Add support for dark mode.

Author: ZCG-coder

gui/test.cpp

@@ -70,16 +70,12 @@ int main()
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
 
-    // Setup Dear ImGui style
-    ImGui::StyleColorsDark();
-    // ImGui::StyleColorsLight();
-
     // Setup Platform/Renderer backends
     ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
     ImGui_ImplOpenGL3_Init(glsl_version);
 
     bool done = false;
-    ImVec4 clear_color = ImVec4(0.45, 0.55, 0.60, 1.00);
+    ImVec4 clear_color = ImVec4(0.22, 0.22, 0.22, 1.00);
     std::array<char, 100> buf{};
     loadFonts(&io);
 
@@ -114,11 +110,20 @@ int main()
         ImGui::InputText("Input", buf.data(), buf.size());
         ImGui::End();
 
+        if (isDarkModeEnabled())
+        {
+            glClearColor(0.22, 0.22, 0.22, 1.0);
+            ImGui::StyleColorsDark();
+        }
+        else
+        {
+            glClearColor(0.95, 0.95, 0.95, 1.0);
+            ImGui::StyleColorsLight();
+        }
+
         // Rendering
         ImGui::Render();
         glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
-        glClearColor(
-            clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
         SDL_GL_SwapWindow(window);

include/CMakeLists.txt

@@ -38,15 +38,19 @@ IF (STP_BUILD_GUI EQUAL 1)
 
     # If we have freetype, we can use it to render text
     FIND_PACKAGE(Freetype QUIET)
-    if (FREETYPE_FOUND)
+    IF (FREETYPE_FOUND)
         MESSAGE(STATUS "Found Freetype")
         ADD_LIBRARY(imgui_freetype STATIC "${STP_BASE_DIRECTORY}/include/imgui/misc/freetype/imgui_freetype.cpp")
         TARGET_INCLUDE_DIRECTORIES(imgui_freetype PRIVATE "${STP_BASE_DIRECTORY}/include/imgui")
         TARGET_LINK_LIBRARIES(imgui_freetype PRIVATE ${FREETYPE_LIBRARIES})
         TARGET_LINK_LIBRARIES(imgui PRIVATE imgui_freetype)
         TARGET_INCLUDE_DIRECTORIES(imgui_freetype PRIVATE ${FREETYPE_INCLUDE_DIRS})
         TARGET_COMPILE_DEFINITIONS(imgui PRIVATE IMGUI_ENABLE_FREETYPE)
-    endif()
+    ENDIF()
+
+    IF (CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+        TARGET_LINK_LIBRARIES(imgui PRIVATE "-framework CoreFoundation")
+    ENDIF()
 
     TARGET_LINK_LIBRARIES(imgui PRIVATE SDL2::SDL2)
     TARGET_INCLUDE_DIRECTORIES(imgui PRIVATE ${SDL2_INCLUDE_DIRS})

include/gui.hpp

@@ -12,6 +12,47 @@ using namespace std::literals;
 
 namespace steppable::gui::__internals
 {
+#ifdef MACOSX
+    #include <CoreFoundation/CoreFoundation.h>
+
+    bool isDarkModeEnabled()
+    {
+        bool isDarkMode = false;
+        CFPreferencesAppSynchronize(CFSTR("AppleInterfaceStyle"));
+        CFPropertyListRef value = CFPreferencesCopyAppValue(CFSTR("AppleInterfaceStyle"), kCFPreferencesAnyApplication);
+        if (value != nullptr)
+        {
+            const auto* interfaceStyle = static_cast<CFStringRef>(value);
+            if (CFStringCompare(interfaceStyle, CFSTR("Dark"), 0) == kCFCompareEqualTo)
+                isDarkMode = true;
+            CFRelease(value);
+        }
+        return isDarkMode;
+    }
+#elif defined(LINUX)
+    bool isDarkModeEnabled() { return std::filesystem::exists("/usr/share/themes/Adwaita-dark/gtk-3.0"); }
+#elif defined(WINDOWS)
+    bool isDarkModeEnabled()
+    {
+        HKEY key;
+        if (RegOpenKeyExA(HKEY_CURRENT_USER,
+                          "Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                          0,
+                          KEY_QUERY_VALUE,
+                          &key) == ERROR_SUCCESS)
+        {
+            DWORD value = 0;
+            DWORD size = sizeof(DWORD);
+            if (RegQueryValueExA(key, "AppsUseLightTheme", nullptr, nullptr, reinterpret_cast<LPBYTE>(&value), &size) ==
+                ERROR_SUCCESS)
+                return value == 0;
+        }
+        return false;
+    }
+#else
+    bool isDarkModeEnabled() { return false; }
+#endif
+
     inline void addIfExistent(const ImGuiIO* io,
                               const std::filesystem::path& path,
                               const ImFontConfig* config,