Fix referenced entry color on macOS dark mode (#2984)

Introduce macUtils()->isDarkMode() function to detect Mojave dark
mode and correct reference entry text color. Fixes #860.

src/gui/entry/EntryModel.cpp

@@ -30,6 +30,9 @@
 #include "core/Global.h"
 #include "core/Group.h"
 #include "core/Metadata.h"
+#ifdef Q_OS_MACOS
+#include "gui/macutils/MacUtils.h"
+#endif
 
 EntryModel::EntryModel(QObject* parent)
     : QAbstractTableModel(parent)
@@ -270,6 +273,11 @@ QVariant EntryModel::data(const QModelIndex& index, int role) const
     } else if (role == Qt::ForegroundRole) {
         if (entry->hasReferences()) {
             QPalette p;
+#ifdef Q_OS_MACOS
+            if (macUtils()->isDarkMode()) {
+                return QVariant(p.color(QPalette::Inactive, QPalette::Dark));
+            }
+#endif
             return QVariant(p.color(QPalette::Active, QPalette::Mid));
         } else if (entry->foregroundColor().isValid()) {
             return QVariant(entry->foregroundColor());

src/gui/macutils/AppKit.h

@@ -35,6 +35,7 @@ public:
     bool activateProcess(pid_t pid);
     bool hideProcess(pid_t pid);
     bool isHidden(pid_t pid);
+    bool isDarkMode();
 
 private:
     void *self;

src/gui/macutils/AppKitImpl.h

@@ -30,5 +30,6 @@
 - (bool) activateProcess:(pid_t) pid;
 - (bool) hideProcess:(pid_t) pid;
 - (bool) isHidden:(pid_t) pid;
+- (bool) isDarkMode;
 
 @end

src/gui/macutils/AppKitImpl.mm

@@ -127,4 +127,12 @@ bool AppKit::isHidden(pid_t pid)
     return [static_cast<id>(self) isHidden:pid];
 }
 
+bool AppKit::isDarkMode()
+{
+    NSDictionary *dict = [[NSUserDefaults standardUserDefaults] persistentDomainForName:NSGlobalDomain];
+    id style = [dict objectForKey:@"AppleInterfaceStyle"];
+    return ( style && [style isKindOfClass:[NSString class]]
+            && NSOrderedSame == [style caseInsensitiveCompare:@"dark"] );
+}
+
 @end

src/gui/macutils/MacUtils.cpp

@@ -70,3 +70,8 @@ bool MacUtils::isHidden()
 {
     return m_appkit->isHidden(m_appkit->ownProcessId());
 }
+
+bool MacUtils::isDarkMode()
+{
+    return m_appkit->isDarkMode();
+}

src/gui/macutils/MacUtils.h

@@ -37,6 +37,7 @@ public:
     bool raiseOwnWindow();
     bool hideOwnWindow();
     bool isHidden();
+    bool isDarkMode();
 
 private:
     explicit MacUtils(QObject* parent = nullptr);