Summary
This document tries to give an overview about status of splitting QGIS into several libraries which could be then used by third party applications. For more information refer to QGIS_Architecture_Roadmap. Tasks marked as done are already in SVN trunk and will be a part of 0.9 release.
Refactoring has started in January 2006 by Tim - code from one directory has been split into several directories:
- core library
- gui library
- qgis application
Tasks
Tasks already completed:
Remove GUI dependencies from QgsSpatialRefSys and move it together with QgsCoordinateTransform to core library
Remove legend dependencies from QgsMapLayer
Store coordinate transform outside of map layer
Remove some dependencies in core lib to gui lib in QgsDistanceArea
Use QImage instead of QPixmap for rendering core because QPixmaps need X server
Remove usage of QMessageBox and similar gui stuff from core lib and providers
Remove QgsRenderer's dependency on QgsProject
Prepare QgsVectorLayer to be moved to core lib
Remove dependency on attribute table
Remove dependency on attribute actions
Prepare QgsRasterLayer to be moved to core lib
Think how to work with user's QGIS DB when using in 3rd party app
- for now we will use the same DB as used directly in QGIS: ~/.qgis/qgis.db
make providers dependent only on core lib
make plugins independent from QgisApp
move QgsProject to core library
start gui library from scratch with inserting only classes prepared to be reusable
move mapcanvas (with some tools) there
move projection selector there
Remove unnecessary classes (which are not intended to be used by other apps) from core lib
Think what to do with unused / unfinished / deprecated classes in core and gui libs - delete them!
repair visibility settings in legend and project load/save
create support for building with CMake make system - Linux and Windows build works
Start using QGraphicsView from Qt4.2 instead of Q3Canvas
resolved most of the warnings in core and gui libraries
python bindings (more info: PythonBindings)
possibility to use in 3rd party application
support for plugins written in python
scripting support (python console in QGIS)
improved and simplified vector data provider interface
use QVariant for feature attributes instead of plain QString
enable saving shapefiles for all types of vector layers
Some tasks that has to be done (still growing):
- vectors handling
develop QgsDataSource interface, see Redesign_of_QGis_data_model
- get rid of WKB and use only GEOS to handle geometries
- Move (possibly all) plugin management to a special class, making no difference between C++ and python bindings
- Add to core lib some more subdirectories with groups of classes logically connected (vector, provider, geometry)
- rethink general behaviour of map layer registry and how legend(s) work with it
fix many TODOs created during the architecture changes (mostly marked with [MD])
QgsRasterLayer needs refactoring
- make possible rendering in separate thread (to allow stopping drawing, updating during rendering and more)
convert remaining std::cout and std::cerr to usage of QgsLogger
- start writing tests (primarily for classes in libraries)
- finish python bindings
Global tasks:
- update list of classes to the current state
- make QGIS API easy to use in applications
Remove usage of QSettings and QgsProject for classes intended to be used in 3rd party apps
- create better structure for code: only CORE and GUI library, both containing subdirs for easier navigation
Class list
Core library
Class |
Description |
Python |
class with some basic enumerations and constants |
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accessors for application-wide data |
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class to print debug/warning/error messages to the console |
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Providers |
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metadata class for describing a data provider |
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singleton class for registering data providers |
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base class for spatial data provider implementations |
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base class for all vector data providers |
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base class for all raster data providers |
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Geometry and spatial references: |
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represents 2D point |
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a simple line composed of two endpoints |
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a rectangle specified by double values |
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encapsulates a single feature including id and field/value |
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encapsulates a field in an attribute table or data source |
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represents geometry in WKB/WKT, contains functions for geoprocessing |
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identifies particular vertex in a given OGC geometry |
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class that clips line segments and polygons |
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distance and area calculations on the ellipsoid |
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class for storing a spatial reference system (SRS) |
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class for doing transformations between two map coordinate systems |
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wrapper class for spatial indexing library |
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Exceptions: |
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QGIS exception class (derived from std::exception) |
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for qgis I/O exceptions |
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for files missing layers while reading project files |
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coordinate system exception |
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Searching: |
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Flex + Bison sources |
parser engine |
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interface for parsing and evaluation of search strings |
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definition of node for parsed tree of search string |
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Layers: |
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base class for all map layer types |
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singleton class for keeping track of loaded layers |
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vector layer backed by a data source provider |
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Mapping rendering stuff: |
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class for rendering map layer set |
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class for transformation between map and device coordinates |
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calculates scale based on map extent and units |
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class for rendering labels |
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storage of attributes for label rendering |
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Renderers: (in "renderer" dir) |
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abstract base for all renderers. Renderer holds info needed to draw the contents of vector layer |
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renderer class which interpolates RGB values between min,max of the classification field |
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renders and contains the information for graduated symbol rendering |
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render class to display all the features with a single QgsSymbol |
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renderer class to show every feature with unique value |
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Symbology: (in "symbology" dir) |
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namespace containing useful methods for symbology widgets |
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encapsulates settings for drawing and classification |
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catalogue of point symbols |
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Raster layers: (in "raster" dir) |
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provides capability to render raster datasets |
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container for statistics about a single raster band |
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provides details of the viewable area that a raster will be rendered into |
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used to store pyramid info for the raster layer |
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color table |
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Attribute actions: |
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encapsulates an action and associated information |
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stores and controls management and execution of actions for layer attributes |
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QGIS Project files: |
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implements persistent project state |
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helper classes for QgsProject |
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Misc: |
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Tracks a HTTP request with its response |
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Interface for showing messages from QGIS in GUI independent way |
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Displays messages to console |
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provides a context based help browser for a dialog |
