PanelListBox Widget

[mickes27]

This is a pull request with PanelListBox Widget. The idea for this widget is to provide more flexibility for ListBox, so user can use Panel instead of Text.

Example code:

const auto panelListBox = tgui::PanelListBox::create();
panelListBox->setPosition(10, 10);
panelListBox->setSize(300, 400);

const auto panel1 = panelListBox->addItem();
const auto panel2 = panelListBox->addItem();
const auto panel3 = panelListBox->addItem();
panelListBox->addItem();
panelListBox->addItem();
panelListBox->addItem();

const auto button = tgui::Button::create("Delete");
panel1->add(button);

const auto pic = tgui::Picture::create("Texture1.png");
panel2->add(pic);

const auto label = tgui::Label::create("Some panel");
panel3->add(label);

gui.add(panelListBox);

gui.mainLoop();

Which results in following PanelListBox:

There are still some functions which are missing, for example:

• Chaning items in place
• Using arrow keys to navigate list
• Double clicks
• Mouse press/release events

I'd be glad for any comments how can I improve this code.

[texus]

Thank you for contributing this. I didn't have time yet to look at it in-depth and to test the code, but on first sight it already looks great except for some minor details.

• The code style for if/else statements and loops doesn't match the rest of TGUI. One line in a body doesn't require braces, but if there are braces then they should always be on a separate line (see https://www.sfml-dev.org/style.php#parenthesis-braces)
• I would rename SignalPanel to either SignalSelectedPanel or SignalPanelListBoxItem, to make it a bit less vague.
• Changing items in place is probably not needed, but a function should exist to insert a panel at given an index.
• Double clicks and mouse press/release events: those are nice to have features, but as long as nobody needs them then I don't consider them as required functionality.
• One other nice to have would be that you could change the template, so that you could add certain widgets once and they would appear on all panels created afterwards.

[mickes27]

Added new commit. Fixed the formatting errors (now it should follow SFML guidelines). Also, added method for getting panel template, so it can be freely changed. I was thinking about using some kind of void changePanelTemplate(Panel::Ptr template), however I think that just returning used template gives us more flexibility (we already have eveyrthing we were using, so there is no need to additional getting existing widgets and customization)

[texus]

Thanks again for creating the widget. I did make a few minor changes when I merged it:

• While testing I found one minor issue: if setSize wasn't called then the items didn't work properly. I've fixed this by having a setSize call at the end of the constructor.
• There were quite some lines with only whitespace on them.
• I removed the ItemsWidth property. I missed its existence during the review and my fix with setSize in the constructor caused tests to fail, so I had to either quickly fix ItemsWidth or remove it. I don't really believe it should exist, and it's implementation wouldn't have worked when the layout parameter wasn't a constant, but was there perhaps a use case that you had in mind for which you added it?

[mickes27]

I introduced ItemsWidth property for more flexibility (it was in first iteration, where horizontal scrollbar was still used). In that case user could potentially use larger panels than list box size. I think that it was unnecessary, if we decide that horizontal scrollbar is never shown and we should not exceed whole widget size.