fix(material/sort): simplify animations

For a long time the sort header's animation was set up by rendering out 4 `div` elements and then arranging them to look like an arrow. This is somewhat complicated to maintain, difficult to customize, in some cases it leads to weird visual bugs and ends up triggering excessive change detections. On top of that, because it depends on `@angular/animations`, it is prone to memory leaks (see angular/angular#54149).

These changes aim to simplify the component and make it more robust by using an `svg` icon and dealing with the animations.

Fixes #9758.
Fixes #9844.
Fixes #10088.
Fixes #15451.
Fixes #19441.
Fixes #10242.

Author: crisbeto

src/material/sort/sort-animations.ts

@@ -24,6 +24,8 @@ const SORT_ANIMATION_TRANSITION =
 /**
  * Animations used by MatSort.
  * @docs-private
+ * @deprecated No longer being used, to be removed.
+ * @breaking-change 21.0.0
  */
 export const matSortAnimations: {
   readonly indicator: AnimationTriggerMetadata;

src/material/sort/sort-header.html

@@ -11,6 +11,11 @@
 <div class="mat-sort-header-container mat-focus-indicator"
      [class.mat-sort-header-sorted]="_isSorted()"
      [class.mat-sort-header-position-before]="arrowPosition === 'before'"
+     [class.mat-sort-header-descending]="this._sort.direction === 'desc'"
+     [class.mat-sort-header-ascending]="this._sort.direction === 'asc'"
+     [class.mat-sort-header-recently-cleared-ascending]="_recentlyCleared() === 'asc'"
+     [class.mat-sort-header-recently-cleared-descending]="_recentlyCleared() === 'desc'"
+     [class.mat-sort-header-animations-disabled]="_animationModule === 'NoopAnimations'"
      [attr.tabindex]="_isDisabled() ? null : 0"
      [attr.role]="_isDisabled() ? null : 'button'">
 
@@ -26,18 +31,10 @@
 
   <!-- Disable animations while a current animation is running -->
   @if (_renderArrow()) {
-    <div class="mat-sort-header-arrow"
-        [@arrowOpacity]="_getArrowViewState()"
-        [@arrowPosition]="_getArrowViewState()"
-        [@allowChildren]="_getArrowDirectionState()"
-        (@arrowPosition.start)="_disableViewStateAnimation = true"
-        (@arrowPosition.done)="_disableViewStateAnimation = false">
-      <div class="mat-sort-header-stem"></div>
-      <div class="mat-sort-header-indicator" [@indicator]="_getArrowDirectionState()">
-        <div class="mat-sort-header-pointer-left" [@leftPointer]="_getArrowDirectionState()"></div>
-        <div class="mat-sort-header-pointer-right" [@rightPointer]="_getArrowDirectionState()"></div>
-        <div class="mat-sort-header-pointer-middle"></div>
-      </div>
+    <div class="mat-sort-header-arrow">
+      <svg viewBox="0 -960 960 960" focusable="false" aria-hidden="true">
+        <path d="M440-240v-368L296-464l-56-56 240-240 240 240-56 56-144-144v368h-80Z"/>
+      </svg>
     </div>
   }
 </div>

src/material/sort/sort-header.scss

@@ -1,16 +1,7 @@
-@use '@angular/cdk';
-
 @use '../core/tokens/m2/mat/sort' as tokens-mat-sort;
 @use '../core/tokens/token-utils';
 @use '../core/focus-indicators/private';
 
-$header-arrow-margin: 6px;
-$header-arrow-container-size: 12px;
-$header-arrow-stem-size: 10px;
-$header-arrow-pointer-length: 6px;
-$header-arrow-thickness: 2px;
-$header-arrow-hint-opacity: 0.38;
-
 .mat-sort-header-container {
   display: flex;
   cursor: pointer;
@@ -51,93 +42,96 @@ $header-arrow-hint-opacity: 0.38;
   flex-direction: row-reverse;
 }
 
