Documented new changes

Rewritten some contributed code

3 files changed, 34 insertions, 28 deletions

diff --git a/README.md b/README.md
index a4ebca3..9963724 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ Options:
   -p, --pretend			do not perform write operations.
   -m, --machine-readable	produce machine-readable output.
   -n, --min-value		set minimum brightness, defaults to 1.
+  -e, --exponent[=K]		changes percentage curve to exponential.
   -s, --save			save previous state in a temporary file.
   -r, --restore			restore previous saved state.
   -h, --help			print this help.
diff --git a/brightnessctl.1 b/brightnessctl.1
index fa798c7..83faf8d 100644
--- a/brightnessctl.1
+++ b/brightnessctl.1
@@ -49,6 +49,16 @@ Set minimum brightness when using delta values, defaults to 1.
 .RE
 
 .sp
+\fB\-e, \-\-exponent\fP=\fIK\fP
+.RS 4
+Changes percentage scaling curve to exponential (linear by default). Default exponent is 4.
+
+Percentage equation: % = \fI[VALUE]\fR^\fI[K]\fR * \fI[MAX]\fR * 100^-\fI[K]\fR.
+
+The exponential curve may make the adjustments perceptually equal.
+.RE
+
+.sp
 \fB\-s, \-\-save\fP
 .RS 4
 Save state in a temporary file.
diff --git a/brightnessctl.c b/brightnessctl.c
index ab87ef3..f46b2bd 100644
--- a/brightnessctl.c
+++ b/brightnessctl.c
@@ -305,46 +305,43 @@ void list_devices(struct device **devs) {
 		print_device(dev);
 }
 
-float val_to_percent(long val,struct device *d) {
-	if (val < 0) return 0;
-	return powf(powf(100,p.exponent)*val/d->max_brightness,1.0f/p.exponent);
+float val_to_percent(long val, struct device *d) {
+	if (val < 0)
+		return 0;
+	return powf(powf(100, p.exponent) * val / d->max_brightness, 1.0f / p.exponent);
 }
 
-unsigned long percent_to_val(float percent,struct device *d) {
-	float r = (powf(percent,p.exponent)*d->max_brightness)*(powf(100,-p.exponent));
-	return r < 0 ? 0 : (unsigned long)r;
+unsigned long percent_to_val(float percent, struct device *d) {
+	float r = (powf(percent, p.exponent) * d->max_brightness) * powf(100, -p.exponent);
+	return (unsigned long) r;
 }
 
 void print_device(struct device *dev) {
-	char *format = p.mach ? "%s,%s,%d,%d%%,%d\n":
+	char *format = p.mach ? "%s,%s,%d,%d%%,%d\n" :
 		"Device '%s' of class '%s':\n\tCurrent brightness: %d (%d%%)\n\tMax brightness: %d\n\n";
 	fprintf(stdout, format,
 		dev->id, dev->class,
 		dev->curr_brightness,
-		(int) val_to_percent(dev->curr_brightness,dev),
+		(int) val_to_percent(dev->curr_brightness, dev),
 		dev->max_brightness);
 }
 
 void apply_value(struct device *d, struct value *val) {
-	long new;
+	long new = d->curr_brightness;
 	if (val->d_type == DIRECT) {
-			if(val->v_type == ABSOLUTE)
-				new = val->val > d->max_brightness ? d->max_brightness : val->val;
-			else 
-				new = percent_to_val(val->val,d);
-	} else {//DELTA
-		if(val->v_type == ABSOLUTE) {
-			new = d->curr_brightness + (val->sign == PLUS ? val->val : -val->val);
-		} else {
-			new = percent_to_val(val_to_percent(d->curr_brightness,d) + ((long)(val->sign == PLUS ? val->val : -val->val)),d);
-			if(new == d->curr_brightness) {
-				if(val->sign == PLUS) 
-					new += 1;
-				else
-					new -= 1;
-			}
-		}
+		new = val->v_type == ABSOLUTE ? val->val : percent_to_val(val->val, d);
+		goto apply;
+	}
+	long mod = val->val;
+	if (val->sign == MINUS)
+		mod *= -1;
+	if (val->v_type == RELATIVE) {
+		mod = percent_to_val(val_to_percent(d->curr_brightness, d) + mod, d) - d->curr_brightness;
+		if (val->val != 0 && mod == 0)
+			mod = val->sign == PLUS ? 1 : -1;
 	}
+	new += mod;
+apply:
 	if (new < p.min)
 		new = p.min;
 	if (new < 0)
@@ -598,9 +595,7 @@ Options:\n\
   -p, --pretend\t\t\tdo not perform write operations.\n\
   -m, --machine-readable\tproduce machine-readable output.\n\
   -n, --min-value\t\tset minimum brightness, defaults to 1.\n\
-  -e, --exponent\t\tchange percent value mapping to polynominal.\n\
-			\t\t\t%%=x^k*max*100^-k, k defaults to 4.\n\
-			\t\t\tTry changing the value until the changes \"feel\" equal.\n\
+  -e, --exponent[=K]\t\tchanges percentage curve to exponential.\n\
   -s, --save\t\t\tsave previous state in a temporary file.\n\
   -r, --restore\t\t\trestore previous saved state.\n\
   -h, --help\t\t\tprint this help.\n\