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Minor changes:

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- Correct some comments so they reflect what the code is now doing.
- Make return None explicit in a few places.
- Wrap render_cover() in an if to check that cover_tuple is valid. This doesn't change behavior because the thrown exception would do the same thing, but being explicit is nice.
This commit is contained in:
Charles Haley 2024-01-27 11:35:32 +00:00
parent f3e214903b
commit c1b727ff52
1 changed files with 26 additions and 26 deletions
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48
src/calibre/gui2/library/alternate_views.py
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@ -919,15 +919,13 @@ class GridView(QListView):
try: try:
# Fetch the cover from the cache or file system # Fetch the cover from the cache or file system
cover_tuple = self.fetch_cover_from_cache(book_id) cover_tuple = self.fetch_cover_from_cache(book_id)
if cover_tuple is not None:
# Render/resize the cover. # Render/resize the cover.
thumb = self.make_thumbnail(cover_tuple) thumb = self.make_thumbnail(cover_tuple)
except Exception: except Exception:
import traceback import traceback
traceback.print_exc() traceback.print_exc()
# Tell the GUI to redisplay the cover. These can queue, but # Tell the GUI to redisplay the thumbnail with the new image
# the work is limited to painting the cover if it is visible
# so there shouldn't be much performance lag. Using a
# dispatcher to eliminate the queue would probably be worse.
self.update_item.emit(book_id, thumb) self.update_item.emit(book_id, thumb)
finally: finally:
@ -953,27 +951,29 @@ class GridView(QListView):
otherwise None. otherwise None.
''' '''
if self.ignore_render_requests.is_set(): if self.ignore_render_requests.is_set():
return return None
db = self.dbref() db = self.dbref()
if db is None: if db is None:
return return None
tc = self.thumbnail_cache tc = self.thumbnail_cache
cdata, timestamp = tc[book_id] # None, None if not cached. cdata, timestamp = tc[book_id] # None, None if not cached.
if timestamp is None: if timestamp is None:
# Cover not in cache. Try to read the cover from the library. # Cover not in cache. Try to read the cover from the library.
has_cover, cdata, timestamp = db.new_api.cover_or_cache(book_id, 0, as_what='pil_image') has_cover, cdata, timestamp = db.new_api.cover_or_cache(book_id, 0, as_what='pil_image')
if has_cover: if has_cover:
# There is a cover.jpg. Convert the byte string to an image. # There is a cover.jpg, already rendered as a pil_image
cache_valid = False cache_valid = False
else: else:
# No cover.jpg # No cover.jpg
cache_valid = None cache_valid = None
else: else:
# A cover is in the cache. Check whether it is up to date. # A cover is in the cache. Check whether it is up to date.
has_cover, tcdata, timestamp = db.new_api.cover_or_cache(book_id, timestamp, as_what='pil_image') has_cover, tcdata, timestamp = db.new_api.cover_or_cache(book_id, timestamp,
as_what='pil_image')
if has_cover: if has_cover:
if tcdata is None: if tcdata is None:
# The cached cover is up-to-date. # The cached cover is up-to-date. Convert the cached bytes
# to a PIL image
cache_valid = True cache_valid = True
cdata = Image.open(BytesIO(cdata)) cdata = Image.open(BytesIO(cdata))
else: else:
@ -983,10 +983,9 @@ class GridView(QListView):
# We found a cached cover for a book without a cover. This can # We found a cached cover for a book without a cover. This can
# happen in older version of calibre that can reuse book_ids # happen in older version of calibre that can reuse book_ids
# between libraries and books in one library have covers where # between libraries and books in one library have covers where
# they don't in another library. Versions of calibre with this # they don't in another library. This version doesn't have the
# source code don't have this problem because the cache UUID is # problem because the cache UUID is set when the database
# set when the database changes instead of when the cache thread # changes instead of when the cache thread is created.
# is created.
tc.invalidate((book_id,)) tc.invalidate((book_id,))
cache_valid = None cache_valid = None
cdata = None cdata = None
@ -998,7 +997,7 @@ class GridView(QListView):
def make_thumbnail(self, cover_tuple): def make_thumbnail(self, cover_tuple):
# Render the cover image data to the thumbnail size and correct format. # Render the cover image data to the thumbnail size and correct format.
