Implement xdg_positioner.set_parent_size and set_parent_configure (xdg-shell stable v5) by Copilot · Pull Request #4874 · canonical/mir

Copilot · 2026-04-21T10:46:01Z

xdg_positioner.set_parent_size and set_parent_configure (added in xdg-shell stable protocol v3, required for v5 compliance) were stubbed with TODO warnings. This implements set_parent_size and retains set_parent_configure as a TODO stub pending the necessary infrastructure.

What's new?

set_parent_size: Stores the client's expected parent geometry at popup placement time. Flows through SurfaceSpecification → WindowSpecification → BasicWindowManager, where it replaces parent_scene_surface->content_size() during constrained popup placement in both place_new_surface() and modify_window(). Uses value_or() for a cleaner fallback to the actual parent content size. This fixes popup positioning when a parent is mid-resize.
set_parent_size validation: Non-positive dimensions are now rejected with a ProtocolError(invalid_input), matching the existing set_size() validation pattern.
set_parent_configure: Remains a TODO stub (log_warning) — no unused state is stored. Infrastructure to act on the parent configure serial (e.g. ack_configure on XdgSurfaceStable) is not yet in place.
WindowSpecification::parent_size() accessor added as MirAL 5.8 public API, with corresponding symbols.map and Debian symbols entries.
Unit tests: modify_window_uses_provided_parent_size and place_new_surface_uses_provided_parent_size verify that when parent_size is set on the positioner, anchor clamping uses the provided size rather than the actual surface content_size().

How to test

Use a Wayland client that creates reactive popups tied to a resizing parent window (e.g. a menu anchored to a toolbar that shrinks). With the fix, the popup placement correctly uses the client-provided parent size rather than the stale actual surface size during the resize cycle.

Checklist

Tests added and pass
Adequate documentation added
(optional) Added Screenshots or videos

…le positioner Agent-Logs-Url: https://github.com/canonical/mir/sessions/4669666b-2d76-4fc5-a6c4-49ffa69b0c6d Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Agent-Logs-Url: https://github.com/canonical/mir/sessions/4669666b-2d76-4fc5-a6c4-49ffa69b0c6d Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Agent-Logs-Url: https://github.com/canonical/mir/sessions/26c86e6a-5a56-443f-ad63-fd9c40e17bf3 Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Copilot

Pull request overview

Implements missing xdg-shell stable v5 positioner requests by plumbing xdg_positioner.set_parent_size through Mir’s surface/window specifications into popup placement logic, and capturing set_parent_configure for future synchronization. Also exposes the new parent_size() accessor as a MirAL 5.8 public API (including ABI/symbol updates).

Changes:

Add parent_size to mir::shell::SurfaceSpecification, propagate it through miral::WindowSpecification, and use it in BasicWindowManager popup placement calculations.
Implement xdg_positioner.set_parent_size (store parent size) and set_parent_configure (store configure serial) in the stable xdg-shell frontend.
Extend MirAL ABI metadata (symbols.map, Debian symbols) for WindowSpecification::parent_size().

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`src/server/shell/surface_specification.cpp`	Includes `parent_size` in emptiness/equality/update propagation checks.
`src/server/frontend_wayland/xdg_shell_stable.cpp`	Implements stable-v5 positioner setters for parent size/configure serial.
`src/miral/window_specification_internal.h`	Adds `parent_size` storage to internal `WindowSpecification::Self`.
`src/miral/window_specification_internal.cpp`	Copies `parent_size` into the produced `SurfaceSpecification`.
`src/miral/window_specification.cpp`	Plumbs `parent_size` from `SurfaceSpecification` and adds accessors.
`src/miral/basic_window_manager.cpp`	Uses `parent_size` (if set) instead of parent surface `content_size()` for constrained popup placement.
`src/include/server/mir/shell/surface_specification.h`	Declares `parent_size` in the server-side surface specification.
`include/miral/miral/window_specification.h`	Adds public MirAL 5.8 `WindowSpecification::parent_size()` API.
`src/miral/symbols.map`	Adds new `MIRAL_5.8` symbol version entry for `parent_size()`.
`debian/libmiral7.symbols`	Adds Debian symbols entries for the new MirAL 5.8 API.

AlanGriffiths · 2026-04-21T13:27:32Z

@copilot apply changes based on the comments in this thread

Agent-Logs-Url: https://github.com/canonical/mir/sessions/e051af04-0b25-4293-90f5-97955b7c2e11 Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Copilot · 2026-04-21T13:50:21Z

@copilot apply changes based on the comments in this thread

Done in ca5abde. Applied all three changes from that review thread:

Added input validation for set_parent_size (rejects non-positive dimensions with ProtocolError(invalid_input))
Added modify_window_uses_provided_parent_size unit test
Added place_new_surface_uses_provided_parent_size unit test

Both tests set parent_size = {200, 200} while the actual parent content size is 600x400. They place an aux_rect with its northeast corner at x+260 — within the actual parent but outside the provided parent_size — and verify that constrain_to() clamps the anchor to x+200.

tarek-y-ismail · 2026-04-24T07:55:40Z

+    auto parent_size() -> mir::optional_value<Size>&;
+
+    /// The expected size of the parent window for constrained popup placement.
+    ///
+    /// Set when the compositor should use a specific parent geometry (rather than
+    /// the current parent geometry) to constrain the popup placement. This is used
+    /// when repositioning a popup in response to a parent resize.
+    ///
+    /// \returns the expected parent size
+    /// \remark Since MirAL 5.8
+    auto parent_size() const -> mir::optional_value<Size> const&;


"deducing this" would've allowed us to have only one definition, but it requires the function to be defined in the header, which is a big no-no for miral 🫠

tarek-y-ismail · 2026-04-24T08:06:24Z

+    /// Serial of the parent's xdg_surface configure event this positioner is a response to.
+    /// Stored for popup repositioning synchronization (protocol: xdg_positioner.set_parent_configure).
+    std::optional<uint32_t> parent_configure_serial;



This isn't used anywhere. Is this some set up for future work?

