Add special font configuration for flatpak

cmake/Flatpak.cmake

@@ -0,0 +1,16 @@
+if(NOT NEOCHAT_FLATPAK)
+    # Only include this if we build a Flatpak
+    return()
+endif()
+
+include(GNUInstallDirs)
+
+# Include FontConfig config which uses the Emoji One font from the
+# KDE Flatpak SDK.
+install(
+    FILES
+        ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Flatpak/99-noto-mono-color-emoji.conf
+    DESTINATION
+        ${CMAKE_INSTALL_SYSCONFDIR}/fonts/conf.d/
+)
+

cmake/Flatpak/99-noto-mono-color-emoji.conf

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
+<fontconfig>
+  <alias>
+    <family>serif</family>
+    <prefer>
+      <family>Emoji One</family>
+    </prefer>
+  </alias>
+  <alias>
+    <family>sans-serif</family>
+    <prefer>
+      <family>Emoji One</family>
+    </prefer>
+  </alias>
+  <alias>
+    <family>monospace</family>
+    <prefer>
+      <family>Emoji One</family>
+    </prefer>
+  </alias>
+</fontconfig>
+