Simple guide on how to setup app icon for Flutter on Linux

flutter_linux_icon.md

How to setup app icon for Flutter on Linux

First, add your icon as a Flutter asset in pubspec.yaml if you haven't already:

 flutter:
   uses-material-design: true

   assets:
     - CHANGELOG.md
+    - assets/icon.png

Next, add the following #include and using statements to the start of linux/my_application.cc:

+#include <filesystem> 
+using namespace std;
+using namespace std::filesystem;

 #include "my_application.h"

 #include <flutter_linux/flutter_linux.h>
 #ifdef GDK_WINDOWING_X11

Finally, in the same file, add the following code inside my_application_activate right after the window variable is declared. Make sure to replace assets/icon.png with the icon filename you specified in pubspec.yaml if it differs.

 static void my_application_activate(GApplication* application) {
   MyApplication* self = MY_APPLICATION(application);
   GtkWindow* window =
       GTK_WINDOW(gtk_application_window_new(GTK_APPLICATION(application)));
   
+  const string iconFilename = "assets/icon.png";
+  path execDir = canonical(read_symlink("/proc/self/exe")).parent_path();
+  path iconPath = execDir / "data/flutter_assets" / iconFilename;
+  gtk_window_set_icon_from_file(GTK_WINDOW(window), iconPath.c_str(), NULL);
 
   // Use a header bar when running in GNOME as this is the common style used

If you get a compilation error telling you that the filesystem namespace could not be found, you'll have to update the C++ standard version to 17 by modifying linux/CMakeLists.txt:

 function(APPLY_STANDARD_SETTINGS TARGET)
-  target_compile_features(${TARGET} PUBLIC cxx_std_14)
+  target_compile_features(${TARGET} PUBLIC cxx_std_17)
   target_compile_options(${TARGET} PRIVATE -Wall -Werror)
   target_compile_options(${TARGET} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:-O3>")
   target_compile_definitions(${TARGET} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:NDEBUG>")
 endfunction()

my_application_additions.cc

// linux/my_application.cc

// at the start of the file
#include <filesystem>
using namespace std;
using namespace std::filesystem;

// inside my_application_activate after the window declaration
const string iconFilename = "<ICON_ASSET_PATH>";
path execDir = canonical(read_symlink("/proc/self/exe")).parent_path();
path iconPath = execDir / "data/flutter_assets" / iconFilename;
gtk_window_set_icon_from_file(GTK_WINDOW(window), iconPath.c_str(), NULL);

Thank you! Works, however is there any other way to just pack another image with the Linux build? Similar to how the Windows build does already.