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structure for storing the component parts of a PgSQL/RDBMS datasource URI |
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custom event to be fired when layer count has been fully calculated |
used only by postgresql provider |
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custom event to be fired when layer extent has been fully calculated |
used only by postgresql provider |
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executes external program/script, optionally captures output |
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generic vector file writer |
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GUI library
constants used throughout the QGIS GUI |
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abstract interface for exposing functions for use by plugins |
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color button |
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file dialog which lets user select encoding for a data provider |
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file dropable LineEdit |
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simple dialog for showing longer messages |
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Map canvas: |
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map canvas class for displaying all GIS data types |
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base class for map canvas items |
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class which holds the rendered map |
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base class for map canvas tools |
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tool for panning in map canvas |
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tool for zooming in/out using rubberband |
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overview canvas |
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widget for panning in overview canvas |
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rubberband for drawing multilines and polygons |
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map canvas item for drawing vertex markers |
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Projection support: |
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widget for selection of projection |
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dialog for setting projection system for a layer |
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QGIS application
Class |
Description |
Notes |
main window for the QGIS application |
too big class, should be refactored |
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implementation of QgisInterface |
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about dialog for QGIS |
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spatial bookmark item (stored in sqlite3) |
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dialog with spatial bookmarks |
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internal clipboard for storage of features |
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interface class for map layer plugins |
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dialog for setting user options and preferences |
routines with qgis database should be moved somewhere else |
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dialog for configuring connection info for a PostgreSQL db |
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query builder for PostgreSQL |
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dialog used for project-wide settings |
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custom projection widget for defining parameters of a projection |
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dialog for displaying results of identify tool |
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so far doesn't make use of map canvas |
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a QListViewItem that can sort numerically |
Attributes handling: |
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dialog for setting new attribute |
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dialog for deleting attributes |
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dialog for advanced searching by attribute |
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attribute action dialog |
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dialog for viewing/editing attributes |
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customized QTable for displaying attribute table |
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dialog for browsing and editing attribute table |
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Layer properties: |
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unified property dialog for vector layers |
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dialog for setting up how raster layers are displayed |
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widget for setting symbology for a vector layer |
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class for choosing marker SVG images by clicking icons |
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dialog to set the symbology for the legend type single symbol |
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dialog for graduated symbols |
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dialog for selecting pattern for rendering vector layers |
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dialog for continuous color renderer |
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?? |
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?? |
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widget for selecting point style |
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widget for selecting line style |
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widget for selecting fill style |
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dialog for settings line styles |
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dialog for setting new vector geometry type and attributes |
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dialog for setting rendering of labels for vector layers |
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Map canvas tools: |
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tool for digitizing |
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tool for selecting features using rubberband |
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tool for adding/moving/deleting vertices |
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tool and widget for measuring distances and areas |
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Plugin management: |
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contains info about loadable plugin - name, description and full path |
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stores info about loaded plugin, including pointer to the inst. object |
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plugin manager for loading/unloading plugins |
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singleton class for keeping track of installed plugins |
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PostgreSQL GUI stuff: |
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dialog to create connections and add tables from PostgreSQL |
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WMS GUI stuff: |
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dialog for configuring connection info for WMS server |
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dialog to create connections and add layers from WMS |
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dialog for setting transformation from source to destination fields (using copy/paste) |
not implemented yet |
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class to represent an attribute table related to a map layer |
used nowhere? |
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Composer: |
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dialog for composing map output |
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composer canvas |
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stores map composition for printing |
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base class for composer items |
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represents map window |
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represents label |
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represents picture |
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represents scale bar |
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represents vector legend |
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Legend: |
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legend treeview |
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abstract base class for all legend items |
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special legend item, items below are treated as a group |
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container for layer file group |
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container for layer properties |
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container for symbology |
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container for layer, including layer file(s), symbology, properties |
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legend item for layer file |
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legend item for representing layer property |
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item for symbology |
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item for symbology of a vector layer |
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Python support: |
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dialog with embedded python console |
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routines for interfacing Python |
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