X11: Print an error to STDERR instead of refusing to start when the user sets a custom window icon larger than 128128

Fixes #6507

docs/changelog.rst

@@ -43,6 +43,8 @@ Detailed list of changes
 
 - kitten @ ls: Add user variables set on windows to the output (:iss:`6502`)
 
+- X11: Print an error to STDERR instead of refusing to start when the user sets a custom window icon larger than 128128 (:iss:`6507`)
+
 0.29.2 [2023-07-27]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kitty/glfw.c

@@ -703,6 +703,11 @@ set_default_window_icon(PyObject UNUSED *self, PyObject *args) {
     uint8_t *data;
     if(!PyArg_ParseTuple(args, "s", &path)) return NULL;
     if (png_path_to_bitmap(path, &data, &width, &height, &sz)) {
+#ifndef __APPLE__
+        if (!global_state.is_wayland && (width > 128 || height > 128)) {
+            return PyErr_Format(PyExc_ValueError, "The window icon is too large (%dx%d). On X11 max window icon size is: 128x128. Create a file called ~/.config/kitty.app-128.png containing a 128x128 image to use as the window icon on X11.", width, height);
+        }
+#endif
         logo.width = width; logo.height = height;
         logo.pixels = data;
     }

kitty/main.py

@@ -201,14 +201,17 @@ def get_icon128_path(base_path: str) -> str:
 
 def set_x11_window_icon() -> None:
     custom_icon_path = get_custom_window_icon()[1]
-    if custom_icon_path is not None:
-        custom_icon128_path = get_icon128_path(custom_icon_path)
-        if safe_mtime(custom_icon128_path) is None:
-            set_default_window_icon(custom_icon_path)
+    try:
+        if custom_icon_path is not None:
+            custom_icon128_path = get_icon128_path(custom_icon_path)
+            if safe_mtime(custom_icon128_path) is None:
+                set_default_window_icon(custom_icon_path)
+            else:
+                set_default_window_icon(custom_icon128_path)
         else:
-            set_default_window_icon(custom_icon128_path)
-    else:
-        set_default_window_icon(get_icon128_path(logo_png_file))
+            set_default_window_icon(get_icon128_path(logo_png_file))
+    except ValueError as err:
+        log_error(err)
 
 
 def _run_app(opts: Options, args: CLIOptions, bad_lines: Sequence[BadLine] = ()) -> None: