Visual query editor tab in QGIS plugin

[Dimitar Misev]

Currently the Query Editor tab shows just a text box, which is not so good because users have to know WCPS and it's easy to make mistakes when writing a query. Syntax highlighting/completion seems difficult in python.

We could experiment with a graphical solution instead.

A WCPS query has this general shape:

for $covIter1 in (covName, ...),
    $covIter2 in (covName, ...),
    ...
let $aliasVar1 := covExpr,
    $aliasVar2 := covExpr,
    ...
where booleanExpr
return processingExpr

We can break the Query Editor in a couple of sections:

1. Input Datacubes (the for clause)
   • a button "Add datacube" shows a dialog to search through the available datacubes
   • the selected datacube is added to a small list of datacube name and a button for each that allows to remove an entry

2. Filter Datacubes (the where clause)
   • a button "Set filter condition" expands a text area where an expression can be written

3. Result Expression (the return clause)
   • text area allows to write the expression

4. Result Format
   • a drop-down allows to select a couple of common formats (none, png, jpg, tiff, netcdf, json)
   • a text box "Custom" allows to enter the format manually
   • a button "Format parameters" expands a text area where format parameters can be entered