AW: [Qgis-developer] Legend vs. Layers

[Aurora Geomatics]

Hello,

Thought I would wade into the discussion here, Layers VS Legends

On 7-Feb-09, at 7:49 AM, Hugentobler Marco wrote:

> I think the legend is more than a layer list because it shows e.g.  
> the classifications of vector layers using classification attribute,  
> symbols for the individual classes and their values. For me that  
> already explains something about the 'colours, symbols, line  
> patterns used on the map' and about their semantics.

Features are represented in Layers and Legends

The biggest discerning factors between Layers and a Legend are:

1.	Layers visually inform a user as to the specific "Level/Hierarchy"  
of a feature polygon, line, point, image, and/or file with respect to  
other Layers.
	A Legend visually informs a map reader of the graphical symbolization  
represented for a feature based on defining attributes and grouped not  
by the "Level" it is drawn, but by the grouping of its Like Attributes.

2. 	A Layers table must list all features contained within a map  
display.
	A Legend is not required to list all features contained within a map  
display.

3. 	Legends often contain more map/reader information than is  
contained within the Map View.

for example -

Point features are normally placed on Higher "Levels" than Polylines,  
Polygons, and Images and are grouped in a hierarchically manner in a  
Layers table.
However, in a Legend it may make more sense to a map reader to group,  
for instance, Lakes, Rivers, Well Points together under WATER, rather  
than groups of Polylines, Polygons, and Images.

> I don't care too much about the label of the legend, so no problem  
> for me if you want to change it to 'Layers' or 'Layer list'. I just  
> don't think it is usefull to rename all the legend classes in QGIS  
> (e.g. QgsLegendLayer -> QgsLayerListLayer ).

I certainly agree with this point.  The Layer vs. Legend debate (I  
believe) is more for an End User UI than Developer codings.

It may be worth some thought though for future proofing the code, if  
ever a true Legend implementation is added to QGIS (like in ArcGIS).


just some thoughts,

Mars