Linux: CefPrintHandler not used on CEF145 (worked on CEF143/144)

[edgardogho]

Describe the bug
On 145.0.28+g51162e8+chromium-145.0.7632.160 / Chromium 145.0.7632.160 or (beta) 146.0.5+g4db0d88+chromium-146.0.7680.65 / Chromium 146.0.7680.65 the CefPrintHandler is not used.

To Reproduce
Steps to reproduce the behavior:
Put a breakpoint on client_handler.h:

CefRefPtr<CefPrintHandler> GetPrintHandler() override {
    return print_handler_; // breakpoint here
  }

Expected behavior
print_handler_ should be used to handle print events initiated on the browser.

Versions (please complete the following information):

• OS: Linux 64 bits (Ubuntu 24 and others)
• CEF Version: 145 / 146

Additional context
Happens on cefclient and also my own c++ app based on cefclient.

[edgardogho]

On cef_binary_144.0.16+g4231b34+chromium-144.0.7559.231_linux64 the call to GetPrintHandler does happen.
So this seems to have started with 145.

[magreenblatt]

Are you running with --ozone-platform=x11 --disable-features=EnableOopPrintDrivers ?

[edgardogho]

No change. I am using --disable-features=EnableOopPrintDrivers on my app as well and wont call the handler there as well.
Tried on 145 and 146 with --ozone-platform=x11 --disable-features=EnableOopPrintDrivers and combinations of those, no luck.
I am using alloy style. If I dont use alloy style I get the google print dialog. On Alloy style I get a regular linux print dialog, but I can't intercept it with my own print handler.

[edgardogho]

Digging a bit deeper, on branch 7559 (144) on ui/linux/linux_ui.cc, it calls:
PrintingContextLinuxDelegate* PrintingContextLinuxDelegate::instance() {
But on branch 7632 (145) I don't see calls to that instance().

[edgardogho]

I'm trying to troubleshoot this but I can't find where things get broken...
from what I can see, chrome_browser_main_extra_parts_cef.cc is properly doing

 auto printing_delegate = new CefPrintingContextLinuxDelegate();
  auto default_delegate = ui::PrintingContextLinuxDelegate::SetInstance(printing_delegate);
  printing_delegate->SetDefaultDelegate(default_delegate);

when cefclient starts.
This calls set SetInstance on linux_ui.cc, and then properly the SetDefaultDelegate on print_dialog_linux.cc (part of CEF). Up to that point all seems normal I guess.
But then if I go to tests > Print , there is no more calls on print_dialog_linux.cc (so the CefPrintingContextLinuxDelegate is no longer used).

[edgardogho]

I think its related to this:
https://chromium.googlesource.com/chromium/src/+/883ea32a69ca10d15392e0cde3c9d5ef79245e7d
On branch 7559 those print_dialog_linux_factory and portal files did not exist (and worked fine), so I guess the current patch was still valid, but after that it no longer works so the CefPrintingContextLinuxDelegate is no longer used.

[edgardogho]

Not 100% sure, but I think if I patch:
https://chromium.googlesource.com/chromium/src/+/refs/tags/145.0.7632.160/components/printing/common/print_dialog_linux_factory.cc

from:

std::unique_ptr<PrintDialogLinuxInterface>
PrintDialogLinuxFactory::CreatePrintDialog(PrintingContextLinux* context,
                                           bool show_system_dialog) {
#if BUILDFLAG(USE_DBUS)
  if (show_system_dialog &&
      base::FeatureList::IsEnabled(features::kLinuxXdgPrintPortal)) {
    // A fallback dialog will not be created because ShowDialog is never
    // called in the OOP print service.
    return std::make_unique<PrintDialogLinuxPortal>(context);
  }
#endif
  if (auto* linux_ui = ui::LinuxUi::instance()) {
    return linux_ui->CreatePrintDialog(context);
  }
  return nullptr;
}

To:

std::unique_ptr<PrintDialogLinuxInterface>
PrintDialogLinuxFactory::CreatePrintDialog(PrintingContextLinux* context,
                                           bool show_system_dialog) {
/*#if BUILDFLAG(USE_DBUS)
  if (show_system_dialog &&
      base::FeatureList::IsEnabled(features::kLinuxXdgPrintPortal)) {
    // A fallback dialog will not be created because ShowDialog is never
    // called in the OOP print service.
    return std::make_unique<PrintDialogLinuxPortal>(context);
  }
#endif*/
  if (auto* linux_ui = ui::PrintingContextLinuxDelegate::instance()) {
    return linux_ui->CreatePrintDialog(context);
  }
  return nullptr;
}

It works.

[edgardogho]

I rebuilt and applied the following patch and now cefclient and my app are working again with CefPrintHandler

diff --git a/components/printing/common/print_dialog_linux_factory.cc b/components/printing/common/print_dialog_linux_factory.cc
index 30a4d97249..35b1f2a1ff 100644
--- a/components/printing/common/print_dialog_linux_factory.cc
+++ b/components/printing/common/print_dialog_linux_factory.cc
@@ -30,15 +30,15 @@ PrintDialogLinuxFactory::~PrintDialogLinuxFactory() {
 std::unique_ptr<PrintDialogLinuxInterface>
 PrintDialogLinuxFactory::CreatePrintDialog(PrintingContextLinux* context,
                                            bool show_system_dialog) {
-#if BUILDFLAG(USE_DBUS)
+/*#if BUILDFLAG(USE_DBUS)
   if (show_system_dialog &&
       base::FeatureList::IsEnabled(features::kLinuxXdgPrintPortal)) {
     // A fallback dialog will not be created because ShowDialog is never
     // called in the OOP print service.
     return std::make_unique<PrintDialogLinuxPortal>(context);
   }
-#endif
-  if (auto* linux_ui = ui::LinuxUi::instance()) {
+#endif*/
+  if (auto* linux_ui = ui::PrintingContextLinuxDelegate::instance()) {
     return linux_ui->CreatePrintDialog(context);
   }
   return nullptr;

[magreenblatt]

Did you try --disable-features=LinuxXdgPrintPortal ?

[edgardogho]

That seems better than just commenting out the first part...
so.. with this patch:

diff --git a/components/printing/common/print_dialog_linux_factory.cc b/components/printing/common/print_dialog_linux_factory.cc
index 30a4d97249..92ce652a4a 100644
--- a/components/printing/common/print_dialog_linux_factory.cc
+++ b/components/printing/common/print_dialog_linux_factory.cc
@@ -38,7 +38,7 @@ PrintDialogLinuxFactory::CreatePrintDialog(PrintingContextLinux* context,
     return std::make_unique<PrintDialogLinuxPortal>(context);
   }
 #endif
-  if (auto* linux_ui = ui::LinuxUi::instance()) {
+  if (auto* linux_ui = ui::PrintingContextLinuxDelegate::instance()) {
     return linux_ui->CreatePrintDialog(context);
   }
   return nullptr;
@@ -55,7 +55,7 @@ PrintDialogLinuxFactory::CreatePrintDialogForSettings(
     return std::make_unique<PrintDialogLinuxPortal>(context);
   }
 #endif
-  if (auto* linux_ui = ui::LinuxUi::instance()) {
+  if (auto* linux_ui = ui::PrintingContextLinuxDelegate::instance()) {
     return linux_ui->CreatePrintDialog(context);
   }
   return nullptr;

and using --disable-features=LinuxXdgPrintPortal it also uses CefPrintHandler.
I'm not 100% sure about the second part of the patch.. the one for CreatePrintDialogForSettings. I'm not sure when that is used.