Layout builder

[rodja]

One idea from #117 was to create a subset of layout commands which are easier to understand and discover than the classic css/quasar/tailwind techniques. The "Layout Builder" is one such attempt.

Features

This branch currently sketches out the following features (meaning it's not a full implementation but rather a proof of concept):

• auto completion + documentation for simple to understand layout and styling aspects
• using the builder pattern in combination with string literals for auto completion
• logical grouping of layout aspects (e.g. align.center and align.children are fundamentally different in css but presented together)
• the Layout of an existing element can be modify by accessing its layout property
• Layouts can also be created independently because they are self contained classes
• element.props and element.classes take precedence over element.layout definitions to allow customizations
• Layouts can be used as contexts to create generic groups, rows, columns: with ui.layout('horizontal')
• specialized Layouts provide additional styling (e.g. ButtonLayout to configure shape etc.)
• a Layout can be applied to (multiple) other Layouts via add
• a Layout can be duplicated by calling .copy()
• invalid layout aspects can raise error reports (e.g. margin.top.auto() is not possible with css)
• binding to Layout values like opacity

A demo of this features is implemented in the layout_demo.py.

ToDos / Ideas

• Layout.row() and Layout.column() should use a GroupLayout which provides arrangement of children (e.g. gap, align.children, ...)
• Some mechanism to allow Grid and Masonry Layouts

Questions

• How does the name "Layout" affect header/footer/drawer and tabs? Should we rename the latter? Or incorporate it?
• How to provide smart colors which change automatically for dark mode?
• Can we return the specialized Layout type in base class methods? (e.g. ui.button().layout.align.center() should return ButtonLayout)
• Should we use tailwind classes for color to support dark: selector or use Quasar colors to support Theming with ui.colors?

[HilkopterBob]

a layout builder would be awesome♥

[falkoschindler]

@rodja What do you think: With 1.3.0 being (almost) released now, it's getting harder and harder to merge this PR. And it's stale for months now. Should we close it and come back once we have new ideas on how to proceed?

[rodja]

Yes, the code is not lost