Core: Clarify Callback_VideoCopiedToXFB and FrameUpdate

Source/Core/Core/Core.cpp

@@ -858,15 +858,15 @@ void VideoThrottle()
 
 // --- Callbacks for backends / engine ---
 
-// Should be called from GPU thread when a frame is drawn
-void Callback_VideoCopiedToXFB(bool video_update)
+// Called from Renderer::Swap (GPU thread) when a new (non-duplicate)
+// frame is presented to the host screen
+void Callback_FramePresented()
 {
-  if (video_update)
-    s_drawn_frame++;
+  s_drawn_frame++;
 }
 
-// Called at field boundaries in `VideoInterface::Update()`
-void FrameUpdate()
+// Called from VideoInterface::Update (CPU thread) at emulated field boundaries
+void Callback_NewField()
 {
   Movie::FrameUpdate();
   if (s_frame_step)

Source/Core/Core/Core.h

@@ -25,8 +25,8 @@ namespace Core
 bool GetIsThrottlerTempDisabled();
 void SetIsThrottlerTempDisabled(bool disable);
 
-void Callback_VideoCopiedToXFB(bool video_update);
-void FrameUpdate();
+void Callback_FramePresented();
+void Callback_NewField();
 
 enum class State
 {

Source/Core/Core/HW/VideoInterface.cpp

@@ -820,7 +820,7 @@ void Update(u64 ticks)
   // and/or update movie state before dealing with anything else
 
   if (s_half_line_count == 0 || s_half_line_count == GetHalfLinesPerEvenField())
-    Core::FrameUpdate();
+    Core::Callback_NewField();
 
   // If an SI poll is scheduled to happen on this half-line, do it!
 

Source/Core/VideoCommon/RenderBase.cpp

@@ -1283,7 +1283,7 @@ void Renderer::Swap(u32 xfb_addr, u32 fb_width, u32 fb_stride, u32 fb_height, u6
       {
         // Remove stale EFB/XFB copies.
         g_texture_cache->Cleanup(m_frame_count);
-        Core::Callback_VideoCopiedToXFB(true);
+        Core::Callback_FramePresented();
       }
 
       // Handle any config changes, this gets propogated to the backend.