The Chromium code base is composed of architectural layers, with the primary application layers being “content” and “chrome”. The “content” layer includes WebContents as the primary browser object and provides implementations for most of the generic web platform and application/process management functionality. The “chrome” layer includes Browser as the primary browser object and provides implementations for many advanced features including datalist/autofill (issue
#906), extensions (issue #1947), gamepad (issue #1751), webhid (issue #2847), webmidi (issue #1028), async clipboard (issue #2921), input_type=color (issue #899), etc.
For historical reasons CEF browser windows are based on the “content” layer WebContents object. Adding support for additional “chrome” layer features is a serious effort because it involves careful understanding and cherry-picking of the related functionality from “chrome” into the CEF code base. Over time we have added dependencies on the “chrome” layer targets to support some features in CEF (extensions, print preview, etc) and to avoid code duplication. As a result, CEF binaries already contain most/all of the code that would be required to launch a stand-alone “chrome” Browser window.
If we could create a CEF browser window based on the “chrome” Browser object we would get much of the “chrome” layer functionality “for free”. To be usable in CEF the “chrome” window would need to support a subset of existing CEF callbacks/intercepts (e.g. loading progress, network requests, etc.), and be inserted into the existing Views framework structure (issue
#1749). The “chrome” window would not support off-screen rendering, though parenting to a native (non-Views) window should be possible and likely required on macOS.
Given the above, the scope for this issue is to identify the subset of “chrome” initialization code that is required to launch and embed a Views-based Browser window object, and then hook up a TBD minimum subset of existing CEF callbacks to work with that object. MVP is an off-by-default option to create “chrome”-based browsers in cefclient/cefsimple. These browsers will initially contain many chrome-specific UI features (shortcut keys, dialogs, etc.) that might not be desired in release-quality client applications. Additional callback functionality and behavioral tweaks may be added over time as needed/appropriate.