Change icon in headerbar

data/countdown.gresource.xml

@@ -6,6 +6,7 @@
 -->
 <gresources>
   <gresource prefix="/uk/me/bcowan/Countdown">
+    <file preprocess="xml-stripblanks">icons/scalable/actions/timer-symbolic.svg</file>
     <file preprocess="xml-stripblanks">ui/about.ui</file>
     <file preprocess="xml-stripblanks">ui/countdown.ui</file>
     <file preprocess="xml-stripblanks">ui/countdown-label.ui</file>

data/icons/scalable/actions/timer-symbolic.svg

+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" height="16px" viewBox="0 0 16 16" width="16px"><path d="m 8 0 c -0.296875 -0.00390625 -0.578125 0.125 -0.773438 0.347656 c -0.191406 0.226563 -0.273437 0.523438 -0.226562 0.816406 v 2.835938 h 2 v -1.914062 c 2.378906 0.398437 4.320312 2.195312 4.855469 4.613281 c 0.613281 2.753906 -0.765625 5.546875 -3.320313 6.738281 c -2.554687 1.191406 -5.578125 0.453125 -7.296875 -1.785156 c -1.714843 -2.238282 -1.644531 -5.351563 0.167969 -7.507813 c 0.351562 -0.425781 0.296875 -1.054687 -0.125 -1.410156 c -0.425781 -0.355469 -1.054688 -0.300781 -1.410156 0.121094 c -2.40625 2.871093 -2.496094 7.042969 -0.214844 10.011719 c 2.277344 2.972656 6.332031 3.964843 9.726562 2.382812 c 3.390626 -1.582031 5.238282 -5.324219 4.429688 -8.980469 c -0.8125 -3.660156 -4.066406 -6.269531 -7.8125 -6.269531 z m -3.011719 3.988281 c -0.40625 0.003907 -0.769531 0.25 -0.925781 0.625 c -0.152344 0.378907 -0.0625 0.808594 0.230469 1.09375 l 1.777343 1.777344 c -0.183593 0.6875 0.011719 1.425781 0.515626 1.929687 c 0.78125 0.78125 2.046874 0.78125 2.828124 0 s 0.78125 -2.046874 0 -2.828124 c -0.503906 -0.503907 -1.242187 -0.699219 -1.929687 -0.515626 l -1.777344 -1.777343 c -0.1875 -0.195313 -0.445312 -0.300781 -0.71875 -0.304688 z m 0 0" fill="#222222"/></svg>

data/ui/about.ui.in

@@ -12,7 +12,7 @@
     <property name="version">@VCS_TAG@</property>
     <property name="comments" translatable="yes">Countdown counts time down to a set time</property>
     <property name="developer-name">Bruce Cowan</property>
-    <property name="application-icon">appointment-new</property>
+    <property name="application-icon">timer</property>
     <property name="license-type">lgpl-3-0</property>
   </object>
 </interface>

data/ui/countdown.blp

@@ -13,7 +13,7 @@ template ApplicationWindow : Adw.ApplicationWindow {
 
     HeaderBar {
       MenuButton _set_time_button {
-        icon-name: "appointment-new";
+        icon-name: "timer";
         popover: .TimePopover {
             datetime: bind countdown_label.target bidirectional;
         };