[render] fix flickering on double click with imgui

Author: alemuntoni

vclib/render/include/vclib/bgfx/canvas.h

@@ -179,6 +179,13 @@ class CanvasBGFX
      */
     void onPaint()
     {
+        bgfx::setViewFrameBuffer(mViewId, mFbh);
+        bgfx::touch(mViewId);
+
+        // ask the derived frame to draw all the drawer objects:
+        DerivedRenderApp::CNV::draw(derived());
+        DerivedRenderApp::CNV::postDraw(derived());
+
         const bool newReadRequested =
             (mReadRequest != std::nullopt && !mReadRequest->isSubmitted());
 
@@ -193,20 +200,7 @@ class CanvasBGFX
             }
         }
         else {
-            bgfx::setViewFrameBuffer(mViewId, mFbh);
-            bgfx::touch(mViewId);
-
-            // ask the derived frame to draw all the drawer objects:
-            DerivedRenderApp::CNV::draw(derived());
-
             mCurrFrame = bgfx::frame();
-
-            // this is required only when using Qt in macOS
-#if defined(__APPLE__)
-            bgfx::frame();
-#endif // __APPLE__
-
-            DerivedRenderApp::CNV::postDraw(derived());
         }
 
         if (mReadRequest != std::nullopt) {
@@ -217,6 +211,11 @@ class CanvasBGFX
             // solicit new frame
             derived()->update();
         }
+
+        // this is required only when using Qt in macOS
+#if defined(__APPLE__)
+        bgfx::frame();
+#endif // __APPLE__
     }
 
     /**

vclib/render/include/vclib/bgfx/context.h

@@ -55,8 +55,8 @@ class Context
         bgfx::RendererType::Count;
 
     // singleton
-    static Context*   sInstancePtr;
-    static std::mutex sMutex;
+    inline static Context*   sInstancePtr = nullptr;
+    inline static std::mutex sMutex;
 
 public:
     // default values, used for optional parameters

vclib/render/include/vclib/render/drawers/abstract_viewer_drawer.h

@@ -212,8 +212,9 @@ class AbstractViewerDrawer :
         // viewport
         auto size = DerivedRenderApp::DRW::canvasSize(derived());
 
-        const Point4f vp       = {.0f, .0f, float(size.x()), float(size.y())};
-        auto          callback = [=, this](const ReadData& dt) {
+        const Point4f vp = {.0f, .0f, float(size.x()), float(size.y())};
+
+        auto callback = [=, this](const ReadData& dt) {
             mReadRequested = false;
 
             const auto& data = std::get<FloatData>(dt);

vclib/render/src/vclib/bgfx/context.cpp

@@ -29,9 +29,6 @@
 
 namespace vcl {
 
-Context*   Context::sInstancePtr = nullptr;
-std::mutex Context::sMutex;
-
 void Context::init(void* windowHandle, void* displayHandle)
 {
     std::lock_guard<std::mutex> lock(sMutex);