From 6ac4529f3bec08db1d946d6d174194c386f7c573 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Wed, 30 Aug 2023 05:21:33 -0500
Subject: [PATCH] possibly fix HiDPI input problem on macOS/Wayland

issue #1425
---
 .../backends/imgui_impl_sdl2.cpp              | 21 +++++--------------
 extern/imgui_patched/imgui.cpp                |  1 +
 extern/imgui_patched/imgui.h                  |  1 +
 src/gui/gui.cpp                               |  2 ++
 4 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/extern/imgui_patched/backends/imgui_impl_sdl2.cpp b/extern/imgui_patched/backends/imgui_impl_sdl2.cpp
index 919f490e..ddbad7be 100644
--- a/extern/imgui_patched/backends/imgui_impl_sdl2.cpp
+++ b/extern/imgui_patched/backends/imgui_impl_sdl2.cpp
@@ -322,14 +322,8 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
                 mouse_pos.y += window_y;
             }
             // Fix for high DPI mac/idevice/wayland
-            ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
-            if (!platform_io.Monitors.empty() && platform_io.Monitors[0].DpiScale > 1.0f)
-            {
-                // The Framebuffer is scaled by an integer ceiling of the actual ratio, so 2.0 not 1.685 on Mac!
-                //printf("multiply by %f\n",platform_io.Monitors[0].DpiScale);
-                mouse_pos.x *= std::ceil(platform_io.Monitors[0].DpiScale);
-                mouse_pos.y *= std::ceil(platform_io.Monitors[0].DpiScale);
-            }
+            mouse_pos.x *= io.InputScale;
+            mouse_pos.y *= io.InputScale;
             io.AddMouseSourceEvent(event->motion.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);
             io.AddMousePosEvent(mouse_pos.x, mouse_pos.y);
             return true;
@@ -627,13 +621,8 @@ static void ImGui_ImplSDL2_UpdateMouseData()
                 mouse_y -= window_y;
             }
             // Fix for high DPI mac/idevice/wayland
-            ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
-            if (!platform_io.Monitors.empty() && platform_io.Monitors[0].DpiScale > 1.0f)
-            {
-                // The Framebuffer is scaled by an integer ceiling of the actual ratio, so 2.0 not 1.685 on Mac!
-                mouse_x *= std::ceil(platform_io.Monitors[0].DpiScale);
-                mouse_y *= std::ceil(platform_io.Monitors[0].DpiScale);
-            }
+            mouse_x *= io.InputScale;
+            mouse_y *= io.InputScale;
             io.AddMousePosEvent((float)mouse_x, (float)mouse_y);
         }
     }
@@ -793,7 +782,7 @@ void ImGui_ImplSDL2_NewFrame()
         io.DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
         io.DisplaySize = ImVec2((float)display_w, (float)display_h);
         //printf("write %d/%d to DpiScale\n",display_w,w);
-        platform_io.Monitors[0].DpiScale=(float)display_w/(float)w;
+        io.InputScale=(float)display_w/(float)w;
     }
 
     // Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
diff --git a/extern/imgui_patched/imgui.cpp b/extern/imgui_patched/imgui.cpp
index 7d5313b8..71aee935 100644
--- a/extern/imgui_patched/imgui.cpp
+++ b/extern/imgui_patched/imgui.cpp
@@ -1273,6 +1273,7 @@ ImGuiIO::ImGuiIO()
     DisplaySize = ImVec2(-1.0f, -1.0f);
     DeltaTime = 1.0f / 60.0f;
     IniSavingRate = 5.0f;
+    InputScale = 1.0f;
     IniFilename = "imgui.ini"; // Important: "imgui.ini" is relative to current working dir, most apps will want to lock this to an absolute path (e.g. same path as executables).
     LogFilename = "imgui_log.txt";
 #ifndef IMGUI_DISABLE_OBSOLETE_KEYIO
diff --git a/extern/imgui_patched/imgui.h b/extern/imgui_patched/imgui.h
index 2acd2532..e7966cab 100644
--- a/extern/imgui_patched/imgui.h
+++ b/extern/imgui_patched/imgui.h
@@ -2060,6 +2060,7 @@ struct ImGuiIO
     ImVec2      DisplaySize;                    // <unset>          // Main display size, in pixels (generally == GetMainViewport()->Size). May change every frame.
     float       DeltaTime;                      // = 1.0f/60.0f     // Time elapsed since last frame, in seconds. May change every frame.
     float       IniSavingRate;                  // = 5.0f           // Minimum time between saving positions/sizes to .ini file, in seconds.
+    float       InputScale;                     // = 1.0f           // Used by backend in system managed scale situations.
     const char* IniFilename;                    // = "imgui.ini"    // Path to .ini file (important: default "imgui.ini" is relative to current working dir!). Set NULL to disable automatic .ini loading/saving or if you want to manually call LoadIniSettingsXXX() / SaveIniSettingsXXX() functions.
     const char* LogFilename;                    // = "imgui_log.txt"// Path to .log file (default parameter to ImGui::LogToFile when no file is specified).
     void*       UserData;                       // = NULL           // Store your own data.
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index f9c76d12..45adf116 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -3628,6 +3628,8 @@ bool FurnaceGUI::loop() {
       if (prevScrW!=scrW || prevScrH!=scrH) {
         logV("size change 2: %dx%d (from %dx%d)",scrW,scrH,prevScrW,prevScrH);
       }
+
+      ImGui::GetIO().InputScale=(float)canvasW/(float)scrW;
     }
 
     wantCaptureKeyboard=ImGui::GetIO().WantTextInput;