#1141 Get rid of exif usage in thumbnails creation for jpeg files

[John]

Please, get rid of exif usage in thumbnails creation for jpeg files. Sometimes it's working. Sometimes it's not generating thumbnails for edited jpeg files, so for some unknown reason there is a thumb that is created for an old image. When an image is edited in an external app then thumbnail is not updated, though not each time. As I see, it depends on app that saves image. Some app uses one library for image handling, another app uses another library. For example, after saving edited image in imagemagick (CLI) and phototonic, thumbnail is created not for updated image, but for the old image. When image is saved in lximage-qt, resized for example, then thumbnail is created correctly for the edited file. As I got, Internal exif thumbnail generation causes this on jpeg images. File /src/base/fm-thumbnail-loader.c, function generate_thumbnails_with_builtin. https://github.com/lxde/libfm/blob/5346a5390a0881d5713a71e15f371132680056ee/src/base/fm-thumbnail-loader.c#L911
When it's disabled in the source code, thumbnail for any jpg image is creating properly.
It should resolve https://sourceforge.net/p/pcmanfm/bugs/1139/ and similar bugs.
Thanks.

[John]

Maybe this issue is applied not just to jpeg files, I noticed it on jpeg files.