Implemented callback system with a registration function that manipulates a stack.

Stack access is protected by a mutex. Writes block until mutex is gotten, reads will try again later in event handler.

src/GUI/GUI.cpp

@@ -85,6 +85,22 @@ bool App::OnInit()
     */
     
     // run callback functions during idle on the main frame
+    this->Bind(wxEVT_IDLE, 
+        [this](wxIdleEvent& e) { 
+            std::function<void()> func {nullptr}; // 
+            // try to get the mutex. If we can't, just skip this idle event and get the next one.
+            if (!this->callback_register.try_lock()) return;
+            // pop callback
+            if (cb.size() >= 1) { 
+                func = cb.top();
+                cb.pop();
+            }
+            // unlock mutex
+            this->callback_register.unlock();
+            try { // call the function if it's not nullptr;
+                if (func != nullptr) func();
+            } catch (std::exception& e) { Slic3r::Log::error(LogChannel, LOG_WSTRING("Exception thrown: " <<  e.what())); }
+        });
     /*
     EVT_IDLE($frame, sub {
         while (my $cb = shift @cb) {
@@ -184,4 +200,13 @@ void App::load_presets() {
 */
 }
 
+void App::CallAfter(std::function<void()> cb_function) {
+    // set mutex
+    this->callback_register.lock();
+    // push function onto stack
+    this->cb.emplace(cb_function);
+    // unset mutex
+    this->callback_register.unlock();
+}
+
 }} // namespace Slic3r::GUI

src/GUI/GUI.hpp

@@ -5,10 +5,13 @@
 #include "Notifier.hpp"
 #include <string>
 #include <vector>
+#include <stack>
+#include <mutex>
 
 
 namespace Slic3r { namespace GUI {
 
+
 // Friendly indices for the preset lists.
 enum class PresetID {
     PRINT = 0,
@@ -29,6 +32,11 @@ public:
     /// Move/resize a named TopLevelWindow (includes Frames) from Settings
     void restore_window_pos(wxTopLevelWindow* window, const wxString& name );
 
+    /// Function to add callback functions to the idle loop stack.
+    void CallAfter(std::function<void()> cb_function); 
+
+
+
 private:
     std::shared_ptr<Settings> gui_config; // GUI-specific configuration options
     std::unique_ptr<Notifier> notifier {nullptr};
@@ -37,8 +45,15 @@ private:
     void load_presets();
 
     wxString datadir {""};
-    const std::string LogChannel {"GUI"}; //< Which log these messages should go to.
+    const std::string LogChannel {"APP"}; //< Which log these messages should go to.
+
+    /// Lock to guard the callback stack
+    std::mutex callback_register;
+    
+    /// callbacks registered to run during idle event.
+    std::stack<std::function<void()> > cb {};
 };
 
+
 }} // namespace Slic3r::GUI
 #endif // GUI_HPP