Best choice for a long String GUI handling?

  • I need to show information in my GUI. This is a very long String (a chromosome's nucleotid sequence: AGGCTATGCA....), thounsands of characters.
    Also, I need to show several of these Strings aligned one under the other:


    The user should select a column (He can select a "letter" position, the full column).

    Whats the best Widget to show this long information and make some basic manipulation (select columns, replace some "letter" in a sequence..).

    Thank you for your advices.

  • Hi,

    for column selection I suggest you to use TableWidget or TreeWidget (depending of your app architecture you could use Views instead of Widgets).

  • Hi mcosta, thank you for your advice.

    I ve already tried with my own TableView, but It causes a laggy performance. Maybe Tables are not designed for a such function, included TableWidget, isnt? TreeWidget is faster? I dunno if TreeWidget provides a confortable navigation for so long String. Mmm

  • Use a SimpleText inside a View that scrolls? The SimpleText's QDocument will tell you what index (which you can convert to column with a little math) of the text a mouse click is in. Set the layout width of the Document so that it wraps at the length of the longer sequence. Sorry, I don't have the details.

    Isn't there some other open source code that displays aligned sequences, from which you can get ideas?

  • Heya bootchk, and ty for your reply.

    I've not understood what you mean with QDocument. Maybe several QTextEdit inside a QWidget, is that?

  • Yes.

    (Sorry for the confusion. I use a QGraphicsScene. I should have said QGraphicsTextItem or QTextEdit instead of "simple text".) Both QGTI and QTextEdit are similar: they have a document() method to get the QTextDocument. That has a documentLayout() method to get a QTextLayout. That has a lineForTextPosition() method to get a line (at a cursor position). And so forth, you can determine the line and "column" in that line, where the user puts the visual cursor, or even using mouse event coords (as I recall.) The object model of the various classes (Document, Layout, etc) is not easy to understand, but it is not unusual, it has been used for a long time.

  • Ok, I use now a QTextEdit. I thought It's a better idea use just one QTextEdit, and every line (row) will be occuped for a chromosome. I setted Vertical Scroll as "always", but I cannot force an String to occupe only one line.


    Ok, now I use lineWrapMode = no wrap.

    My problem now is: how to set a new line: chromosomes are now written at the same line.

    *Anyway: * QTextEdit is still low performance when I load more than 10 - 12 chromosomes. Some others applications, even if they seem a bit "old" in terms of GUI, can move this amount of data. Maybe another Widget faster?

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