[Qgis-developer] Legend refactoring - part II - ready for merge

Sun Aug 24 02:08:09 PDT 2014

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Hi

On 24/08/2014 09:51, Tim Sutton wrote:
> Hi Martin
> 
> On 22/08/2014 13:02, Martin Dobias wrote:
>> Hi all
> 
>> In recent weeks I have been busy with the second part of legend 
>> refactoring. The main goals were: - clean up the mess with legend
>> - there are three different ways of legend
>> presentation/rendering: 1. in legend widget (now layer tree
>> view), 2. composer legend, 3. WMS legend - make legend rendering
>> independent from composer - so it can be used elsewhere - in WMS
>> or in GUI - allow different strategies how legend for a layer is
>> created - until now the legend generation was hardcoded - this
>> should allow things like data-defined legend, labeling / diagrams
>> in legend - allow new types of legend items - for greater
>> flexibility of item appearance - e.g. show a gradient color ramp
>> for raster layer
> 
>> The code is in my repository: 
>> https://github.com/wonder-sk/QGIS/compare/legend-refactoring-part2
>
>>  To introduce the important new classes: - QgsLegendRenderer -
>> takes care of rendering of the legend - similar to how
>> QgsMapRenderer handles rendering of map - QgsLegendSettings -
>> contains user configuration of the legend (fonts, colors, sizes,
>> spacing) - similar to QgsMapSettings for map - QgsMapLayerLegend
>> - base class for legend implementations. For a layer an
>> implementation should return a list of legend nodes -
>> QgsLayerTreeModelLegendNode - base class for legend node
>> implementation. Provides data(), flags() methods used in the
>> layer tree model and provides draw() method for rendering of
>> legend in composer/WMS
> 
>> The QgsMapLayerLegend and QgsLayerTreeModelLegendNode classes
>> are used by QgsLayerTreeModel to generate and display legend in
>> a tree. QgsLegendRenderer makes use of QgsLayerTreeModel and
>> allows the legend nodes do their legend rendering.
> 
>> An example of custom legend node: - screenshot: 
>> http://i.imgur.com/GtvTlQ7.png - code: 
>> https://gist.github.com/wonder-sk/c5d925833bcd54b9e401
> 
>> An example of custom dock widget using legend renderer: - 
>> screenshot: http://i.imgur.com/EAvE96u.png - code: 
>> https://gist.github.com/wonder-sk/211b7130b58e50d78e6d (in the 
>> screenshot above you can also see legend node icon embedded in 
>> layer node)
> 
>> There are not many changes visible to the user - the changes are
>>  mainly visible for developers. From the few user-visible
>> changes: - in layer tree view - if a layer has just one legend
>> item, it will be shown on the left side of the layer name instead
>> of occupying another line. This is what already happens in
>> composer. - in composer legend item settings - 1) there is tree
>> view with just one column, label style is set in popup menu, 2)
>> when auto-update is on, the tree view is synchronized with
>> project's layer tree and it is read-only. When auto-update is
>> off, it is possible to manipulate the source legend tree
> 
>> Regarding backward compatibility, there are two things worth 
>> mentioning: - QgsComposerLegend::model() will return
>> QgsLegendModel which is not in use anymore. There is
>> QgsComposerLegend::modelV2() as a replacement. The way how the
>> models work is significantly different and I don't see a way of
>> fixing that without a complex and fragile synchronization logic.
>> Anyway, according to Nathan's plugin analyser tool there are no
>> plugins using composer's legend model - reading of older projects
>> with composer legend ignores the customization (e.g. renamed
>> items, reordered items, removed items). If time allows, I will
>> try to address this before the release
> 
>> So... please have a look if you are interested and enjoy the 
>> endless possibilities of new legends :-) If there are no
>> objections I will merge it during the next week.
> 
> 
> Ah wow - I've been playing with it here and it is so much nicer
> from the UI point of view. Two things I picked up though.
> 
> * I don't know how to reproduce it exactly but it seems that when
> I change the text for a layer name in general properties it updates
> the legend fine but after using QGIS a little more I notice that
> the layer name reverts to its previous state. I will post more
> details if I figure out how to replicate this.

Ok on a little further investigation it seems this is an issue with
renaming gpx layers - I suspect the driver is at fault here since it
does it in QGIS 2.4 too.

Regards

Tim

> 
> * Do you have any strategy for dealing with symbols larger than
> the thumbnail in the legend? e.g. if you set the size of a circle
> to 8 it basically draws a square. This is not a regression as the
> old legend implementation suffered the same thing, but I was hoping
> a new implementation could offer a fix for this. I know there are
> limits to what we can do in the space of the legend but perhaps
> having some simple system whereby symbol previews are
> proportionally scaled such that the largest icon will always fit
> into the space provided and the smaller ones are relatively reduced
> in scale? Perhaps someone else has some creative ideas on how to
> improve their visual representation in the legend?
> 
> Great stuff as always Martin!
> 
> Regards
> 
> Tim
> 
> 
> 
>> Regards Martin _______________________________________________ 
>> Qgis-developer mailing list Qgis-developer at lists.osgeo.org 
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
> 
> 
> 

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Tim Sutton
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