feat(core): add support for 1..n mediaQuery overrides during printing

When printing developers can now configure how layouts should render
by specifying 1..n mediaQuery aliases. This feature allows totally different
print outputs without modifying the currently layout.

Implement PrintHook service to intercept print mediaQuery activation events.
  * add fxShow.print and fxHide.print support to show/hide elements during printing
  * suspend activation changes in MediaMarshaller while print-mode is active
  * trigger MediaObserver to notify subscribers with print mqAlias(es)
  * use PrintHook to intercept activation changes in MediaMarshaller while print-mode is active
  * trigger MediaObserver to notify subscribers with print mqAlias(es)

Using the new `printWithBreakpoint` allows developers to specify a breakpoint that should be used to render layouts only during printing. With the configuration below, the breakpoint associated with the **`md`** alias will be used.

```ts
    FlexLayoutModule.withConfig({
      useColumnBasisZero: false,
      printWithBreakpoints: ['md', 'gt-sm', 'gt-xs']
    })
```
Shown below is the print layout rendered in floating dialog over the normal layout using 'lg' breakpoints.

![angular-layout-printing](https://user-images.githubusercontent.com/210413/50407211-2e04ca00-0798-11e9-8f35-b4e9e2fca864.jpg)

Fixes #603.

Author: ThomasBurleson

docs/documentation/BreakPoints.md

@@ -42,7 +42,7 @@ import {BREAKPOINT} from '@angular/flex-layout';
 const PRINT_BREAKPOINTS = [{
   alias: 'xs.print',
   suffix: 'XsPrint',
-  mediaQuery: 'print and (max-width: 297px)',
+  mediaQuery: 'screen and (max-width: 297px)',
   overlapping: false
 }];
 
