VideoCommon/BoundingBox: Make interface for querying bounding box data

Rather than expose the bounding box members directly, we can instead
provide an interface for code to use. This makes it nicer to transition
from global data, as the interface function names are already in
place.

Source/Core/VideoCommon/BoundingBox.cpp

@@ -3,20 +3,71 @@
 // Refer to the license.txt file included.
 
 #include "VideoCommon/BoundingBox.h"
+
+#include <algorithm>
+#include <array>
+
 #include "Common/ChunkFile.h"
 #include "Common/CommonTypes.h"
 
 namespace BoundingBox
 {
-// External vars
-bool active = false;
-u16 coords[4] = {0x80, 0xA0, 0x80, 0xA0};
+namespace
+{
+// Whether or not bounding box is enabled.
+bool s_is_active = false;
+
+// Current bounding box coordinates.
+std::array<u16, 4> s_coordinates{
+    0x80,
+    0xA0,
+    0x80,
+    0xA0,
+};
+}  // Anonymous namespace
+
+void Enable()
+{
+  s_is_active = true;
+}
+
+void Disable()
+{
+  s_is_active = false;
+}
+
+bool IsEnabled()
+{
+  return s_is_active;
+}
+
+u16 GetCoordinate(Coordinate coordinate)
+{
+  return s_coordinates[static_cast<u32>(coordinate)];
+}
+
+void SetCoordinate(Coordinate coordinate, u16 value)
+{
+  s_coordinates[static_cast<u32>(coordinate)] = value;
+}
+
+void Update(u16 left, u16 right, u16 top, u16 bottom)
+{
+  const u16 new_left = std::min(left, GetCoordinate(Coordinate::Left));
+  const u16 new_right = std::max(right, GetCoordinate(Coordinate::Right));
+  const u16 new_top = std::min(top, GetCoordinate(Coordinate::Top));
+  const u16 new_bottom = std::max(bottom, GetCoordinate(Coordinate::Bottom));
+
+  SetCoordinate(Coordinate::Left, new_left);
+  SetCoordinate(Coordinate::Right, new_right);
+  SetCoordinate(Coordinate::Top, new_top);
+  SetCoordinate(Coordinate::Bottom, new_bottom);
+}
 
-// Save state
 void DoState(PointerWrap& p)
 {
-  p.Do(active);
-  p.Do(coords);
+  p.Do(s_is_active);
+  p.DoArray(s_coordinates);
 }
 
 }  // namespace BoundingBox