ImGui: Remember position of movable overlays

Remember the position of various moveable overlays so users don't have
to move them every time they start a new game.

Window data is stored in Config/ImGui.ini.

Affected overlays:
- NetPlay Chat
- NetPlay Golf
- Movie statistics
- All of the overlays in the Graphics->Advanced tab
- Scissor Rectangles

Source/Core/Common/CommonPaths.h

@@ -107,6 +107,7 @@
 #define DUALSHOCKUDPCLIENT_CONFIG "DSUClient.ini"
 #define FREELOOK_CONFIG "FreeLook.ini"
 #define RETROACHIEVEMENTS_CONFIG "RetroAchievements.ini"
+#define IMGUI_CONFIG "ImGui.ini"
 
 // Files in the directory returned by GetUserPath(D_LOGS_IDX)
 #define MAIN_LOG "dolphin.log"

Source/Core/Common/FileUtil.cpp

@@ -898,6 +898,7 @@ static void RebuildUserDirectories(unsigned int dir_index)
     s_user_paths[F_FREELOOKCONFIG_IDX] = s_user_paths[D_CONFIG_IDX] + FREELOOK_CONFIG;
     s_user_paths[F_RETROACHIEVEMENTSCONFIG_IDX] =
         s_user_paths[D_CONFIG_IDX] + RETROACHIEVEMENTS_CONFIG;
+    s_user_paths[F_IMGUICONFIG_IDX] = s_user_paths[D_CONFIG_IDX] + IMGUI_CONFIG;
     s_user_paths[F_MAINLOG_IDX] = s_user_paths[D_LOGS_IDX] + MAIN_LOG;
     s_user_paths[F_MEM1DUMP_IDX] = s_user_paths[D_DUMP_IDX] + MEM1_DUMP;
     s_user_paths[F_MEM2DUMP_IDX] = s_user_paths[D_DUMP_IDX] + MEM2_DUMP;
@@ -935,6 +936,7 @@ static void RebuildUserDirectories(unsigned int dir_index)
     s_user_paths[F_FREELOOKCONFIG_IDX] = s_user_paths[D_CONFIG_IDX] + FREELOOK_CONFIG;
     s_user_paths[F_RETROACHIEVEMENTSCONFIG_IDX] =
         s_user_paths[D_CONFIG_IDX] + RETROACHIEVEMENTS_CONFIG;
+    s_user_paths[F_IMGUICONFIG_IDX] = s_user_paths[D_CONFIG_IDX] + IMGUI_CONFIG;
     break;
 
   case D_CACHE_IDX:

Source/Core/Common/FileUtil.h

@@ -96,6 +96,7 @@ enum
   F_FREELOOKCONFIG_IDX,
   F_GBABIOS_IDX,
   F_RETROACHIEVEMENTSCONFIG_IDX,
+  F_IMGUICONFIG_IDX,
   NUM_PATH_INDICES
 };
 

Source/Core/VideoCommon/OnScreenUI.cpp

@@ -4,6 +4,7 @@
 #include "VideoCommon/OnScreenUI.h"
 
 #include "Common/EnumMap.h"
+#include "Common/FileUtil.h"
 #include "Common/Profiler.h"
 #include "Common/Timer.h"
 
@@ -54,8 +55,7 @@ bool OnScreenUI::Initialize(u32 width, u32 height, float scale)
     return false;
   }
 
-  // Don't create an ini file. TODO: Do we want this in the future?
-  ImGui::GetIO().IniFilename = nullptr;
+  ImGui::GetIO().IniFilename = File::GetUserPath(F_IMGUICONFIG_IDX).data();
   SetScale(scale);
 
   PortableVertexDeclaration vdecl = {};

Source/Core/VideoCommon/PerformanceMetrics.cpp

@@ -83,9 +83,9 @@ double PerformanceMetrics::GetLastSpeedDenominator() const
 void PerformanceMetrics::DrawImGuiStats(const float backbuffer_scale)
 {
   const float bg_alpha = 0.7f;
-  const auto imgui_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoSavedSettings |
-                           ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoNav |
-                           ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoFocusOnAppearing;
+  const auto imgui_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoScrollbar |
+                           ImGuiWindowFlags_NoNav | ImGuiWindowFlags_AlwaysAutoResize |
+                           ImGuiWindowFlags_NoFocusOnAppearing;
 
   const double fps = GetFPS();
   const double vps = GetVPS();