feat(content): add fixedSlotPlacement prop (#29233)

Issue number: Internal

---------

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issue. -->

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->
Content in the `fixed` slot is always placed after the main content in
the DOM.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- A new `fixedSlotPlacement` prop on Content allows developers to place
fixed content either before or after the main content in the DOM

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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  2. Update the BREAKING.md file with the breaking change.
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## Other information

Dev build: `8.0.0-dev.11712072527.1dd97c66`

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screenshots of how the component looks before and after the change. -->

⚠️This feature will not be part of the v8.0 release. As a result, do not
merge this into `feature-8.0`. However, I am putting this PR up based
off `feature-8.0` so it can get reviewed by the team.

---------

Co-authored-by: Liam DeBeasi <liamdebeasi@users.noreply.github.com>

core/src/components/content/content.tsx

@@ -75,6 +75,15 @@ export class Content implements ComponentInterface {
    */
   @Prop() fullscreen = false;
 
+  /**
+   * Controls where the fixed content is placed relative to the main content
+   * in the DOM. This can be used to control the order in which fixed elements
+   * receive keyboard focus.
+   * For example, if a FAB in the fixed slot should receive keyboard focus before
+   * the main page content, set this property to `'before'`.
+   */
+  @Prop() fixedSlotPlacement: 'after' | 'before' = 'after';
+
   /**
    * If `true` and the content does not cause an overflow scroll, the scroll interaction will cause a bounce.
    * If the content exceeds the bounds of ionContent, nothing will change.
@@ -423,7 +432,7 @@ export class Content implements ComponentInterface {
   }
 
   render() {
-    const { isMainContent, scrollX, scrollY, el } = this;
+    const { fixedSlotPlacement, isMainContent, scrollX, scrollY, el } = this;
     const rtl = isRTL(el) ? 'rtl' : 'ltr';
     const mode = getIonMode(this);
     const forceOverscroll = this.shouldForceOverscroll();
@@ -446,6 +455,9 @@ export class Content implements ComponentInterface {
         }}
       >
         <div ref={(el) => (this.backgroundContentEl = el)} id="background-content" part="background"></div>
+
+        {fixedSlotPlacement === 'before' ? <slot name="fixed"></slot> : null}
+
         <div
           class={{
             'inner-scroll': true,
@@ -467,7 +479,7 @@ export class Content implements ComponentInterface {
           </div>
         ) : null}
 
-        <slot name="fixed"></slot>
+        {fixedSlotPlacement === 'after' ? <slot name="fixed"></slot> : null}
       </Host>
     );
   }

core/src/components/content/test/content.spec.ts

@@ -0,0 +1,31 @@
+import { newSpecPage } from '@stencil/core/testing';
+
+import { Content } from '../content';
+
+describe('content: fixed slot placement', () => {
+  it('should should fixed slot after content', async () => {
+    const page = await newSpecPage({
+      components: [Content],
+      html: '<ion-content></ion-content>',
+    });
+
+    const content = page.body.querySelector('ion-content')!;
+    const fixedSlot = content.shadowRoot!.querySelector('slot[name="fixed"]')!;
+    const scrollEl = content.shadowRoot!.querySelector('[part="scroll"]')!;
+
+    expect(fixedSlot.nextElementSibling).not.toBe(scrollEl);
+  });
+
+  it('should should fixed slot before content', async () => {
+    const page = await newSpecPage({
+      components: [Content],
+      html: `<ion-content fixed-slot-placement="before"></ion-content>`,
+    });
+
+    const content = page.body.querySelector('ion-content')!;
+    const fixedSlot = content.shadowRoot!.querySelector('slot[name="fixed"]')!;
+    const scrollEl = content.shadowRoot!.querySelector('[part="scroll"]')!;
+
+    expect(fixedSlot.nextElementSibling).toBe(scrollEl);
+  });
+});