legend scale dependency issues

[percy]

Sloppy on my part, sorry!

I borrowed this code from another part of the app, and then modified it 
into a dynamic legend generator. That zoom extent business is some "junk 
DNA" that I didn't remove because it didn't look like it was doing 
anything.

I'll strip the code to the bare minimum and report back. I guess since 
the map->setExtent() never gets called again after that code block I 
would assume it has no effect. We'll see :-)

Thanks for noticing this.

Daniel Morissette wrote:
> The code that you included in your last email seems to be missing the 
> stuff that handles the zoom. i.e. a comment suggests that you create a 
> $extent_obj for this, which is either initialized from the values in 
> the $extent[] array, or from the $map->extents which have just been 
> set from the contents of the $extent[] array, so in both case you get 
> more or less the same result minus the width/height ratio adjustment 
> that MapServer does automatically on $map->setExtent()... and there is 
> nothing to adjust the extents to reflect the last zoom operation and 
> pass that to $map->setExtents().
>
> What does the $extent[] array contain when this code starts being 
> executed? Is it the extents before or after applying the zoom?
>
> Daniel
>
> percy wrote:
>> Thanks Daniel, but I've been testing this pretty hard as you can see 
>> from the code snippet below (testing parts are commented out). The 
>> layers are getting turned on and off correctly in the section right 
>> before the call to processlegendtemplate...
>>
>> $map = ms_newMapObj($mymap);
>>     if ($extent['x1'] && $extent['y1'] &&
>>         $extent['x2'] && $extent['y2']) {
>>         // set the extent
>>         $map->setExtent($extent['x1'], $extent['y1'], $extent['x2'], 
>> $extent['y2']);
>>
>>         // set up extent object for use in zoom (!?!?)
>>         $extent_obj = ms_newRectObj();
>>         $extent_obj->setExtent($extent['x1'], $extent['y1'], 
>> $extent['x2'], $extent['y2']);
>>     } else {
>>         $extent_obj = ms_newRectObj();
>>
>> $extent_obj->setExtent ($map->extent->minx, $map->extent->miny, 
>> $map->extent->maxx, $map->extent->maxy);
>>     }
>> //now handle turning the layers on or off
>> if (count($layers)>0) {
>> //echo "I see more than 0 layers\n";
>>   for ($i=0; $i<$map->numlayers; ++$i) {
>>     $oLayer=$map->getLayer($i);
>> //    echo "got layer number".$i;
>>     if (in_array($oLayer->name,$layers)) {
>>       $oLayer->set("status",MS_ON);
>> //      echo "turning on layer  ".$oLayer->name;
>> //      echo $oLayer->status;
>>     } else {
>>       $oLayer->set("status",MS_OFF);
>> //      echo "turning OFF layer  ".$oLayer->name;
>>     }
>>   }
>> }
>> $my_html=$map->processLegendTemplate(null);
>> //echo $_SERVER['QUERY_STRING'];
>> echo $my_html;
>>
>>
>>
>> Daniel Morissette wrote:
>>> percy wrote:
>>>>
>>>> When you zoom in on the map, the scale dependencies all work great 
>>>> for the map, but the legend is always out of whack. I am using 
>>>> php/mapscript to generate a processlegendtemplate() request. For 
>>>> debugging this issue, I have also tried just a straight 
>>>> drawlegend() request and I get similarly odd behavior. The geologic 
>>>> faults, which are set to show up at a scale of 1:500,000 don't show 
>>>> up in the legend until zoomed in to around 1:100,000. (though 
>>>> sometimes if I zoom in small increments, they'll show up sooner...)
>>>>
>>>
>>> The problem could be related to the order in which you make calls in 
>>> your PHP script. The legend object uses the last calculated scale in 
>>> its tests to decide which layer/classes to include in the legend, so 
>>> if you call processlegendtemplate() before the extents and scale 
>>> have been updated to reflect the last zoom operation then you could 
>>> get this kind of behavior.
>>>
>>> I just did a quick check in the code and $map->setExtent() does 
>>> update the scale value, so if you call that with the right extents 
>>> before processing the legend then you should be fine.
>>>
>>> Daniel
>>
>
>

-- 
David Percy
Geospatial Data Manager
Geology Department
Portland State University
http://gisgeek.pdx.edu
503-725-3373