Support grouping of column questions for matrix dropdown into a single chart

[tsv2013]

var json = {
  "title": "question11",
  "pages": [
    {
      "name": "page2",
      "elements": [
        {
          "type": "matrixdropdown",
          "name": "question4",
          "title": "Please select the top 3 processes that you perceived as most difficult or troublesome.",
          "isRequired": true,
          "showHeader": false,
          "columns": [
            {
              "name": "1st Most Difficult",
              "isRequired": true
            },
            {
              "name": "2nd Most Difficult",
              "isRequired": true
            },
            {
              "name": "3rd Most Difficult",
              "isRequired": true
            }
          ],
          "choices": [
            "Process 1",
            "Process 2",
            "Process 3",
            "Process 4",
            "Process 5",
            "Process 6"
          ],
          "rows": [
            "Process"
          ]
        }
      ]
    }
  ]
};

We get the following visualization for matrix dropdown:

It shows a separate visualizer for each column

We need to support grouping data into a single chart:

[tsv2013]

Right now you can get the

for matrix dropdown with same choices for all columns

[tsv2013]

visPanel.visualizers[0].matrixDropdownVisualizer.transposeData = true

[ontanj]

I believe a bug was introduced here. It appears to me that when multiple rows are used, only the last row is presented in the visualizer. It looks like this feature has been developed with only one row in mind.

A ticket for this was also created at the support forum.

[tsv2013]

Yes, it was implemented for very specific case where our customer has one row and several columns with the same choices.

Multi-row case is not supported at this moment. I leave this as a suggestion here and in in the support forum.

[tsv2013]

I've restricted grouping for the matrices with the one row only via the above commit.

[tsv2013]

Moved multirow implementation to backlog due to customer issue https://surveyjs.answerdesk.io/ticket/details/t8637/visualizing-matrix-bug was resolved via this quick fix.