@copilot this needs fixing

Fixed in 84da320 — removed the unused parent_configure_serial field and reverted set_parent_configure to its original TODO/log_warning stub, since there's no infrastructure yet to act on the serial.

…ure to TODO stub Agent-Logs-Url: https://github.com/canonical/mir/sessions/74dbe151-a144-4306-9f7b-745b3208620e Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Copilot AI assigned Copilot and AlanGriffiths Apr 21, 2026

Copilot started work on behalf of AlanGriffiths April 21, 2026 10:46 View session

Copilot AI linked an issue Apr 21, 2026 that may be closed by this pull request

XDG shell stable protocol version 5 implementation incomplete #2865

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Copilot AI changed the title ~~[WIP] Fix incomplete implementation of XDG shell stable protocol version 5~~ Implement xdg_positioner.set_parent_size and set_parent_configure (xdg-shell stable v5) Apr 21, 2026

Copilot finished work on behalf of AlanGriffiths April 21, 2026 11:11

Copilot AI requested a review from AlanGriffiths April 21, 2026 11:11

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Comment thread src/miral/basic_window_manager.cpp Outdated

Copilot started work on behalf of AlanGriffiths April 21, 2026 11:54 View session

AlanGriffiths force-pushed the copilot/fix-xdg-shell-protocol-5-implementation branch from 97fff7d to 9a6c9f1 Compare April 21, 2026 11:56

Copilot finished work on behalf of AlanGriffiths April 21, 2026 11:57

Copilot AI requested a review from AlanGriffiths April 21, 2026 11:57

Copilot AI and others added 3 commits April 21, 2026 14:18

Implement set_parent_size and set_parent_configure for XDG shell stab…

c2b4242

…le positioner Agent-Logs-Url: https://github.com/canonical/mir/sessions/4669666b-2d76-4fc5-a6c4-49ffa69b0c6d Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Add documentation comment to parent_configure_serial field

9d87e93

Agent-Logs-Url: https://github.com/canonical/mir/sessions/4669666b-2d76-4fc5-a6c4-49ffa69b0c6d Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Simplify parent_size lookup using value_or()

20fe301

Agent-Logs-Url: https://github.com/canonical/mir/sessions/26c86e6a-5a56-443f-ad63-fd9c40e17bf3 Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

AlanGriffiths force-pushed the copilot/fix-xdg-shell-protocol-5-implementation branch from ad1207f to 20fe301 Compare April 21, 2026 13:18

AlanGriffiths marked this pull request as ready for review April 21, 2026 13:19

AlanGriffiths requested a review from a team as a code owner April 21, 2026 13:19

Copilot AI review requested due to automatic review settings April 21, 2026 13:19

Copilot started reviewing on behalf of AlanGriffiths April 21, 2026 13:19 View session

Copilot AI reviewed Apr 21, 2026

View reviewed changes

Comment thread src/miral/basic_window_manager.cpp

Comment thread src/miral/basic_window_manager.cpp

Comment thread src/server/frontend_wayland/xdg_shell_stable.cpp

Copilot started work on behalf of AlanGriffiths April 21, 2026 13:27 View session

Add parent_size validation and unit tests for popup placement

ca5abde

Agent-Logs-Url: https://github.com/canonical/mir/sessions/e051af04-0b25-4293-90f5-97955b7c2e11 Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Copilot finished work on behalf of AlanGriffiths April 21, 2026 13:51

AlanGriffiths approved these changes Apr 21, 2026

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tarek-y-ismail requested changes Apr 24, 2026

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Copilot started work on behalf of AlanGriffiths April 30, 2026 13:20 View session

Remove unused parent_configure_serial field; revert set_parent_config…

84da320

…ure to TODO stub Agent-Logs-Url: https://github.com/canonical/mir/sessions/74dbe151-a144-4306-9f7b-745b3208620e Co-authored-by: AlanGriffiths <9048879+AlanGriffiths@users.noreply.github.com>

Copilot finished work on behalf of AlanGriffiths April 30, 2026 13:23

Copilot AI requested a review from AlanGriffiths April 30, 2026 13:23

AlanGriffiths requested a review from tarek-y-ismail April 30, 2026 13:24

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Implement xdg_positioner.set_parent_size and set_parent_configure (xdg-shell stable v5)#4874

Implement xdg_positioner.set_parent_size and set_parent_configure (xdg-shell stable v5)#4874
Copilot wants to merge 5 commits intomainfrom
copilot/fix-xdg-shell-protocol-5-implementation

Copilot AI commented Apr 21, 2026 •

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