patch 8.1.0249: GTK: when screen DPI changes Vim does not handle it

Problem:    GTK: when screen DPI changes Vim does not handle it.
Solution:   Handle the gtk-xft-dpi signal. (Roel van de Kraats,
            closes #2357)

src/gui_gtk_x11.c

@@ -788,6 +788,29 @@ property_event(GtkWidget *widget,
 }
 #endif /* defined(FEAT_CLIENTSERVER) */
 
+/*
+ * Handle changes to the "Xft/DPI" setting
+ */
+    static void
+gtk_settings_xft_dpi_changed_cb(GtkSettings *gtk_settings UNUSED,
+                                GParamSpec *pspec UNUSED,
+                                gpointer data UNUSED)
+{
+    // Create a new PangoContext for this screen, and initialize it
+    // with the current font if necessary.
+    if (gui.text_context != NULL)
+	g_object_unref(gui.text_context);
+
+    gui.text_context = gtk_widget_create_pango_context(gui.mainwin);
+    pango_context_set_base_dir(gui.text_context, PANGO_DIRECTION_LTR);
+
+    if (gui.norm_font != NULL)
+    {
+	// force default font
+	gui_mch_init_font(*p_guifont == NUL ? NULL : p_guifont, FALSE);
+	gui_set_shellsize(TRUE, FALSE, RESIZE_BOTH);
+    }
+}
 
 #if GTK_CHECK_VERSION(3,0,0)
 typedef gboolean timeout_cb_type;
@@ -4383,6 +4406,15 @@ gui_mch_init(void)
     /* Pretend we don't have input focus, we will get an event if we do. */
     gui.in_focus = FALSE;
 
+    // Handle changes to the "Xft/DPI" setting.
+    {
+	GtkSettings *gtk_settings =
+			 gtk_settings_get_for_screen(gdk_screen_get_default());
+
+	g_signal_connect(gtk_settings, "notify::gtk-xft-dpi",
+			   G_CALLBACK(gtk_settings_xft_dpi_changed_cb), NULL);
+    }
+
     return OK;
 }
 

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    249,
 /**/
     248,
 /**/