Got rid of segfault when uploading VBOs.

Added go-to-zero function.
Reworked how work pos is obtained.

grbl_machine.cpp

@@ -1,5 +1,7 @@
 #include <iostream>
 #include <sstream>
+#include <utility>
+#include <array>
 #include "grbl_machine.h"
 #include "string_utils.h"
 
@@ -96,15 +98,29 @@ void grbl::machine::check_program(const grbl::program& pgm) {
     switch_to_state(grbl_machine_state::check_program);
 }
 
-void grbl::machine::run_program(const grbl::program& pgm, std::string work_offset) {
+void grbl::machine::set_work_offset(std::string work_offset) {
+    std::cout << "Setting work offsset " << work_offset << std::endl;
+//    if (state != grbl_machine_state::disconnected) {
+    pipe->send(work_offset);
+//    awaiting_responses++;
+//    while (awaiting_responses > 0);
+
+    current_work_offset = work_offset;
+
+    auto pieces = split_string(parameters[work_offset], ",");
+    current_work_offset_values[0] = std::stof(pieces[0]);
+    current_work_offset_values[1] = std::stof(pieces[1]);
+    current_work_offset_values[2] = std::stof(pieces[2]);
+//    }
+
+}
+
+void grbl::machine::run_program(const grbl::program& pgm, const std::string& work_offset) {
     running_program = pgm;
     std::cout << "running program (" << running_program.filename << ") with " << running_program.number_of_instructions() << " instructions"
               << " on work offset " << work_offset << std::endl;
 
-    // set desired offset
-    while (awaiting_responses > 0);
-    pipe->send(work_offset);
-    while (awaiting_responses > 0);
+    set_work_offset(work_offset);
 
     switch_to_state(grbl_machine_state::run_program);
 }
@@ -576,6 +592,31 @@ void grbl::machine::zero_offset_axis(int offset_index, int axis) {
     listener->on_parameters_reloaded();
 }
 
+void grbl::machine::go_to_zero(bool x, bool y, bool z) {
+    std::string command = "G0";
+    if (x) command += "X0";
+    if (y) command += "Y0";
+    if (z) command += "Z0";
+
+    while (awaiting_responses > 0);
+    pipe->send(command);
+    awaiting_responses++;
+    while (awaiting_responses > 0);
+}
+
+const float *grbl::machine::get_current_work_offset_values() const {
+    return current_work_offset_values;
+}
+
+std::array<float, 3> grbl::machine::get_work_pos() const {
+    std::array<float, 3> result = {
+            last_report.machine_pos[0] - current_work_offset_values[0],
+            last_report.machine_pos[1] - current_work_offset_values[1],
+            last_report.machine_pos[2] - current_work_offset_values[2],
+    };
+    return result;
+}
+
 bool grbl::jog_state::no_jogging() const {
     return !(up_pressed || down_pressed || left_pressed || right_pressed || z_up_pressed || z_down_pressed);
 }