QScrollArea: Area is not updated while an arrow key is held pressed

titan73

While the key is pressed only a scroll bar is updated but not the area. The area is update when the arrow key is released.
I'd like to change my code to fix that.

I tried reimplementing keyPressEvent and forcing updating or repainting the viewport at the end like:

void keyPressEvent(QKeyEvent *event) override {
    int step = 20; // Set your custom scroll step here

    switch (event->key()) {
        case Qt::Key_Up:
            verticalScrollBar()->setValue(verticalScrollBar()->value() - step);
            break;
        case Qt::Key_Down:
            verticalScrollBar()->setValue(verticalScrollBar()->value() + step);
            break;
        case Qt::Key_Left:
            horizontalScrollBar()->setValue(horizontalScrollBar()->value() - step);
            break;
        case Qt::Key_Right:
            horizontalScrollBar()->setValue(horizontalScrollBar()->value() + step);
            break;
        default:
            QScrollArea::keyPressEvent(event); // Call base class implementation for other keys
    }

    // Solution 1:
    // Force the viewport to update
    viewport()->update();

    // Solution 2:
    // Force the viewport to repaint
    viewport()->repaint();

    // Solution 3
    // Force the viewport to update
    viewport()->update();
   // Ensure the widget inside the scroll area is updated
   if (widget()) {
         widget()->update();
   }

While the key is held pressed keyPressEvent is called several time but the area is still not updated

How can I fix that? Is it really necessary to reimplement keyPressEvent?

I'm developping in Qt 5.

TIA

titan73

It seems it's an environment issue not related to the Qt code.
On Ubuntu 22.04 under Virtual Box => the issue appears
On RedHat 8.9 under a container with Ubuntu 22.04 => the issue does not appear.
Thanks
Let's mark this issue as solved.

Axel Spoerl

First and foremost: Please update to Qt6, maybe the problem is solved by that.
Are you sure the code is actually hit? Are the update() calls updating the right widget?

titan73

The code I try to modify is open source software. The gui code is big and can't be ported easily. I don't know there is a plan to switch to Qt6.
I added a trace and keyPressEvent is called regularly while the key is held pressed. I did an update on our LayoutScroll which inherits from QScrollArea and also out LayoutViewer which inherits from QWidget.

The classes are there: https://github.com/The-OpenROAD-Project/OpenROAD/blob/master/src/gui/src/layoutViewer.cpp
And the class that instantiate them: https://github.com/The-OpenROAD-Project/OpenROAD/blob/master/src/gui/src/layoutTabs.cpp

JonB

@titan73 I would suggest you produce a minimal, standalone program to illustrate (and play with) if you want help here.

titan73

It seems it's an environment issue not related to the Qt code.
On Ubuntu 22.04 under Virtual Box => the issue appears
On RedHat 8.9 under a container with Ubuntu 22.04 => the issue does not appear.
Thanks
Let's mark this issue as solved.