Add [dosbox] CFGTOOL theme setting + OS dark mode detection

CHANGELOG

@@ -22,7 +22,7 @@ NEXT
   - Fixed TTF mode didn't change to graphic mode when machine = Hercules
     (maron2000)
   - Configuration tool: (aybe)
-    - more Windows 3.1 styling: buttons, colors, focus, layout
+    - more Windows 3.1 look'n'feel (themes w/ host dark mode detection)
     - enhance main window layout, it is now visible in its entirety
     - fix layout issues, off by one in rectangle drawing functions
     - fix 'list iterators incompatible' when pressing the Tab key

src/dosbox.cpp

@@ -1422,6 +1422,11 @@ void DOSBOX_SetupConfigSections(void) {
     const char* quit_settings[] = { "true", "false", "1", "0", "auto", "autofile", nullptr };
     const char* autofix_settings[] = { "true", "false", "1", "0", "both", "a20fix", "loadfix", "none", nullptr };
     const char* color_themes[] = { "default", "black", "red", "green", "yellow", "blue", "magenta", "cyan", "white", nullptr };
+    const char* color_themes_config[] = {
+        "Windows Default", "Arizona", "Black Leather Jacket", "Bordeaux", "Cinnamon", "Designer", "Emerald City",
+        "Fluorescent","HotDog Stand", "LCD Default Screen Settings", "LCD Reversed - Dark", "LCD Reversed - Light",
+        "Mahogany", "Monochrome", "Ocean", "Pastel", "Patchwork", "Plasma Power Saver", "Rugby", "The Blues",
+        "Tweed", "Valentine", "Wingtips", nullptr };
     const char* irqsgus[] = { "5", "3", "7", "9", "10", "11", "12", nullptr };
     const char* irqssb[] = { "7", "5", "3", "9", "10", "11", "12", "0", "-1", nullptr };
     const char* dmasgus[] = { "3", "0", "1", "5", "6", "7", nullptr };
@@ -1575,6 +1580,13 @@ void DOSBOX_SetupConfigSections(void) {
     Pstring->Set_help("You can specify a different background color theme for the welcome banner from the default one.");
     Pstring->SetBasic(true);
 
+    Pstring = secprop->Add_path("configuration tool theme", Property::Changeable::WhenIdle, "");
+    Pstring->Set_values(color_themes_config);
+    Pstring->Set_help(
+                      "Theme for the configuration tool.\n"
+                      "If not set, host dark mode setting will be followed.\n");
+    Pstring->SetBasic(true);
+
     Pstring = secprop->Add_string("dpi aware",Property::Changeable::OnlyAtStart,"auto");
     Pstring->Set_values(truefalseautoopt);
     Pstring->Set_help("Set this option (auto by default) to indicate to your OS that DOSBox-X is DPI aware.\n"

src/gui/sdl_gui.cpp

@@ -3314,6 +3314,30 @@ class ConfigurationWindow : public GUI::ToplevelWindow {
         Section_prop * section=static_cast<Section_prop *>(control->GetSection("dosbox"));
         advopt->setChecked(section->Get_bool("show advanced options") || advOptUser);
 
+        // apply theme
+        {
+            auto theme = std::string(section->Get_string("configuration tool theme"));
+
+            if(theme.empty())
+            {
+                bool dark = false;
+
+#if defined(WIN32) && !defined(HX_DOS)
+                // ReSharper disable once CppDeclaratorDisambiguatedAsFunction
+                bool HostDarkMode(); // NOLINT(clang-diagnostic-vexing-parse)
+                dark = HostDarkMode();
+#endif
+                TryApplyTheme(
+                              dark
+                                  ? GUI::ThemeWindows31LCDReversedDark::GetName()
+                                  : GUI::ThemeWindows31LCDReversedLight::GetName());
+            }
+            else
+            {
+                TryApplyTheme(theme);
+            }
+        }
+
         strcpy(tmp1, (MSG_Get("SAVE")+std::string("...")).c_str());
 
         const auto xSave = gridbtnx + (gridbtnwidth + margin) * 2;

src/gui/sdlmain.cpp

@@ -363,6 +363,33 @@ bool UpdateWindows11RoundCorners(HWND hWnd, CornerPreference cornerPreference) {
     }
     return false;
 }
+
+bool HostDarkMode()
+{
+    // https://gist.github.com/rounk-ctrl/b04e5622e30e0d62956870d5c22b7017
+
+    using PFNSHOULDAPPSUSEDARKMODE = bool (WINAPI *)();
+
+    const auto module = ::LoadLibrary("uxtheme.dll");
+
+    if(module)
+    {
+        auto* pfnShouldAppsUseDarkMode = reinterpret_cast<PFNSHOULDAPPSUSEDARKMODE>(
+            GetProcAddress(module, MAKEINTRESOURCEA(132)));
+
+        if(pfnShouldAppsUseDarkMode)
+        {
+            const auto dark = pfnShouldAppsUseDarkMode();
+
+            return dark;
+        }
+
+        FreeLibrary(module);
+    }
+
+    return false;
+}
+
 #endif
 
 #if defined(WIN32)