Added a C++ version of raylib's loading thread example.

Author: pkeir

examples/core/core_loading_thread.cpp

@@ -0,0 +1,151 @@
+/*******************************************************************************
+*
+*   raylib example - loading thread
+*
+*   This example has been created using raylib-cpp (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license
+*   (View raylib.h for details)
+*
+*   Copyright (c) 2014-2019 Ramon Santamaria (@raysan5)
+*   Copyright (c) 2021 Paul Keir (University of the West of Scotland)
+*
+*******************************************************************************/
+
+#include "raylib-cpp.hpp"
+#include <thread>                           // C++11 standard library threads
+#include <atomic>                           // C++ atomic data types
+#include <chrono>                           // For: chrono::steady_clock::now()
+#include <system_error>                     // May be thrown by thread c'tor
+
+// Using C++ std::atomic_bool (aka. std::atomic<bool>) for synchronization.
+// n.b. A plain built-in type can't be used for inter-thread synchronization
+std::atomic_bool dataLoaded{false};
+static void LoadDataThread();     // Loading data thread function declaration
+static int dataProgress = 0;      // Data progress accumulator
+
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    raylib::Window window(screenWidth, screenHeight,
+                          "raylib [core] example - loading thread");
+
+    std::thread threadId;         // Loading data thread id
+
+    enum { STATE_WAITING, STATE_LOADING, STATE_FINISHED } state = STATE_WAITING;
+    int framesCounter = 0;
+
+    SetTargetFPS(60);             // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------
+
+    // Main game loop
+    while (!window.ShouldClose()) // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------
+        switch (state)
+        {
+            case STATE_WAITING:
+                if (IsKeyPressed(KEY_ENTER))
+                {
+                    try {
+                        threadId = std::thread(LoadDataThread);
+                        TraceLog(LOG_INFO,
+                            "Loading thread initialized successfully");
+                    } catch (std::system_error e) {
+                        TraceLog(LOG_ERROR, "Error: %s", e.what());
+                    }
+
+                    state = STATE_LOADING;
+                }
+                break;
+
+            case STATE_LOADING:
+                framesCounter++;
+                if (dataLoaded.load())
+                {
+                    framesCounter = 0;
+                    state = STATE_FINISHED;
+                }
+                break;
+
+            case STATE_FINISHED:
+                if (IsKeyPressed(KEY_ENTER))
+                {
+                    // Reset everything to launch again
+                    dataLoaded = false;
+                    dataProgress = 0;
+                    state = STATE_WAITING;
+                }
+                break;
+
+            default:
+              break;
+        }
+        //----------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            switch (state)
+            {
+                case STATE_WAITING:
+                    DrawText("PRESS ENTER to START LOADING DATA",
+                              150, 170, 20, DARKGRAY);
+                    break;
+
+                case STATE_LOADING:
+                    DrawRectangle(150, 200, dataProgress, 60, SKYBLUE);
+                    if ((framesCounter/15)%2)
+                        DrawText("LOADING DATA...", 240, 210, 40, DARKBLUE);
+                    break;
+
+                case STATE_FINISHED:
+                    DrawRectangle(150, 200, 500, 60, LIME);
+                    DrawText("DATA LOADED!", 250, 210, 40, GREEN);
+                    break;
+
+                default:
+                    break;
+            }
+
+            DrawRectangleLines(150, 200, 500, 60, DARKGRAY);
+
+        EndDrawing();
+        //----------------------------------------------------------------------
+    }
+
+    if (threadId.joinable()) // The user might quit without creating a thread.
+      threadId.join();       // Good etiquette, but may take a second.
+
+    return 0;
+}
+
+// Loading data thread function definition
+static void LoadDataThread()
+{
+    using namespace std::chrono;
+    int timeCounter = 0;            // Time counted in ms
+
+    auto prevTime = steady_clock::now();
+
+    // We simulate data loading with a time counter for 5 seconds
+    while (timeCounter < 5000)
+    {
+        auto currentTime = steady_clock::now() - prevTime;
+        timeCounter = duration_cast<milliseconds>(currentTime).count();
+
+        // We accumulate time over a global variable to be used in
+        // main thread as a progress bar
+        dataProgress = timeCounter/10;
+    }
+
+    // When data has finished loading, we set global variable
+    dataLoaded = true;
+}