HostDisplay: Add an option to decouple display fps from emulator fps

Makes Android so much faster...

src/core/host_display.cpp

@@ -2,6 +2,7 @@
 #include "common/file_system.h"
 #include "common/log.h"
 #include "common/string_util.h"
+#include "common/timer.h"
 #include "stb_image.h"
 #include "stb_image_resize.h"
 #include "stb_image_write.h"
@@ -14,6 +15,25 @@ HostDisplayTexture::~HostDisplayTexture() = default;
 
 HostDisplay::~HostDisplay() = default;
 
+void HostDisplay::SetDisplayMaxFPS(float max_fps)
+{
+  m_display_frame_interval = (max_fps > 0.0f) ? (1.0f / max_fps) : 0.0f;
+}
+
+bool HostDisplay::ShouldSkipDisplayingFrame()
+{
+  if (m_display_frame_interval == 0.0f)
+    return false;
+
+  const u64 now = Common::Timer::GetValue();
+  const double diff = Common::Timer::ConvertValueToSeconds(now - m_last_frame_displayed_time);
+  if (diff < m_display_frame_interval)
+    return true;
+
+  m_last_frame_displayed_time = now;
+  return false;
+}
+
 void HostDisplay::SetSoftwareCursor(std::unique_ptr<HostDisplayTexture> texture, float scale /*= 1.0f*/)
 {
   m_cursor_texture = std::move(texture);

src/core/host_display.h

@@ -94,6 +94,9 @@ public:
   const s32 GetDisplayTopMargin() const { return m_display_top_margin; }
   const float GetDisplayAspectRatio() const { return m_display_aspect_ratio; }
 
+  void SetDisplayMaxFPS(float max_fps);
+  bool ShouldSkipDisplayingFrame();
+
   void ClearDisplayTexture()
   {
     m_display_texture_handle = nullptr;
@@ -181,6 +184,8 @@ protected:
 
   WindowInfo m_window_info;
 
+  u64 m_last_frame_displayed_time = 0;
+
   s32 m_mouse_position_x = 0;
   s32 m_mouse_position_y = 0;
 
@@ -191,6 +196,7 @@ protected:
   s32 m_display_active_width = 0;
   s32 m_display_active_height = 0;
   float m_display_aspect_ratio = 1.0f;
+  float m_display_frame_interval = 0.0f;
 
   void* m_display_texture_handle = nullptr;
   s32 m_display_texture_width = 0;

src/core/host_interface.cpp

@@ -463,6 +463,7 @@ void HostInterface::SetDefaultSettings(SettingsInterface& si)
   si.SetBoolValue("Display", "Fullscreen", false);
   si.SetBoolValue("Display", "VSync", true);
   si.SetStringValue("Display", "PostProcessChain", "");
+  si.SetFloatValue("Display", "MaxFPS", 0.0f);
 
   si.SetBoolValue("CDROM", "ReadThread", true);
   si.SetBoolValue("CDROM", "RegionCheck", true);

src/core/settings.cpp

@@ -177,6 +177,7 @@ void Settings::Load(SettingsInterface& si)
   display_show_resolution = si.GetBoolValue("Display", "ShowResolution", false);
   video_sync_enabled = si.GetBoolValue("Display", "VSync", true);
   display_post_process_chain = si.GetStringValue("Display", "PostProcessChain", "");
+  display_max_fps = si.GetFloatValue("Display", "MaxFPS", 0.0f);
 
   cdrom_read_thread = si.GetBoolValue("CDROM", "ReadThread", true);
   cdrom_region_check = si.GetBoolValue("CDROM", "RegionCheck", true);
@@ -304,6 +305,7 @@ void Settings::Save(SettingsInterface& si) const
     si.DeleteValue("Display", "PostProcessChain");
   else
     si.SetStringValue("Display", "PostProcessChain", display_post_process_chain.c_str());
+  si.SetFloatValue("Display", "MaxFPS", display_max_fps);
 
   si.SetBoolValue("CDROM", "ReadThread", cdrom_read_thread);
   si.SetBoolValue("CDROM", "RegionCheck", cdrom_region_check);

src/core/settings.h

@@ -123,6 +123,7 @@ struct Settings
   bool display_show_speed = false;
   bool display_show_resolution = false;
   bool video_sync_enabled = true;
+  float display_max_fps = 0.0f;
 
   bool cdrom_read_thread = true;
   bool cdrom_region_check = true;