[PATCH wayland-protocols 0/7] xdg-shell: Tooltips revisited and xdg_positioner

[Jonas Ådahl]

Hi,

This is the continuation of the previous patch series meaning to split up
xdg_surface into different per-role interfaces, while making it possible to map
more types of surfaces. It enables using xdg_shell to create tooltips and other
non-grabbing popups, as well as introduces a declarative system for enabling
clients to position its child surfaces (such as menus and popovers) within the
"work area" of the compositor.

Regarding the new popup interface, it should make it possible to use popups for
both grabbing popup chains such as menus with sub menus, as well as tooltips
and non-grabbing popups. The one-popup-chain rule still exists, but one can now
have multiple popups on the same surface. For example it is possible to a
non-grabbing pop over surface, while still showing tooltips on the toplevel
surface.

One currently unsolved stacking related issue is how to avoid newly created
popups being stacked above previous ones. For example a tooltip on a menu item
will stacked under a sub menu surface if the sub menu is created after the
tooltip.

The new positioning API is meant to provide a declarative high level
description of how the compositor should try to position the child surface if
it would overflow outside of some compositor specific "work area" (in the
protocol referred to as "constrained"). With this it should be possible to
describe most if not all common menu positioning semantics out there, with the
possibility to adding more rules later.

With the new API, a client will perform the following operations to map a menu
that is to be expanded right of and below some user interface element (such as
button), flips vertically to the other side of the button if doesn't fit below,
and slides along the x-axis if it would end up outside of the left or right
screen edge:

 toplevel_xdg_surface = xdg_surface of the toplevel surface
 button_rect = surface window geometry relative rectangle of the button widget
 menu_window_rect = window geometry of the menu surface

 /* Create base interfaces. */
 menu_wl_surface = wl_compositor.create_surface()
 menu_xdg_surface = xdg_shell.get_xdg_surface(menu_wl_surface)

 /* Set up positioning description. */
 menu_xdg_positioner = xdg_shell.create_positioner()
 menu_xdg_positioner.set_anchor_rect(button_rect)
 menu_xdg_positioner.set_gravity(gravity_bottom|gravity_right)
 menu_xdg_positioner.set_anchor(anchor_bottom|anchor_right)
 menu_xdg_positioner.set_constrain_action(slide_x|flip_y)

 /* Make it a popup. */
 menu_xdg_popup = xdg_surface.get_popup(menu_xdg_surface,
                                        toplevel_xdg_surface,
                                        menu_xdg_positioner)
 menu_xdg_positioner.destroy()

 /* Set up initial required state. */
 menu_xdg_surface.set_window_geometry(menu_window_rect)
 menu_xdg_popup.grab(seat, serial)

 /* Commit intial state (note now content is attached!). */
 menu_wl_surface.commit()

 ... compositor will given the window geometry and parent surface compute a
     resulting position. ....

 *** received from the compositor: menu_xdg_popup.configure(x, y),
                                   menu_xdg_surface.configure(serial)

 menu_wl_surface.attach(buffer_with_menu_content_drawn_into_it)
 menu_wl_surface.commit()

 .. compositor will map the surface at the previously computer position

The currently unsolved problems with the positioning API is whether it is
within scope to provide wl_subsurface like parent-child state synchronization
capabilities, whether a popup can ever be moved once it has been initially
positioned, and whether to allow the client to move the popup after it has been
positioned (by setting new positioners).

Moving could easily be added in a later revision, but parent-child state
synchronization and whether the compositor is allowed move the popup after it
was initially positioned are probably questions that should be answered up
front.


Jonas



Jonas Ådahl (7):
  xdg-shell: Turn xdg_surface into a generic base interface
  xdg-shell: Put xdg_shell events after requests
  xdg-shell: Add error codes for invalid surface state
  xdg-shell: Improve error enum formatting some
  xdg-shell: Make get_popup take a xdg_surface instead of wl_surface
  xdg-shell: Make xdg_popup non-grabbing by default
  xdg-shell: Introduce xdg_positioner

 unstable/xdg-shell/xdg-shell-unstable-v6.xml | 586 ++++++++++++++++++++-------
 1 file changed, 437 insertions(+), 149 deletions(-)

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2.4.3