Only allow one instance of gsr-ui to run

TODO

@@ -117,4 +117,6 @@ All steam game names by ID are available at https://api.steampowered.com/ISteamA
 
 Dont put widget position to int position when scrolling. This makes the UI jitter when it's coming to a halt.
 
-Show a popup asking if the user wants to add the program to system startup when launching the program, with a dismiss option and "Do not show again".
+Show a popup asking if the user wants to add the program to system startup when launching the program, with a dismiss option and "Do not show again".
+
+Show warning if another instance of gpu screen recorder is already running when starting recording?

include/Process.hpp

@@ -17,6 +17,5 @@ namespace gsr {
     pid_t exec_program(const char **args, int *read_fd);
     // Arguments ending with NULL. Returns the exit status of the program or -1 on error
     int exec_program_get_stdout(const char **args, std::string &result);
-    // |output_buffer| should be at least PATH_MAX in size
-    bool read_cmdline_arg0(const char *filepath, char *output_buffer);
+    pid_t pidof(const char *process_name);
 }

src/Process.cpp

@@ -22,6 +22,15 @@ namespace gsr {
         fprintf(stderr, "\n");
     }
 
+    static bool is_number(const char *str) {
+        for(int i = 0; str[i]; ++i) {
+            char c = str[i];
+            if(c < '0' || c > '9')
+                return false;
+        }
+        return true;
+    }
+
     bool exec_program_daemonized(const char **args) {
         /* 1 argument */
         if(args[0] == nullptr)
@@ -134,7 +143,8 @@ namespace gsr {
         return exit_status;
     }
 
-    bool read_cmdline_arg0(const char *filepath, char *output_buffer) {
+    // |output_buffer| should be at least PATH_MAX in size
+    bool read_cmdline_arg0(const char *filepath, char *output_buffer, int output_buffer_size) {
         output_buffer[0] = '\0';
 
         const char *arg0_end = NULL;
@@ -151,13 +161,40 @@ namespace gsr {
         if(!arg0_end)
             goto err;
 
-        memcpy(output_buffer, buffer, arg0_end - buffer);
-        output_buffer[arg0_end - buffer] = '\0';
-        close(fd);
-        return true;
+        if((arg0_end - buffer) + 1 <= output_buffer_size) {
+            memcpy(output_buffer, buffer, arg0_end - buffer);
+            output_buffer[arg0_end - buffer] = '\0';
+            close(fd);
+            return true;
+        }
 
         err:
         close(fd);
         return false;
     }
+
+    pid_t pidof(const char *process_name) {
+        pid_t result = -1;
+        DIR *dir = opendir("/proc");
+        if(!dir)
+            return -1;
+
+        char cmdline_filepath[PATH_MAX];
+        char arg0[PATH_MAX];
+
+        struct dirent *entry;
+        while((entry = readdir(dir)) != NULL) {
+            if(!is_number(entry->d_name))
+                continue;
+
+            snprintf(cmdline_filepath, sizeof(cmdline_filepath), "/proc/%s/cmdline", entry->d_name);
+            if(read_cmdline_arg0(cmdline_filepath, arg0, sizeof(arg0)) && strcmp(process_name, arg0) == 0) {
+                result = atoi(entry->d_name);
+                break;
+            }
+        }
+
+        closedir(dir);
+        return result;
+    }
 }

src/main.cpp

@@ -4,6 +4,7 @@
 #include "../include/GlobalHotkeysX11.hpp"
 #include "../include/GlobalHotkeysLinux.hpp"
 #include "../include/gui/Utils.hpp"
+#include "../include/Process.hpp"
 
 #include <unistd.h>
 #include <signal.h>
@@ -170,6 +171,13 @@ int main(int argc, char **argv) {
         usage();
     }
 
+    const pid_t gsr_ui_pid = gsr::pidof("gsr-ui");
+    if(gsr_ui_pid != -1) {
+        const char *args[] = { "gsr-notify", "--text", "Another instance of GPU Screen Recorder UI is already running", "--timeout", "5.0", "--icon-color", "ff0000", "--bg-color", "ff0000", nullptr };
+        gsr::exec_program_daemonized(args);
+        return 1;
+    }
+
     // Cant get window texture when prime-run is used
     disable_prime_run();