1. Correct work fullscreen mode for html
2. Mobile touches in browser (relative canvas)
3. Mouse in browser (relative canvas)

html_fullscreen_extension_init() - init extension
it is auto call

html_fullscreen_extension_available() - check extension available for current platform

html_fullscreen() - resize canvas to browser_width, browser_height
usually it's already like that

html_fullscreen_by_width(width) - additional method, adapts the canvas so that the specified width is equal to the specified one, and the height is adaptive
html_fullscreen_by_height(height) - analog for height
html_fullscreen_custom(width, height) - resize canvas

html_fullscreen_touches_raw() - receives touches from the browser
this method can return the same object

html_fullscreen_touches() - analog html_fullscreen_touches_raw, return copy object use this

• Touch Object:

{
  // from js
  "id",
  "xcf", // value from 0 to 1 (x_touch / canvas_width)
  "ycf", // ..
  "xradius",
  "yradius",
  "angle",
  "force",
  //
  "win_x", // xcf * window_get_width(), it's most likely always useless, just use - camera_x + camera_w * xcf
  "win_y", // ..
  "gui_x", // xcf * display_get_gui_width()
  "gui_y", // ..
}

html_fullscreen_touches_count() - count touches

html_fullscreen_mouse_xcf() - value from 0 to 1 (x_mouse / canvas_width, actually it's not quite like that)
html_fullscreen_mouse_ycf() - ..
html_fullscreen_mouse_win_x() - ..
html_fullscreen_mouse_win_y() - ..
html_fullscreen_mouse_gui_x() - ..
html_fullscreen_mouse_gui_y() - ..

I tested this in google and yandex browser on mobile (android) and desktop (windows)