GUI support for QML Widgets

[ghtmtt]

QML widgets are really useful, but they lack a little bit in usability "user side". It would be nice to have a small GUI that helps users to add.

It would be potentially nice to have a basic usage/tab and an advanced ones (where powerful users can add code).

Some general considerations:

• default colors (currently only by code strings manually added)
• for Pie charts:
  • plus button to add additional slices
  • checkbox to have the slice exploded
  • small table (matrix style) with label and value to add
• for Bar charts:
  • knowing that it is not straightforward, but the current modality with the example it to basically add arrays (because of many years and more values for each year)

[signedav]

Color

Possibly we can make it possible for the user to choose a Theme instead of choosing colors for each element (slice) of the chart. https://doc.qt.io/qt-5.9/qtcharts-chartthemes-example.html This would keep the GUI slim and gives already some possibilities.

Plus Button

We could evaluate the number of elements (slices) from the table with the label and value.

label	value
First slice	25
Second slice	45
Third slice	30
...

With the plus button, possibly we could add columns, instead. So the user could create the Bar Charts (and other charts like area chart etc.) as well.

label	value1	value2	value3	value4	value5
Bob	25	25	25	25	25
Susan	45	45	45	45	45
James	30	30	30	30	30
...

Would lead to

But maybe we should keep it simple in the basic and just have "two dimensions"

[ghtmtt]

Thanks @signedav that would be a great enhancement for the usability of the widget.

Would it be possible to reuse the color picker of QGIS?