Refactor xcomposite into abstract capture api

Refactor c++ files into c files, more usable

include/library_loader.h

@@ -0,0 +1,41 @@
+#ifndef GSR_LIBRARY_LOADER_H
+#define GSR_LIBRARY_LOADER_H
+
+#include <dlfcn.h>
+#include <stdio.h>
+
+typedef struct {
+    void **func;
+    const char *name;
+} dlsym_assign;
+
+static void* dlsym_print_fail(void *handle, const char *name, bool required) {
+    dlerror();
+    void *sym = dlsym(handle, name);
+    char *err_str = dlerror();
+
+    if(!sym)
+        fprintf(stderr, "%s: dlsym(handle, \"%s\") failed, error: %s\n", required ? "error" : "warning", name, err_str ? err_str : "(null)");
+
+    return sym;
+}
+
+/* |dlsyms| should be null terminated */
+static bool dlsym_load_list(void *handle, const dlsym_assign *dlsyms) {
+    bool success = true;
+    for(int i = 0; dlsyms[i].func; ++i) {
+        *dlsyms[i].func = dlsym_print_fail(handle, dlsyms[i].name, true);
+        if(!*dlsyms[i].func)
+            success = false;
+    }
+    return success;
+}
+
+/* |dlsyms| should be null terminated */
+static void dlsym_load_list_optional(void *handle, const dlsym_assign *dlsyms) {
+    for(int i = 0; dlsyms[i].func; ++i) {
+        *dlsyms[i].func = dlsym_print_fail(handle, dlsyms[i].name, false);
+    }
+}
+
+#endif /* GSR_LIBRARY_LOADER_H */