Extremely low GIMP performance if linked with SDK 10.14+ due to canvas problems

GIMP Version: 2.10.12 Operating System: macOS 10.14.6 and 10.15.1 beta

Package: MacPorts, built with +quartz

Issue Description

When drawing with any brush tool, the brush will lag a LOT. It's so slow that when drawing circles with my mouse, the brush actually draws polygons. This also affects tools like smudge and eraser. EDIT: This does not happen in the version downloadable on the official site.

Performance Log

gimp-performance.log

Performance Log Description

Started logging -> drew something with airbrush -> drew something with paint brush -> stopped logging

Additional Information

From Oleksii Samorukov

Currently there are 2 workarounds:

• Use SDK before 10.14 to compile GIMP (tested on 10.9-10.13)
• Pass -sdk_version 10.9 linker flag (could be done with -Wl,-sdk_version,10.9), to the ld, tested on SDK 10.14 and 10.15