output cpp log to c#

Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsExample.cs

  using FontStyle = Unity.UIWidgets.ui.FontStyle;
  using ui_ = Unity.UIWidgets.widgets.ui_;
 
- namespace UIWidgetsSample {
+ using AOT;
+ using System;
+ using System.Runtime.InteropServices;
+
+namespace UIWidgetsSample {
-        
-         
-         protected void OnEnable() {
-             // if you want to use your own font or font icons.
-             // FontManager.instance.addFont(Resources.Load<Font>(path: "path to your font"), "font family name");
+
+        public delegate void LogDelegate(IntPtr message, int iSize);
-             // load custom font with weight & style. The font weight & style corresponds to fontWeight, fontStyle of
-             // a TextStyle object
-             // FontManager.instance.addFont(Resources.Load<Font>(path: "path to your font"), "Roboto", FontWeight.w500,
-             //    FontStyle.italic);
+        [DllImport("libUIWidgets_d.dll")]
+        public static extern void InitCSharpDelegate(LogDelegate log);
-             // add material icons, familyName must be "Material Icons"
-             // FontManager.instance.addFont(Resources.Load<Font>(path: "path to material icons"), "Material Icons");
+        //C# Function for C++'s call
+        [MonoPInvokeCallback(typeof(LogDelegate))]
+        public static void LogMessageFromCpp(IntPtr message, int iSize)
+        {
+            Debug.Log(Marshal.PtrToStringAnsi(message, iSize));
+        }
+
+        protected void OnEnable() {
+            // if you want to use your own font or font icons.
+            // FontManager.instance.addFont(Resources.Load<Font>(path: "path to your font"), "font family name");
+
+            // load custom font with weight & style. The font weight & style corresponds to fontWeight, fontStyle of
+            // a TextStyle object
+            // FontManager.instance.addFont(Resources.Load<Font>(path: "path to your font"), "Roboto", FontWeight.w500,
+            //    FontStyle.italic);
+
+            // add material icons, familyName must be "Material Icons"
+            // FontManager.instance.addFont(Resources.Load<Font>(path: "path to material icons"), "Material Icons");
+
+            // Pass the C# Debug function reference to C++ to save, and then C++ calls C# through the function pointer
+             UIWidgetsExample.InitCSharpDelegate(UIWidgetsExample.LogMessageFromCpp);
 
              base.OnEnable();
          }

engine/src/shell/platform/unity/uiwidgets_panel.cc

 #include "shell/common/switches.h"
 #include "uiwidgets_system.h"
 #include "unity_external_texture_gl.h"
+#include "uiwidgets_log.h"
 
 namespace uiwidgets {
 
 UIWidgetsPanel_onMouseDown(UIWidgetsPanel* panel, float x, float y,
                            int button) {
   panel->OnMouseDown(x, y, button);
+  UnityLog("OnMouseDown");
+  UnityLog("OnMouseUp");
 }
 
 UIWIDGETS_API(void)

engine/src/shell/platform/unity/uiwidgets_log.h

+#include "runtime/mono_api.h"
+
+namespace uiwidgets {
+    //use UnityLog just like printf, and this will output the result to unity
+#define UnityLog(...)   {char log_str[512] = { 0 }; sprintf_s(log_str, __VA_ARGS__); Debug::Log(log_str, strlen(log_str));}
+extern "C"
+{
+    class Debug
+    {
+    public:
+        static void (*Log)(char* message,int iSize);
+    };
+
+    void (*Debug::Log)(char* message, int iSize);
+    // export c++ function interface for c#
+    UIWIDGETS_API(void) InitCSharpDelegate(void (*Log)(char* message, int iSize)){Debug::Log = Log;}
+}
+
+} // namespace uiwidgets