# Rendering isn't needed if the cover came from the cache and the cache # Rendering isn't needed if the cover came from the cache and the cache
# is valid. Put a newly rendered image into the cache. Returns the # is valid. Put newly rendered images into the cache. Returns the
# thumbnail as a PIL Image. This method is called on the cover thread. # thumbnail as a PIL Image. This method is called on the cover thread.
cdata = cover_tuple.cdata cdata = cover_tuple.cdata
@ -1006,11 +1005,11 @@ class GridView(QListView):
tc = self.thumbnail_cache tc = self.thumbnail_cache
thumb = None thumb = None
if cover_tuple.has_cover: if cover_tuple.has_cover:
# cdata contains either the resized thumbnail, the full cover.jpg, # cdata contains either the resized thumbnail, the full cover.jpg
# or None if cover.jpg isn't valid # rendered as a PIL image, or None if cover.jpg isn't valid
if cdata.getbbox() is None and cover_tuple.cache_valid: if cdata.getbbox() is None and cover_tuple.cache_valid:
# Something wrong with the cover data in the cache. Remove it # Something wrong with the cover data in the cache. Remove it
# from the cache and render it again. # from the cache and queue it to render again.
tc.invalidate((book_id,)) tc.invalidate((book_id,))
self.render_queue.put(book_id) self.render_queue.put(book_id)
return None return None
@ -1019,8 +1018,7 @@ class GridView(QListView):
# image. We might have the image from cover.jpg, in which case # image. We might have the image from cover.jpg, in which case
# make it into a thumbnail. # make it into a thumbnail.
if cdata is not None: if cdata is not None:
# We have a cover from the file system. Scale it by creating # We have an image from cover.jpg. Scale it by creating a thumbnail
# a thumbnail
dpr = self.device_pixel_ratio dpr = self.device_pixel_ratio
page_width = int(dpr * self.delegate.cover_size.width()) page_width = int(dpr * self.delegate.cover_size.width())
page_height = int(dpr * self.delegate.cover_size.height()) page_height = int(dpr * self.delegate.cover_size.height())
@ -1029,7 +1027,7 @@ class GridView(QListView):
if scaled: if scaled:
# The image is the wrong size. Scale it. # The image is the wrong size. Scale it.
if self.ignore_render_requests.is_set(): if self.ignore_render_requests.is_set():
return return None
# The PIL thumbnail operation works in-place, changing # The PIL thumbnail operation works in-place, changing
# the source image. # the source image.
cdata.thumbnail((int(nwidth), int(nheight))) cdata.thumbnail((int(nwidth), int(nheight)))
@ -1057,13 +1055,15 @@ class GridView(QListView):
# Cover was removed, but it exists in cache. Remove it from the cache # Cover was removed, but it exists in cache. Remove it from the cache
tc.invalidate((book_id,)) tc.invalidate((book_id,))
thumb = None thumb = None
# Conversion to QPixmap needs RGBA data. Do it here rather than in the
# GUI thread. This check doesn't need to be wrapped in
# if thumb is not None:
# because None is a first-class object with no attributes.
if getattr(thumb, 'mode', None) == 'RGB':
thumb = thumb.convert('RGBA')
# Return the thumbnail, which is either None or a PIL Image. If not None # Return the thumbnail, which is either None or a PIL Image. If not None
# the image will be converted to a QPixmap on the GUI thread. Putting # the image will be converted to a QPixmap on the GUI thread. Putting
# None into the CoverCache ensures re-rendering won't try again. # None into the CoverCache ensures re-rendering won't try again.
if getattr(thumb, 'mode', None) == 'RGB':
# Conversion to QPixmap needs RGBA data so do it here rather than
# in the GUI thread
thumb = thumb.convert('RGBA')
return thumb return thumb
def re_render(self, book_id, thumb): def re_render(self, book_id, thumb):