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The missing error() caused an assertion failure in
SlaveBasePrivate::verifyState("get()") - it is not allowed to
return from get() without calling error() or finished().

Use the metadata devicePixelRatio to scale up dimensions of thumbnails generated.
Sets the devicePixelRatio on the output QPixmap according to the thumbnail generated.
Make the Text Thumbnail creator devicePixelRatio aware.
Follows xdg thumbnail specs 0.9 https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.html

BUG: 342053
FIXED-IN: 21.08

Thumbnails: Refactor, Make scaleDownImage an anonymous function, remove unnecessary old smooth scaling hack

Fabian Vogt authored May 04, 2021 and Nate Graham committed May 29, 2021

The SHM is created by the application, which might've done a different size
calculation. Verify that the data fits instead of writing past the end and
crashing.

CCBUG: 430862

Task: https://phabricator.kde.org/T14518

This is a leftover from the sub-thumbnail creating/drawing split.
See commit 900db615 ("Avoid massive overdrawing with
sequenceIndex != 0").

Adds a class member m_randomGenerator

If you want git blame to ignore formatting revisions run:
git config blame.ignoreRevsFile .git-blame-ignore-revs

David Lerch authored Mar 27, 2021 and Méven Car committed Apr 11, 2021

The call to create() itself might modify it, so we can't do it before.

The calling code in kio already checks if the directory itself is on a
slow (e.g. network) filesystem, but following symlinks inside it subverts
this check.

Skipping thumbnails has the effect of prefering plain files instead of
symlinks. This still gives a good approximation of the directory contents
(and even a better one if the symlinks point to files in the same
directory, as duplicates are avoided).

Commit 752651a5 changed to use a QGuiApplication, but the HTML
thumbnailer (provided by Konqueror) still needs QWidget-based
web page rendering classes.

QPixmap requires only QGuiApplication.

Insert a nullptr into the cache when a plugin fails to load, e.g.
because some symbols are unresolvable. Also log a warning stating the
error cause.

The cache is implicitly cleared by the kioslave idle logic.

In case the cached thumbnail loaded successfully the isNull check is
unreachable due to the early `return true`.

The QSaveFile is only needed if there is thumbnail creator for the
format of the current file.

Minimum Qt version set in CMakeLists.txt is 5.11, so the checks are
redundant.

QImage::load(<path>) tries to find a fallback image if the file does
not exist, by appending extensions of all supported file formats, as
QImageReader defaults to format autodetection.

Check if the file exists, and only then try to load it.

Cached thumbnails should not depend on varying properties of the caller,
like iconAlpha, iconSize and theme of the overlay icon.

Also, the current mime type icons are hardly visible and unrecognizable
with dolphins default opacity of ~25%.

BUG: 425789

Despite the name, fileUrl is already a QByteArray encoded URL here.

According to the spec, at least Thumb::URI and Thumb::MTime are required.

KIO::PreviewJob discards any thumbnails without these and recreates
the thumbnails.

If the inner loop is not run, skipped will be 0 and the loop is left
anyway.

As `skipped` is always reset to 0, the condition is always true.

Change the skipValidItems calculation to make it more obvious it
calculates the remainder, and is always a positive value.

Declare skipped inside the loop, as it is only used inside the loop.

No functional changes.

The branches can be simplified to an arithmetic operation.

Replace the `yPos <= maxYPos)` check in the inner loop with an more
explicit check whenever a thumnail is drawn.

`(yPos <= maxYPos) && !validThumbnails)` is redundant, as yPos is only
incremented whenever validThumbnails is incremented. Move the
validThumbnails check into the loop.

Stefan Brüns authored Aug 28, 2020 and David Faure committed Aug 29, 2020

The URI is only required when a thumbnail is created or looked up.

Stefan Brüns authored Aug 21, 2020 and David Faure committed Aug 29, 2020

Commit 8ed64be9 ("Enlarge image in folder preview when there's only
one image") made createSubThumbnail part of drawSubThumbnail. As a side
effect, when skipValidItems is > 0, the thumbnail is not only fetched
but also drawn in the top left position.

Split fetching and drawing again.

This is visible in the file dialogs (dolphin only uses sequenceIndex==0),
when hovering a directory with the mouse.

Stefan Brüns authored Aug 21, 2020 and David Faure committed Aug 29, 2020

Scaling down a large thumbnail is considerably faster than creating the
thumbnail from scratch.

Stefan Brüns authored Aug 21, 2020 and David Faure committed Aug 29, 2020

If a thumbnail already exists, the mimetype of the original file and
available plugins do not matter.

Saves accessing the original file, and allows thumbnails for file types
which are not natively supported by KIO.