From b9ad43e8b1cfaa7213be0eb33ed179285c33c67a Mon Sep 17 00:00:00 2001
From: Neil Hodgson <nyamatongwe@gmail.com>
Date: Sun, 19 Sep 2021 11:55:08 +1000
Subject: Respond to changes in system font scaling by clearing any cached
 layout data.

---
 doc/ScintillaHistory.html |  3 +++
 gtk/ScintillaGTK.cxx      | 13 +++++++++++++
 gtk/ScintillaGTK.h        |  1 +
 3 files changed, 17 insertions(+)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 1b16f2d18..3f9dd09e5 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -609,6 +609,9 @@
 	DejaVu Sans Mono 10.
 	</li>
 	<li>
+	On GTK, respond to changes in system font scaling by clearing any cached layout data.
+	</li>
+	<li>
 	On Cocoa, fix memory leak caused by circular references.
 	<a href="https://sourceforge.net/p/scintilla/bugs/2268/">Bug #2268</a>.
 	</li>
diff --git a/gtk/ScintillaGTK.cxx b/gtk/ScintillaGTK.cxx
index 7b47d6348..92973a083 100755
--- a/gtk/ScintillaGTK.cxx
+++ b/gtk/ScintillaGTK.cxx
@@ -231,6 +231,7 @@ ScintillaGTK::ScintillaGTK(_ScintillaObject *sci_) :
 	im_context(nullptr),
 	lastNonCommonScript(G_UNICODE_SCRIPT_INVALID_CODE),
 	settings(nullptr),
+	settingsHandlerId(0),
 	lastWheelMouseTime(0),
 	lastWheelMouseDirection(0),
 	wheelMouseIntensity(0),
@@ -277,6 +278,9 @@ ScintillaGTK::~ScintillaGTK() {
 	}
 	ClearPrimarySelection();
 	wPreedit.Destroy();
+	if (settingsHandlerId) {
+		g_signal_handler_disconnect(settings, settingsHandlerId);
+	}
 	if (settings) {
 		g_object_unref(settings);
 	}
@@ -357,6 +361,15 @@ void ScintillaGTK::RealizeThis(GtkWidget *widget) {
 	cursor = gdk_cursor_new_for_display(pdisplay, GDK_LEFT_PTR);
 	gdk_window_set_cursor(PWindow(scrollbarh), cursor);
 	UnRefCursor(cursor);
+
+	using NotifyLambda = void (*)(GObject *, GParamSpec *, ScintillaGTK *);
+	if (settings) {
+		settingsHandlerId = g_signal_connect(settings, "notify::gtk-xft-dpi",
+			G_CALLBACK(static_cast<NotifyLambda>([](GObject *, GParamSpec *, ScintillaGTK *sciThis) {
+				sciThis->InvalidateStyleRedraw();
+			})),
+			this);
+	}
 }
 
 void ScintillaGTK::Realize(GtkWidget *widget) {
diff --git a/gtk/ScintillaGTK.h b/gtk/ScintillaGTK.h
index da2f74c90..022471699 100755
--- a/gtk/ScintillaGTK.h
+++ b/gtk/ScintillaGTK.h
@@ -63,6 +63,7 @@ class ScintillaGTK : public ScintillaBase {
 	GUnicodeScript lastNonCommonScript;
 
 	GtkSettings *settings;
+	gulong settingsHandlerId;
 
 	// Wheel mouse support
 	unsigned int linesPerScroll;
-- 
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