= !MapGuide RFC 133 - Additional Stylization Expression Functions =

This page contains a change request (RFC) for the !MapGuide Open Source project.
More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.


== Status ==

||RFC Template Version||(1.0)||
||Submission Date||18 Apr 2013||
||Last Modified||18 Apr 2013||
||Author||Jackie Ng||
||RFC Status||draft||
||Implementation Status||ready||
||Proposed Milestone||2.6||
||Assigned PSC guide(s)||(when determined)||
||'''Voting History'''||(vote date)||
||+1||||
||+0||||
||-0||||
||-1||||
||no vote|| ||

== Overview ==

This RFC proposes to add support for additional expression engine functions to allow for greater stylization flexibility

== Motivation ==

There are several scenarios that the current stylization expression function suite fails to address, mostly centered around tooltips:

 * Ability to stylize based on current map scale (eg. Scale-dependent tooltips)
 * Ability to stylize based on view location (eg. View-specific tooltips)
 * Ability to construct useful tooltips for debugging/informative purposes due to key information that about the stylized feature that is missing

This RFC expands the suite of FDO stylization functions to fulfil these scenarios

== Proposed Solution ==

Implement the following FDO expression engine functions in the Stylization library:

 * HTMLCOLOR(r, g, b)+
 * FEATURESOURCE()
 * LAYERDEFINITION()
 * MAPSCALE()
 * MAPCENTERX()
 * MAPCENTERY()

+ Denotes a MapGuide-specific stylization function

Each function is described in detail below

=== HTMLCOLOR(r, g, b) ===

Returns the HTML color string based on the integer red, green and blue values provided. This function is more useful for tooltip construction where the existing ARGB() function is inadequate.

=== FEATURESOURCE() ===

Returns the resource ID of the Feature Source where this stylized feature originates from

Implementation details:

Store the Feature Source id into the RS_FeatureClassInfo class that is created and set before rendering begins and is also referred to by other stylization 

functions. Evaluating this function returns this set value.

=== LAYERDEFINITION() ===

Returns the resource ID of the Layer Definition that is being used to stylize this feature

Implementation details:

Store the Layer Definition id into the RS_LayerUIInfo class that is created and set before rendering begins and is also referred to by other stylization 

functions. Evaluating this function returns this set value.

=== MAPSCALE() ===

Returns the current scale of the map being rendered.

Implementation details:

We store the map scale into the RS_MapUIInfo class that is created and set before rendering begins and is also referred to by other stylization functions. 

Evaluating this function returns this set value.

=== MAPCENTERX() ===

Returns the X coordinate of the map's current view center

Implementation details:

We store the X coordinate into the RS_MapUIInfo class that is created and set before rendering begins and is also referred to by other stylization functions. 

Evaluating this function returns this set value.

=== MAPCENTERY() ===

Returns the Y coordinate of the map's current view center

Implementation details:

We store the Y coordinate into the RS_MapUIInfo class that is created and set before rendering begins and is also referred to by other stylization functions. 

Evaluating this function returns this set value.

== Implications ==

Layer definitions that use expressions containing theming functions will be stylized correctly only on MapGuide servers from a release that implements those functions.

== Test Plan ==

Render some labels exercising all of the above functions for a layer in a map at various positions and zoom levels. The labels rendered out should contain the expected values returned by these functions.

== Funding / Resources ==

Community