Hide Widgets In Qt Designer When App Launches

Give your cute (Qt) GUI some pop

Close your eyes… take a long breath in… and breathe out… clear up your mind… and think about your favorite application (it should be the one you are working on 😛 ). Keep your eyes closed and visualize all the graphical elements of the application: buttons, frames, panels, texts, scroll-bars, menus… how many do you count ? That's a lot to think about, isn't it? If you have scroll-bars, it probably means that there is not enough space to show all the widgets at once, and that you need extra space.

Now, put yourself in the shoes of someone who plays with your application for the first time… don't you feel overwhelmed by the amount of visual information? Where to click ? What buttons are important ? Which ones are not ?

I'll skip the pamphlet explaining why it's a bad idea to have a heavy UI. You can open your eyes now and let me present you another way of showing useful widgets at the right time and hiding them when not needed:ctkPopupWidget

Popup to control a 2D view

As a result we managed to cleanup the UI of the Slicer main window:

As its name indicates, ctkPopupWidget is:

part of CTK (Apache 2 license), used in 3D Slicer
a popup: with full control over where and how to popup
a widget: respects all the properties of a Qt widget (e.g. parent/child relationship, background transparency)

Popup to control the range of a slider

ctkPopupWidget is easy to use, let's look at a line by line example:

QSpinBox* spinBox = new QSpinBox ( parentWidget ) ;// the spinbox is the parent of the popup,

ctkPopupWidget* popup = new ctkPopupWidget ( spinBox ) ; // the popup is placed relative to the spinbox

QHBoxLayout* popupLayout = new QHBoxLayout ( popup ) ;

// populate the popup with a vertical QSlider:

QSlider* popupSlider = new QSlider ( Qt :: Vertical , popup ) ;

// add here the signal/slot connection between the slider and the spinbox

popupLayout -> addWidget ( popupSlider ) ; // Control where to display the the popup relative to the parent

popupSlider -> setAlignment ( Qt :: Left | Qt :: Top ) ; // at the top left corner

popupSlider -> setHorizontalDirection ( Qt :: RightToLeft ) ; // open outside the parent

popupSlider -> setVerticalDirection ( ctkBasePopupWidget :: TopToBottom ) ; // at the left of the spinbox sharing the top border

// Control the animation

popupSlider -> setAnimationEffect ( ctkBasePopupWidget :: ScrollEffect ) ; // could also be FadeEffect

popupSlider -> setOrientation ( Qt :: Horizontal ) ; // how to animate, could be Qt::Vertical or Qt::Horizontal|Qt::Vertical

popupSlider -> setEasingCurve ( QEasingCurve :: OutQuart ) ; // how to accelerate the animation, QEasingCurve::Type

popupSlider -> setEffectDuration ( 100 ) ; // how long in ms.

// Control the behavior

popupSlider -> setAutoShow ( true ) ; // automatically open when the mouse is over the spinbox

popupSlider -> setAutoHide ( true ) ; // automatically hide when the mouse leaves the popup or the spinbox.

See below the result of the previous code, the slider popup opens on the left of the spinbox.

Another example of use for a popup slider: as a view item delegate

Popup in a custom QItemDelegate

Most of these properties have a good default value and don't need to be manually set.
Here is the complete API for ctkPopupWidget.

See below more popup tuning:

Note that you can also design the popup UI using Qt Designer. All you then need to do is:

QSpinBox* spinBox = new QSpinBox ( parentWidget ) ;

ctkPopupWidget* popup = new ctkPopupWidget ( spinBox ) ;

Ui_myPopup :: setupUi ( popup ) ; // sets the child widgets and the popup properties.

A popup widget follows its parent when moved, hides if the parent is hidden or disabled. Popups can be nested, pinned, unpinned, flattened (dynamically change from a popup mode into a regular widget).

Pin and Unpin

There are still a few corner cases that can be improved, the fade effect is still a bit experimental and there are a few issues with dialogs or windows moved over the popup. Nonetheless, we started to add a "popup mode" to some widgets in CTK, e.g. ctkSliderWidget::setPopupSlider(bool).

As a side note, you can also consider ctkCollapsibleButton and ctkCollapsibleGroupBox as other alternatives to conveniently "show"/"hide" widgets.

Any question? let me know.