Thumbnails: refactor extraction to use one code-path for all platforms

Thumbnail extraction now shares code between Linux/Windows,
allowing thumbnails from Zstd compressed blend files to be extracted.

The main logic is placed in blendthumb_extract.cc and is built as static
library. For windows there is DLL which is registered during blender
install and which then reads and generates thumbnails.

For other platforms there is blender-thumbnailer executable file which
takes blend file as an input and generates PNG file. As a result
Python script blender-thumbnailer.py is no longer needed.

The thumbnail extractor shares the same code-path as Blenders file
reading, so there is no need to duplicate any file reading logic.
This means reading compressed blend files is supported (broken since
the recent move Zstd compression - D5799).

This resolves T63736.

Contributors:

- @alausic original patch.
- @LazyDodo windows fixes/support.
- @campbellbarton general fixes/update.
- @lukasstockner97 Zstd support.

Reviewed By: sybren, mont29, LazyDodo, campbellbarton

Ref D6408

1 files changed, 1 insertions, 4 deletions

diff --git a/source/blender/CMakeLists.txt b/source/blender/CMakeLists.txt
index 84d31bccc53..0a494677d96 100644
--- a/source/blender/CMakeLists.txt
+++ b/source/blender/CMakeLists.txt
@@ -131,6 +131,7 @@ add_subdirectory(io)
 add_subdirectory(functions)
 add_subdirectory(makesdna)
 add_subdirectory(makesrna)
+add_subdirectory(blendthumb)
 
 if(WITH_COMPOSITOR)
   add_subdirectory(compositor)
@@ -159,7 +160,3 @@ endif()
 if(WITH_FREESTYLE)
   add_subdirectory(freestyle)
 endif()
-
-if(WIN32)
-  add_subdirectory(blendthumb)
-endif()