Bug [#2382]. Fix reverse arrow cursor when scaled.

4 files changed, 104 insertions, 46 deletions

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index f60eb3933..503df317e 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -594,6 +594,10 @@
 	<a href="https://sourceforge.net/p/scintilla/feature-requests/1486/">Feature #1486</a>.
 	</li>
 	<li>
+	On Win32 fix reverse arrow cursor when scaled.
+	<a href="https://sourceforge.net/p/scintilla/bugs/2382/">Bug #2382</a>.
+	</li>
+	<li>
 	On Win32 hide cursor when typing if that system preference has been chosen.
 	<a href="https://sourceforge.net/p/scintilla/bugs/2333/">Bug #2333</a>.
 	</li>
diff --git a/win32/PlatWin.cxx b/win32/PlatWin.cxx
index 65e27b63a..40302102b 100644
--- a/win32/PlatWin.cxx
+++ b/win32/PlatWin.cxx
@@ -167,6 +167,9 @@ GetWindowDpiAwarenessContextSig fnGetWindowDpiAwarenessContext = nullptr;
 using GetScaleFactorForMonitorSig = HRESULT(WINAPI *)(HMONITOR, DEVICE_SCALE_FACTOR *);
 GetScaleFactorForMonitorSig fnGetScaleFactorForMonitor = nullptr;
 
+using GetThreadDpiAwarenessContextSig = DPI_AWARENESS_CONTEXT(WINAPI *)();
+GetThreadDpiAwarenessContextSig fnGetThreadDpiAwarenessContext = nullptr;
+
 using SetThreadDpiAwarenessContextSig = DPI_AWARENESS_CONTEXT(WINAPI *)(DPI_AWARENESS_CONTEXT);
 SetThreadDpiAwarenessContextSig fnSetThreadDpiAwarenessContext = nullptr;
 
@@ -175,6 +178,7 @@ void LoadDpiForWindow() noexcept {
 	fnGetDpiForWindow = DLLFunction<GetDpiForWindowSig>(user32, "GetDpiForWindow");
 	fnGetSystemMetricsForDpi = DLLFunction<GetSystemMetricsForDpiSig>(user32, "GetSystemMetricsForDpi");
 	fnAdjustWindowRectExForDpi = DLLFunction<AdjustWindowRectExForDpiSig>(user32, "AdjustWindowRectExForDpi");
+	fnGetThreadDpiAwarenessContext = DLLFunction<GetThreadDpiAwarenessContextSig>(user32, "GetThreadDpiAwarenessContext");
 	fnSetThreadDpiAwarenessContext = DLLFunction<SetThreadDpiAwarenessContextSig>(user32, "SetThreadDpiAwarenessContext");
 
 	using GetDpiForSystemSig = UINT(WINAPI *)(void);
@@ -393,7 +397,7 @@ HMONITOR MonitorFromWindowHandleScaling(HWND hWnd) noexcept {
 	return monitor;
 }
 
-int GetDeviceScaleFactorWhenGdiScalingActive(HWND hWnd) noexcept {
+float GetDeviceScaleFactorWhenGdiScalingActive(HWND hWnd) noexcept {
 	if (fnAreDpiAwarenessContextsEqual) {
 		PLATFORM_ASSERT(fnGetWindowDpiAwarenessContext && fnGetScaleFactorForMonitor);
 		if (fnAreDpiAwarenessContextsEqual(DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED, fnGetWindowDpiAwarenessContext(hWnd))) {
@@ -401,10 +405,10 @@ int GetDeviceScaleFactorWhenGdiScalingActive(HWND hWnd) noexcept {
 			const HMONITOR hMonitor = MonitorFromWindowHandleScaling(hRootWnd);
 			DEVICE_SCALE_FACTOR deviceScaleFactor;
 			if (S_OK == fnGetScaleFactorForMonitor(hMonitor, &deviceScaleFactor))
-				return (static_cast<int>(deviceScaleFactor) + 99) / 100; // increase to first integral multiple of 1
+				return deviceScaleFactor / 100.f;
 		}
 	}
-	return 1;
+	return 1.f;
 }
 
 std::shared_ptr<Font> Font::Allocate(const FontParameters &fp) {
@@ -2778,56 +2782,102 @@ void Window::InvalidateRectangle(PRectangle rc) {
 	::InvalidateRect(HwndFromWindowID(wid), &rcw, FALSE);
 }
 
