Implemention: Base gamma adjustment on the gamma ramps at startup

.gitignore

@@ -45,6 +45,8 @@ src/redshift-gtk/redshift-gtk
 contrib/redshift.spec
 src/redshift
 src/redshift-gtk/__pycache__/
+/data/systemd/redshift.service
+/data/systemd/redshift-gtk.service
 
 # gettext
 /po/POTFILES

DESIGN

@@ -58,7 +58,7 @@ I've been mostly consistent with the naming throughout the source code
 (I hope).
 
 First adjustment methods: There is "randr" which is the preferred
-because it has support for multiple outputs per X screen whic is lacking
+because it has support for multiple outputs per X screen which is lacking
 in "vidmode". Both are APIs in the X server that allow for manipulation
 of gamma ramps, which is what Redshift uses to change the screen color
 temperature. There's also "wingdi" which is for the Windows version,

redshift.1

@@ -60,6 +60,9 @@ One shot mode (do not continuously adjust color temperature)
 \fB\-O\fR TEMP
 One shot manual mode (set color temperature)
 .TP
+\fB\-P\fR
+Preserve current calibrations
+.TP
 \fB\-p\fR
 Print mode (only print parameters and exit)
 .TP
@@ -106,6 +109,9 @@ Screen brightness at night
 \fBgamma\fR = R:G:B
 Gamma adjustment to apply
 .TP
+\fBpreserve-calibrations\fR = 0 or 1
+Disable or enable preservation of currently applied calibrations.
+.TP
 \fBadjustment\-method\fR = name
 Select adjustment method. Options for the adjustment method can be
 given under the configuration file heading of the same name.

src/colorramp.c

@@ -18,6 +18,7 @@
    Copyright (c) 2013  Ingo Thies <[email protected]>
 */
 
+#include <stdlib.h>
 #include <stdint.h>
 #include <math.h>
 
@@ -282,7 +283,8 @@ interpolate_color(float a, const float *c1, const float *c2, float *c)
 
 void
 colorramp_fill(uint16_t *gamma_r, uint16_t *gamma_g, uint16_t *gamma_b,
-	       int size, int temp, float brightness, const float gamma[3])
+	       int size, int temp, float brightness, const float gamma[3],
+	       uint16_t *calib_r, uint16_t *calib_g, uint16_t *calib_b)
 {
 	/* Approximate white point */
 	float white_point[3];
@@ -298,4 +300,34 @@ colorramp_fill(uint16_t *gamma_r, uint16_t *gamma_g, uint16_t *gamma_b,
 		gamma_g[i] = F((float)i/size, 1) * (UINT16_MAX+1);
 		gamma_b[i] = F((float)i/size, 2) * (UINT16_MAX+1);
 	}
+
+	/* Apply gamma ramps used when Redshift started on top of
+	   the effects of Redshift. It would be easier to put
+	   Redshift's effects on top if this, but then calibrations
+	   whould become incorrect. */
+	if (calib_r == NULL)
+		return;
+	uint16_t *calib[3];
+	calib[0] = calib_r;
+	calib[1] = calib_g;
+	calib[2] = calib_b;
+	uint16_t *filter[3];
+	filter[0] = gamma_r;
+	filter[1] = gamma_g;
+	filter[2] = gamma_b;
+	int size_ = size - 1;
+	for (int c = 0; c < 3; c++) {
+		uint16_t *cfilter = filter[c];
+		uint16_t *ccalib = calib[c];
+		for (int i = 0; i < size; i++) {
+			/* We a rounding a bit. We could do linear
+			   interpolation or even (precalculated)
+			   polynomial interpolation, but it is
+			   probably not worth it. */
+			int y = cfilter[i];
+			y = (float)(y * size_) / UINT16_MAX + 0.5;
+			y = y < 0 ? 0 : (y > size_ ? size_ : y);
+			cfilter[i] = ccalib[y];
+		}
+	}
 }

src/colorramp.h

@@ -23,6 +23,7 @@
 #include <stdint.h>
 
 void colorramp_fill(uint16_t *gamma_r, uint16_t *gamma_g, uint16_t *gamma_b,
-		    int size, int temp, float brightness, const float gamma[3]);
+		    int size, int temp, float brightness, const float gamma[3],
+		    uint16_t *calib_r, uint16_t *calib_g, uint16_t *calib_b);
 
 #endif /* ! REDSHIFT_COLORRAMP_H */

src/config-ini.c

@@ -297,3 +297,34 @@ config_ini_get_section(config_ini_state_t *state, const char *name)
 
 	return NULL;
 }
+
+config_ini_section_t **
+config_ini_get_sections(config_ini_state_t *state, const char *name)
+{
+	config_ini_section_t **sections = malloc(1 * sizeof(config_ini_section_t*));
+	if (sections == NULL) {
+		perror("malloc");
+		return NULL;
+	}
+
+	int ptr = 0;
+	config_ini_section_t *section = state->sections;
+	while (section != NULL) {
+		if (strcasecmp(section->name, name) == 0) {
+			sections[ptr++] = section;
+
+			if ((ptr & -ptr) == ptr) {
+				sections = realloc(sections, (ptr << 1) * sizeof(config_ini_section_t*));
+				if (sections == NULL) {
+					perror("realloc");
+					return NULL;
+				}
+			}
+		}
+
+		section = section->next;
+	}
+
+	sections[ptr] = NULL;
+	return sections;
+}

src/config-ini.h

@@ -46,4 +46,7 @@ void config_ini_free(config_ini_state_t *state);
 config_ini_section_t *config_ini_get_section(config_ini_state_t *state,
 					     const char *name);
 
+config_ini_section_t **config_ini_get_sections(config_ini_state_t *state,
+					       const char *name);
+
 #endif /* ! REDSHIFT_CONFIG_INI_H */