From e4c2298e5e1e846b1ac61176cceb9c17010fbd6f Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Mon, 4 Apr 2022 13:30:08 +0100
Subject: [PATCH] Use window scale factor for all MSW wxDCs associated with
 windows

This ensures that we use correct font sizes with the DCs and, in
particular, fixes the font size in wxAutoBufferedPaintDC when using DPI
scaling different from 100% after the changes of e3557b8c0a (Respect
bitmap content scale factor in wxMSW wxMemoryDC, 2022-03-26).

See #22234.
---
 include/wx/msw/dc.h  | 3 +++
 src/msw/dc.cpp       | 7 +++++++
 src/msw/dcclient.cpp | 8 ++++----
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/wx/msw/dc.h b/include/wx/msw/dc.h
index 7b7c402437..cbfbccd3f4 100644
--- a/include/wx/msw/dc.h
+++ b/include/wx/msw/dc.h
@@ -171,6 +171,9 @@ protected:
         m_isClipBoxValid = false;
     }
 
+    // Unlike the public SetWindow(), this one doesn't call InitializePalette().
+    void InitWindow(wxWindow* window);
+
     // create an uninitialized DC: this should be only used by the derived
     // classes
     wxMSWDCImpl( wxDC *owner ) : wxDCImpl( owner ) { Init(); }
diff --git a/src/msw/dc.cpp b/src/msw/dc.cpp
index 0cc9531e2b..6dbca59f88 100644
--- a/src/msw/dc.cpp
+++ b/src/msw/dc.cpp
@@ -470,6 +470,13 @@ WXHDC wxDC::GetHDC() const
 // wxMSWDCImpl
 // ---------------------------------------------------------------------------
 
+void wxMSWDCImpl::InitWindow(wxWindow* window)
+{
+    m_window = window;
+    if ( m_window )
+        m_contentScaleFactor = m_window->GetDPIScaleFactor();
+}
+
 wxMSWDCImpl::wxMSWDCImpl( wxDC *owner, WXHDC hDC ) :
     wxDCImpl( owner )
 {
diff --git a/src/msw/dcclient.cpp b/src/msw/dcclient.cpp
index 4cad631f0b..9ef4a5cd15 100644
--- a/src/msw/dcclient.cpp
+++ b/src/msw/dcclient.cpp
@@ -156,7 +156,7 @@ wxWindowDCImpl::wxWindowDCImpl( wxDC *owner, wxWindow *window ) :
 {
     wxCHECK_RET( window, wxT("invalid window in wxWindowDCImpl") );
 
-    m_window = window;
+    InitWindow(window);
     m_hDC = (WXHDC) ::GetWindowDC(GetHwndOf(m_window));
 
     // m_bOwnsDC was already set to false in the base class ctor, so the DC
@@ -199,7 +199,7 @@ wxClientDCImpl::wxClientDCImpl( wxDC *owner, wxWindow *window ) :
 {
     wxCHECK_RET( window, wxT("invalid window in wxClientDCImpl") );
 
-    m_window = window;
+    InitWindow(window);
     m_hDC = (WXHDC)::GetDC(GetHwndOf(window));
 
     // m_bOwnsDC was already set to false in the base class ctor, so the DC
@@ -263,7 +263,7 @@ wxPaintDCImpl::wxPaintDCImpl( wxDC *owner, wxWindow *window ) :
 
     paintStack.top().createdPaintDC = true;
 
-    m_window = window;
+    InitWindow(window);
 
     // do we have a DC for this window in the cache?
     m_hDC = FindDCInCache(m_window);
@@ -352,7 +352,7 @@ wxPaintDCExImpl::wxPaintDCExImpl(wxDC *owner, wxWindow *window, WXHDC dc)
 {
     wxCHECK_RET( dc, wxT("wxPaintDCEx requires an existing device context") );
 
-    m_window = window;
+    InitWindow(window);
     m_hDC = dc;
 }