Add config option for custom app icon. Takes an absolute path to an image file. Falls back to default icons when custom icon cannot be loaded.

This resolves the following issues:
https://github.com/qutebrowser/qutebrowser/issues/7714
https://github.com/qutebrowser/qutebrowser/issues/4009

It can be used by adding this line to the config.py:
`c.app.icon = '/Users/luke/Pictures/browser.png'`

.gitignore

@@ -55,3 +55,5 @@ TODO
 /misc/nsis/include
 /misc/nsis/plugins
 /wheels
+/wheels
+.DS_Store

qutebrowser/app.py

@@ -168,15 +168,36 @@ def init(*, args: argparse.Namespace) -> None:
 
 def _init_icon():
     """Initialize the icon of qutebrowser."""
+    
     fallback_icon = QIcon()
-    for size in [16, 24, 32, 48, 64, 96, 128, 256, 512]:
-        filename = 'icons/qutebrowser-{size}x{size}.png'.format(size=size)
+
+    def load_default_icons():
+        for size in [16, 24, 32, 48, 64, 96, 128, 256, 512]:
+            filename = 'icons/qutebrowser-{size}x{size}.png'.format(size=size)
+            pixmap = QPixmap()
+            pixmap.loadFromData(resources.read_file_binary(filename))
+            if pixmap.isNull():
+                log.init.warning("Failed to load: {}".format(filename))
+            else:
+                fallback_icon.addPixmap(pixmap)
+
+    icon_custom = config.val.app.icon
+    if icon_custom != None:
+        # Use the custom icon if possible
         pixmap = QPixmap()
-        pixmap.loadFromData(resources.read_file_binary(filename))
-        if pixmap.isNull():
-            log.init.warning("Failed to load {}".format(filename))
-        else:
-            fallback_icon.addPixmap(pixmap)
+        try:
+            pixmap.loadFromData(resources.read_absolute_file_binary(icon_custom))
+            if pixmap.isNull():
+                log.init.warning("Failed to load custom icon: {}. Falling back to default".format(icon_custom))
+                load_default_icons()
+            else:
+                fallback_icon.addPixmap(pixmap)
+        except FileNotFoundError:
+            log.init.warning("Custom icon not found: {}. Falling back to default".format(icon_custom))
+            load_default_icons()
+    else:
+        load_default_icons()
+
     icon = QIcon.fromTheme('qutebrowser', fallback_icon)
     if icon.isNull():
         log.init.warning("Failed to load icon")

qutebrowser/browser/webengine/notification.py

@@ -970,8 +970,21 @@ class DBusNotificationAdapter(AbstractNotificationAdapter):
             hints["x-kde-origin-name"] = origin_url_str
 
         if icon.isNull():
-            filename = 'icons/qutebrowser-64x64.png'
-            icon = QImage.fromData(resources.read_file_binary(filename))
+            icon_custom = config.val.app.icon
+            icon_default = 'icons/qutebrowser-64x64.png'
+
+            def get_icon_data():
+                if icon_custom == None:
+                    return resources.read_file_binary(icon_default)
+
+                try:
+                    return resources.read_absolute_file_binary(icon_custom)
+                except FileNotFoundError:
+                    log.init.warning("Custom icon not found: {}. Falling back to default".format(icon_custom))
+                    return resources.read_file_binary(icon_default)
+                    
+            
+            icon = QImage.fromData(get_icon_data())
 
         key = self._quirks.icon_key or "image-data"
         data = self._convert_image(icon)

qutebrowser/config/configdata.yml

@@ -4094,3 +4094,15 @@ logging.level.console:
   desc: >-
     Level for console (stdout/stderr) logs.
     Ignored if the `--loglevel` or `--debug` CLI flags are used.
+
+## app
+
+app.icon:
+  type:
+    name: String
+    none_ok: true
+  default: null
+  restart: true
+  desc: >-
+    The absolute path to a custom icon for the qutebrowser app.
+    Note that this only sets the icon for the app while it is running.

qutebrowser/utils/resources.py

@@ -121,3 +121,18 @@ def read_file_binary(filename: str) -> bytes:
     path = _path(filename)
     with _keyerror_workaround():
         return path.read_bytes()
+
+
+def read_absolute_file_binary(filepath: str) -> bytes:
+    """Get the contents of an binary file at an absolute path. 
+    This file may exist outside of qutebrowser-owned directories.
+
+    Args:
+        filepath: The absolute filepath to open as string.
+
+    Return:
+        The file contents as a bytes object.
+    """
+    path = pathlib.Path(filepath)
+    with _keyerror_workaround():
+        return path.read_bytes()