Fixed sigsev caused by modifying UI from outside the UI thread.

WIP on jogging layout.

main.cpp

@@ -167,6 +167,34 @@ public:
             cnc.go_to_zero(true, true, true);
         });
 
+        // jogging
+        layer->add<Label>("Jogging", "sans-bold", 20);
+        auto holder = new Widget(layer);
+
+        holder->set_layout(new GridLayout(Orientation::Horizontal, 2, Alignment::Middle, 0, 0));
+
+        auto jogBtnsHolder = holder->add<Widget>();
+        jogBtnsHolder->set_layout(new GridLayout(Orientation::Horizontal, 3, Alignment::Middle, 0, 6));
+
+        jogBtnsHolder->add<Label>("");
+        jogBtnsHolder->add<ToolButton>(FA_ARROW_ALT_CIRCLE_UP);
+        jogBtnsHolder->add<Label>("");
+
+        jogBtnsHolder->add<ToolButton>(FA_ARROW_ALT_CIRCLE_LEFT);
+        jogBtnsHolder->add<ToolButton>(FA_HOME);
+        jogBtnsHolder->add<ToolButton>(FA_ARROW_ALT_CIRCLE_RIGHT);
+
+        jogBtnsHolder->add<Label>("");
+        jogBtnsHolder->add<ToolButton>(FA_ARROW_ALT_CIRCLE_DOWN);
+        jogBtnsHolder->add<Label>("");
+
+        auto jogZBtnsHolder = holder->add<Widget>();
+        jogZBtnsHolder->set_layout(new BoxLayout(Orientation::Vertical, Alignment::Minimum, 0, 6));
+
+        jogZBtnsHolder->add<ToolButton>(FA_ANGLE_UP);
+        jogZBtnsHolder->add<ToolButton>(FA_HOME);
+        jogZBtnsHolder->add<ToolButton>(FA_ANGLE_DOWN);
+
         // work parameters
         layer->add<Label>("Work parameters", "sans-bold", 20);
         auto x = new Widget(layer);
@@ -359,11 +387,11 @@ public:
 
     grbl::realtime_status_report last_report;
 
+    volatile bool machine_initialized = false;
+
     void on_init_completed() override {
-        fill_in_settings();
-        fill_in_parameters();
-        refresh_offset();
-        update_dro();
+        machine_initialized = true;
+        // need to do UI related things in UI thread
     }
 
     void on_realtime_status_report(grbl::realtime_status_report report) override {
@@ -555,6 +583,20 @@ public:
         }
     }
 
+    void draw(NVGcontext *ctx) override {
+        // not pretty but need to do this in UI thread
+        if (machine_initialized) {
+            fill_in_settings();
+            fill_in_parameters();
+
+            refresh_offset();
+            update_dro();
+            machine_initialized = false;
+        }
+
+        Widget::draw(ctx);
+    }
+
     virtual void draw_contents() {
         auto fb_size = framebuffer_size();