-namespace {
-
-void FlipBitmap(HBITMAP bitmap, int width, int height) noexcept {
-	HDC hdc = ::CreateCompatibleDC({});
-	if (hdc) {
-		HBITMAP prevBmp = SelectBitmap(hdc, bitmap);
-		::StretchBlt(hdc, width - 1, 0, -width, height, hdc, 0, 0, width, height, SRCCOPY);
-		SelectBitmap(hdc, prevBmp);
-		::DeleteDC(hdc);
-	}
-}
-
-}
-
 HCURSOR LoadReverseArrowCursor(UINT dpi) noexcept {
-	HCURSOR reverseArrowCursor {};
+	class CursorHelper {
+	public:
+		ICONINFO info{};
+		BITMAP bmp{};
+		bool HasBitmap() const noexcept {
+			return bmp.bmWidth > 0;
+		}
 
-	bool created = false;
-	HCURSOR cursor = ::LoadCursor({}, IDC_ARROW);
+		CursorHelper(const HCURSOR cursor) noexcept {
+			Init(cursor);
+		}
+		~CursorHelper() {
+			CleanUp();
+		}
 
-	if (dpi != uSystemDPI) {
-		const int width = SystemMetricsForDpi(SM_CXCURSOR, dpi);
-		const int height = SystemMetricsForDpi(SM_CYCURSOR, dpi);
-		HCURSOR copy = static_cast<HCURSOR>(::CopyImage(cursor, IMAGE_CURSOR, width, height, LR_COPYFROMRESOURCE | LR_COPYRETURNORG));
-		if (copy) {
-			created = copy != cursor;
-			cursor = copy;
+		CursorHelper &operator=(const HCURSOR cursor) noexcept {
+			CleanUp();
+			Init(cursor);
+			return *this;
+		}
+
+		bool MatchesSize(const int width, const int height) noexcept {
+			return bmp.bmWidth == width && bmp.bmHeight == height;
 		}
-	}
 
-	ICONINFO info;
-	if (::GetIconInfo(cursor, &info)) {
-		BITMAP bmp {};
-		if (::GetObject(info.hbmMask, sizeof(bmp), &bmp)) {
-			FlipBitmap(info.hbmMask, bmp.bmWidth, bmp.bmHeight);
+		HCURSOR CreateFlippedCursor() noexcept {
+			if (info.hbmMask)
+				FlipBitmap(info.hbmMask, bmp.bmWidth, bmp.bmHeight);
 			if (info.hbmColor)
 				FlipBitmap(info.hbmColor, bmp.bmWidth, bmp.bmHeight);
 			info.xHotspot = bmp.bmWidth - 1 - info.xHotspot;
 
-			reverseArrowCursor = ::CreateIconIndirect(&info);
+			return ::CreateIconIndirect(&info);
+		}
+
+	private:
+		void Init(const HCURSOR &cursor) noexcept {
+			if (::GetIconInfo(cursor, &info)) {
+				::GetObject(info.hbmMask, sizeof(bmp), &bmp);
+				PLATFORM_ASSERT(HasBitmap());
+			}
+		}
+
+		void CleanUp() noexcept {
+			if (info.hbmMask)
+				::DeleteObject(info.hbmMask);
+			if (info.hbmColor)
+				::DeleteObject(info.hbmColor);
+			info = {};
+			bmp = {};
+		}
+
+		static void FlipBitmap(const HBITMAP bitmap, const int width, const int height) noexcept {
+			HDC hdc = ::CreateCompatibleDC({});
+			if (hdc) {
+				HBITMAP prevBmp = SelectBitmap(hdc, bitmap);
+				::StretchBlt(hdc, width - 1, 0, -width, height, hdc, 0, 0, width, height, SRCCOPY);
+				SelectBitmap(hdc, prevBmp);
+				::DeleteDC(hdc);
+			}
+		}
+	};
+
+	HCURSOR reverseArrowCursor {};
+
+	const int width = SystemMetricsForDpi(SM_CXCURSOR, dpi);
+	const int height = SystemMetricsForDpi(SM_CYCURSOR, dpi);
+
+	DPI_AWARENESS_CONTEXT oldContext = nullptr;
+	if (fnAreDpiAwarenessContextsEqual && fnAreDpiAwarenessContextsEqual(fnGetThreadDpiAwarenessContext(), DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED)) {
+		oldContext = fnSetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+		PLATFORM_ASSERT(oldContext != nullptr);
+	}
+
+	const HCURSOR cursor = static_cast<HCURSOR>(::LoadImage({}, IDC_ARROW, IMAGE_CURSOR, width, height, LR_SHARED));
+	if (cursor) {
+		CursorHelper cursorHelper(cursor);
+
+		if (cursorHelper.HasBitmap() && !cursorHelper.MatchesSize(width, height)) {
+			const HCURSOR copy = static_cast<HCURSOR>(::CopyImage(cursor, IMAGE_CURSOR, width, height, LR_COPYFROMRESOURCE | LR_COPYRETURNORG));
+			if (copy) {
+				cursorHelper = copy;
+				::DestroyCursor(copy);
+			}
 		}
 
