From 2c9922804157b642767b0ccbad430149229e3d50 Mon Sep 17 00:00:00 2001
From: Joel Linn <jl@conductive.de>
Date: Sun, 1 Dec 2019 21:37:52 +0100
Subject: [PATCH] [UI] Use ticks as frame time instead of file time. File time
 is not as accurate as its resolution suggests. This results in a zero time
 delta between frames for high fps.

---
 src/xenia/ui/window.cc | 20 ++++++++++++--------
 src/xenia/ui/window.h  |  4 ++--
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/xenia/ui/window.cc b/src/xenia/ui/window.cc
index 0f955924a..306faec9a 100644
--- a/src/xenia/ui/window.cc
+++ b/src/xenia/ui/window.cc
@@ -173,12 +173,15 @@ void Window::OnPaint(UIEvent* e) {
 
   ++frame_count_;
   ++fps_frame_count_;
-  uint64_t now_ns = xe::Clock::QueryHostSystemTime();
-  if (now_ns > fps_update_time_ns_ + 1000 * 10000) {
+  static auto tick_frequency = Clock::QueryHostTickFrequency();
+  auto now_ticks = Clock::QueryHostTickCount();
+  // Average fps over 1 second.
+  if (now_ticks > fps_update_time_ticks_ + tick_frequency * 1) {
     fps_ = static_cast<uint32_t>(
         fps_frame_count_ /
-        (static_cast<double>(now_ns - fps_update_time_ns_) / 10000000.0));
-    fps_update_time_ns_ = now_ns;
+        (static_cast<double>(now_ticks - fps_update_time_ticks_) /
+         tick_frequency));
+    fps_update_time_ticks_ = now_ticks;
     fps_frame_count_ = 0;
   }
 
@@ -186,12 +189,13 @@ void Window::OnPaint(UIEvent* e) {
 
   // Prepare ImGui for use this frame.
   auto& io = imgui_drawer_->GetIO();
-  if (!last_paint_time_ns_) {
+  if (!last_paint_time_ticks_) {
     io.DeltaTime = 0.0f;
-    last_paint_time_ns_ = now_ns;
+    last_paint_time_ticks_ = now_ticks;
   } else {
-    io.DeltaTime = (now_ns - last_paint_time_ns_) / 10000000.0f;
-    last_paint_time_ns_ = now_ns;
+    io.DeltaTime = (now_ticks - last_paint_time_ticks_) /
+                   static_cast<float>(tick_frequency);
+    last_paint_time_ticks_ = now_ticks;
   }
   io.DisplaySize = ImVec2(static_cast<float>(scaled_width()),
                           static_cast<float>(scaled_height()));
diff --git a/src/xenia/ui/window.h b/src/xenia/ui/window.h
index 6cbc7a250..2cb5c8c34 100644
--- a/src/xenia/ui/window.h
+++ b/src/xenia/ui/window.h
@@ -180,9 +180,9 @@ class Window {
 
   uint32_t frame_count_ = 0;
   uint32_t fps_ = 0;
-  uint64_t fps_update_time_ns_ = 0;
+  uint64_t fps_update_time_ticks_ = 0;
   uint64_t fps_frame_count_ = 0;
-  uint64_t last_paint_time_ns_ = 0;
+  uint64_t last_paint_time_ticks_ = 0;
 
   bool modifier_shift_pressed_ = false;
   bool modifier_cntrl_pressed_ = false;