From a95db00606dd07f954dfe54d175e183e21bb00ed Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Mon, 27 Mar 2023 11:34:21 -0400
Subject: [PATCH 1/2] Limit cursor clipping to the render area

---
 src/d2dx/RenderContext.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/d2dx/RenderContext.cpp b/src/d2dx/RenderContext.cpp
index 9beb040..67f95c8 100644
--- a/src/d2dx/RenderContext.cpp
+++ b/src/d2dx/RenderContext.cpp
@@ -400,7 +400,7 @@ void RenderContext::Present()
 	UpdateViewport(_renderRect);
 
 	RenderContextPixelShader pixelShader;
-	
+
 	switch (_d2dxContext->GetOptions().GetFiltering())
 	{
 	default:
@@ -1026,11 +1026,15 @@ void RenderContext::ClipCursor()
 		return;
 	}
 
-	RECT clipRect;
-	::GetClientRect(_hWnd, &clipRect);
+	RECT clipRect = {
+		_renderRect.offset.x,
+		_renderRect.offset.y,
+		_renderRect.offset.x + _renderRect.size.width,
+		_renderRect.offset.y + _renderRect.size.height
+	};
 	::ClientToScreen(_hWnd, (LPPOINT)&clipRect.left);
-	::ClientToScreen(_hWnd, (LPPOINT)&clipRect.right);
-	::ClipCursor(&clipRect);
+    ::ClientToScreen(_hWnd, (LPPOINT)&clipRect.right);
+    ::ClipCursor(&clipRect);
 }
 
 void RenderContext::UnclipCursor()

From 6824ce31ab01f27b0370b3cbb16f7284287b3229 Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Mon, 27 Mar 2023 11:34:21 -0400
Subject: [PATCH 2/2] Only lock the cursor when the mouse interacts with the
 client area

---
 src/d2dx/RenderContext.cpp | 23 +++++++++++++++++------
 src/d2dx/RenderContext.h   | 12 +++++++++++-
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/d2dx/RenderContext.cpp b/src/d2dx/RenderContext.cpp
index 67f95c8..f3dd92b 100644
--- a/src/d2dx/RenderContext.cpp
+++ b/src/d2dx/RenderContext.cpp
@@ -85,6 +85,7 @@ RenderContext::RenderContext(
 	GetClientRect(hWnd, &clientRect);
 
 	SetWindowSubclass((HWND)hWnd, d2dxSubclassWndProc, 1234, (DWORD_PTR)this);
+	_isActiveWindow = GetForegroundWindow() == hWnd;
 
 	const int32_t widthFromClientRect = clientRect.right - clientRect.left;
 	const int32_t heightFromClientRect = clientRect.bottom - clientRect.top;
@@ -685,17 +686,20 @@ static LRESULT CALLBACK d2dxSubclassWndProc(
 {
 	RenderContext* renderContext = (RenderContext*)dwRefData;
 
-	if (uMsg == WM_ACTIVATEAPP)
+	if (uMsg == WM_ACTIVATE)
 	{
 		if (wParam)
 		{
-			renderContext->ClipCursor();
+			renderContext->SetActiveWindow(true);
 		}
 		else
 		{
-			renderContext->UnclipCursor();
+			renderContext->SetActiveWindow(false);
 		}
 	}
+	else if (uMsg == WM_MOVING) {
+		renderContext->UnclipCursor();
+	}
 	else if (uMsg == WM_SYSKEYDOWN || uMsg == WM_KEYDOWN)
 	{
 		if (wParam == VK_RETURN && (HIWORD(lParam) & KF_ALTDOWN))
@@ -719,6 +723,11 @@ static LRESULT CALLBACK d2dxSubclassWndProc(
 #ifdef NDEBUG
 		ShowCursor_Real(FALSE);
 #endif
+		if (uMsg != WM_MOUSEMOVE)
+		{
+			renderContext->ClipCursor(false);
+		}
+
 		Offset mousePos = { LOWORD(lParam), HIWORD(lParam) };
 
 		Size gameSize;
@@ -921,7 +930,7 @@ void RenderContext::SetSizes(
 		SetWindowPos_Real(_hWnd, HWND_TOP, 0, 0, _desktopSize.width, _desktopSize.height, SWP_SHOWWINDOW | SWP_NOSENDCHANGING | SWP_FRAMECHANGED);
 	}
 
-	ClipCursor();
+	ClipCursor(true);
 
 	if (!_d2dxContext->GetOptions().GetFlag(OptionsFlag::NoTitleChange))
 	{
@@ -1019,9 +1028,9 @@ void RenderContext::GetCurrentMetrics(
 	}
 }
 
-void RenderContext::ClipCursor()
+void RenderContext::ClipCursor(bool resizing)
 {
-	if (_d2dxContext->GetOptions().GetFlag(OptionsFlag::NoClipCursor))
+	if (!_isActiveWindow || (resizing != _isCursorClipped) || _d2dxContext->GetOptions().GetFlag(OptionsFlag::NoClipCursor))
 	{
 		return;
 	}
@@ -1035,11 +1044,13 @@ void RenderContext::ClipCursor()
 	::ClientToScreen(_hWnd, (LPPOINT)&clipRect.left);
     ::ClientToScreen(_hWnd, (LPPOINT)&clipRect.right);
     ::ClipCursor(&clipRect);
+    _isCursorClipped = true;
 }
 
 void RenderContext::UnclipCursor()
 {
 	::ClipCursor(NULL);
+	_isCursorClipped = false;
 }
 
 float RenderContext::GetFrameTime() const
diff --git a/src/d2dx/RenderContext.h b/src/d2dx/RenderContext.h
index cc1b919..27c158c 100644
--- a/src/d2dx/RenderContext.h
+++ b/src/d2dx/RenderContext.h
@@ -113,7 +113,15 @@ namespace d2dx
 
 		virtual ScreenMode GetScreenMode() const override;
 
-		void ClipCursor();
+		void SetActiveWindow(bool active) {
+			if (!active)
+			{
+				UnclipCursor();
+			}
+			_isActiveWindow = active;
+		}
+
+		void ClipCursor(bool resizing);
 		void UnclipCursor();
 
 	private:
@@ -210,6 +218,8 @@ namespace d2dx
 		EventHandle _frameLatencyWaitableObject;
 		int64_t _timeStart;
 		bool _hasAdjustedWindowPlacement = false;
+		bool _isActiveWindow = false;
+		bool _isCursorClipped = false;
 
 		double _prevTime;
 		double _frameTimeMs;