macOS: Allow tests to mark themselves as not supporting high-DPI

Some tests are not written to handle running on a retina screen,
resulting in additional test failures when trying to fix a CI test
failure on a local retina-enabled machine.

Change-Id: I0fed33c38792b686ac83abba2bfbc45623382200
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

mkspecs/features/testcase.prf

@@ -9,6 +9,18 @@ testcase_exceptions: CONFIG += exceptions
 # Set in qt_build_config.prf
 testcase_no_bundle: CONFIG -= app_bundle
 
+# Allow testcases to mark themselves as not supporting high-DPI
+testcase_lowdpi {
+    macos {
+        !isEmpty(QMAKE_INFO_PLIST): \
+            error("QMAKE_INFO_PLIST already set, can't apply testcase_lowdpi")
+
+        QMAKE_INFO_PLIST = $$QMAKESPEC/Info.plist.disable_highdpi
+    } else {
+        # TODO: Add support for other platforms if possible
+    }
+}
+
 benchmark: type = benchmark
 else: type = check
 

mkspecs/macx-clang/Info.plist.disable_highdpi

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>NSHighResolutionCapable</key>
+	<string>NO</string>
+</dict>
+</plist>