From 5166ddea2bf02dc422b70824f121d65e23b56427 Mon Sep 17 00:00:00 2001
From: Maarten Bent <MaartenBent@users.noreply.github.com>
Date: Sun, 31 May 2020 23:16:20 +0200
Subject: [PATCH] Create cursors with correct size when DPI changes

GetIconInfo does not return DPI aware results.
Adjust it to the DPI of the display that shows the cursor.
---
 src/msw/cursor.cpp | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/msw/cursor.cpp b/src/msw/cursor.cpp
index d57f980ea5..47b0caeed1 100644
--- a/src/msw/cursor.cpp
+++ b/src/msw/cursor.cpp
@@ -36,6 +36,8 @@
     #include "wx/module.h"
 #endif
 
+#include "wx/display.h"
+
 #include "wx/msw/private.h"
 #include "wx/msw/missing.h" // IDC_HAND
 
@@ -263,12 +265,20 @@ wxPoint wxCursor::GetHotSpot() const
 namespace
 {
 
-void ReverseBitmap(HBITMAP bitmap, int width, int height)
+wxSize ScaleAndReverseBitmap(HBITMAP& bitmap, float scale)
 {
+    BITMAP bmp;
+    if ( !::GetObject(bitmap, sizeof(bmp), &bmp) )
+        return wxSize();
+    wxSize cs(bmp.bmWidth * scale, bmp.bmHeight * scale);
+
     MemoryHDC hdc;
     SelectInHDC selBitmap(hdc, bitmap);
-    ::StretchBlt(hdc, width - 1, 0, -width, height,
-                 hdc, 0, 0, width, height, SRCCOPY);
+    if ( scale != 1 )
+        ::SetStretchBltMode(hdc, HALFTONE);
+    ::StretchBlt(hdc, cs.x - 1, 0, -cs.x, cs.y, hdc, 0, 0, bmp.bmWidth, bmp.bmHeight, SRCCOPY);
+
+    return cs;
 }
 
 HCURSOR CreateReverseCursor(HCURSOR cursor)
@@ -277,14 +287,15 @@ HCURSOR CreateReverseCursor(HCURSOR cursor)
     if ( !info.GetFrom(cursor) )
         return NULL;
 
-    BITMAP bmp;
-    if ( !::GetObject(info.hbmMask, sizeof(bmp), &bmp) )
-        return NULL;
+    const unsigned displayID = (unsigned)wxDisplay::GetFromPoint(wxGetMousePosition());
+    wxDisplay disp(displayID == 0u || displayID < wxDisplay::GetCount() ? displayID : 0u);
+    const float scale = (float)disp.GetPPI().y / wxGetDisplayPPI().y;
 
-    ReverseBitmap(info.hbmMask, bmp.bmWidth, bmp.bmHeight);
+    wxSize cursorSize = ScaleAndReverseBitmap(info.hbmMask, scale);
     if ( info.hbmColor )
-        ReverseBitmap(info.hbmColor, bmp.bmWidth, bmp.bmHeight);
-    info.xHotspot = (DWORD)bmp.bmWidth - 1 - info.xHotspot;
+        ScaleAndReverseBitmap(info.hbmColor, scale);
+    info.xHotspot = (DWORD)(cursorSize.x - 1 - info.xHotspot * scale);
+    info.yHotspot = (DWORD)(info.yHotspot * scale);
 
     return ::CreateIconIndirect(&info);
 }