+@keyframes _mat-sort-header-recently-cleared-ascending {
+  from {
+    transform: translateY(0);
+    opacity: 1;
+  }
+
+  to {
+    transform: translateY(-25%);
+    opacity: 0;
+  }
+}
+
+@keyframes _mat-sort-header-recently-cleared-descending {
+  from {
+    transform: translateY(0) rotate(180deg);
+    opacity: 1;
+  }
+
+  to {
+    transform: translateY(25%) rotate(180deg);
+    opacity: 0;
+  }
+}
+
 .mat-sort-header-arrow {
-  height: $header-arrow-container-size;
-  width: $header-arrow-container-size;
-  min-width: $header-arrow-container-size;
+  $timing: 225ms cubic-bezier(0.4, 0, 0.2, 1);
+  height: 12px;
+  width: 12px;
   position: relative;
-  display: flex;
+  transition: transform $timing, opacity $timing;
+  opacity: 0;
+  overflow: visible;
 
   @include token-utils.use-tokens(tokens-mat-sort.$prefix, tokens-mat-sort.get-token-slots()) {
     @include token-utils.create-token-slot(color, arrow-color);
   }
 
-  // Start off at 0 since the arrow may become visible while parent are animating.
-  // This will be overwritten when the arrow animations kick in. See #11819.
-  opacity: 0;
-
-  &,
-  [dir='rtl'] .mat-sort-header-position-before & {
-    margin: 0 0 0 $header-arrow-margin;
+  .mat-sort-header:hover & {
+    opacity: 0.54;
   }
 
-  .mat-sort-header-position-before &,
-  [dir='rtl'] & {
-    margin: 0 $header-arrow-margin 0 0;
+  .mat-sort-header .mat-sort-header-sorted & {
+    opacity: 1;
   }
-}
 
-.mat-sort-header-stem {
-  background: currentColor;
-  height: $header-arrow-stem-size;
-  width: $header-arrow-thickness;
-  margin: auto;
-  display: flex;
-  align-items: center;
-
-  @include cdk.high-contrast {
-    width: 0;
-    border-left: solid $header-arrow-thickness;
+  .mat-sort-header-descending & {
+    transform: rotate(180deg);
   }
-}
 
-.mat-sort-header-indicator {
-  width: 100%;
-  height: $header-arrow-thickness;
-  display: flex;
-  align-items: center;
-  position: absolute;
-  top: 0;
-  left: 0;
-}
+  .mat-sort-header-recently-cleared-ascending & {
+    transform: translateY(-25%);
+  }
 
-.mat-sort-header-pointer-middle {
-  margin: auto;
-  height: $header-arrow-thickness;
-  width: $header-arrow-thickness;
-  background: currentColor;
-  transform: rotate(45deg);
+  .mat-sort-header-recently-cleared-ascending & {
+    transition: none; // Without this the animation looks glitchy on Safari.
+    animation: _mat-sort-header-recently-cleared-ascending $timing forwards;
+  }
 
-  @include cdk.high-contrast {
-    width: 0;
-    height: 0;
-    border-top: solid $header-arrow-thickness;
-    border-left: solid $header-arrow-thickness;
+  .mat-sort-header-recently-cleared-descending & {
+    transition: none; // Without this the animation looks glitchy on Safari.
+    animation: _mat-sort-header-recently-cleared-descending $timing forwards;
   }
-}
 
-.mat-sort-header-pointer-left,
-.mat-sort-header-pointer-right {
-  background: currentColor;
-  width: $header-arrow-pointer-length;
-  height: $header-arrow-thickness;
-  position: absolute;
-  top: 0;
+  // Set the durations to 0, but keep the actual animation, since we still want it to play.
+  .mat-sort-header-animations-disabled & {
+    transition-duration: 0ms;
+    animation-duration: 0ms;
+  }
 
-  @include cdk.high-contrast {
-    width: 0;
-    height: 0;
-    border-left: solid $header-arrow-pointer-length;
-    border-top: solid $header-arrow-thickness;
+  svg {
+    // Even though this is 24x24, the actual `path` inside ends up being 12x12.
+    width: 24px;
+    height: 24px;
+    fill: currentColor;
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    margin: -12px 0 0 -12px;
+
+    // Without this transform the element twitches at the end of the transition on Safari.
+    transform: translateZ(0);
   }
-}
 
-.mat-sort-header-pointer-left {
-  transform-origin: right;
-  left: 0;
-}
+  &,
+  [dir='rtl'] .mat-sort-header-position-before & {
+    margin: 0 0 0 6px;
+  }
 
-.mat-sort-header-pointer-right {
-  transform-origin: left;
-  right: 0;
+  .mat-sort-header-position-before &,
+  [dir='rtl'] & {
+    margin: 0 6px 0 0;
+  }
 }