It is possible to change the color space of a fill layer using the "Convert Layer Color Space..." action. If being able to do so isn't a bug itself, then it has issues doing it correctly -- going from RGB to CMYK, for example, produces many vertical lines.
Yes, I can confirm the issue. We should only enable the action for paint layers.
Git commit 55b91419718d139b5f6b1558d57066f5a9bcc76b by Boudewijn Rempt. Committed on 03/01/2017 at 11:26. Pushed by rempt into branch 'master'. This also removes some unused API to pass a colorspace to KisSelectionBasedLayer::resetCache(); that was never used, since no generator ever returned anything but 0 in the colorSpace() method, which is now also removed. M +1 -6 libs/image/generator/kis_generator.cpp M +0 -7 libs/image/generator/kis_generator.h M +2 -1 libs/image/generator/kis_generator_layer.cpp M +4 -7 libs/image/kis_colorspace_convert_visitor.cpp M +9 -1 libs/image/kis_colorspace_convert_visitor.h M +3 -7 libs/image/kis_selection_based_layer.cpp M +1 -1 libs/image/kis_selection_based_layer.h https://commits.kde.org/krita/55b91419718d139b5f6b1558d57066f5a9bcc76b
Git commit f025b5edecfd2313ca18859b0cb78c8056f2aa8c by Boudewijn Rempt. Committed on 03/01/2017 at 11:31. Pushed by rempt into branch 'krita/3.1'. This also removes some unused API to pass a colorspace to KisSelectionBasedLayer::resetCache(); that was never used, since no generator ever returned anything but 0 in the colorSpace() method, which is now also removed. M +1 -6 libs/image/generator/kis_generator.cpp M +0 -7 libs/image/generator/kis_generator.h M +2 -1 libs/image/generator/kis_generator_layer.cpp M +4 -7 libs/image/kis_colorspace_convert_visitor.cpp M +9 -1 libs/image/kis_colorspace_convert_visitor.h M +7 -8 libs/image/kis_selection_based_layer.cpp M +1 -1 libs/image/kis_selection_based_layer.h https://commits.kde.org/krita/f025b5edecfd2313ca18859b0cb78c8056f2aa8c