Add pop-out player for audio/video in web UI (#14870)

Fix #11160

app/javascript/styles/mastodon/components.scss

@@ -163,7 +163,8 @@
 }
 
 .icon-button {
-  display: inline-block;
+  display: inline-flex;
+  align-items: center;
   padding: 0;
   color: $action-button-color;
   border: 0;
@@ -245,6 +246,14 @@
       background: rgba($base-overlay-background, 0.9);
     }
   }
+
+  &__counter {
+    display: inline-block;
+    width: 14px;
+    margin-left: 4px;
+    font-size: 12px;
+    font-weight: 500;
+  }
 }
 
 .text-icon-button {
@@ -1139,24 +1148,6 @@
   align-items: center;
   display: flex;
   margin-top: 8px;
-
-  &__counter {
-    display: inline-flex;
-    margin-right: 11px;
-    align-items: center;
-
-    .status__action-bar-button {
-      margin-right: 4px;
-    }
-
-    &__label {
-      display: inline-block;
-      width: 14px;
-      font-size: 12px;
-      font-weight: 500;
-      color: $action-button-color;
-    }
-  }
 }
 
 .status__action-bar-button {
@@ -7034,3 +7025,100 @@ noscript {
     }
   }
 }
+
+.picture-in-picture {
+  position: fixed;
+  bottom: 20px;
+  right: 20px;
+  width: 300px;
+
+  &__footer {
+    border-radius: 0 0 4px 4px;
+    background: lighten($ui-base-color, 4%);
+    padding: 10px;
+    padding-top: 12px;
+    display: flex;
+    justify-content: space-between;
+  }
+
+  &__header {
+    border-radius: 4px 4px 0 0;
+    background: lighten($ui-base-color, 4%);
+    padding: 10px;
+    display: flex;
+    justify-content: space-between;
+
+    &__account {
+      display: flex;
+      text-decoration: none;
+    }
+
+    .account__avatar {
+      margin-right: 10px;
+    }
+
+    .display-name {
+      color: $primary-text-color;
+      text-decoration: none;
+
+      strong,
+      span {
+        display: block;
+        text-overflow: ellipsis;
+        overflow: hidden;
+      }
+
+      span {
+        color: $darker-text-color;
+      }
+    }
+  }
+
+  .video-player,
+  .audio-player {
+    border-radius: 0;
+  }
+
+  @media screen and (max-width: 415px) {
+    width: 210px;
+    bottom: 10px;
+    right: 10px;
+
+    &__footer {
+      display: none;
+    }
+
+    .video-player,
+    .audio-player {
+      border-radius: 0 0 4px 4px;
+    }
+  }
+}
+
+.picture-in-picture-placeholder {
+  box-sizing: border-box;
+  border: 2px dashed lighten($ui-base-color, 8%);
+  background: $base-shadow-color;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  margin-top: 10px;
+  font-size: 16px;
+  font-weight: 500;
+  cursor: pointer;
+  color: $darker-text-color;
+
+  i {
+    display: block;
+    font-size: 24px;
+    font-weight: 400;
+    margin-bottom: 10px;
+  }
+
+  &:hover,
+  &:focus,
+  &:active {
+    border-color: lighten($ui-base-color, 12%);
+  }
+}