feat(progress-bar): update styles to iOS 17 specs (#28759)

Issue number: Internal

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

Ionic's progress bar implementation deviates from the appearance of a
progress bar on iOS 17.

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

- Progress bar is updated to have rounded corners (around the
container).
- Increases progress bar height to `4px`
- Solid progress bars (progress bars with a buffer value of `1`) will
have a consistent background appearance.
- Buffer progress bars will continue to have the colored background
appearance as they do in v7.

## Does this introduce a breaking change?

- [x] Yes
- [ ] No

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See
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### Breaking Changes

- `--buffer-background` has been removed in favor of `--background`. 

## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

Accomplishing rounded caps for the inner progress with Ionic's scale
transformation was not viable. To maintain 60fps animations for the
progress, rounded corners were applied to the container.

---------

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

core/src/components/progress-bar/progress-bar.ios.scss

@@ -1,8 +1,22 @@
 @import "./progress-bar";
+@import "./progress-bar.ios.vars";
 
 // iOS Progress bar
 // --------------------------------------------------
 
 :host {
-  height: 3px;
+  @include border-radius($progress-bar-ios-border-radius);
+
+  height: $progress-bar-ios-height;
+}
+
+:host(.progress-bar-solid) {
+  /**
+   * On iOS the unfilled portion of the progress bar
+   * is always a consistent background color. We
+   * only apply this style when the progress bar is
+   * solid (with a buffer value of 1). This maintains
+   * the custom Ionic appearance for a buffered progress bar.
+   */
+  --background: #{$background-color-step-100};
 }

core/src/components/progress-bar/progress-bar.ios.vars.scss

@@ -0,0 +1,8 @@
+// iOS Progress bar
+// --------------------------------------------------
+
+/// @prop - Height of the progress bar
+$progress-bar-ios-height: 4px !default;
+
+/// @prop - Border radius of the progress bar container
+$progress-bar-ios-border-radius: 9999px !default;

core/src/components/progress-bar/progress-bar.md.scss

@@ -1,8 +1,14 @@
 @import "./progress-bar";
+@import "./progress-bar.md.vars";
 
 // Material Design Progress bar
 // --------------------------------------------------
 
 :host {
-  height: 4px;
+  height: $progress-bar-md-height;
 }
+
+
+:host(.ion-color) .progress-buffer-bar {
+  background: #{current-color(base, 0.3)};
+}

core/src/components/progress-bar/progress-bar.md.vars.scss

@@ -0,0 +1,5 @@
+// MD Progress bar
+// --------------------------------------------------
+
+/// @prop - Height of the progress bar
+$progress-bar-md-height: 4px !default;

core/src/components/progress-bar/progress-bar.scss

@@ -8,11 +8,9 @@
   /**
    * @prop --background: Background of the progress track, or the buffer bar if `buffer` is set
    * @prop --progress-background: Background of the progress bar representing the current value
-   * @prop --buffer-background: DEPRECATED, use `--background` instead
    */
   --background: #{ion-color(primary, base, 0.3)};
   --progress-background: #{ion-color(primary, base)};
-  --buffer-background: var(--background);
 
   display: block;
 
@@ -75,7 +73,7 @@
 }
 
 .progress-buffer-bar {
-  background: var(--buffer-background);
+  background: var(--background);
 
   z-index: 1;
 }
@@ -123,7 +121,7 @@
 // ------------------------------------------------------------------------
 
 .buffer-circles {
-  background-image: radial-gradient(ellipse at center, var(--buffer-background) 0%, var(--buffer-background) 30%, transparent 30%);
+  background-image: radial-gradient(ellipse at center, var(--background) 0%, var(--background) 30%, transparent 30%);
 
   /* stylelint-disable property-disallowed-list */
   background-repeat: repeat-x;
@@ -158,10 +156,6 @@
 // Progress Bar: Color
 // ------------------------------------------------------------------------
 
-:host(.ion-color) .progress-buffer-bar {
-  background: #{current-color(base, 0.3)};
-}
-
 :host(.ion-color) .buffer-circles {
   background-image: radial-gradient(ellipse at center, #{current-color(base, 0.3)} 0%, #{current-color(base, 0.3)} 30%, transparent 30%);
 }

core/src/components/progress-bar/progress-bar.tsx

@@ -59,6 +59,8 @@ export class ProgressBar implements ComponentInterface {
     const { color, type, reversed, value, buffer } = this;
     const paused = config.getBoolean('_testing');
     const mode = getIonMode(this);
+    // If the progress is displayed as a solid bar.
+    const progressSolid = buffer === 1;
     return (
       <Host
         role="progressbar"
@@ -70,6 +72,7 @@ export class ProgressBar implements ComponentInterface {
           [`progress-bar-${type}`]: true,
           'progress-paused': paused,
           'progress-bar-reversed': document.dir === 'rtl' ? !reversed : reversed,
+          'progress-bar-solid': progressSolid,
         })}
       >
         {type === 'indeterminate' ? renderIndeterminate() : renderProgress(value, buffer)}

core/src/components/progress-bar/test/basic/index.html

@@ -15,11 +15,11 @@
 
     <style>
       .custom-bar-background {
-        --buffer-background: red;
+        --background: red;
       }
 
       .no-bar-background {
-        --buffer-background: none;
+        --background: none;
       }
 
       ion-content ion-progress-bar {

core/src/components/progress-bar/test/buffer/index.html

@@ -14,14 +14,6 @@
     <script type="module" src="../../../../../dist/ionic/ionic.esm.js"></script>
 
     <style>
-      .custom-bar-background {
-        --buffer-background: red;
-      }
-
-      .no-bar-background {
-        --buffer-background: none;
-      }
-
       ion-content ion-progress-bar {
         margin: 10px 0;
       }

core/src/components/progress-bar/test/determinate/index.html

@@ -15,11 +15,11 @@
 
     <style>
       .custom-bar-background {
-        --buffer-background: red;
+        --background: red;
       }
 
       .no-bar-background {
-        --buffer-background: none;
+        --background: none;
       }
 
       ion-content ion-progress-bar {