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Variabili

Funzionalità introdotta da Nyall Dawson nella QGIS 2.12 Lyon

Questo gruppo contiene variabili dinamiche relative all'applicazione, al file di progetto e ad altre impostazioni. Significa che alcune funzioni potrebbero non essere disponibili in base al contesto:

  • seleziona per espressione exp
  • calcolatore di campi calc
  • geometry generator epsilos
  • proprietà del layer mod
  • compositore di stampe print

In QGIS, puoi utilizzare le variabili per memorizzare dati utili con valori ricorrenti (ad esempio il titolo del progetto o il nome completo dell’utente) che possono essere utilizzati nelle espressioni. Le variabili possono essere definite a livello globale dell’applicazione, a livello di progetto, a livello di layer, a livello di composizione e a livello di elemento del compositore. Proprio come le regole CSS a cascata, le variabili possono essere sovrascritte, ad esempio una variabile a livello di progetto sovrascrive le variabili di livello globale di qualsiasi applicazione impostate con lo stesso nome.

Puoi utilizzare queste variabili per creare stringhe di testo o altre espressioni personalizzate utilizzando il carattere '@' prima del nome della variabile.

Elenco variabili

Riguardano (aggiornato a QGIS 3.20 Odense):

Variable Description
algorithm_id The unique ID of an algorithm
animation_end_time End of the animation’s overall temporal time range (as a datetime value)
animation_interval Duration of the animation’s overall temporal time range (as an interval value)
animation_start_time Start of the animation’s overall temporal time range (as a datetime value)
atlas_feature The current atlas feature (as feature object)
atlas_featureid The current atlas feature ID
atlas_featurenumber The current atlas feature number in the layout
atlas_filename The current atlas file name
atlas_geometry The current atlas feature geometry
atlas_layerid The current atlas coverage layer ID
atlas_layername The current atlas coverage layer name
atlas_pagename The current atlas page name
atlas_totalfeatures The total number of features in atlas
canvas_cursor_point The last cursor position on the canvas in the project’s geographical coordinates
cluster_color The color of symbols within a cluster, or NULL if symbols have mixed colors
cluster_size The number of symbols contained within a cluster
current_feature The feature currently being edited in the attribute form or table row
current_geometry The geometry of the feature currently being edited in the form or the table row
current_parent_feature represents the feature currently being edited in the parent form. Only usable in an embedded form context.
current_parent_geometry represents the geometry of the feature currently being edited in the parent form. Only usable in an embedded form context.
form_mode What the form is used for, like AddFeatureMode, SingleEditMode, MultiEditMode, SearchMode, AggregateSearchMode or IdentifyMode as string.
frame_duration Temporal duration of each animation frame (as an interval value)
frame_number Current frame number during animation playback
frame_rate Number of frames per second during animation playback
fullextent_maxx Maximum x value from full canvas extent (including all layers)
fullextent_maxy Maximum y value from full canvas extent (including all layers)
fullextent_minx Minimum x value from full canvas extent (including all layers)
fullextent_miny Minimum y value from full canvas extent (including all layers)
geometry_part_count The number of parts in rendered feature’s geometry
geometry_part_num The current geometry part number for feature being rendered
geometry_point_count The number of points in the rendered geometry’s part
geometry_point_num The current point number in the rendered geometry’s part
geometry_ring_num Current geometry ring number for feature being rendered (for polygon features only). The exterior ring has a value of 0.
grid_axis The current grid annotation axis (eg, ‘x’ for longitude, ‘y’ for latitude)
grid_number The current grid annotation value
item_id The layout item user ID (not necessarily unique)
item_uuid The layout item unique ID
layer The current layer
layer_crs The Coordinate Reference System Authority ID of the current layer
layer_id The ID of current layer
layer_ids The IDs of all the map layers in the current project as a list
layer_name The name of current layer
layers All the map layers in the current project as a list
layout_dpi The composition resolution (DPI)
layout_name The layout name
layout_numpages The number of pages in the layout
layout_page The page number of the current item in the layout
layout_pageheight The active page height in the layout (in mm for standard paper sizes, or whatever unit was used for custom paper size)
layout_pageoffsets Array of Y coordinate of the top of each page. Allows to dynamically position items on pages in a context where page sizes may change
layout_pagewidth The active page width in the layout (in mm for standard paper sizes, or whatever unit was used for custom paper size)
legend_column_count The number of columns in the legend
legend_filter_by_map Indicates if the content of the legend is filtered by the map
legend_filter_out_atlas Indicates if the atlas is filtered out of the legend
legend_split_layers Indicates if layers can be split in the legend
legend_title The title of the legend
legend_wrap_string The character(s) used to wrap the legend text
map_crs The Coordinate reference system of the current map
map_crs_acronym The acronym of the Coordinate reference system of the current map
map_crs_definition The full definition of the Coordinate reference system of the current map
