WIP to add a minimal brightness percentage to mate-power-manager

WIP-gpm-min-brightness.patch

diff --git a/data/org.mate.power-manager.gschema.xml.in b/data/org.mate.power-manager.gschema.xml.in
index db0593a..0cbfcf4 100644
--- a/data/org.mate.power-manager.gschema.xml.in
+++ b/data/org.mate.power-manager.gschema.xml.in
@@ -345,5 +345,10 @@
       <summary>When to show the notification icon</summary>
       <description>Display options for the notification icon.</description>
     </key>
+    <key name="brightness-min" type="d">
+      <default>0.0</default>
+      <summary>Minimal LCD brightness</summary>
+      <description>The minimal brightness of the display. Possible values are between 0.0 and 100.0.</description>
+    </key>
   </schema>
 </schemalist>
diff --git a/src/gpm-backlight.c b/src/gpm-backlight.c
index f687a53..fa487ac 100644
--- a/src/gpm-backlight.c
+++ b/src/gpm-backlight.c
@@ -114,7 +114,7 @@ gpm_backlight_get_brightness (GpmBacklight *backlight, guint *brightness, GError
 	}
 
 	/* gets the current brightness */
-	ret = gpm_brightness_get (backlight->priv->brightness, &level);
+	ret = gpm_backlight_brightness_get_internal (backlight->priv->brightness, &level);
 	if (ret) {
 		*brightness = level;
 	} else {
@@ -149,7 +149,7 @@ gpm_backlight_set_brightness (GpmBacklight *backlight, guint percentage, GError
 	backlight->priv->master_percentage = percentage;
 
 	/* sets the current policy brightness */
-	ret = gpm_brightness_set (backlight->priv->brightness, percentage, &hw_changed);
+	ret = gpm_backlight_brightness_set_internal (backlight->priv->brightness, percentage, &hw_changed);
 	if (!ret) {
 		g_set_error_literal (error, gpm_backlight_error_quark (),
 				      GPM_BACKLIGHT_ERROR_GENERAL,
@@ -266,6 +266,34 @@ gpm_common_sum_scale (gfloat value1, gfloat value2, gfloat factor)
 	return value2 + (diff * factor);
 }
 
+/* gets the brightness value converted to the range we expose (min, max) */
+static gboolean
+gpm_backlight_brightness_get_internal (GpmBacklight *backlight, guint *percentage)
+{
+	guint value;
+	if (! gpm_brightness_get (backlight->priv->brightness, &value))
+		return FALSE;
+
+	if (percentage) {
+		gdouble min_brightness = g_settings_get_double (backlight->priv->settings, GPM_SETTINGS_BRIGHTNESS_MIN);
+
+		value = (guint) ((value - min_brightness) * 100 / (100 - min_brightness));
+		*percent = CLAMP (value, 0, 100);
+	}
+
+	return TRUE;
+}
+
+/* sets the brightness value converted from the range we expose (min, max) */
+static gboolean
+gpm_backlight_brightness_set_internal (GpmBacklight *backlight, guint percentage, gboolean *hw_changed)
+{
+	gdouble min_brightness = g_settings_get_double (backlight->priv->settings, GPM_SETTINGS_BRIGHTNESS_MIN);
+	guint value = (guint) (min_brightness + percentage * (100 - min_brightness) / 100);
+
+	return gpm_brightness_set (backlight->priv->brightness, value, hw_changed);
+}
+
 /**
  * gpm_backlight_brightness_evaluate_and_set:
  **/
@@ -343,7 +371,7 @@ gpm_backlight_brightness_evaluate_and_set (GpmBacklight *backlight, gboolean int
 	value = (guint) ((brightness * 100.0f) + 0.5);
 
 	/* only do stuff if the brightness is different */
-	gpm_brightness_get (backlight->priv->brightness, &old_value);
+	gpm_backlight_brightness_get_internal (backlight->priv->brightness, &old_value);
 	if (old_value == value) {
 		g_debug ("values are the same, no action");
 		return FALSE;
@@ -357,7 +385,7 @@ gpm_backlight_brightness_evaluate_and_set (GpmBacklight *backlight, gboolean int
 		gpm_backlight_dialog_show (backlight);
 	}
 
-	ret = gpm_brightness_set (backlight->priv->brightness, value, &hw_changed);
+	ret = gpm_backlight_brightness_set_internal (backlight->priv->brightness, value, &hw_changed);
 	/* we emit a signal for the brightness applet */
 	if (ret && hw_changed) {
 		g_debug ("emitting brightness-changed : %i", value);
@@ -435,11 +463,12 @@ gpm_backlight_button_pressed_cb (GpmButton *button, const gchar *type, GpmBackli
 
 	if (g_strcmp0 (type, GPM_BUTTON_BRIGHT_UP) == 0) {
 		/* go up one step */
+		/* FIXME: */
 		ret = gpm_brightness_up (backlight->priv->brightness, &hw_changed);
 
 		/* show the new value */
 		if (ret) {
-			gpm_brightness_get (backlight->priv->brightness, &percentage);
+			gpm_backlight_brightness_get_internal (backlight->priv->brightness, &percentage);
 			gpm_backlight_dialog_init (backlight);
 			msd_media_keys_window_set_volume_level (MSD_MEDIA_KEYS_WINDOW (backlight->priv->popup),
 								percentage);
@@ -461,11 +490,12 @@ gpm_backlight_button_pressed_cb (GpmButton *button, const gchar *type, GpmBackli
 		}
 	} else if (g_strcmp0 (type, GPM_BUTTON_BRIGHT_DOWN) == 0) {
 		/* go up down step */
+		/* FIXME: */
 		ret = gpm_brightness_down (backlight->priv->brightness, &hw_changed);
 
 		/* show the new value */
 		if (ret) {
-			gpm_brightness_get (backlight->priv->brightness, &percentage);
+			gpm_backlight_brightness_get_internal (backlight->priv->brightness, &percentage);
 			gpm_backlight_dialog_init (backlight);
 			msd_media_keys_window_set_volume_level (MSD_MEDIA_KEYS_WINDOW (backlight->priv->popup),
 								percentage);
diff --git a/src/gpm-common.h b/src/gpm-common.h
index b2b0b1a..1ced3b8 100644
--- a/src/gpm-common.h
+++ b/src/gpm-common.h
@@ -65,6 +65,7 @@ G_BEGIN_DECLS
 #define GPM_SETTINGS_IDLE_DIM_TIME			"idle-dim-time"
 #define GPM_SETTINGS_BRIGHTNESS_AC			"brightness-ac"
 #define GPM_SETTINGS_BRIGHTNESS_DIM_BATT		"brightness-dim-battery"
+#define GPM_SETTINGS_BRIGHTNESS_MIN			"brightness-min"
 
 /* keyboard backlight */
 #define GPM_SETTINGS_KBD_BACKLIGHT_BATT_REDUCE     "kbd-backlight-battery-reduce"