threaded brush preview rendering

src/node_stroke_preview.cpp

@@ -7,6 +7,21 @@
 #include "canvas.h"
 #include "app.h"
 
+std::atomic_int NodeStrokePreview::s_instances{ 0 };
+std::atomic_bool NodeStrokePreview::s_running{ false };
+std::thread NodeStrokePreview::s_renderer;
+BlockingQueue<NodeStrokePreview*> NodeStrokePreview::s_queue;
+
+void NodeStrokePreview::terminate_renderer()
+{
+    if (s_running && s_renderer.joinable())
+    {
+        s_running = false;
+        s_queue.UnlockGetters();
+        s_renderer.join();
+    }
+}
+
 Node* NodeStrokePreview::clone_instantiate() const
 {
     return new NodeStrokePreview();
@@ -224,7 +239,7 @@ std::vector<NodeStrokePreview::StrokeFrame> NodeStrokePreview::stroke_draw_compu
     return ret;
 }
 
-void NodeStrokePreview::draw_stroke()
+void NodeStrokePreview::draw_stroke_immediate()
 {
     if (m_size.x == 0 || m_size.y == 0)
         return;
@@ -458,6 +473,35 @@ void NodeStrokePreview::draw_stroke()
     glClearColor(cc[0], cc[1], cc[2], cc[3]);
 }
 
+void NodeStrokePreview::draw_stroke()
+{
+    if (m_size.x == 0 || m_size.y == 0)
+        return;
+    s_queue.mutex.lock();
+    if (!s_running)
+    {
+        s_running = true;
+        s_renderer = std::thread([] {
+            while (s_running)
+            {
+                auto node = s_queue.Get();
+                if (node)
+                {
+                    node->async_start();
+                    gl_state gl;
+                    gl.save();
+                    node->draw_stroke_immediate();
+                    gl.restore();
+                    node->async_end();
+                    std::this_thread::sleep_for(std::chrono::milliseconds(30));
+                }
+            }
+        });
+    }
+    s_queue.mutex.unlock();
+    s_queue.PostUnique(this);
+}
+
 void NodeStrokePreview::draw()
 {
     //glEnable(GL_BLEND);