Vertical scroll to parent

General JUCE discussion
1

I’ve got a viewport inside a viewport. The inner viewport i want to respond to horizontal scroll events but if a vertical scroll happens i want to scroll the outer one.

At the moment if the mouse is over the inner viewport it scrolls horizontally whether i drag vertically or horizontally on the trackpad.

It’s rows of album covers, a bit like netflix…

Any ideas?

2

Is this a hard question or just incomprehensible? :slight_smile:

3

Do you have the correct setScrollBarsShown config for each Viewport?

4

The inner one is correct: I’ve disabled all the vertical scrolling options.

5

I’m not sure what the answer is. I had a similar setup with a Midi editor, with an inner Viewport with vertical scrolling for Midi notes, and the outer Viewport with horizontal scrolling for time, and I don’t recall having any issues… I’ll try to go back and look at the code…

6

Thanks! Interesting if it worked for you. Unless its’ a new JUCE thing, we are on some older build, I’ll check the JUCE commits…

7

Looking back, the horizontal (time) viewport was inside the vertical (note) viewport. And here are the setScrollBarsShown lines:

midiEditorVerticalViewport->setScrollBarsShown (true, false, true, false);

midiEditorTimeViewport->setScrollBarsShown (false, false, false, true);
8

Well if it worked for you that’s good news :slight_smile: I’ll go digging.

9

I have no idea how this could have worked :slight_smile:

It only works for me if I modify Viewport something like below. See the changed if statement on about line 10.

bool Viewport::useMouseWheelMoveIfNeeded (const MouseEvent& e, const MouseWheelDetails& wheel)
{
    if (! (e.mods.isAltDown() || e.mods.isCtrlDown() || e.mods.isCommandDown()))
    {
        const bool canScrollVert = (allowScrollingWithoutScrollbarV || getVerticalScrollBar().isVisible());
        const bool canScrollHorz = (allowScrollingWithoutScrollbarH || getHorizontalScrollBar().isVisible());

        auto deltaX = rescaleMouseWheelDistance (wheel.deltaX, singleStepX);
        auto deltaY = rescaleMouseWheelDistance (wheel.deltaY, singleStepY);

        if (canScrollHorz && std::abs(deltaX) > 0 || canScrollVert && std::abs(deltaY) > 0) // < added test to see if scroll was horizontal or vertical
        {
            auto pos = getViewPosition();

            if (deltaX != 0 && deltaY != 0 && canScrollHorz && canScrollVert)
            {
                pos.x -= deltaX;
                pos.y -= deltaY;
            }
            else if (canScrollHorz && (deltaX != 0 || e.mods.isShiftDown() || ! canScrollVert))
            {
                pos.x -= deltaX != 0 ? deltaX : deltaY;
            }
            else if (canScrollVert && deltaY != 0)
            {
                pos.y -= deltaY;
            }

            if (pos != getViewPosition())
            {
                setViewPosition (pos);
                return true;
            }
        }
    }

    return false;
}

But that doesn’t look like a great solution as it goes funny if I drag diagonally.

Maybe it’d be better to pass all mousewheel events to the parent viewport, but however I do it looks like I’ll need a custom Viewport class.

10

This fixes it for me - looks like I’ll need a custom Viewport class.

void Viewport::mouseWheelMove (const MouseEvent& e, const MouseWheelDetails& wheel)
{
    (void)useMouseWheelMoveIfNeeded (e, wheel);
    Component::mouseWheelMove (e, wheel);
}
11

This is only any use when you have nested viewports that scroll in different directions, otherwise the behaviour would be weird :slight_smile: