Pass OnPaint callback in constructor

This can catch the paint events happened before onload event.

atom/browser/api/atom_api_web_contents.cc

@@ -314,7 +314,8 @@ WebContents::WebContents(v8::Isolate* isolate,
     options.Get("transparent", &transparent);
 
     content::WebContents::CreateParams params(session->browser_context());
-    auto* view = new OffScreenWebContentsView(transparent);
+    auto* view = new OffScreenWebContentsView(
+        transparent, base::Bind(&WebContents::OnPaint, base::Unretained(this)));
     params.view = view;
     params.delegate_view = view;
 
@@ -608,15 +609,8 @@ void WebContents::DidChangeThemeColor(SkColor theme_color) {
 
 void WebContents::DocumentLoadedInFrame(
     content::RenderFrameHost* render_frame_host) {
-  if (!render_frame_host->GetParent()) {
-    if (IsOffScreen()) {
-      auto* rwhv = web_contents()->GetRenderWidgetHostView();
-      static_cast<OffScreenRenderWidgetHostView*>(rwhv)->SetPaintCallback(
-          base::Bind(&WebContents::OnPaint, base::Unretained(this)));
-    }
-
+  if (!render_frame_host->GetParent())
     Emit("dom-ready");
-  }
 }
 
 void WebContents::DidFinishLoad(content::RenderFrameHost* render_frame_host,

atom/browser/osr/osr_render_widget_host_view.cc

@@ -338,15 +338,17 @@ class AtomBeginFrameTimer : public cc::DelayBasedTimeSourceClient {
 
 OffScreenRenderWidgetHostView::OffScreenRenderWidgetHostView(
     bool transparent,
+    const OnPaintCallback& callback,
     content::RenderWidgetHost* host,
     NativeWindow* native_window)
     : render_widget_host_(content::RenderWidgetHostImpl::From(host)),
       native_window_(native_window),
       software_output_device_(nullptr),
+      transparent_(transparent),
+      callback_(callback),
       frame_rate_(60),
       frame_rate_threshold_ms_(0),
       last_time_(base::Time::Now()),
-      transparent_(transparent),
       scale_factor_(kDefaultScaleFactor),
       is_showing_(!render_widget_host_->is_hidden()),
       size_(native_window->GetSize()),
@@ -783,20 +785,13 @@ void OffScreenRenderWidgetHostView::OnSetNeedsBeginFrames(bool enabled) {
   }
 }
 
-void OffScreenRenderWidgetHostView::SetPaintCallback(
-    const OnPaintCallback& callback) {
-  callback_ = callback;
-}
-
 void OffScreenRenderWidgetHostView::OnPaint(
     const gfx::Rect& damage_rect,
     const gfx::Size& bitmap_size,
-    const int pixel_size,
+    int pixel_size,
     void* bitmap_pixels) {
   TRACE_EVENT0("electron", "OffScreenRenderWidgetHostView::OnPaint");
-
-  if (!callback_.is_null())
-    callback_.Run(damage_rect, bitmap_size, pixel_size, bitmap_pixels);
+  callback_.Run(damage_rect, bitmap_size, pixel_size, bitmap_pixels);
 }
 
 void OffScreenRenderWidgetHostView::SetPainting(bool painting) {

atom/browser/osr/osr_render_widget_host_view.h

@@ -63,6 +63,7 @@ class OffScreenRenderWidgetHostView
       public content::DelegatedFrameHostClient {
  public:
   OffScreenRenderWidgetHostView(bool transparent,
+                                const OnPaintCallback& callback,
                                 content::RenderWidgetHost* render_widget_host,
                                 NativeWindow* native_window);
   ~OffScreenRenderWidgetHostView() override;
@@ -189,10 +190,9 @@ class OffScreenRenderWidgetHostView
   void DestroyPlatformWidget();
 #endif
 
-  void SetPaintCallback(const OnPaintCallback& callback);
   void OnPaint(const gfx::Rect& damage_rect,
                const gfx::Size& bitmap_size,
-               const int pixel_size,
+               int pixel_size,
                void* bitmap_pixels);
 
   void SetPainting(bool painting);
@@ -214,6 +214,7 @@ class OffScreenRenderWidgetHostView
   NativeWindow* native_window_;
   OffScreenOutputDevice* software_output_device_;
 
+  const bool transparent_;
   OnPaintCallback callback_;
 
   int frame_rate_;
@@ -221,7 +222,6 @@ class OffScreenRenderWidgetHostView
 
   base::Time last_time_;
 
-  const bool transparent_;
   float scale_factor_;
   bool is_showing_;
   gfx::Vector2dF last_scroll_offset_;

atom/browser/osr/osr_web_contents_view.cc

@@ -6,8 +6,10 @@
 
 namespace atom {
 
-OffScreenWebContentsView::OffScreenWebContentsView(bool transparent)
+OffScreenWebContentsView::OffScreenWebContentsView(
+    bool transparent, const OnPaintCallback& callback)
     : transparent_(transparent),
+      callback_(callback),
       web_contents_(nullptr) {
 }
 
@@ -66,8 +68,8 @@ content::RenderWidgetHostViewBase*
   OffScreenWebContentsView::CreateViewForWidget(
     content::RenderWidgetHost* render_widget_host, bool is_guest_view_hack) {
   auto relay = NativeWindowRelay::FromWebContents(web_contents_);
-  view_ = new OffScreenRenderWidgetHostView(transparent_, render_widget_host,
-                                            relay->window.get());
+  view_ = new OffScreenRenderWidgetHostView(
+      transparent_, callback_, render_widget_host, relay->window.get());
   return view_;
 }
 
@@ -75,8 +77,8 @@ content::RenderWidgetHostViewBase*
   OffScreenWebContentsView::CreateViewForPopupWidget(
     content::RenderWidgetHost* render_widget_host) {
   auto relay = NativeWindowRelay::FromWebContents(web_contents_);
-  view_ = new OffScreenRenderWidgetHostView(transparent_, render_widget_host,
-                                            relay->window.get());
+  view_ = new OffScreenRenderWidgetHostView(
+      transparent_, callback_, render_widget_host, relay->window.get());
   return view_;
 }
 

atom/browser/osr/osr_web_contents_view.h

@@ -15,12 +15,12 @@ namespace atom {
 class OffScreenWebContentsView : public content::WebContentsView,
                                  public content::RenderViewHostDelegateView {
  public:
-  explicit OffScreenWebContentsView(bool transparent);
+  OffScreenWebContentsView(bool transparent, const OnPaintCallback& callback);
   ~OffScreenWebContentsView();
 
   void SetWebContents(content::WebContents*);
 
-  // content::WebContentsView
+  // content::WebContentsView:
   gfx::NativeView GetNativeView() const override;
   gfx::NativeView GetContentNativeView() const override;
   gfx::NativeWindow GetTopLevelNativeWindow() const override;
@@ -62,6 +62,7 @@ class OffScreenWebContentsView : public content::WebContentsView,
 
  private:
   const bool transparent_;
+  OnPaintCallback callback_;
 
   // Weak refs.
   OffScreenRenderWidgetHostView* view_;