Implement xrdb reading without popen

Avoid using the shell, awk and cut command

src/main.c

@@ -7,7 +7,7 @@
   #include <windows.h>
 #elif __linux__
   #include <unistd.h>
-  #include <stdlib.h>
+  #include "xrdb_parse.h"
 #elif __APPLE__
   #include <mach-o/dyld.h>
 #endif
@@ -15,40 +15,17 @@
 
 SDL_Window *window;
 
-
 static double get_scale(void) {
+#if _WIN32
   float dpi;
   SDL_GetDisplayDPI(0, NULL, &dpi, NULL);
-#if _WIN32
   return dpi / 96.0;
 #elif __linux__
-  FILE *stream;
-  char *xrdb = "xrdb -query | grep dpi | cut -f 2";
-
-  // In case something goes wrong in popen (e.g., fork or exec calls) or any
-  // other calls listed below we return the dpi equal to 1.
-  if ((stream = popen(xrdb, "r")) == NULL)
-    return 1.0;
-
-  char *line = NULL;
-  size_t buffer = 0;
-  ssize_t length = getline(&line, &buffer, stream);
-
-  if (length == -1) {
-    free(line);
-    pclose(stream);
-    return 1.0;
+  int xft_dpi = xrdb_find_dpi();
+  if (xft_dpi > 0) {
+    return xft_dpi / 96.0;
   }
-
-  if (pclose(stream)) {
-    free(line);
-    return 1.0;
-  }
-
-  dpi = strtol(line, NULL, 10) / 96.0;
-  free(line);
-
-  return dpi;
+  return 1.0;
 #else
   return 1.0;
 #endif