map_crs_description The name of the Coordinate reference system of the current map
map_crs_ellipsoid The acronym of the ellipsoid of the Coordinate reference system of the current map
map_crs_proj4 The Proj4 definition of the Coordinate reference system of the current map
map_crs_projection The descriptive name of the projection method used by the Coordinate reference system of the map (e.g. ‘Albers Equal Area’)
map_crs_wkt The WKT definition of the Coordinate reference system of the current map
map_end_time The end of the map’s temporal time range (as a datetime value)
map_extent The geometry representing the current extent of the map
map_extent_center The point feature at the center of the map
map_extent_height The current height of the map
map_extent_width The current width of the map
map_id The ID of current map destination. This will be ‘canvas’ for canvas renders, and the item ID for layout map renders
map_interval The duration of the map’s temporal time range (as an interval value)
map_layer_ids The list of map layer IDs visible in the map
map_layers The list of map layers visible in the map
map_rotation The current rotation of the map
map_scale The current scale of the map
map_start_time The start of the map’s temporal time range (as a datetime value)
map_units The units of map measurements
model_path Full path (including file name) of current model (or project path if model is embedded in a project).
model_folder Folder containing current model (or project folder if model is embedded in a project).
model_name Name of current model
model_group Group for current model
notification_message Content of the notification message sent by the provider (available only for actions triggered by provider notifications).
parent Refers to the current feature in the parent layer, providing access to its attributes and geometry when filtering an aggregate function
project_abstract The project abstract, taken from project metadata
project_area_units The area unit for the current project, used when calculating areas of geometries
project_author The project author, taken from project metadata
project_basename The basename of current project’s filename (without path and extension)
project_creation_date The project creation date, taken from project metadata
project_crs The Coordinate reference system of the project
project_crs_arconym The acronym of the Coordinate reference system of the project
project_crs_definition The full definition of the Coordinate reference system of the project
project_crs_description The description of the Coordinate reference system of the project
project_crs_ellipsoid The ellipsoid of the Coordinate reference system of the project
project_crs_proj4 The Proj4 representation of the Coordinate reference system of the project
project_crs_wkt The WKT (well known text) representation of the coordinate reference system of the project
project_distance_units The distance unit for the current project, used when calculating lengths of geometries and distances
project_ellipsoid The name of the ellipsoid of the current project, used when calculating geodetic areas or lengths of geometries
project_filename The filename of the current project
project_folder The folder of the current project
project_home The home path of the current project
project_identifier The project identifier, taken from the project’s metadata
project_keywords The project keywords, taken from the project’s metadata
project_last_saved Date/time when project was last saved.
project_path The full path (including file name) of the current project
project_title The title of current project
project_units The units of the project’s CRS
qgis_locale The current language of QGIS
qgis_os_name The current Operating system name, eg ‘windows’, ‘linux’ or ‘osx’
qgis_platform The QGIS platform, eg ‘desktop’ or ‘server’
qgis_release_name The current QGIS release name
qgis_short_version The current QGIS version short string
qgis_version The current QGIS version string
qgis_version_no The current QGIS version number
row_number Stores the number of the current row
snapping_results Gives access to snapping results while digitizing a feature (only available in add feature)
scale_value The current scale bar distance value
symbol_angle The angle of the symbol used to render the feature (valid for marker symbols only)
symbol_color The color of the symbol used to render the feature
symbol_count The number of features represented by the symbol (in the layout legend)
symbol_id The Internal ID of the symbol (in the layout legend)
symbol_label The label for the symbol (either a user defined label or the default autogenerated label - in the layout legend)
symbol_layer_count Total number of symbol layers in the symbol
symbol_layer_index Current symbol layer index
symbol_marker_column Column number for marker (valid for point pattern fills only).
symbol_marker_row Row number for marker (valid for point pattern fills only).
user_account_name The current user’s operating system account name
user_full_name The current user’s operating system user name
value The current value
with_variable Allows setting a variable for usage within an expression and avoid recalculating the same value repeatedly
zoom_level Zoom level of the tile that is being rendered (derived from the current map scale). Normally in interval [0, 20].

Screenshot livelli

  • Proprietà Progetto
  • Gruppo sul calcolatore di campi,Seleziona per espressione

  • Generatore di geometria- stile epsilos

  • Selezione per espressione exp

  • Calcolatore di campi,Seleziona per espressione calc

  • Compositore di stampe print

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