--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/pidgin/pidginstylecontext.c Mon Jan 11 00:20:09 2021 -0600
@@ -0,0 +1,76 @@
+/*
+ * 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/pidginstylecontext.h"
+
+/* Assume light mode */
+static gboolean dark_mode_have_cache = FALSE;
+static gboolean dark_mode_cached_value = FALSE;
+
+/******************************************************************************
+ * Public API
+ *****************************************************************************/
+gboolean
+pidgin_style_context_is_dark(GtkStyleContext *context) {
+ GdkRGBA bg;
+ gdouble luminance = 0.0;
+
+ if(context == NULL) {
+ if(dark_mode_have_cache) {
+ return dark_mode_cached_value;
+ }
+
+ context = gtk_style_context_new();
+ } else {
+ g_object_ref(G_OBJECT(context));
+ }
+
+ gtk_style_context_get(context, GTK_STATE_FLAG_NORMAL,
+ GTK_STYLE_PROPERTY_BACKGROUND_COLOR, &bg,
+ NULL);
+ g_object_unref(G_OBJECT(context));
+
+ /* 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);
+
+ dark_mode_cached_value = (luminance < 0x7FFF);
+ dark_mode_have_cache = TRUE;
+
+ return dark_mode_cached_value;
+}
+
+void
+pidgin_style_context_adjust_contrast(GtkStyleContext *context, GdkRGBA *rgba) {
+ if(pidgin_style_context_is_dark(context)) {
+ 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);
+ }
+}