Switching from Old to New Symbology and Labeling
Version 17 (Giovanni Manghi, 07/28/2012 07:42 am)
This document describes missing bits in the new symbology and labeling engines
h2. Symbology and labelling
h3. Missing features in New Symbology/Labelling that are available in Old Symbology/Labelling
* Data driven symbol for point layers: in old symbology the user select a column name that holds the name of a symbol (referring to one file available trough the QGIS symbol library) to get data driven symbology. This feature is missing in new symbology and is very handy when doing thematic maps.
* In old symbology the user can select (in the "unique value renderer") multiple symbology classes using the "ctrl" key or just by dragging the mouse, then it can change the symbol for all the selected classes. In the new symbology the user can still select multiple classes, but it just can change a few properties (by right clicking the mouse) but not the symbol. Moreover the "change" symbol button is active but it has not effect, and this puzzles the users. One could say that a workaround is the rule based renderer, but in many cases is not handy as just selecting classes manually (while in the rule based renderer must be build a rule). The use cases are many. The ticket related to this issue is
* Overall transparency slider missing for categorized/graduated symbology: this is available in old symbology when rendered other than the "single symbol" one. In the new symbology multiple classes can be selected and then the transparency can be set with the mouse right button dialog, but if the classes number is high this is very annoying/difficult to use. A "select all" (classes) button would workaround somehow this issue
* In new symbology there is no real equivalent (in terms of resulting colors) to the "unique value" renderer in the old symbology. In the new symbology the colours used when selecting a "random" pallette are not really as random as they should be
Old symbology, unique value renderer using the "id" field
New symbology using a "random" color ramp with 99 colors, and the "categorized" renderer and the "id" field
* In new labelling engine the label offset can't be set for both x/y axes, as it is possible in the old engine
* In new labelling engine the labels do rotate only if the "data defined settings" are set the "X/Y coordinate" fields (and of course the "rotation" one) and this columns are filled with the proper value -> this means that once selecting the "rotation" field the labels do not rotate automatically unless selecting one by one all the labels (that makes qgis fill the "x/y coordinate" columns"). This is obviously cumbersome and not functional. In the old labelling engine this was not required.
h3. Categorized renderer
* The term "color ramp" as a term for different types of "color tables" is problematic. A ramp is for me the equivalent of a gradient. I just discovered today that color ramps also cover "random colors" and "color brewer" color tables. Which is nice. I would call the parent "color table" and the three types: color ramp (or gradient), random colors, color brewer.
: +1 --[[User_Anitagraser|Anitagraser]] 16:18, 19 January 2011 (UTC)
h3. Rule based Renderer
* Needs ability to re-order rules once they are added (up and down buttons)
* Needs alias columns for the legend. Currently the rule is displayed in the legend, which is not very nice (should be fixed in #3222)
* Needs an icon for the GUI (combobox with the renderer choice)
* Needs to ability to use symbol levels. Currently it is impossible. A simple fix is to use only the first matching rule when symbol levels are on (patch proposed in #3222). A better fix would be to have the possibility to choose whether or not to stop after first matching rules (with or without symbol levels). Even better would be, for each rule, to say if this is the last rule to be matched (ignoring the following if it's matched) or not.
* Improvements from Mayeul once they are ready (#3222)
* The GUI feels inconsistent: It uses the terms "rule" and "filter" randomly - while I guess both mean the same thing.
* Maybe this could also offer data-defined symbology (e.g. data-defined fill color)
* Ability to turn off selected rules/groups of rules.
* Ability to copy and paste a rule.
h3. Point Displacement
* Needs an icon for the GUI (combobox with the renderer choice)
h3. SVG patterns
* Need for data-defined rotation of the patterns
h3. Simple Markers
* Should allow to specify stroke-width for simple markers. Used to work in old symbology. (see #3458)
* Should allow to specify fill pattern for simple markers. The patch at #3430 does this, and enables layers using the feature to be switched from old symbology to new symbology successfully.
h3. SVG symbols
* need for hierarchical display of SVG symbols, corresponding to the folders in the SVG directory
h3. SVG repository for symbols, patterns and markers
* separation of SVG symbols for point symbols, markers and patterns
* Online symbol repositories for easy extraction/installation of symbols from the web
h3. Line Decorations/Marker Lines
* The polyline symbology type "Line decoration" should be removed because it is already covered by type "Outline: Marker Line".
* Likewise, the polygon symbol layer type "Outline: Line decoration" is unnecessary and should be removed.
* Old label engine settings should be replaced by new label engine settings in layer properties, or removed and delegated to the current label settings dialogue
* multiple scale ranges for different label settings instead of just one min/max scale range per layer, this would remove the need to introduce additional layers, just for the purpose of different label settings for a specific scale range
* Buffer transparency missing in new label settings
* Ability to rotate label either based on a field or with a fixed value independently of choosing an x and y field for the label position.
* Labels should be preserved as text in SVG output (as used to be the case in old labeling engine).
* Curved labels need as "improvement" (as at the momement are barely usable): in this ticket #4855 there are samples to allow understand that if a line is simple, almast flat, but made of a few nodes than the curved labels is not drawn. On the other end curved lines created with the cad tools or with the freehand plugin (so with many many nodes) get always the curved label.
* There is a serious issue #4634 with both "around centroid" and "over centroid" options (maybe related also to this #4079)
* There are options that when used are causing QGIS to *crash* #3802
* labels buffers are broken #3652
h2. Symbology and Labeling tickets
See QGIS bugtracker, category "Symbology":/projects/quantum-gis/issues?category_id=37&set_filter=1&status_id=o and "Labelling":/projects/quantum-gis/issues?category_id=54&set_filter=1&status_id=o