@@ -73,7 +73,7 @@ export class MyAppModule {
 }
 ```
 
-With the above changes, when printing on mobile-sized viewports the **`xs.print`** mediaQuery will activate. Please note
+With the above changes, when printing on mobile-sized viewports the **`xs.print`** mediaQuery will onMediaChange. Please note
 that the provider is a **multi-provider**, meaning it can be provided multiple times and in a variety of
 presentations. The type signature of `BREAKPOINT` is the following:
 
@@ -157,4 +157,4 @@ export class CustomShowHideDirective extends ShowHideDirective {
     this._cacheInput("showXsPrint", negativeOf(val));
   }
 }
-```
+```

docs/documentation/fxHide-API.md

@@ -24,7 +24,7 @@ e.g.
 
 ### Using Responsive API
 
-When a mediaQuery range activates, the directive instances will be notified. If the current activate mediaQuery range 
+When a mediaQuery range activates, the directive instances will be notified. If the current activated mediaQuery range 
 (and its associated alias) are not used, then the static API value is restored as the fallback value.
 
 The *fallback* solution uses a **`largest_range-to-smallest_range`** search algorithm. Consider the following:

docs/documentation/fxShow-API.md

@@ -24,7 +24,7 @@ e.g.
 
 ### Using Responsive API
 
-When a mediaQuery range activates, the directive instances will be notified. If the current activate mediaQuery range 
+When a mediaQuery range activates, the directive instances will be notified. If the current activated mediaQuery range 
 (and its associated alias) are not used, then the static API value is restored as the fallback value.
 
 The *fallback* solution uses a **`largest_range-to-smallest_range`** search algorithm. Consider the following:

src/apps/demo-app/src/app/app.module.ts

@@ -1,19 +1,12 @@
 import {BrowserModule} from '@angular/platform-browser';
 import {NgModule} from '@angular/core';
 import {BrowserAnimationsModule} from '@angular/platform-browser/animations';
-import {FlexLayoutModule, BREAKPOINT} from '@angular/flex-layout';
+import {FlexLayoutModule} from '@angular/flex-layout';
 
 import {RoutingModule} from './routing.module';
 import {AppComponent} from './app.component';
 import {DemoMaterialModule} from './material.module';
 
-const PRINT_BREAKPOINTS = [{
-  alias: 'xs.print',
-  suffix: 'XsPrint',
-  mediaQuery: 'print and (max-width: 297px)',
-  overlapping: false
-}];
-
 @NgModule({
   declarations: [
     AppComponent,
@@ -23,9 +16,11 @@ const PRINT_BREAKPOINTS = [{
     BrowserAnimationsModule,
     RoutingModule,
     DemoMaterialModule,
-    FlexLayoutModule.withConfig({useColumnBasisZero: false}),
+    FlexLayoutModule.withConfig({
+      useColumnBasisZero: false,
+      printWithBreakpoints: ['md', 'gt-sm', 'gt-xs']
+    }),
   ],
-  providers: [{provide: BREAKPOINT, useValue: PRINT_BREAKPOINTS, multi: true}],
   bootstrap: [AppComponent]
 })
 export class AppModule { }

src/apps/demo-app/src/styles.scss

@@ -8,6 +8,12 @@ body {
   font-size: 16px;
   line-height: 1.4;
   -webkit-font-smoothing: antialiased;
+  -webkit-print-color-adjust: exact !important;
+}
+
+@page {
+   size: auto;   /* auto is the initial value */
+   margin: 2cm;
 }
 
 h3 {

src/lib/core/add-alias.ts

@@ -14,7 +14,7 @@ import {extendObject} from '../utils/object-extend';
  * and suffix (if available).
  */
 export function mergeAlias(dest: MediaChange, source: BreakPoint | null): MediaChange {
-  return extendObject(dest, source ? {
+  return extendObject(dest || {}, source ? {
         mqAlias: source.alias,
         suffix: source.suffix
       } : {});

src/lib/core/base/base2.ts

@@ -37,7 +37,7 @@ export abstract class BaseDirective2 implements OnChanges, OnDestroy {
   }
   set activatedValue(value: string) {
     this.marshal.setValue(this.nativeElement, this.DIRECTIVE_KEY, value,
-      this.marshal.activatedBreakpoint);
+      this.marshal.activatedAlias);
   }
 
   /** Cache map for style computation */

src/lib/core/breakpoints/break-point-registry.ts

@@ -11,7 +11,7 @@ import {BreakPoint} from './break-point';
 import {BREAKPOINTS} from './break-points-token';
 import {sortAscendingPriority} from './breakpoint-tools';
 
-type OptionalBreakPoint = BreakPoint | null;
+export type OptionalBreakPoint = BreakPoint | null;
 
 /**
  * Registry of 1..n MediaQuery breakpoint ranges
@@ -30,7 +30,7 @@ export class BreakPointRegistry {
    * Search breakpoints by alias (e.g. gt-xs)
    */
   findByAlias(alias: string): OptionalBreakPoint {
-    return this.findWithPredicate(alias, (bp) => bp.alias == alias);
+    return !alias ? null : this.findWithPredicate(alias, (bp) => bp.alias == alias);
   }
 
   findByQuery(query: string): OptionalBreakPoint {

src/lib/core/match-media/match-media.spec.ts

@@ -25,7 +25,7 @@ describe('match-media', () => {
 
   // Single async inject to save references; which are used in all tests below
   beforeEach(async(inject([MatchMedia], (service: MockMatchMedia) => {
-    matchMedia = service;      // inject only to manually activate mediaQuery ranges
+    matchMedia = service;      // inject only to manually onMediaChange mediaQuery ranges
   })));
   afterEach(() => {
     matchMedia.clearAll();
@@ -121,7 +121,7 @@ describe('match-media-observable', () => {
     [MediaObserver, MatchMedia, BreakPointRegistry],
     (_mediaObserver: MediaObserver, _matchMedia: MockMatchMedia,
      _breakPoints: BreakPointRegistry) => {
-      matchMedia = _matchMedia;      // inject only to manually activate mediaQuery ranges
+      matchMedia = _matchMedia;      // inject only to manually onMediaChange mediaQuery ranges
       breakPoints = _breakPoints;
       mediaObserver = _mediaObserver;
     })));

src/lib/core/match-media/match-media.ts

@@ -65,8 +65,9 @@ export class MatchMedia {
         const matches: Array<MediaChange> = this.registerQuery(mqList);
         if (matches.length) {
           const lastChange = matches.pop()!;
-
-          matches.forEach(observer.next);
+          matches.forEach((e: MediaChange) => {
+            observer.next(e);
+          });
           this._source.next(lastChange); // last match is cached
         }
         observer.complete();

src/lib/core/match-media/mock/mock-match-media.spec.ts

@@ -183,7 +183,7 @@ describe('mock-match-media', () => {
     subscription.unsubscribe();
   });
 
-  it('can activate with either a mediaQuery or an alias', () => {
+  it('can onMediaChange with either a mediaQuery or an alias', () => {
     let activates = 0;
     let bpGtSM = breakPoints.findByAlias('gt-sm'),
       bpLg = breakPoints.findByAlias('lg');

src/lib/core/match-media/mock/mock-match-media.ts

@@ -68,7 +68,7 @@ export class MockMatchMedia extends MatchMedia {
   }
 
   /**
-   * Manually activate any overlapping mediaQueries to simulate
+   * Manually onMediaChange any overlapping mediaQueries to simulate
    * similar functionality in the window.matchMedia()
    */
   private _activateWithOverlaps(mediaQuery: string, useOverlaps: boolean): boolean {
@@ -92,7 +92,7 @@ export class MockMatchMedia extends MatchMedia {
           break;
       }
 
-      // Simulate activate of overlapping gt-<xxxx> mediaQuery ranges
+      // Simulate onMediaChange of overlapping gt-<xxxx> mediaQuery ranges
       switch (alias) {
         case 'xl'   :
           this._activateByAlias('gt-lg, gt-md, gt-sm, gt-xs');
@@ -223,7 +223,7 @@ export class MockMediaQueryList implements MediaQueryList {
     return this;
   }
 
-  /** Add a listener to our internal list to activate later */
+  /** Add a listener to our internal list to onMediaChange later */
   addListener(listener: MediaQueryListListener) {
     if (this._listeners.indexOf(listener) === -1) {
       this._listeners.push(listener);

src/lib/core/match-media/server-match-media.ts

@@ -63,7 +63,7 @@ export class ServerMediaQueryList implements MediaQueryList {
     return this;
   }
 
-  /** Add a listener to our internal list to activate later */
+  /** Add a listener to our internal list to onMediaChange later */
   addListener(listener: MediaQueryListListener) {
     if (this._listeners.indexOf(listener) === -1) {
       this._listeners.push(listener);
@@ -109,7 +109,7 @@ export class ServerMediaQueryList implements MediaQueryList {
  * Special server-only implementation of MatchMedia that uses the above
  * ServerMediaQueryList as its internal representation
  *
- * Also contains methods to activate and deactivate breakpoints
+ * Also contains methods to onMediaChange and deactivate breakpoints
  */
 @Injectable()
 export class ServerMatchMedia extends MatchMedia {