From 3a57bc6de52cc5c9551d8c92fc995d7f9ab44607 Mon Sep 17 00:00:00 2001
From: Jakub Melka <Mgr.Jakub.Melka@gmail.com>
Date: Thu, 27 Jun 2024 14:15:05 +0200
Subject: [PATCH] Issue #181: where is the dark mode?

---
 Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp | 19 +++++++++++++++----
 Pdf4QtLibWidgets/sources/pdfwidgetutils.h   |  6 ++++--
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp b/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
index 333b846..7b37898 100644
--- a/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
+++ b/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
@@ -20,6 +20,7 @@
 
 #include <map>
 #include <set>
+#include <optional>
 
 #include <QMenu>
 #include <QAction>
@@ -30,6 +31,7 @@
 #include <QGroupBox>
 #include <QMessageBox>
 #include <QApplication>
+#include <QStyleHints>
 
 #include "pdfdbgheap.h"
 
@@ -44,6 +46,8 @@ int qt_default_dpi_y() { return 96; }
 namespace pdf
 {
 
+std::optional<bool> s_isDarkThemeOverride;
+
 static constexpr bool isScalingNeeded()
 {
     return QT_VERSION_MAJOR < 6;
@@ -172,13 +176,20 @@ void PDFWidgetUtils::style(QWidget* widget)
     }
 }
 
+void PDFWidgetUtils::overrideDarkTheme(bool isDarkTheme)
+{
+    s_isDarkThemeOverride = isDarkTheme;
+}
+
 bool PDFWidgetUtils::isDarkTheme()
 {
-    QPalette palette = QApplication::palette();
-    QColor backgroundColor = palette.color(QPalette::Window);
-    QColor textColor = palette.color(QPalette::WindowText);
+    if (s_isDarkThemeOverride.has_value())
+    {
+        return s_isDarkThemeOverride.value();
+    }
 
-    return backgroundColor.lightness() < textColor.lightness();
+    Qt::ColorScheme colorScheme = QApplication::styleHints()->colorScheme();
+    return colorScheme == Qt::ColorScheme::Dark;
 }
 
 void PDFWidgetUtils::convertActionForDarkTheme(QAction* action, QSize iconSize, qreal devicePixelRatioF)
diff --git a/Pdf4QtLibWidgets/sources/pdfwidgetutils.h b/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
index 186cf56..b539b6f 100644
--- a/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
+++ b/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
@@ -60,8 +60,10 @@ public:
     /// Apply style to the widget
     static void style(QWidget* widget);
 
-    /// Vrátí true, pokud je aktuálně nastavená dark theme
-    /// pro aplikaci.
+    /// Overrides automatically detected dark theme / light theme settings
+    static void overrideDarkTheme(bool isDarkTheme);
+
+    /// Returns true if the dark theme is currently set for the application.
     static bool isDarkTheme();
 
     /// Converts an action's icon for use in a dark theme.