[cef] handle all command line args in app

One can provide many arguments already when starting cef_main.
But in principle there is special method in SimpleApp to append
command line arguments when required.

Allows to properly use CEF for both on-screen and off-screen outputs
simulataneousely

Author: linev

gui/cefdisplay/inc/simple_app.h

@@ -81,7 +81,7 @@ class SimpleApp : public CefApp,
 #endif
 
 
-   void StartWindow(THttpServer *serv, const std::string &url, const std::string &cont, CefRect &rect);
+   void StartWindow(THttpServer *serv, const std::string &url, const std::string &cont, CefRect &rect, bool is_headless = false);
 
    // CefRenderProcessHandler methods
    // void OnContextCreated(CefRefPtr<CefBrowser> browser, CefRefPtr<CefFrame> frame,

gui/cefdisplay/src/RCefWebDisplayHandle.cxx

@@ -97,7 +97,7 @@ std::unique_ptr<ROOT::RWebDisplayHandle> RCefWebDisplayHandle::CefCreator::Displ
       CefRect rect((args.GetX() > 0) ? args.GetX() : 0, (args.GetY() > 0) ? args.GetY() : 0,
             (args.GetWidth() > 0) ? args.GetWidth() : 800, (args.GetHeight() > 0) ? args.GetHeight() : 600);
 
-      fCefApp->StartWindow(args.GetHttpServer(), args.GetFullUrl(), args.GetPageContent(), rect);
+      fCefApp->StartWindow(args.GetHttpServer(), args.GetFullUrl(), args.GetPageContent(), rect, args.IsHeadless());
 
       if (args.IsHeadless())
          handle->WaitForContent(wait_tmout, args.GetExtraArgs());
@@ -136,43 +136,18 @@ std::unique_ptr<ROOT::RWebDisplayHandle> RCefWebDisplayHandle::CefCreator::Displ
    bool supress_log = (settings.log_severity == LOGSEVERITY_DISABLE) ||
                       (settings.log_severity == LOGSEVERITY_FATAL);
 
-   TApplication *root_app = gROOT->GetApplication();
-
-   std::vector<const char *> cef_argv = { root_app->Argv(0) };
 
 #ifdef OS_WIN
 
-   CefMainArgs main_args(args.IsHeadless() ? (HINSTANCE) 0 : GetModuleHandle(nullptr));
+   // CefMainArgs main_args(args.IsHeadless() ? (HINSTANCE) 0 : GetModuleHandle(nullptr));
+
+   CefMainArgs main_args(GetModuleHandle(nullptr));
 
 #else
 
-   if (args.IsHeadless()) {
-      cef_argv.emplace_back("--user-data-dir=.");
-      cef_argv.emplace_back("--allow-file-access-from-files");
-      cef_argv.emplace_back("--disable-web-security");
-#ifdef OS_LINUX
-      cef_argv.emplace_back("--disable-gpu");
-      cef_argv.emplace_back("--ignore-gpu-blocklist");
-      cef_argv.emplace_back("--use-gl=swiftshader");
-      cef_argv.emplace_back("--enable-unsafe-swiftshader");
-#endif
-#ifdef OS_MACOSX
-      cef_argv.emplace_back("--use-angle=metal");
-      cef_argv.emplace_back("--ignore-gpu-blocklist");
-      cef_argv.emplace_back("--enable-webgl");
-      cef_argv.emplace_back("--enable-gpu");
-      cef_argv.emplace_back("--enable-gpu-rasterization");
-#endif
-      cef_argv.emplace_back("--off-screen-rendering-enabled");
-      if (use_views)
-         cef_argv.emplace_back("--ozone-platform=headless");
-   } else {
-#ifdef OS_MACOSX
-      cef_argv.emplace_back("--use-angle=metal");
-      cef_argv.emplace_back("--ignore-gpu-blocklist");
-      cef_argv.emplace_back("--enable-webgl");
-#endif
-   }
+   TApplication *root_app = gROOT->GetApplication();
+
+   std::vector<const char *> cef_argv = { root_app->Argv(0) };
 
    if (supress_log) {
       cef_argv.emplace_back("--disable-logging");

gui/cefdisplay/src/simple_app.cxx

@@ -117,7 +117,8 @@ class SimpleBrowserViewDelegate : public CefBrowserViewDelegate {
 SimpleApp::SimpleApp(bool use_viewes, bool supress_log,
                      THttpServer *serv, const std::string &url, const std::string &cont,
                      int width, int height, bool headless)
-   : CefApp(), CefBrowserProcessHandler(), fUseViewes(use_viewes), fSupressLog(supress_log), fFirstServer(serv), fFirstUrl(url), fFirstContent(cont), fFirstHeadless(headless)
+   : CefApp(), CefBrowserProcessHandler(), fUseViewes(use_viewes), fSupressLog(supress_log),
+     fFirstServer(serv), fFirstUrl(url), fFirstContent(cont), fFirstHeadless(headless)
 {
    fFirstRect.Set(0, 0, width, height);
 
@@ -157,18 +158,41 @@ void SimpleApp::OnBeforeCommandLineProcessing(const CefString &process_type, Cef
       command_line->AppendSwitchWithValue("enable-logging", "none");
    }
 
-#ifdef OS_MACOSX
+   if (fNextHeadless) {
+      command_line->AppendSwitchWithValue("user-data-dir", ".");
+      command_line->AppendSwitch("allow-file-access-from-files");
+      command_line->AppendSwitch("disable-web-security");
+      command_line->AppendSwitch("off-screen-rendering-enabled");
+   }
 
+#ifdef OS_MACOSX
    if (fNextHeadless) {
+      command_line->AppendSwitch("headless");
       command_line->AppendSwitchWithValue("use-angle", "swiftshader");
       command_line->AppendSwitch("enable-unsafe-swiftshader");
       command_line->AppendSwitch("disable-gpu");
+      // command_line->AppendSwitch("enable-gpu-rasterization");
+      // if (fUseViewes)
+      //   command_line->AppendSwitchWithValue("ozone-platform", "headless");
    } else {
       command_line->AppendSwitchWithValue("use-angle", "metal");
       command_line->AppendSwitch("ignore-gpu-blocklist");
       command_line->AppendSwitch("enable-webgl");
    }
 #endif
+
+#ifdef OS_LINUX
+   if (fNextHeadless) {
+      command_line->AppendSwitch("headless");
+      command_line->AppendSwitchWithValue("use-gl", "swiftshader");
+      command_line->AppendSwitch("disable-gpu");
+      command_line->AppendSwitch("ignore-gpu-blocklist");
+      command_line->AppendSwitch("enable-unsafe-swiftshader");
+
+      if (fUseViewes)
+         command_line->AppendSwitchWithValue("ozone-platform", "headless");
+   }
+#endif
 }
 
 void SimpleApp::OnBeforeChildProcessLaunch(CefRefPtr<CefCommandLine> command_line)
@@ -180,18 +204,18 @@ void SimpleApp::OnContextInitialized()
    CEF_REQUIRE_UI_THREAD();
 
    if (!fFirstUrl.empty() || !fFirstContent.empty()) {
-      StartWindow(fFirstServer, fFirstUrl, fFirstContent, fFirstRect);
+      StartWindow(fFirstServer, fFirstUrl, fFirstContent, fFirstRect, fFirstHeadless);
       fFirstUrl.clear();
       fFirstContent.clear();
    }
 }
 
 
-void SimpleApp::StartWindow(THttpServer *serv, const std::string &addr, const std::string &cont, CefRect &rect)
+void SimpleApp::StartWindow(THttpServer *serv, const std::string &addr, const std::string &cont, CefRect &rect, bool is_headless)
 {
    CEF_REQUIRE_UI_THREAD();
 
-   bool is_batch = addr.empty() && !cont.empty();
+   bool is_batch = (addr.empty() && !cont.empty()) || is_headless;
 
    if (!fGuiHandler)
       fGuiHandler = new GuiHandler(fUseViewes);