From 9938be93a19ae3eb09ec7704d800991eb7fc0f12 Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Thu, 28 May 2020 08:26:52 +1000
Subject: Bug [#2171]. Check for DPI change in WM_DPICHANGED_AFTERPARENT
 instead of every paint.

---
 win32/ScintillaWin.cxx | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index 28b6e950c..f2f6976f5 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -99,6 +99,9 @@
 #ifndef WM_DPICHANGED
 #define WM_DPICHANGED 0x02E0
 #endif
+#ifndef WM_DPICHANGED_AFTERPARENT
+#define WM_DPICHANGED_AFTERPARENT 0x02E3
+#endif
 
 #ifndef UNICODE_NOCHAR
 #define UNICODE_NOCHAR                  0xFFFF
@@ -376,8 +379,6 @@ class ScintillaWin :
 	Sci::Position TargetAsUTF8(char *text) const;
 	Sci::Position EncodedFromUTF8(const char *utf8, char *encoded) const;
 
-	void CheckDpiChanged();
-
 	bool PaintDC(HDC hdc);
 	sptr_t WndPaint();
 
@@ -901,14 +902,6 @@ Sci::Position ScintillaWin::EncodedFromUTF8(const char *utf8, char *encoded) con
 	}
 }
 
-void ScintillaWin::CheckDpiChanged() {
-	const UINT dpiNow = DpiForWindow(wMain.GetID());
-	if (dpi != dpiNow) {
-		dpi = dpiNow;
-		InvalidateStyleData();
-	}
-}
-
 bool ScintillaWin::PaintDC(HDC hdc) {
 	if (technology == SC_TECHNOLOGY_DEFAULT) {
 		AutoSurface surfaceWindow(hdc, this);
@@ -939,7 +932,6 @@ bool ScintillaWin::PaintDC(HDC hdc) {
 }
 
 sptr_t ScintillaWin::WndPaint() {
-	CheckDpiChanged();
 	//ElapsedPeriod ep;
 
 	// Redirect assertions to debug output and save current state
@@ -1965,6 +1957,15 @@ sptr_t ScintillaWin::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam
 			InvalidateStyleRedraw();
 			break;
 
+		case WM_DPICHANGED_AFTERPARENT: {
+				const UINT dpiNow = DpiForWindow(wMain.GetID());
+				if (dpi != dpiNow) {
+					dpi = dpiNow;
+					InvalidateStyleRedraw();
+				}
+			}
+			break;
+
 		case WM_CONTEXTMENU:
 			return ShowContextMenu(iMessage, wParam, lParam);
 
-- 
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