Use page title text by default as source of the top bar title when top bar title is not provided

[ulusoyca]

Description

Addresses issue: #26

In many cases, users of this library forget to provide top bar title assuming that their page will never be scrollable. This PR aims to improve the library's usability by providing a default topBarTitle widget using the pageTitle.

The key changes include:

• If topBarTitle not provided, the data of the pageTitle widget (if it is a Text widget) or the first direct "Text" child of the pageTitle widget will be used as the source of the data for the topBarTitle Text widget.

The following scrollable page produces the attached video. Note that topBarTitle is not provided and the source of the title is the descendent of the pageTitle:

WoltModalSheetPage.withCustomSliverList(
        mainContentPadding: EdgeInsetsDirectional.zero,
        stickyActionBar: StickyActionBarWrapper(
          padding: EdgeInsets.zero,
          child: Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: WoltElevatedButton(
              onPressed: () {
                Navigator.of(modalSheetContext).pop();
                pageIndexNotifier.value = 0;
              },
              child: const Text('Close'),
            ),
          ),
        ),
        pageTitle: const Padding(
          padding: EdgeInsets.symmetric(horizontal: 16),
          child: ModalSheetTitle('A very long text as page title to test the look in top bar title.'),
        ),
        heroImageHeight: 200,
        heroImage: const Image(
          image: AssetImage('lib/assets/images/material_colors_hero.png'),
          fit: BoxFit.cover,
        ),
        backButton: WoltModalSheetBackButton(onBackPressed: () {
          pageIndexNotifier.value = pageIndexNotifier.value - 1;
        }),
        closeButton: WoltModalSheetCloseButton(onClosed: () {
          Navigator.of(modalSheetContext).pop();
          pageIndexNotifier.value = 0;
        }),
        sliverList: SliverList(
          delegate: SliverChildBuilderDelegate(
            (_, index) => ColorTile(color: allMaterialColors[index]),
            childCount: allMaterialColors.length,
          ),
        ),
      );

trimmed_title.mov

[TahaTesser]

LGTM with comments

[TahaTesser]

Nice

[TahaTesser]

This might be fine as an initial implementation but this needs to be improved.
I would recommend adding a TODO here and an issue in the repository to improve this later.

[ulusoyca]

@TahaTesser can you please mention how it can be improved?

[TahaTesser]

Using a custom child layout determine the element before the layout happens. Also, it returns a sized box, this widget should. not render at all if there are no conditions met.

The current look-up is only in the init, so what happens if the title text widget is removed? Does it update the widget?

Text is inside Expanded which will render the widget too wide. It should align with the text direction and ability to customize padding. Lower level widget like NavigationToolbar already has these features.

[ulusoyca]

@TahaTesser Thanks, in my next PR, I will apply your suggestions. Merging this PR for now.

[arpadhani]

nit move these to constants outside so they can be referenced and easily changed in multiple places

[ulusoyca]

@arpadhani this is a test file. I don't think there is a reason to move these to outside.