juce viewport使用

1、设置内容组件

void PropertyPanel::init()
{
    messageWhenEmpty = TRANS("(nothing selected)");

    addAndMakeVisible (viewport);
    viewport.setViewedComponent (propertyHolderComponent = new PropertyHolderComponent());
    viewport.setFocusContainer (true);
}

2、设置大小

void PropertyPanel::resized()
{
    viewport.setBounds (getLocalBounds());
    updatePropHolderLayout();
}

3、布局内容。

void PropertyPanel::updatePropHolderLayout() const
{
    const int maxWidth = viewport.getMaximumVisibleWidth();
    propertyHolderComponent->updateLayout (maxWidth);

    const int newMaxWidth = viewport.getMaximumVisibleWidth();
    if (maxWidth != newMaxWidth)
    {
        // need to do this twice because of scrollbars changing the size, etc.
        propertyHolderComponent->updateLayout (newMaxWidth);
    }
}

具体原理还是没如何弄明白，应当是监听了子控件的大小变化。