changeset 1818:c5ee0746bdef background-mode

Determine whether a dark background is indicated

--- a/system/System.cpp	Tue Jan 14 15:48:22 2020 +0000
+++ b/system/System.cpp	Fri Jan 17 21:36:07 2020 +0000
@@ -27,6 +27,10 @@
 #include <unistd.h>
 #endif
 
+#ifdef _MSC_VER
+#include <winrt/Windows.UI.ViewManagement.h>
+#endif
+
 #ifdef __APPLE__
 #include <sys/param.h>
 #include <sys/sysctl.h>
@@ -334,6 +338,21 @@
     }
 }
 
+bool
+OSThemeIsDark()
+{
+    SVCERR << "OSThemeIsDark() called" << endl;
+#ifdef _MSC_VER
+    using namespace winrt::Windows::UI::ViewManagement;
+    UISettings settings;
+    auto background = settings.GetColorValue(UIColorType::Background);
+    if (int(background.R) + int(background.G) + int(background.B) < 384) {
+        return true;
+    }
+#endif
+    return false;
+}
+
 double mod(double x, double y) { return x - (y * floor(x / y)); }
 float modf(float x, float y) { return x - (y * floorf(x / y)); }
 

--- a/system/System.h	Tue Jan 14 15:48:22 2020 +0000
+++ b/system/System.h	Fri Jan 17 21:36:07 2020 +0000
@@ -163,6 +163,11 @@
 // if unknown. (Hence signed return type)
 extern ssize_t GetDiscSpaceMBAvailable(const char *path);
 
+// Return true if the OS desktop is set to use a dark mode
+// theme. Return false if it is set to a light theme or if the theme
+// is unknown.
+extern bool OSThemeIsDark();
+
 extern void StoreStartupLocale();
 extern void RestoreStartupLocale();