[gnome-power-manager] Use the correct backlight step value when using the legacy fallback device

[Richard Hughes <rhughes src gnome org>]

commit 7eb15d541a4e5071d2916342c83c3ceeaacb3d60
Author: Will Woods <wwoods redhat com>
Date:   Tue Aug 31 13:36:03 2010 +0100

    Use the correct backlight step value when using the legacy fallback device
    
    The 'legacy fallback' backlight handling code in gnome-power-manager
    increments/decrements the backlight value by one whenever the brightness
    buttons are pressed.
    
    On systems like the Apple MacBook, where the backlight has upwards of 1024
    brightness levels, this doesn't work.
    
    The attached patch uses the gpm_brightness_get_step function (like the
    xrandr-based code does) to properly step the backlight value.
    
    Signed-off-by: Richard Hughes <richard hughsie com>

 src/gpm-brightness.c |   26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)
---
diff --git a/src/gpm-brightness.c b/src/gpm-brightness.c
index bff3411..231a065 100644
--- a/src/gpm-brightness.c
+++ b/src/gpm-brightness.c
@@ -675,6 +675,7 @@ gboolean
 gpm_brightness_up (GpmBrightness *brightness, gboolean *hw_changed)
 {
 	gboolean ret = FALSE;
+	guint step;
 
 	g_return_val_if_fail (GPM_IS_BRIGHTNESS (brightness), FALSE);
 
@@ -695,8 +696,15 @@ gpm_brightness_up (GpmBrightness *brightness, gboolean *hw_changed)
 		if (brightness->priv->extension_levels < 0)
 			brightness->priv->extension_levels = gpm_brightness_helper_get_value ("get-max-brightness");
 		brightness->priv->extension_current = gpm_brightness_helper_get_value ("get-brightness");
-		if (brightness->priv->extension_current < brightness->priv->extension_levels)
-			ret = gpm_brightness_helper_set_value ("set-brightness", ++brightness->priv->extension_current);
+
+		/* increase by the step, limiting to the maximum possible levels */
+		if (brightness->priv->extension_current < brightness->priv->extension_levels) {
+			step = gpm_brightness_get_step (brightness->priv->extension_levels);
+			brightness->priv->extension_current += step;
+			if (brightness->priv->extension_current > brightness->priv->extension_levels)
+				brightness->priv->extension_current = brightness->priv->extension_levels;
+			ret = gpm_brightness_helper_set_value ("set-brightness", brightness->priv->extension_current);
+		}
 		if (hw_changed != NULL)
 			*hw_changed = ret;
 		brightness->priv->cache_trusted = FALSE;
@@ -718,6 +726,7 @@ gboolean
 gpm_brightness_down (GpmBrightness *brightness, gboolean *hw_changed)
 {
 	gboolean ret = FALSE;
+	guint step;
 
 	g_return_val_if_fail (GPM_IS_BRIGHTNESS (brightness), FALSE);
 
@@ -735,9 +744,18 @@ gpm_brightness_down (GpmBrightness *brightness, gboolean *hw_changed)
 
 	/* legacy fallback */
 	if (!ret) {
+		if (brightness->priv->extension_levels < 0)
+			brightness->priv->extension_levels = gpm_brightness_helper_get_value ("get-max-brightness");
 		brightness->priv->extension_current = gpm_brightness_helper_get_value ("get-brightness");
-		if (brightness->priv->extension_current > 0)
-			ret = gpm_brightness_helper_set_value ("set-brightness", --brightness->priv->extension_current);
+
+		/* decrease by the step, limiting to zero */
+		if (brightness->priv->extension_current > 0) {
+			step = gpm_brightness_get_step (brightness->priv->extension_levels);
+			brightness->priv->extension_current -= step;
+			if (brightness->priv->extension_current < 0)
+				brightness->priv->extension_current = 0;
+			ret = gpm_brightness_helper_set_value ("set-brightness", brightness->priv->extension_current);
+		}
 		if (hw_changed != NULL)
 			*hw_changed = ret;
 		brightness->priv->cache_trusted = FALSE;