[Qgis-user] Expression to read field value from composer layout?

[Patrick Dunford]

OK

Is it then possible I might have to write my own function to get the 
values from the Qgis API?

I already have a Python script that runs in the main window console that 
contains this code

layoutTitle = "Landscape 16:9 Header Nav Copyright Filename 2021"

project = QgsProject.instance()
projectLayoutManager = project.layoutManager()
layout = projectLayoutManager.layoutByName(layoutTitle)

fileNameLabel = layout.itemById('Filename')
fileNameText = fileNameLabel.text()

How would I adapt that to a custom function in the Function Editor and 
assuming it is for the current layout.

Thanks

On 4/08/21 11:44 pm, Stefan Giese (WhereGroup) wrote:
>
> Hi Patrick,
>
> I think that you can not get the text from the label with the 
> item_variables function. The keys are limited to the predefinded 
> variables like:
>
> _project_transform_context,item_id,item_uuid,layer_ids,layers,layout_dpi,layout_name,layout_numpages,layout_page,layout_pageheight,layout_pageoffsets,layout_pagewidth,miles_km,project_abstract,project_area_units,project_author,project_basename,project_creation_date,project_crs,project_crs_acronym,project_crs_definition,project_crs_description,project_crs_ellipsoid,project_crs_proj4,project_crs_wkt,project_distance_units,project_ellipsoid,project_filename,project_folder,project_home,project_identifier,project_keywords,project_last_saved,project_path,project_title,project_units,qgis_locale,qgis_os_name,qgis_platform,qgis_release_name,qgis_short_version,qgis_version,qgis_version_no,test,user_account_name,user_full_name
>
> But you can use your own variable like filename and access it from 
> anywhere:
>
>
>
> Am 04.08.2021 um 13:27 schrieb Patrick Dunford:
>>
>> I'm looking through the documentation and there is this example:
>>
>>
>>       14.2.2.13. Layout Functions
>>       <https://docs.qgis.org/3.10/en/docs/user_manual/working_with_vector/expression.html#id24>
>>
>> This group contains functions to manipulate print layout items 
>> properties.
>>
>> Function
>>
>> 	
>>
>> Description
>>
>> item_variables
>>
>> 	
>>
>> Returns a map of variables from a layout item inside this print layout
>>
>> *An example:*
>>
>>  *
>>
>>     Get the scale of the ‘Map 0’ in the current print layout:
>>
>>     map_get(  item_variables('Map 0'),  'map_scale')
>>
>>
>> How do I find out how to get the text value of the layout item 
>> "Filename" on the current print layout?
>>
>>
>> On 4/08/21 2:40 pm, Patrick Dunford wrote:
>>> It is just an ordinary text field on a composer layout I think. I 
>>> don't use the atlas functionality.
>>>
>>> On 4/08/21 10:19 am, Nyall Dawson wrote:
>>>> On Wed, 4 Aug 2021 at 06:17, Patrick Dunford 
>>>> <enzedrailmaps at gmail.com> wrote:
>>>>> Good day
>>>>>
>>>>> I am wishing to create a value in a field on a composer layout that
>>>>> reads the value of another field on the layout and calculates a 
>>>>> value to
>>>>> be displayed.
>>>>>
>>>>> For example, I have an existing field called Filename on the 
>>>>> layout and
>>>>> in a python script running in the main window console, I have this 
>>>>> code
>>>>> that reads the value of the Filename field as follows:
>>>>>
>>>>> layoutTitle = "Landscape 16:9 Header Nav Copyright Filename 2021"
>>>>>
>>>>> project = QgsProject.instance()
>>>>> projectLayoutManager = project.layoutManager()
>>>>> layout = projectLayoutManager.layoutByName(layoutTitle)
>>>>>
>>>>> fileNameLabel = layout.itemById('Filename')
>>>>> fileNameText = fileNameLabel.text()
>>>>>
>>>>>
>>>>> Obviously I am hoping that doing this from a field within the layout
>>>>> that reads another field on the same layout will be much simpler than
>>>>> the above. How exactly would I achieve that?
>>>> Just to clarify -- by "field" do you mean "a field value from the
>>>> atlas layer", or "a text label item"?
>>>>
>>>> Nyall
>>
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> -- 
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> Stefan Giese
> Projektleiter/Consultant
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