From 035e27150608f577851c0e2ce33065e1f7d4a14f Mon Sep 17 00:00:00 2001
From: "Shih-Yuan Lee (FourDollars)" <fourdollars@gmail.com>
Date: Wed, 26 Apr 2017 16:14:26 +0800
Subject: [PATCH] power: Avoid using zero brightness by settings.

Some PCs still turn off the backlight by zero brightness even when the
maximum brightness level is less than 100.

https://bugzilla.gnome.org/show_bug.cgi?id=782155
---
 ...gnome.settings-daemon.plugins.power.gschema.xml.in.in |  5 +++++
 plugins/power/gsd-backlight-helper.c                     | 16 ++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/data/org.gnome.settings-daemon.plugins.power.gschema.xml.in.in b/data/org.gnome.settings-daemon.plugins.power.gschema.xml.in.in
index 1f87ec7..dcf16c6 100644
--- a/data/org.gnome.settings-daemon.plugins.power.gschema.xml.in.in
+++ b/data/org.gnome.settings-daemon.plugins.power.gschema.xml.in.in
@@ -10,6 +10,11 @@
       <summary>Dim the screen after a period of inactivity</summary>
       <description>If the screen should be dimmed to save power when the computer is idle.</description>
     </key>
+    <key name="no-zero-brightness" type="b">
+      <default>false</default>
+      <summary>No zero brightness</summary>
+      <description>Unconditionally avoid using zero brightness level.</description>
+    </key>
     <key name="sleep-inactive-ac-timeout" type="i">
       <default>0</default>
       <summary>Sleep timeout computer when on AC</summary>
diff --git a/plugins/power/gsd-backlight-helper.c b/plugins/power/gsd-backlight-helper.c
index 00bc263..1064f16 100644
--- a/plugins/power/gsd-backlight-helper.c
+++ b/plugins/power/gsd-backlight-helper.c
@@ -39,6 +39,8 @@
 #define GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER		4
 #define GSD_BACKLIGHT_HELPER_EXIT_CODE_NO_DEVICES		5
 
+#define GSD_POWER_SETTINGS_SCHEMA "org.gnome.settings-daemon.plugins.power"
+
 static gboolean
 gsd_backlight_helper_write (const gchar *filename, gint value, GError **error)
 {
@@ -120,13 +122,15 @@ gsd_backlight_helper_get_max (const gchar *filename, GError **error)
 }
 
 static gint
-clamp_minimum (gint max, gint value)
+clamp_minimum (gint max, gint value, gboolean no_zero_brightness)
 {
 	gint minimum;
 	/* If the interface has less than 100 possible values, it's
 	 * likely that 0 doesn't turn the backlight off so we let 0 be
-	 * set in that case. */
-	if (max > 99)
+	 * set in that case.
+	 *
+	 * Avoid using zero brightness level by settings. */
+	if (max > 99 || no_zero_brightness == TRUE)
 		minimum = 1;
 	else
 		minimum = 0;
@@ -242,6 +246,9 @@ main (int argc, char *argv[])
 	if (set_brightness != -1) {
 		gboolean ret = FALSE;
 		gint max = gsd_backlight_helper_get_max (filename, &error);
+		GSettings *settings = g_settings_new (GSD_POWER_SETTINGS_SCHEMA);
+		gboolean no_zero_brightness = g_settings_get_int (settings,
+								  "no-zero-brightness");
 
 		if (max < 0) {
 			g_print ("%s: %s\n",
@@ -253,7 +260,7 @@ main (int argc, char *argv[])
 		}
 
 		if (type == GSD_BACKLIGHT_TYPE_RAW)
-			set_brightness = clamp_minimum (max, set_brightness);
+			set_brightness = clamp_minimum (max, set_brightness, no_zero_brightness);
 
 		ret = gsd_backlight_helper_write (filename, set_brightness, &error);
 		if (!ret) {
@@ -264,6 +271,7 @@ main (int argc, char *argv[])
 			retval = GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID;
 			goto out;
 		}
+		g_clear_object (&settings);
 	}
 
 	/* success */
-- 
2.7.4