Allow plugins to specify a folder in the zip file to load icons from

kiwidude's plugins use some crazy inefficient code that tries to load an
icon in multiple ways. With this change he can simply do:

get_icons(zfp, name, plugin_name, folder_in_zip_file='images')

This will load the icon efficiently from the user overrides/icon theme,
falling back to the icon from the zip file as a last resort.

Also, change get_icons() to always read the icon data from the zip file.
This is to support upcoming code to change icon themeing to support the
case of switching from one them to another during and when the first
theme has the icon and the second theme doesnt, loading the
fallback/default icon.

src/calibre/customize/zipplugin.py

@@ -13,6 +13,7 @@ import sys
 import threading
 import zipfile
 from collections import OrderedDict
+from collections.abc import Iterable
 from functools import partial
 from importlib.machinery import ModuleSpec
 from importlib.util import decode_source
@@ -54,7 +55,11 @@ def get_resources(zfp, name_or_list_of_names, print_tracebacks_for_missing_resou
     return ans
 
 
-def get_icons(zfp, name_or_list_of_names, plugin_name='', print_tracebacks_for_missing_resources=True):
+def get_icons(
+    zfp: str, name_or_list_of_names: str | Iterable[str],
+    plugin_name: str = '', folder_in_zip_file: str = '',
+    print_tracebacks_for_missing_resources: bool = True,
+):
     '''
     Load icons from the plugin zip file
 
@@ -64,41 +69,34 @@ def get_icons(zfp, name_or_list_of_names, plugin_name='', print_tracebacks_for_m
     :param plugin_name: The human friendly name of the plugin, used to load icons from
                 the current theme, if present.
 
+    :param folder_in_zip_file: Path to a folder in the zip file from which to load the icons.
+                Default is the root of the zip file. Use / as separator.
+
     :param print_tracebacks_for_missing_resources: When True missing resources are reported to STDERR
 
     :return: A dictionary of the form ``{name : QIcon}``. Any names
                 that were not found in the zip file will be null QIcons.
                 If a single path is passed in the return value will
-                be A QIcon.
+                be a QIcon.
     '''
-    from qt.core import QIcon, QPixmap
+    from qt.core import QIcon
+    namelist = (name_or_list_of_names,) if isinstance(name_or_list_of_names, (str, bytes)) else name_or_list_of_names
     ans = {}
-    namelist = [name_or_list_of_names] if isinstance(name_or_list_of_names, (str, bytes)) else name_or_list_of_names
-    failed = set()
-    if plugin_name:
+    with zipfile.ZipFile(zfp) as zf:
         for name in namelist:
-            q = QIcon.ic(f'{plugin_name}/{name}')
-            if q.is_ok():
-                ans[name] = q
-            else:
-                failed.add(name)
-    else:
-        failed = set(namelist)
-    if failed:
-        from_zfp = get_resources(zfp, list(failed), print_tracebacks_for_missing_resources=print_tracebacks_for_missing_resources)
-        if from_zfp is None:
-            from_zfp = {}
-        elif isinstance(from_zfp, (str, bytes)):
-            from_zfp = {namelist[0]: from_zfp}
-
-        for name in failed:
-            p = QPixmap()
-            raw = from_zfp.get(name)
-            if raw:
-                p.loadFromData(raw)
-            ans[name] = QIcon(p)
-    if len(namelist) == 1 and ans:
-        ans = ans.pop(namelist[0])
+            arcname = posixpath.join(folder_in_zip_file, name)
+            theme_name = posixpath.join(plugin_name, name)
+            try:
+                data = zf.read(arcname)
+            except KeyError:
+                data = b''
+                if print_tracebacks_for_missing_resources:
+                    print('Failed to load resource:', repr(name), 'from the plugin zip file:', zfp, file=sys.stderr)
+                    import traceback
+                    traceback.print_exc()
+            ans[name] = QIcon.ic(theme_name, fallback=data)
+    if len(namelist) == 1:
+        return ans[name]
     return ans
 
 

src/calibre/gui2/__init__.py

@@ -41,6 +41,7 @@ from qt.core import (
     QObject,
     QPainterPath,
     QPalette,
+    QPixmap,
     QRectF,
     QResource,
     QSettings,
@@ -251,7 +252,7 @@ class IconResourceManager:
             icon = self.icon_cache[name] = self(name)
         return icon
 
-    def __call__(self, name):
+    def __call__(self, name: str, fallback: bytes = b'') -> QIcon:
         if isinstance(name, QIcon):
             return name
         if not name:
@@ -269,6 +270,11 @@ class IconResourceManager:
                 q = QIcon(f':/icons/calibre-default-{self.color_palette}/images/{name}')
                 if q.is_ok():
                     ans = q
+            if fallback and not ans.is_ok():
+                p = QPixmap()
+                p.loadFromData(fallback)
+                if not p.isNull():
+                    ans = QIcon(p)
         return ans
 
     def icon_as_png(self, name, as_bytearray=False, compression_level=0):