-		::DeleteObject(info.hbmMask);
-		if (info.hbmColor)
-			::DeleteObject(info.hbmColor);
+		if (cursorHelper.HasBitmap()) {
+			reverseArrowCursor = cursorHelper.CreateFlippedCursor();
+		}
 	}
 
-	if (created) {
-		::DestroyCursor(cursor);
+	if (oldContext) {
+		fnSetThreadDpiAwarenessContext(oldContext);
 	}
+
 	return reverseArrowCursor;
 }
 
diff --git a/win32/PlatWin.h b/win32/PlatWin.h
index 8ce798cf1..f010923f2 100644
--- a/win32/PlatWin.h
+++ b/win32/PlatWin.h
@@ -46,7 +46,7 @@ void SetWindowPointer(HWND hWnd, void *ptr) noexcept;
 HMONITOR MonitorFromWindowHandleScaling(HWND hWnd) noexcept;
 
 UINT DpiForWindow(WindowID wid) noexcept;
-int GetDeviceScaleFactorWhenGdiScalingActive(HWND hWnd) noexcept;
+float GetDeviceScaleFactorWhenGdiScalingActive(HWND hWnd) noexcept;
 
 int SystemMetricsForDpi(int nIndex, UINT dpi) noexcept;
 
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index 95bb79825..964b3ee3c 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -364,7 +364,10 @@ class ScintillaWin :
 	static ATOM scintillaClassAtom;
 	static ATOM callClassAtom;
 
-	int deviceScaleFactor = 1;
+	float deviceScaleFactor = 1.f;
+	int GetFirstIntegralMultipleDeviceScaleFactor() const noexcept {
+		 return static_cast<int>(std::ceil(deviceScaleFactor));
+	}
 
 #if defined(USE_D2D)
 	ID2D1RenderTarget *pRenderTarget;
@@ -723,14 +726,15 @@ void ScintillaWin::EnsureRenderTarget(HDC hdc) {
 			}
 
 		} else {
-			drtp.dpiX = 96.f * deviceScaleFactor;
-			drtp.dpiY = 96.f * deviceScaleFactor;
+			const int integralDeviceScaleFactor = GetFirstIntegralMultipleDeviceScaleFactor();
+			drtp.dpiX = 96.f * integralDeviceScaleFactor;
+			drtp.dpiY = 96.f * integralDeviceScaleFactor;
 			drtp.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_UNKNOWN,
 				D2D1_ALPHA_MODE_UNKNOWN);
 
 			D2D1_HWND_RENDER_TARGET_PROPERTIES dhrtp {};
 			dhrtp.hwnd = hw;
-			dhrtp.pixelSize = ::GetSizeUFromRect(rc, deviceScaleFactor);
+			dhrtp.pixelSize = ::GetSizeUFromRect(rc, integralDeviceScaleFactor);
 			dhrtp.presentOptions = (technology == Technology::DirectWriteRetain) ?
 			D2D1_PRESENT_OPTIONS_RETAIN_CONTENTS : D2D1_PRESENT_OPTIONS_NONE;
 
@@ -775,7 +779,7 @@ void ScintillaWin::DisplayCursor(Window::Cursor c) {
 		c = static_cast<Window::Cursor>(cursorMode);
 	}
 	if (c == Window::Cursor::reverseArrow) {
-		::SetCursor(reverseArrowCursor.Load(dpi));
+		::SetCursor(reverseArrowCursor.Load(static_cast<UINT>(dpi * deviceScaleFactor)));
 	} else {
 		wMain.SetCursor(c);
 	}
@@ -3649,7 +3653,7 @@ LRESULT PASCAL ScintillaWin::CTWndProc(
 					surfaceWindow->Init(ps.hdc, hWnd);
 				} else {
 #if defined(USE_D2D)
-					const int scaleFactor = sciThis->deviceScaleFactor;
+					const int scaleFactor = sciThis->GetFirstIntegralMultipleDeviceScaleFactor();
 
 					// Create a Direct2D render target.
 					D2D1_HWND_RENDER_TARGET_PROPERTIES dhrtp {};