From c3b2fad5e680e600fdee13981c43d342483d5635 Mon Sep 17 00:00:00 2001
From: Michele Calgaro <michele.calgaro@yahoo.it>
Date: Wed, 30 Aug 2023 14:27:52 +0900
Subject: Fix rounding error when setting brightness by percentage

Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>
---
 src/hardware.cpp | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

(limited to 'src/hardware.cpp')

diff --git a/src/hardware.cpp b/src/hardware.cpp
index 25d96dd..ef1ba23 100644
--- a/src/hardware.cpp
+++ b/src/hardware.cpp
@@ -30,6 +30,7 @@
 
 // include global header
 #include <fcntl.h>
+#include <math.h>
 
 // include QT header
 #include <tqtimer.h>
@@ -956,7 +957,6 @@ bool HardwareInfo::setBrightnessPercentage(int percent)
 	if (trace) kdDebug() << funcinfo << "IN: " << " percent: " << percent << endl;
 
 	bool retval = false;
-	int maxBrightness = getMaxBrightnessLevel();
 
 	// Use the first backlight in the list
 	TDEGenericHardwareList hwlist = m_hwdevices->listByDeviceClass(TDEGenericDeviceType::Backlight);
@@ -969,22 +969,24 @@ bool HardwareInfo::setBrightnessPercentage(int percent)
 			checkBrightness();
 		}
 
-		// Make sure percentage is within valid range
-		if (percent < 0) {
-			percent = 0;
-		}
-		else if (percent > 100) {
-			percent = 100;
-		}
-		int level = (int)(maxBrightness * percent / 100.0);
-
 		if (!brightness) {
 			kdError() << "Change brightness not supported " << endl;
-		} else {
+		}
+		else {
+			// Make sure percentage is within valid range
+			if (percent < 0) {
+				percent = 0;
+			}
+			else if (percent > 100) {
+				percent = 100;
+			}
+
+			int level = (int)round(getMaxBrightnessLevel() * percent / 100.0);
 			if (currentBrightnessLevel == level) {
 				kdDebug() << "Brightness level not changed, requested level == current level" << endl;
 				retval = true;
-			} else {
+			}
+			else {
 				backlightdevice->setRawBrightness(level);
 				retval = true;
 			}
@@ -1181,10 +1183,9 @@ bool HardwareInfo::setBrightnessUp(int percentageStep) {
 
 	checkCurrentBrightness();
 
-	if (supportBrightness() && getCurrentBrightnessLevel() < getMaxBrightnessLevel() &&
-			percentageStep > 0)
+	if (supportBrightness() && percentageStep > 0)
 	{
-		int currentPerc = (int)(100.0 * getCurrentBrightnessLevel() / getMaxBrightnessLevel());
+		int currentPerc = (int)round(100.0 * getCurrentBrightnessLevel() / getMaxBrightnessLevel());
 		retval = setBrightnessPercentage(currentPerc + percentageStep);
 	}
 
@@ -1206,8 +1207,8 @@ bool HardwareInfo::setBrightnessDown(int percentageStep) {
 
 	checkCurrentBrightness();
 
-	if (supportBrightness() && getCurrentBrightnessLevel() > 0 && percentageStep > 0) {
-		int currentPerc = (int)(100.0 * getCurrentBrightnessLevel() / getMaxBrightnessLevel());
+	if (supportBrightness() && percentageStep > 0) {
+		int currentPerc = (int)round(100.0 * getCurrentBrightnessLevel() / getMaxBrightnessLevel());
 		retval = setBrightnessPercentage(currentPerc - percentageStep);
 	}
 
@@ -1245,7 +1246,7 @@ bool HardwareInfo::getLidclose() const {
  */
 int HardwareInfo::getMaxBrightnessLevel() const {
 	if (brightness)
-		return availableBrightnessLevels;
+		return availableBrightnessLevels - 1;
 	else
 		return -1;
 }
-- 
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