Add stub functions in KIPLATFORM to detect dark mode

These haven't been written yet, but current code can
be adapted to use these now.

libs/kiplatform/gtk/ui.cpp

@@ -23,6 +23,14 @@
 #include <wx/nonownedwnd.h>
 #include <wx/window.h>
 
+
+bool KIPLATFORM::UI::IsDarkTheme()
+{
+    // TODO(ISM): Write this function
+    return false;
+}
+
+
 void KIPLATFORM::UI::ForceFocus( wxWindow* aWindow )
 {
     aWindow->SetFocus();

libs/kiplatform/include/kiplatform/ui.h

@@ -28,6 +28,13 @@ namespace KIPLATFORM
 {
     namespace UI
     {
+        /**
+         * Determine if the desktop interface is currently using a dark theme or a light theme.
+         *
+         * @return true if a dark theme is being used.
+         */
+        bool IsDarkTheme();
+
         /**
          * Pass the current focus to the window. On OSX this will forcefully give the focus to
          * the desired window, while on MSW and GTK it will simply call the wxWidgets SetFocus()

libs/kiplatform/msw/ui.cpp

@@ -23,6 +23,14 @@
 #include <wx/nonownedwnd.h>
 #include <wx/window.h>
 
+
+bool KIPLATFORM::UI::IsDarkTheme()
+{
+    // TODO(ISM): Write this function
+    return false;
+}
+
+
 void KIPLATFORM::UI::ForceFocus( wxWindow* aWindow )
 {
     aWindow->SetFocus();

libs/kiplatform/osx/ui.mm

@@ -26,6 +26,14 @@
 #include <wx/toplevel.h>
 #include <wx/button.h>
 
+
+bool KIPLATFORM::UI::IsDarkTheme()
+{
+    // TODO(ISM): Write this function
+    return false;
+}
+
+
 void KIPLATFORM::UI::ForceFocus( wxWindow* aWindow )
 {
     // On OSX we need to forcefully give the focus to the window