From 5ff2d136f5603f023e54b33701deab7fae729e5f Mon Sep 17 00:00:00 2001
From: alemuntoni <alemuntoni@users.noreply.github.com>
Date: Thu, 9 Jan 2025 11:35:26 +0100
Subject: [PATCH] [render] add postDraw member function to Drawers

---
 vclib/render/include/vclib/bgfx/canvas.h          | 12 +++++++-----
 .../render/include/vclib/render/concepts/drawer.h |  1 +
 .../include/vclib/render/drawers/plain_drawer.h   |  2 ++
 vclib/render/include/vclib/render/renderer.h      | 15 +++++++++++++++
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/vclib/render/include/vclib/bgfx/canvas.h b/vclib/render/include/vclib/bgfx/canvas.h
index caab25370..007f7881a 100644
--- a/vclib/render/include/vclib/bgfx/canvas.h
+++ b/vclib/render/include/vclib/bgfx/canvas.h
@@ -190,6 +190,13 @@ class CanvasBGFX
         }
         else {
             mCurrFrame = bgfx::frame();
+
+            // this is required only when using Qt in macOS
+#if defined(__APPLE__)
+            bgfx::frame();
+#endif // __APPLE__
+
+            DRT::CNV::postDraw(derived());
         }
 
         if (mReadRequest != std::nullopt) {
@@ -200,11 +207,6 @@ class CanvasBGFX
             // solicit new frame
             derived()->update();
         }
-
-        // this is probably required only when using Qt
-#if defined(__APPLE__) || defined(__linux__)
-        bgfx::frame(); // needed on unix systems
-#endif             // __APPLE__ || __linux__
     }
 
     /**
diff --git a/vclib/render/include/vclib/render/concepts/drawer.h b/vclib/render/include/vclib/render/concepts/drawer.h
index b91afa22c..0dbdbeb2f 100644
--- a/vclib/render/include/vclib/render/concepts/drawer.h
+++ b/vclib/render/include/vclib/render/concepts/drawer.h
@@ -39,6 +39,7 @@ concept DrawerConcept = requires(T&& obj)
         { obj.onResize(uint(), uint()) } -> std::same_as<void>;
         { obj.onDraw(uint()) } -> std::same_as<void>;
         { obj.onDrawContent(uint()) } -> std::same_as<void>;
+        { obj.onPostDraw() } -> std::same_as<void>;
     };
 };
 
diff --git a/vclib/render/include/vclib/render/drawers/plain_drawer.h b/vclib/render/include/vclib/render/drawers/plain_drawer.h
index 3889ba807..3fd07117c 100644
--- a/vclib/render/include/vclib/render/drawers/plain_drawer.h
+++ b/vclib/render/include/vclib/render/drawers/plain_drawer.h
@@ -45,6 +45,8 @@ class PlainDrawer
 
     virtual void onDrawContent(uint viewId) {}
 
+    virtual void onPostDraw() {}
+
 protected:
     auto* derived() { return static_cast<DRT*>(this); }
 
diff --git a/vclib/render/include/vclib/render/renderer.h b/vclib/render/include/vclib/render/renderer.h
index 6b649e02f..f620bb942 100644
--- a/vclib/render/include/vclib/render/renderer.h
+++ b/vclib/render/include/vclib/render/renderer.h
@@ -285,6 +285,14 @@ class Renderer :
          ...);
     }
 
+    void cnvPostDraw()
+    {
+        // call the onPostDraw member function of each Drawer object.
+        // NOTE: use static_cast<Drawers*>(this)->function() to call the
+        // right VIRTUAL function of the Drawer object.
+        (static_cast<Drawers<Renderer>*>(this)->onPostDraw(), ...);
+    }
+
     /***** Member functions called by Drawer objects *****/
     // Documentation is in the Renderer::DRW inner class
 
@@ -528,6 +536,13 @@ class Renderer<WindowManagerT, CanvasT, Drawers...>::CNV
      * `onDrawContent(uint())` function for every Drawer object.
      */
     static void drawContent(Renderer* r) { r->cnvDrawContent(); }
+
+    /**
+     * @brief The CanvasType has finished drawing and has submitted the new
+     * frame, and asks the Renderer to call the `onPostDraw()` function for
+     * every Drawer object.
+     */
+    static void postDraw(Renderer* r) { r->cnvPostDraw(); }
 };
 
 /**