Qt5 requires platform plugins also on Linux, update i686 Dockerfile

Author: skvark

cv2/__init__.py

@@ -9,7 +9,7 @@
 # this makes them available
 globals().update(importlib.import_module('cv2.cv2').__dict__)
 
-if sys.platform == 'darwin':
+if sys.platform == 'darwin' or sys.platform.startswith("linux"):
     os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = os.path.join(
         os.path.dirname(os.path.abspath(__file__)), 'qt', 'plugins'
     )

docker/manylinux2014/Dockerfile_i686

@@ -68,4 +68,10 @@ RUN curl -O -L https://github.com/Kitware/CMake/releases/download/v3.17.0/cmake-
 
 ENV PKG_CONFIG_PATH /usr/local/lib/pkgconfig:/root/ffmpeg_build/lib/pkgconfig
 ENV LDFLAGS -L/root/ffmpeg_build/lib
+
+# in i686, yum metadata ends up with slightly wrong timestamps
+# which inhibits its update
+# https://github.com/skvark/opencv-python/issues/148
+RUN yum clean all
+
 ENV PATH "$HOME/bin:$PATH"

setup.py

@@ -154,6 +154,11 @@ def main():
             (r"lib/qt/plugins/platforms/libqcocoa\.dylib")
         ]
 
+    if sys.platform.startswith("linux") and not build_headless:
+        rearrange_cmake_output_data["cv2.qt.plugins.platforms"] = [
+            (r"lib/qt/plugins/platforms/libqxcb\.so")
+        ]
+
     if build_headless:
         # it seems that cocoa cannot be disabled so on macOS the package is not truly headless
         cmake_args.append("-DWITH_WIN32UI=OFF")