Add simple play/pause controls

res/css/_components.scss

@@ -248,6 +248,7 @@
 @import "./views/toasts/_AnalyticsToast.scss";
 @import "./views/toasts/_NonUrgentEchoFailureToast.scss";
 @import "./views/verification/_VerificationShowSas.scss";
+@import "./views/voice_messages/_PlayPauseButton.scss";
 @import "./views/voice_messages/_Waveform.scss";
 @import "./views/voip/_CallContainer.scss";
 @import "./views/voip/_CallView.scss";

res/css/views/voice_messages/_PlayPauseButton.scss

@@ -0,0 +1,51 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+.mx_PlayPauseButton {
+    position: relative;
+    width: 32px;
+    height: 32px;
+    border-radius: 32px;
+    background-color: $primary-bg-color;
+
+    &::before {
+        content: '';
+        position: absolute; // sizing varies by icon
+        background-color: $muted-fg-color;
+        mask-repeat: no-repeat;
+        mask-size: contain;
+    }
+
+    &.mx_PlayPauseButton_disabled::before {
+        opacity: 0.5;
+    }
+
+    &.mx_PlayPauseButton_play::before {
+        width: 13px;
+        height: 16px;
+        top: 8px; // center
+        left: 12px; // center
+        mask-image: url('$(res)/img/element-icons/play-symbol.svg');
+    }
+
+    &.mx_PlayPauseButton_pause::before {
+        width: 10px;
+        height: 12px;
+        top: 10px; // center
+        left: 11px; // center
+        mask-image: url('$(res)/img/element-icons/pause-symbol.svg');
+    }
+}

res/img/element-icons/pause-symbol.svg

@@ -0,0 +1,4 @@
+<svg width="10" height="12" viewBox="0 0 10 12" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M0 1C0 0.447715 0.447715 0 1 0H2C2.55228 0 3 0.447715 3 1V11C3 11.5523 2.55228 12 2 12H1C0.447715 12 0 11.5523 0 11V1Z" fill="#737D8C"/>
+<path d="M7 1C7 0.447715 7.44772 0 8 0H9C9.55228 0 10 0.447715 10 1V11C10 11.5523 9.55228 12 9 12H8C7.44772 12 7 11.5523 7 11V1Z" fill="#737D8C"/>
+</svg>

res/img/element-icons/play-symbol.svg

@@ -0,0 +1,3 @@
+<svg width="13" height="16" viewBox="0 0 13 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M0 14.2104V1.78956C0 1.00724 0.857827 0.527894 1.5241 0.937906L11.6161 7.14834C12.2506 7.53883 12.2506 8.46117 11.6161 8.85166L1.5241 15.0621C0.857828 15.4721 0 14.9928 0 14.2104Z" fill="#737D8C"/>
+</svg>