diff -r ac53ccf25e25 -r 559881c7bf92 pidgin/pidginstyle.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pidgin/pidginstyle.c	Tue Nov 10 01:11:31 2020 -0600
@@ -0,0 +1,72 @@
+/*
+ * Pidgin - Internet Messenger
+ * Copyright (C) Pidgin Developers <devel@pidgin.im>
+ *
+ * Pidgin is the legal property of its developers, whose names are too numerous
+ * to list here.  Please refer to the COPYRIGHT file distributed with this
+ * source distribution.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this library; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "pidgin/pidginstyle.h"
+
+/* Assume light mode */
+static gboolean dark_mode_have_cache = FALSE;
+static gboolean dark_mode_cached_value = FALSE;
+
+gboolean
+pidgin_style_is_dark(GtkStyle *style) {
+	G_GNUC_BEGIN_IGNORE_DEPRECATIONS
+
+	GdkColor bg;
+	gdouble luminance = 0.0;
+
+	if(style == NULL) {
+		if(dark_mode_have_cache) {
+			return dark_mode_cached_value;
+		}
+
+		style = gtk_widget_get_default_style();
+	}
+
+	bg = style->base[GTK_STATE_NORMAL];
+
+	/* magic values are taken from https://en.wikipedia.org/wiki/Luma_(video)
+	 * Rec._601_luma_versus_Rec._709_luma_coefficients.
+	 */
+	luminance = (0.299 * bg.red) + (0.587 * bg.green) + (0.114 * bg.blue);
+
+	G_GNUC_END_IGNORE_DEPRECATIONS
+
+	dark_mode_cached_value = (luminance < 0x7FFF);
+	dark_mode_have_cache = TRUE;
+
+	return dark_mode_cached_value;
+}
+
+void
+pidgin_style_adjust_contrast(GtkStyle *style, GdkRGBA *rgba) {
+	if (pidgin_style_is_dark(style)) {
+		gdouble h, s, v;
+
+		gtk_rgb_to_hsv(rgba->red, rgba->green, rgba->blue, &h, &s, &v);
+
+		v += 0.3;
+		v = v > 1.0 ? 1.0 : v;
+		s = 0.7;
+
+		gtk_hsv_to_rgb(h, s, v, &rgba->red, &rgba->green, &rgba->blue);
+	}
+}