard Greenwood wrote:
>> 
>>> On Sat, Sep 10, 2011 at 1:35 PM, Mr. Puneet Kishor <punk.kish at gmail.com> wrote:
>>>> Now that I have mode=tile working with Google Maps API v3, I am on my way to implement querying like so
>>>> 
>>>>    0. Bind an infowindow.close() to a click event listener on the map
>>>>    1. Bind an infowindow.open() to a click event listener on the MapServer layer
>>>>    2. Fill the infowindow content with the result from an Ajax query to MapServer
>>>>    3. When the user clicks on the MapServer layer, the Ajax query is fired
>>>>    4. MapServer responds with the query result as a JSON object
>>>>    5. Fill the infowindow with the JSON result
>>>>    6. Close any already open infowindow via #0 above
>>>>    7. Open a new infowindow with the result
>>>> 
>>>> Is the general approach outlined above sound? Any pointers to existing code samples for the above?
>>> 
>>> 
>>> Puneet,
>>> 
>>> I'm doing pretty much that here:
>>>   http://records.sublettewyo.com/mapserver/map.html
>>> I'm using jQuery in this example and putting the info into a jQuery
>>> dialog, however I have used a standard browser window in the past.
>>> Only thing is that I don't thinnk you really need step 0, simply
>>> replace the contents of the container with the new info.
>> 
>> 
>> Yup, I don't have to worry about #0. Howerver, #1 above is problematic, and I don't have a resolution for it yet. Seems like in Google Maps API v3 I can't addListener to an ImageMapType overlay. See, I am adding a MapServer layer as ImageMapType overlay like so
>> 
>>  "mapserverLayer" : new google.maps.ImageMapType({ .. })
>>  map.overlayMapTypes.insertAt(0, mapserverLayer);
>> 
>> 
>> If I do the following --
>> 
>>  google.maps.event.addListener(map, "click", function (event) { }
>> 
>> it works, however, the following doesn't work at all
>> 
>>  google.maps.event.addListener(mapserverLayer, "click", function (event) { }
>> 
>> Which is silly, isn't it? I don't want the entire map to be listening to the "click" events. I just want the MapServer layer to be doing so. Haven't yet found a resolution to this.
>> 
>> 
>>> 
>>> Also, if your data is in PostGIS you can skip mapserver for attribute
>>> queries and do an info query against the PostGIS db via PHP or other
>>> server-side tool.
>>> 
>> 
>> Ok, I am very interested in the above, but I am not sure I understand you. For the most part, I want to click on the map, and find out more about what I clicked on. In order to do that query via Perl MapScript (I don't know PHP) and Pg, I would need to create the $mapObj. I am able to do that fine, but I don't know how to run MapServer in `mode=tile` via MapScript. This is the question I have asked a couple of times -- if I have a pure MapScript app (no map files involved at all, which is what I want), how no earth do I tell the app to use `mode=tile`?
>> 
>> Puneet.
>> 
>> 
> 
> Puneet,
> 
> I do not know how to bind an infowindow.open() to a click event
> listener on the MapServer layer (#1 above) because I do not use the
> Google API. But using Perl, PHP or whatever it is easy to query a
> PostGIS database, and even get GeoJSON back should you want to
> highlight the selected object on the map.
> 
> I am using OpenLayers so I can easily convert the mouse click (or box)
> to a real-world coordinate(s). I pass the point or box to a PHP page
> which connects to a PostGIS db, does the query, and returns JSON. Does
> that help? I'm not sure that I understand everything that you're doing
> and maybe my approach is not appropriate in your case.


I am assuming you are using OL with MapServer WMS. If I could get MapServer WMS (via MapScript) working, it would have been good, but after screwing around for a day and a half unsuccessfully, I gave up (for now).

Then I tried `mode=tile` and it just worked. However, even that is not fully satisfactory as it is not via MapScript. Without MapScript I am severely hampered -- the complexity of the datasets makes for beastly map files. My map file with just one data source is already almost 9000 lines long. In fact, I generate the map file via MapScript, and then further tweak it by hand.

Even with WMS or tile mode, I will have to implement some kind of tile caching either with tilecache or map proxy or some such to improve the performance.

However, since I am not using MapScript (even though I would prefer to), I would have to implement both CGI and MapScript to do what you are suggesting above -- CGI to display the map and MapScript to do the query.

For now, I have been able to get this clicky thing working -- I click on the map, do a `mode=query` and display the result in an infowindow. That part is working.

Ideally, I would like to have a single technology -- MapScript to generate the maps that can be displayed via multiple front-ends -- OL, Gmaps, perhaps Leaflet, and MapScript to query the attributes via clicks and selects on the map. For now, I am flailing.

> 
> Are you in Denver for FOSS4G??
> 

Unfortunately no. Too much work here, and no funding to travel. I am sure you all will have a blast.

Puneet.