Essential parts to implement own Ozone backend
0 likes86 views
This document provides instructions for implementing an Ozone backend using GTK on Chromium. It outlines the key entry points and classes that need to be implemented, including OzonePlatformGtk, GtkOzoneWindow, GtkScreen, and classes for the GPU side like SurfaceFactoryOzone and SurfaceOzoneCanvas. Implementing these classes and interfaces would allow Chromium to draw its content to a GTK window using the new Ozone/GTK backend.
Essential parts to implement own Ozone backend
- 1. Essential parts to implement own Ozone backend Web Engines Hackfest 2021 Maksim Sisov <msisov@iglaia.com>
- 2. What is Ozone (again)? - Abstraction layer beneath the Aura window system. - wrapper for the platform - provides interfaces for everything - Chosen at run time - Many platforms in one binary
- 3. Example: Add Ozone/GTK - Learn by implementing! - Goal: - Add Ozone/Gtk backend that Chromium can draw to. - Steps: - GN: - Entry points: add Ozone/Gtk to GN - Browser side. Implement - OzonePlatform, - PlatformWindow, PlatformScreen. - GPU side. Implement - SurfaceFactoryOzone, - GLOzone (HW accelerated path), SurfaceOzoneCanvas (SW path). - Stub gfx::ClientNativePixmapFactory.
- 5. Ozone and GN - Python script that generates constructor list
- 7. Ozone and GN - Modify //build/config/ozone_extra.gni - Create //ui/ozone/platform/gtk
- 9. Browser side
- 11. OzonePlatformGtk - Functions to implement: - ui::SurfaceFactoryOzone* GetSurfaceFactoryOzone(); - std::unique_ptr<PlatformWindow> CreatePlatformWindow(...); - std::unique_ptr<PlatformScreen> CreateScreen(); - void InitializeUI(const InitParams& params); - void InitializeGPU(const InitParams& params); - const PlatformProperties& GetPlatformProperties(); - All the other virtual functions will return nullptr except: - CursorFactory* GetCursorFactory(); - Will return default cursor factory. - GpuPlatformSupportHost* GetGpuPlatformSupportHost(); - Will return stub. - std::unique_ptr<InputMethod> CreateInputMethod(...); - Wll return default input method.
- 12. GtkOzoneWindow - Important points: - Create native window - gtk_window_new(GTK_WINDOW_TOPLEVEL). - Initialize window and return gfx::AcceleratedWidget for that window - gfx::AcceleratedWidget is a Chromium’s internal representation of widget aka handle for a native window. - X11 => XWindow - Wayland => own counter - Return widget by calling delegate_->OnAcceleratedWidgetAvailable(widget_); - Also: - Implement Show(), SetBounds(), GetBounds() - And add event listeners to get events from server and send to delegate. - All the other pure virtual methods can be left unimplemented.
- 13. GtkScreen - Provide basic implementation that - returns a display for a widget - returns widget at screen point. - For demo, a primary display was hardcoded with the parameters checked from the display settings. The correct solution would be fetching the list of displays as it is done in Ozone/X11/Wayland.
- 14. Are we done?
- 16. GPU side - Implement SurfaceFactoryOzone - returns supported GL implementations (HW acceleration or swiftshader) - They can be -
- 17. GPU side - For demo, we will use SW path instead.
- 18. GPU side - SurfaceOzoneCanvas - Used when HW accelerated path is not available. - Returns SkCanvas where Chromium draws to - When canvas has data written, PresentCanvas is called - When ResizeCanvas is called, SkCanvas becomes invalid. - For GTK, gtk drawing area with cairo image surface was used - - Create gtk frame, - Create drawing area and add to frame - Create cairo image surface - Create SkSurface from cairo image surface - Return SkCanvas from SkSurface - Once PresentCanvas is called - Create cairo region, get gdk drawing context - get cairo context, paint from the cairo image surface into the cairo context
- 19. Are we done now?
- 21. A big picture
- 25. Demo
- 28. Thank you