feat(core): Expose SCSS breakpoints

[MikaStark]

Feature Description

As @angular/flex-layout become deprecated and Angular team does not intend to provide an alternative, we are forced to handle responsive layout by our own.

Writing CSS is ok, but to stick with Material design guidance we must use specific breakpoints. It would be great if @angular/material could expose these breakpoints like it does for palettes and theming. Otherwise we have to declare them ourself for every projects.

Use Case

would simplify scss writting and add opinions about breakpoints (like CDK Layout API)

@use '@angular/material' as mat;

@media #{$mat.gt-xs} {
  // insert your styles
}

[crisbeto]

As far as I can tell, the Material design spec doesn't mention specific breakpoints so anything we provide would be arbitrary.

[MikaStark]

@crisbeto sorry but in fact it did here : https://m2.material.io/design/layout/responsive-layout-grid.html#breakpoints

[dhdaines]

This would be super nice, I have inherited a project that has a mystery "$toolbar-breakpoint: 600px" in it to cope with the fact that a mat-toolbar magically shrinks its height at 600 pixels. Grepping in node_modules is not a substitute for documentation.

[dhdaines]

also it's really fun that these breakpoints are not the same as the ones in bootstrap SCSS, for instance: https://getbootstrap.com/docs/5.0/layout/breakpoints/

[msrumon]

+1. Coming from #3606. We already have the full list here at src/cdk/layout/breakpoints.ts - just publish them as SASS variables and we'll be more than happy.