Tuesday, 6 December 2011

Fusion is actually usable now

I am going to call it right now. If you've been holding back from moving to Fusion due to the assortment of bugs and performance problems, then the version of Fusion that will appear in the next version of MapGuide Open Source and Autodesk Infrastructure Map Server will be the one which will finally sway you across.

Thanks to work undertaken on behalf of Hume City Council, we have finally tackled most of the deal-breaking issues which have made Fusion unsuitable for production use for many years ... Until now.

What issues in particular? Read on below.

Legend Performance

This is the number one showstopper to wider adoption. The root problem with the legend widget performance is that each icon in the legend requires an individual http GETLEGENDIMAGE icon request to the mapagent. Now suppose you have a layer with a 900-rule theme, attempting to preview this layer will grind your browser and the MapGuide Server to 100% CPU usage, because it will fire off 900 individual icon requests (yes you heard that right!). And that's just for one single user!

We solved this problem through a multi-pronged approach:

1. To speed up the server-side initialization, we use the new GetResourceContents API introduced in MapGuide Open Source 2.2 to fetch all our required layer definitions in a single batch. Performance gains will be readily apparent for really chunky Map Definitions with lots (in the 100s) of layers

2. We exploit the data URI feature that supported by most modern browsers. We pre-cache icons by generating the legend icons server-side and embedding them as base64 encoded data URIs as part of the json content that is returned to the legend widget for initialization. Each legend icon represented as a data URI will eliminate a mapagent icon request that would have to be executed. We use a metric of pre-caching 25 layer icons per scale range. For an average Map Definition (like the Sheboygan sample data set) no icon requests are ever made through this optimization. Now for those primitive browsers from Redmond that don't support data URIs, have no fear. Because there is also the next optimization.

3. The theme compression logic that is used by the AJAX viewer now also exists in Fusion. We use that same number (25) to determine the number of style rules that must be exceeded for a theme to be compressed. Compressed themes in Fusion look like so:

And like the AJAX viewer, you have the option of expanding compressed themes. To avoid unnecessarily expanding say: a 900-rule themed layer, we prompt for confirmation. So the choice to flood a mapguide server with icon requests will be yours and yours alone to make ;-). Even if your browser doesn't support data URIs (It means you are using IE6/7. Don't deny it!), the theme compression means that icon requests will be capped at a certain level by default, just like the AJAX viewer.

So with these changes, our map with the 900-rule themed layer now loads just slightly slower than the AJAX viewer, which is a major improvment from never.

Support for Map Definitions with Tiled and Dynamic Layers

This one wasn't our doing, but Autodesk themselves have finally addressed the other long-standing complaint of not being able to view a map that contains a combination of tiled and dynamic layers.

And as an added bonus, if you are using commerical underlays your tiles can also line up with the Google/Bing/Yahoo/OSM tiles if your Map Definition uses a Google-compatible finite scale list (and is using the WGS84.PseudoMercator coordinate system of course). In anticipation of supporting this new feature, I've added support for generating this Google-compatible scale list in the final release of MapGuide Maestro 4.0 which will be coming out soon.


Ever used the Fusion redline widget? Me neither.
So what do you do with the downloaded redline GML file? Hell if I know!
What about if I want to plot the map with the redlines? Dream on. You can't do that!

When the redline widget was first introduced with the query and theme widgets, I was personally surpised that they didn't base the redline widget from the same sample the query and theme widgets were derived from: The Generic Tasks AJAX viewer sample.

So we've thrown out this useless widget and replaced it with one based from the Generic Tasks sample, giving us a redline widget that is much more powerful and useful:

If you've used the Generic Tasks markup sample, this redline widget functions almost the same. For those unfamiliar with the Generic Tasks markup sample, here's what the new Redline widget can do:
  • Configure redline layers with support for labels using the same MapGuide stylization rules
  • Add, Create, Remove and Manage redline layers with respect to the current map
  • Draw geometries using the same digitizing tools provided by OpenLayers
  • Your redlines will be part of the whatever plotting or rendering operation you do on the current map.
  • Redline feature sources can be downloaded as SDF files, allowing for overlaying in AutoCAD Map3D and other Autodesk Geospatial products.
Quick Plot

The Quick Plot widget has improved reliability. This is due to the widget now using the actual MapGuide Rendering APIs to grab the initial un-rotated image and dumping that to a temp file, where the PHP gd library is then used to rotate the image and outputted back to the user. This approach is a more memory efficient use of the PHP gd library, and as a result should result in significantly less occurrences of this useless message:

ProTip: If you get this message, it's due to a failure of some sort in GeneratePicture.php. Inspecting the GeneratePicture.php request in Firebug should give you more information. As there was no mechanism in place to propagate back error messages, GeneratePicture.php fails silently at least from a user perspective. The QuickPlot changes improve memory efficiency and should result in signifcantly reduced (can we say no?) occurrences of this message.

The widget itself can now also have customizable paper and scale lists, which will require hacking the widget's extension XML element.

One small note: If you planning to wedge fusion trunk into an existing MGOS 2.2 installation, this widget will break because it uses APIs introduced in the next version of MGOS/AIMS. Other widgets should work just fine.

General Usability

Having tackled the major showstoppers, I became comfortable enough with the fusion framework to address a whole bunch of bugs and usability issues with other widgets. The Search, Measure and Query widgets have gotten a bunch of bugfixes.

Wrapping things up

All these changes have already landed in Fusion trunk (some have for quite some time now). Given this is usually branched off at some point, where it is then used by the Open and Commerical versions of MapGuide, you can expect these drastic Fusion improvements to a MapGuide release near you.

As a small aside. Many thanks to Hume City Council for providing the funding for us to implement these long overdue improvements. If you went to AU 2011, you may have seen some of our handiwork on display (including our Fusion work) in this presentation.

As a second small aside, if you have to use Internet Explorer, use Internet Explorer 9. Fusion absolutely FLIES in IE9 and even outperforms Firefox/Chrome in some cases! (yes, I am shocked)


Canuckoid said...

Jackie, is this FUSION version available in your Multi-Map GIT hub?

Jackie Ng said...

Nope. I stopped maintenenace of my github copy once all the features and fixes were brought back to trunk

Faisal Kazmi said...

Dear Jackie,
I am developing a mapguide application in asp.net and sql server 2008 and wanna display google maps in background of my own geographical data. however i have searched and found that google maps can only be displayed using fusion and fusion doesn't support asp.net for server side scripting. kindly guide me as how i can display google maps in my application ?

Jackie Ng said...

Use InvokeURL widgets that point to your aspx pages using the MapGuide .net API.

InvokeURL widgets are like InvokeURL command in the AJAX Viewer. They don't care about your backend technology

Faisal Kazmi said...

Thanks Jackie.