ddcutil support

4 files changed, 241 insertions, 80 deletions

diff --git a/.gitignore b/.gitignore
index 72eb06f..71ba227 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
+.ccls-cache/
 brightness
diff --git a/Makefile b/Makefile
index 8317a0b..8584d48 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
-CC = gcc
-CFLAGS = -Wall -Wextra -O2 -std=c11 -fwrapv
+CXX = g++
+CXXFLAGS = -Wall -Wextra -O2 -std=c++11
 INSTALL_DIR = $(HOME)/prefix/bin
 
 BIN = brightness
@@ -16,5 +16,5 @@ install:
 	sudo chmod +s $(INSTALL_DIR)/brightness
 
 
-$(BIN): brightness.c $(wildcard *.h)
-	$(CC) $(CFLAGS) $(filter %.c,$^) -o $@
+$(BIN): brightness.cpp $(wildcard *.h)
+	$(CXX) $(CXXFLAGS) $(filter %.cpp,$^) -o $@
diff --git a/brightness.c b/brightness.c
deleted file mode 100644
index feee058..0000000
--- a/brightness.c
+++ /dev/null
@@ -1,76 +0,0 @@
-// By Tom Smeding (2016)
-// modified for new laptop (2017)
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdarg.h>
-#include <string.h>
-#include <unistd.h>
-#include <sys/types.h>
-
-#define INCREMENT 100
-
-__attribute__((noreturn))
-__attribute__((format (printf, 1, 2)))
-void die(const char *format,...){
-	va_list ap;
-	va_start(ap,format);
-	vprintf(format,ap);
-	va_end(ap);
-	putchar('\n');
-	exit(1);
-}
-
-int get_max_brightness(void){
-	FILE *f=fopen("/sys/class/backlight/intel_backlight/max_brightness","r");
-	if(!f)die("Could not open max_brightness file");
-	int n;
-	fscanf(f,"%d",&n);
-	fclose(f);
-	return n;
-}
-
-int get_brightness(void){
-	FILE *f=fopen("/sys/class/backlight/intel_backlight/brightness","r");
-	if(!f)die("Could not open brightness file");
-	int n;
-	fscanf(f,"%d",&n);
-	fclose(f);
-	return n;
-}
-
-void set_brightness(int n){
-	FILE *f=fopen("/sys/class/backlight/intel_backlight/brightness","w");
-	if(!f)die("Could not open brightness file");
-	fprintf(f,"%d",n);
-	fflush(f);
-	fclose(f);
-}
-
-int main(int argc,char **argv){
-	uid_t uid=geteuid();
-	if(uid!=0){
-		printf("brightness will only work with root.\n");
-		return 1;
-	}
-
-	if(argc==1){
-		printf("max: %d\n",get_max_brightness());
-		printf("current: %d\n",get_brightness());
-	} else if(argc==2){
-		int n;
-		if(strcmp(argv[1],"-")==0){
-			n=get_brightness()-INCREMENT;
-			if(n<0)n=0;
-		} else if(strcmp(argv[1],"+")==0){
-			n=get_brightness()+INCREMENT;
-			int mx=get_max_brightness();
-			if(n>mx)n=mx;
-		} else {
-			char *endp;
-			n=strtol(argv[1],&endp,10);
-			if(argv[1][0]=='\0'||*endp!='\0')die("Invalid number '%s'",argv[1]);
-		}
-		set_brightness(n);
-	}
-}
diff --git a/brightness.cpp b/brightness.cpp
new file mode 100644
index 0000000..c06427d
--- /dev/null
+++ b/brightness.cpp
@@ -0,0 +1,236 @@
+// By Tom Smeding (2016)
+// modified for new laptop (2017)
+// modified for ddcutil support (2022)
+
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <cstdlib>
+#include <cstdarg>
+#include <cstring>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+std::string read_process(const char *procname, const std::vector<const char*> &args) {
+	int pi[2];
+	int ret = pipe(pi);
+	if (ret != 0) {
+		perror("pipe");
+		exit(1);
+	}
+
+	pid_t pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(1);
+	}
+	if (pid == 0) {
+		dup2(pi[1], 1);
+		close(pi[0]);
+		close(pi[1]);
+		char **argv = new char*[args.size() + 2];
+		argv[0] = strdup(procname);
+		for (size_t i = 0; i < args.size(); i++) {
+			argv[i + 1] = strdup(args[i]);
+		}
+		argv[args.size() + 1] = nullptr;
+		fprintf(stderr, "procname = <%s>\n", procname);
+		for (size_t i = 0; i < args.size() + 2; i++) {
+			fprintf(stderr, "argv[%zu] = <%s>\n", i, argv[i]);
+		}
+		execvp(procname, argv);
+		perror("execvp");
+		exit(1);
+	}
+
+	close(pi[1]);
+	std::string output;
+	while (true) {
+		output.resize(output.size() + 1024);
+		ssize_t nr = read(pi[0], &output[output.size() - 1024], 1024);
+		if (nr < 0) {
+			if (errno == EINTR) continue;
+			perror("read");
+			exit(1);
+		}
+		if (nr == 0) break;
+		output.resize(output.size() - 1024 + nr);
+	}
+	close(pi[0]);
+
+	while (true) {
+		int status;
+		int ret = waitpid(pid, &status, 0);
