[UI/D3D12] Small refactoring, allow BeginSwap to return false if no surface

src/xenia/ui/graphics_context.cc

@@ -9,8 +9,13 @@
 
 #include "xenia/ui/graphics_context.h"
 
+#include <cstdlib>
+
+#include "xenia/base/cvar.h"
 #include "xenia/ui/graphics_provider.h"
 
+DEFINE_bool(random_clear_color, false, "Randomize window clear color.", "UI");
+
 namespace xe {
 namespace ui {
 
@@ -26,5 +31,18 @@ bool GraphicsContext::MakeCurrent() { return true; }
 
 void GraphicsContext::ClearCurrent() {}
 
+void GraphicsContext::GetClearColor(float* rgba) {
+  if (cvars::random_clear_color) {
+    rgba[0] = rand() / float(RAND_MAX);  // NOLINT(runtime/threadsafe_fn)
+    rgba[1] = 1.0f;
+    rgba[2] = 0.0f;
+  } else {
+    rgba[0] = 0.0f;
+    rgba[1] = 0.0f;
+    rgba[2] = 0.0f;
+  }
+  rgba[3] = 1.0f;
+}
+
 }  // namespace ui
 }  // namespace xe