macx-clang: Opt-in xcb QPA support with XQuartz

Enable xcb QPA plugin when XQuartz is available. This is done
in a single build, alongside the Cocoa version.

We delegate part of the configuration stage to pkg-config, so
this becomes a requirement. Ensure that

    PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig:/opt/X11/share/pkgconfig

is in your environment, or pkg-config is properly set up.

Tested with the following configure options:

configure \
   -pkg-config \
   -fontconfig -system-freetype \
   -system-xcb -xkb -no-opengl \
   -qt-xkbcommon -qt-xkbcommon-x11

Change-Id: I2eb5a0491172368afc4c629c540cbef08580348d
Reviewed-by: Jake Petroules <jake.petroules@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

mkspecs/macx-clang/qmake.conf

@@ -6,6 +6,25 @@ QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.10
 
 QMAKE_APPLE_DEVICE_ARCHS = x86_64
 
+# Opt-in xcb QPA support with XQuartz:
+#
+# configure \
+#   -pkg-config \
+#   -fontconfig -system-freetype \
+#   -system-xcb -xkb -no-opengl \
+#   -qt-xkbcommon -qt-xkbcommon-x11
+#
+# Ensure that pkg-config is properly configured, or that
+#   PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig:/opt/X11/share/pkgconfig
+# is set in your build environment.
+#
+# Due to irreconcilable differences between Cocoa
+# and X11, OpenGL is currently not supported.
+
+QMAKE_LIBS_X11 = -lX11 -lXext -lm
+QMAKE_LIBDIR_X11 = /opt/X11/lib
+QMAKE_INCDIR_X11 = /opt/X11/include
+
 include(../common/macx.conf)
 include(../common/gcc-base-mac.conf)
 include(../common/clang.conf)

src/gui/configure.json

@@ -928,7 +928,8 @@
         },
         "fontconfig": {
             "label": "Fontconfig",
-            "condition": "!config.win32 && !config.darwin && features.system-freetype && libs.fontconfig",
+            "autoDetect": "!config.darwin",
+            "condition": "!config.win32 && features.system-freetype && libs.fontconfig",
             "output": [ "privateFeature", "feature" ]
         },
         "gbm": {
@@ -1498,6 +1499,13 @@
             "condition": "features.xcb && !features.xkbcommon-system && !features.xkb-config-root",
             "message": "Could not find XKB config root, use -xkb-config-root to set a path to
 XKB configuration data. This is required for keyboard input support."
+        },
+        {
+            "type": "note",
+            "condition": "features.xcb && config.darwin",
+            "message": "XCB support on macOS is minimal and untested. Some features will
+not work properly or at all (e.g. OpenGL, desktop services or accessibility),
+or may depend on your system and XQuartz setup."
         },
         {
             "type": "note",

src/platformsupport/fontdatabases/fontdatabases.pro

@@ -9,25 +9,25 @@ PRECOMPILED_HEADER = ../../corelib/global/qt_pch.h
 
 darwin {
     include($$PWD/mac/coretext.pri)
-} else {
-    qtConfig(freetype) {
-        include($$PWD/freetype/freetype.pri)
-    }
+}
 
-    unix {
+qtConfig(freetype) {
+    include($$PWD/freetype/freetype.pri)
+}
+
+unix {
     include($$PWD/genericunix/genericunix.pri)
     qtConfig(fontconfig) {
         include($$PWD/fontconfig/fontconfig.pri)
     }
-    }
+}
 
-    win32:!winrt {
+win32:!winrt {
     include($$PWD/windows/windows.pri)
-    }
+}
 
-    winrt {
+winrt {
     include($$PWD/winrt/winrt.pri)
-    }
 }
 
 load(qt_module)

src/platformsupport/platformsupport.pro

@@ -16,7 +16,7 @@ qtConfig(evdev)|qtConfig(tslib)|qtConfig(libinput)|qtConfig(integrityhid) {
     input.depends += devicediscovery
 }
 
-unix:!darwin: \
+if(unix:!darwin)|qtConfig(xcb): \
     SUBDIRS += services
 
 qtConfig(opengl): \

src/platformsupport/themes/themes.pro

@@ -6,7 +6,7 @@ CONFIG += static internal_module
 
 DEFINES += QT_NO_CAST_FROM_ASCII
 
-unix:!darwin: \
+if(unix:!darwin)|qtConfig(xcb): \
     include($$PWD/genericunix/genericunix.pri)
 
 HEADERS += \

src/plugins/platforms/xcb/xcb-plugin.pro

@@ -4,6 +4,8 @@ QT += core-private gui-private xcb_qpa_lib-private
 
 DEFINES += QT_NO_FOREACH
 
+macos: CONFIG += no_app_extension_api_only
+
 SOURCES = \
     qxcbmain.cpp
 OTHER_FILES += xcb.json README

src/widgets/kernel/mac.pri

@@ -1,4 +1,4 @@
-!x11:osx {
+macos {
    LIBS_PRIVATE += -framework AppKit -lz
    *-mwerks:INCLUDEPATH += compat
 }