From 49b1a496b1481b77354b20edef94e98231b4f23a Mon Sep 17 00:00:00 2001
From: TellowKrinkle <tellowkrinkle@gmail.com>
Date: Thu, 6 Jan 2022 19:18:47 -0600
Subject: [PATCH] GS: Fix OSD scaling on hidpi displays

---
 pcsx2/Frontend/ImGuiManager.cpp | 12 +++++-------
 pcsx2/gui/AppHost.cpp           |  8 ++++++--
 pcsx2/gui/AppHost.h             |  2 +-
 pcsx2/gui/FrameForGS.cpp        |  2 +-
 4 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/pcsx2/Frontend/ImGuiManager.cpp b/pcsx2/Frontend/ImGuiManager.cpp
index 18fd1d0762..df975af085 100644
--- a/pcsx2/Frontend/ImGuiManager.cpp
+++ b/pcsx2/Frontend/ImGuiManager.cpp
@@ -66,7 +66,7 @@ bool ImGuiManager::Initialize()
 
 	s_global_scale = std::max(1.0f, display->GetWindowScale() * static_cast<float>(EmuConfig.GS.OsdScale / 100.0));
 
-	ImGui::GetIO().DisplayFramebufferScale = ImVec2(display->GetWindowScale(), display->GetWindowScale());
+	ImGui::GetIO().DisplayFramebufferScale = ImVec2(1, 1); // We already scale things ourselves, this would double-apply scaling
 	ImGui::GetIO().DisplaySize.x = static_cast<float>(display->GetWindowWidth());
 	ImGui::GetIO().DisplaySize.y = static_cast<float>(display->GetWindowHeight());
 	ImGui::GetStyle() = ImGuiStyle();
@@ -111,18 +111,18 @@ void ImGuiManager::WindowResized()
 
 	const u32 new_width = display ? display->GetWindowWidth() : 0;
 	const u32 new_height = display ? display->GetWindowHeight() : 0;
-	const float new_scale = (display ? display->GetWindowScale() : 1.0f);
 
 	ImGui::GetIO().DisplaySize = ImVec2(static_cast<float>(new_width), static_cast<float>(new_height));
-	ImGui::GetIO().DisplayFramebufferScale = ImVec2(new_scale, new_scale);
 
 	UpdateScale();
 }
 
 void ImGuiManager::UpdateScale()
 {
-	const float scale =
-		std::max(ImGui::GetIO().DisplayFramebufferScale.x * static_cast<float>(EmuConfig.GS.OsdScale / 100.0), 1.0f);
+	HostDisplay* display = Host::GetHostDisplay();
+	const float window_scale = display ? display->GetWindowScale() : 1.0f;
+	const float scale = std::max(window_scale * static_cast<float>(EmuConfig.GS.OsdScale / 100.0), 1.0f);
+
 	if (scale == s_global_scale)
 		return;
 
@@ -131,8 +131,6 @@ void ImGuiManager::UpdateScale()
 
 	s_global_scale = scale;
 
-	HostDisplay* display = Host::GetHostDisplay();
-
 	ImGui::GetStyle() = ImGuiStyle();
 	ImGui::GetStyle().WindowMinSize = ImVec2(1.0f, 1.0f);
 	SetImGuiStyle();
diff --git a/pcsx2/gui/AppHost.cpp b/pcsx2/gui/AppHost.cpp
index 2011df874d..0adc1b299c 100644
--- a/pcsx2/gui/AppHost.cpp
+++ b/pcsx2/gui/AppHost.cpp
@@ -178,12 +178,14 @@ static std::atomic_bool s_gs_window_resized{false};
 static std::mutex s_gs_window_resized_lock;
 static int s_new_gs_window_width = 0;
 static int s_new_gs_window_height = 0;
+static float s_new_gs_window_scale = 1;
 
-void Host::GSWindowResized(int width, int height)
+void Host::GSWindowResized(int width, int height, float scale)
 {
 	std::unique_lock lock(s_gs_window_resized_lock);
 	s_new_gs_window_width = width;
 	s_new_gs_window_height = height;
+	s_new_gs_window_scale = scale;
 	s_gs_window_resized.store(true);
 }
 
@@ -193,17 +195,19 @@ void Host::CheckForGSWindowResize()
 		return;
 
 	int width, height;
+	float scale;
 	{
 		std::unique_lock lock(s_gs_window_resized_lock);
 		width = s_new_gs_window_width;
 		height = s_new_gs_window_height;
+		scale = s_new_gs_window_scale;
 		s_gs_window_resized.store(false);
 	}
 
 	if (!s_host_display)
 		return;
 
-	s_host_display->ResizeRenderWindow(width, height, s_host_display ? s_host_display->GetWindowScale() : 1.0f);
+	s_host_display->ResizeRenderWindow(width, height, scale);
 	ImGuiManager::WindowResized();
 }
 
diff --git a/pcsx2/gui/AppHost.h b/pcsx2/gui/AppHost.h
index 283e3a416f..91bf5a6f9a 100644
--- a/pcsx2/gui/AppHost.h
+++ b/pcsx2/gui/AppHost.h
@@ -4,7 +4,7 @@
 namespace Host
 {
 	// UI thread
-	void GSWindowResized(int width, int height);
+	void GSWindowResized(int width, int height, float scale);
 
 	// MTGS thread
 	void CheckForGSWindowResize();
diff --git a/pcsx2/gui/FrameForGS.cpp b/pcsx2/gui/FrameForGS.cpp
index 65894380fc..23e130548c 100644
--- a/pcsx2/gui/FrameForGS.cpp
+++ b/pcsx2/gui/FrameForGS.cpp
@@ -384,7 +384,7 @@ void GSPanel::OnResize(wxEvent& event)
 	g_gs_window_info.surface_height = height;
 	g_gs_window_info.surface_scale = scale;
 
-	Host::GSWindowResized(width, height);
+	Host::GSWindowResized(width, height, scale);
 }
 
 void GSPanel::OnMouseEvent( wxMouseEvent& evt )