QAbstractScrollArea forces repainting the whole viewport

[Charletes]

What I am trying to do is implementing a plain text editor. I need to use a QAbstractScrollArea instead of a QScrollArea because I want it to scroll lines instead of pixels when receiving a wheel event. Moreover, I'd like to have in the viewport another widget which shows line numbers and, when receiving horizontal scroll events, scroll only the widget with the text but not the widget with the line numbers.

I have already that working, but every time I move the widgets I receive paint event the whole size of the viewport. I can't use a QScrollArea because I can't scroll horizontally only part of the widgets shown as I need.

How can I tell the QAbstractScrollArea or the viewport() to update() only the needed parts?

[wysota]

What I am trying to do is implementing a plain text editor.

And what is wrong with QPlainTextEdit?

I need to use a QAbstractScrollArea instead of a QScrollArea because I want it to scroll lines instead of pixels when receiving a wheel event.

I don't see how QScrollArea is preventing you from doing that.

Moreover, I'd like to have in the viewport another widget which shows line numbers and, when receiving horizontal scroll events, scroll only the widget with the text but not the widget with the line numbers.

That's not how it's done. Use QAbstractScrollArea::setViewportMargins() and place your line counting widget in the blank space left by the viewport.

[Charletes]

And what is wrong with QPlainTextEdit?

I'd like to be able to implement a column-mode, and as far as I know that can't be done using QPlainTextEditor.

That's not how it's done. Use QAbstractScrollArea::setViewportMargins() and place your line counting widget in the blank space left by the viewport.

I didn't know that it could be done that way. I'll try it, it seems to be easier that way.

Thanks!

[wysota]

I'd like to be able to implement a column-mode, and as far as I know that can't be done using QPlainTextEditor.

I don't know what "column mode" is but there is a good chance it can be implemented on top of what QPlaintTextEdit offers.

[Charletes]

What most text editors call column-mode is the posiblity on writing on several lines at once and being able to select a square of text instead of lines. Emacs call it rectangle mode I think.

[wysota]

I don't see a reason why this couldn't be implemented with QPlainTextEdit.