+		if (ret < 0) {
+			if (errno == EINTR) continue;
+			perror("waitpid");
+			exit(1);
+		}
+		if (WIFEXITED(status)) break;
+	}
+
+	return output;
+}
+
+struct Backlight {
+	virtual ~Backlight() {}
+
+	virtual int increment() const = 0;
+
+	virtual bool suitable() = 0;
+	virtual int get_max_brightness() = 0;
+	virtual int get_brightness() = 0;
+	virtual void set_brightness(int n) = 0;
+	virtual void add_brightness(int n) {
+		n = get_brightness() + n;
+		if (n < 0) n = 0;
+		int maxval = get_max_brightness();
+		if (n > maxval) n = maxval;
+		set_brightness(n);
+	}
+	virtual int convert_absolute_brightness(int n) = 0;  // to percentage
+};
+
+struct IntelBacklight : public Backlight {
+private:
+	int read_int_file(const char *fname) {
+		std::ifstream f{fname};
+		if (!f) {
+			std::cerr << "Could not open brightness file" << std::endl;
+			exit(1);
+		}
+		int n;
+		f >> n;
+		return n;
+	}
+
+public:
+	int increment() const { return 100; }
+
+	bool suitable() {
+		struct stat st;
+		int ret = stat("/sys/class/backlight/intel_backlight", &st);
+		return ret == 0;
+	}
+
+	int get_max_brightness() {
+		return read_int_file("/sys/class/backlight/intel_backlight/max_brightness");
+	}
+
+	int get_brightness() {
+		return read_int_file("/sys/class/backlight/intel_backlight/brightness");
+	}
+
+	void set_brightness(int n) {
+		std::ofstream f{"/sys/class/backlight/intel_backlight/brightness"};
+		if (!f) {
+			std::cerr << "Could not open brightness file" << std::endl;
+			exit(1);
+		}
+		f << n;
+	}
+
+	int convert_absolute_brightness(int n) {
+		return n * 10;
+	}
+};
+
+struct DDCBacklight : public Backlight {
+private:
+	bool have_read = false;
+	int brvalue, brmaxvalue;
+
+	void read_current() {
+		std::string output = read_process("ddcutil", {"getvcp", "-t", "10"});
+		std::istringstream ss{output};
+		std::string word;
+		ss >> word;
+		if (word != "VCP") goto format_err;
+		ss >> word;
+		if (word != "10") goto format_err;
+		ss >> word;
+		if (word != "C") goto format_err;
+		ss >> brvalue;
+		ss >> brmaxvalue;
+		if (!ss) goto format_err;
+		have_read = true;
+		return;
+
+	format_err:
+		std::cerr << "Invalid format from ddcutil" << std::endl;
+		exit(1);
+	}
+
+public:
+	int increment() const { return 10; }
+
+	bool suitable() {
+		struct stat st;
+		int ret = stat("/usr/bin/ddcutil", &st);
+		return ret == 0;
+	}
+
+	int get_brightness() {
+		if (!have_read) read_current();
+		return brvalue;
+	}
+
+	int get_max_brightness() {
+		if (!have_read) read_current();
+		return brmaxvalue;
+	}
+
+	void set_brightness(int n) {
+		std::string argstr = std::to_string(n);
+		read_process("ddcutil", {"setvcp", "10", argstr.data()});
+	}
+
+	void add_brightness(int n) {
+		if (n == 0) return;
+		std::string absargstr = std::to_string(abs(n));
+		read_process("ddcutil", {"setvcp", "10", n > 0 ? "+" : "-", absargstr.data()});
+	}
+
+	int convert_absolute_brightness(int n) {
+		return n;
+	}
+};
+
+int main(int argc,char **argv){
+	uid_t uid = geteuid();
+	if (uid != 0) {
+		std::cerr << "brightness will only work with root." << std::endl;
+		return 1;
+	}
+
+	std::vector<Backlight*> instances{new IntelBacklight{}, new DDCBacklight{}};
+	Backlight *backlight = nullptr;
+	for (Backlight *b : instances) if (b->suitable()) { backlight = b; break; }
+	if (!backlight) {
+		std::cerr << "No idea how to control your monitor, sorry" << std::endl;
+		return 1;
+	}
+
+	if (argc == 1) {
+		std::cout << "max: " << backlight->get_max_brightness() << std::endl;
+		std::cout << "current: " << backlight->get_brightness() << std::endl;
+	} else if (argc == 2) {
+		if (strcmp(argv[1], "-") == 0) {
+			backlight->add_brightness(-backlight->increment());
+		} else if (strcmp(argv[1], "+") == 0) {
+			backlight->add_brightness(backlight->increment());
+		} else {
+			char *endp;
+			int n = strtol(argv[1], &endp, 10);
+			if (argv[1][0] == '\0' || *endp != '\0') {
+				std::cerr << "Invalid number '" << argv[1] << "'" << std::endl;
+			}
+			backlight->set_brightness(backlight->convert_absolute_brightness(n));
+		}
+	}
+}