hide cursor on canvas, add mouse focus event, brush preview solid when small

src/main.cpp

@@ -40,6 +40,8 @@ std::condition_variable render_cv;
 int gl_count = 0;
 std::deque<std::packaged_task<void()>> tasklist;
 std::mutex task_mutex;
+std::deque<std::packaged_task<void()>> main_tasklist;
+std::mutex main_task_mutex;
 float timer_stylus = 0;
 float timer_ink_touch = 0;
 float timer_ink_pen = 0;
@@ -67,6 +69,10 @@ std::string GetLastErrorAsString()
 
 void destroy_window()
 {
+    std::lock_guard<std::mutex> lock(main_task_mutex);
+    main_tasklist.emplace_back([=] {
+        SendMessage(hWnd, WM_USER_CLOSE, 0, 0);
+    });
     SendMessage(hWnd, WM_USER_CLOSE, 0, 0);
 }
 
@@ -122,6 +128,14 @@ void async_unlock()
     }
 }
 
+void win32_show_cursor(bool visible)
+{
+    std::lock_guard<std::mutex> lock(main_task_mutex);
+    main_tasklist.emplace_back([=] {
+        ShowCursor(visible);
+    });
+}
+
 std::string win32_open_file(const char* filter)
 {
     OPENFILENAMEA ofn;
@@ -810,6 +824,24 @@ int main(int argc, char** argv)
             TranslateMessage(&msg);
         }
 
+        // list of tasks for the main thread
+        {
+            std::deque<std::packaged_task<void()>> working_list;
+            {
+                std::lock_guard<std::mutex> lock(main_task_mutex);
+                working_list = std::move(main_tasklist);
+            }
+
+            if (!working_list.empty())
+            {
+                while (!working_list.empty())
+                {
+                    working_list.front()();
+                    working_list.pop_front();
+                }
+            }
+        }
+
         if (!tasklist.empty())
             render_cv.notify_all();
     }