GRASS eszközök hozzáadás¶

Háttér¶

A különböző modulok paraméterei (melyeket a _*Beállítások_*fülön találunk) automatikusan generálódnak az előre definiált QGM (QGIS GRASS module) fájl és magának a GRASS modul vagy a GRASS script –GMO (GRASS module options) beállításainak függvényében. Mivel minden paraméter a QGM fájlban kapcsolódik a megfelelő (vagy több) GMO-hoz, ezért ajánlatos (illetve inkább szükséges) a GMO-k böngészése is. A GMO nem más, mint a GRASS modul kimenete, az _*–interface-description_* kapcsolóval, XML formátumban. Pl.:

r.to.vect --interface-description

Some GRASS modules have too many options which can be confusing for beginners. In QGM it is possible to define only some of them and possibly set some default values and/or hide some options with certain value. That means that more QGIS-GRASS modules can be defined for each GRASS module. For example the module r.to.vect was divided into three QGIS-GRASS modules with predefined „feature” option. The QGM definition is written in XML format file with extension .qgm, one for each QGIS-GRASS module. Configuration files are stored in _*qgis/src/plugins/grass/modules*_ directory and installed in _*share/qgis/grass/modules*_ directory. The name of the file should start with GRASS module name + a word describing the specific task. For example, the module which extracts vector lines from raster is called r.to.vect.line.qgm.

Itt van egy példa konfiguráció fájl:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE qgisgrassmodule SYSTEM "http://mrcc.com/qgisgrassmodule.dtd">
<qgisgrassmodule label="Generate aspect map from DEM" module="r.slope.aspect">
       <option key="elevation" />
       <option key="aspect" />
</qgisgrassmodule>

qgisgrassmodule tag attributes¶

• címke — a menü fában használt leírás

• modul — végrehajtható GRASS modul vagy szkript.

Option tags¶

Each qgisgrassmodule tag can contain one or more option tags:

• option — corresponds to GMO parameter tag, example:

<option key="elevation" />

• flag — corresponds to GMO flag tag, example:

<flag key="o" answer="on" hidden="yes" />

• mező — vektor réteghez mező megadása, egy legördülő listaként jön létre az elérhető mezőkkel. Például (v.to.db.qgm):

<field key="column" layer="map" type="integer,double" label="Attribute field" />

• selection — this is quite interesting and useful type of option. It allows to define list of GRASS vector categories using QGIS interface. Features (and their categories, GRASS feature ID equivalent) can be selected either with «Select Features» tool or in the attribute table. The list of categories is updated dynamically. Example (v.extract.list.qgm):

<selection key="list" layerid="input" label="Cats" />

Common option/flag tag attributes¶

• key — name of module option in GMO.

• answer — default value (overwrites GMO default value); value „on” will switch on a flag.

• hidden — the option will not appear in the dialog, but module will be run with this option (hidden=”yes”).

• label — option label

• advanced — „yes” or „no”, default is „no”. If set to „yes”, the option/flag is add to initially hidden advanced options panel and „Show advanced options >>” button is shown under simple (basic,standard) options

• version_min — minimum GRASS version for which this option/flag is valid

• version_max — maximum GRASS version for which this option/flag is valid

Option tag specific attributes¶

• typeoption — this option can be used with vector layer to define the name of vector input type option, when module is run, the type of selected vector layer will be used for that option. For example (v.overlay.or.qgm):

  <option key="ainput" typeoption="atype" layeroption="alayer" typemask="area,line" />
  

  It means that if a layer is selected from combobox of this option the _*atype*_ option is automaticaly set to the layer’s type, and thus _*atype*_ does not have to be added at all.

• layeroption — equivalent of typeoption for layer.

• typmask — for vector input option defines allowed types. Only the layers of one of defined type are displayed in input. See v.overlay.or.qgm for example.

Field tag specific attributes¶

• layer — the key attribute of the option which defines the vector this field should depend on

• type — defines types of attribute fields which should be added to the field combobox, for example

  <field key="column" layer="map" type="integer,double" label="Attribute field" />
  

  It means that only the attribute fields of type in integer and double precision will appear in combobox. See v.what.vect for example (2 different vectors).

A színfalak mögött¶

The idea QGIS-GRASS modules implementation is to use maximum information from GMO and only simplify the interface. Here are described some rules how information from GMO are used and in which order if not all of them are defined in GMO.

• label — if label attribute is defined in QGM it is used as option label, if it is not defined GMO option label tag is used and if it is not defined GMO option description tag is used

• tooltip — (appeares on mouseover the option) if label is defined (either in QGM or GMO) and description is defined in GMO (thus label and description differ) the GMO description tag is used for tooltip

• multiple values label — if an option is type multiple with defined list of possible values (like upload option of v.distance) and description tag is defined for value tag in GMO then it is used as checkbox label

Kép¶

Each module must be represented also by a picture/icon which symbolizes the modules functionality. The pictures are also stored in plugins/grass/modules as SVG (.svg) or PNG (.png) files.

Currently there are supported 3 schemas for the picture:

• 1 picture

• 2 pictures — QGIS will create icon: 1 -> 2

• 3 pictures — QGIS will create icon: 1 + 2 -> 3

The name of the picture starts with QGIS-GRASS module name to which is appended picture number, for example: v.overlay.and.1.svg, v.overlay.and.2.svg, v.overlay.and.3.svg. It is possible to combine SVG and PNG pictures.

SVG and PNG pictures can be generated from QGIS using Map Composer. The size of PNG images should be larger than the expected icon size, because it is expected to be later used in automatically generated documentation, where pictures will be used in larger size.

QGIS GRASS szkriptek¶

Because it can take long time until a new script is added to stable GRASS release and because some scripts can be useful only for QGIS GUI interface it is possible to add a «GRASS» script to QGIS. The scripts should follow general requirements for GRASS scripts and they are located in qgis/src/plugins/grass/scripts.