cursor-shape: add support for server side cursor shapes

This implements support for the new cursor-shape-v1 protocol. When
available, we use it, instead of client-side cursor surfaces, to
select the xcursor shape.

Note that we still need to keep client side pointers, for:

* backward compatibility
* to be able to "hide" the cursor

Closes #1379

CHANGELOG.md

@@ -53,6 +53,10 @@
 * Support for the new fractional-scaling-v1 Wayland protocol. This
   brings true fractional scaling to Wayland in general, and with this
   release, foot.
+* Support for the new `cursor-shape-v1` Wayland protocol, i.e. server
+  side cursor shapes ([#1379][1379]).
+
+[1379]: https://codeberg.org/dnkl/foot/issues/1379
 
 
 ### Changed

cursor-shape-v1.xml

@@ -0,0 +1,147 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="cursor_shape_v1">
+  <copyright>
+    Copyright 2018 The Chromium Authors
+    Copyright 2023 Simon Ser
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <interface name="wp_cursor_shape_manager_v1" version="1">
+    <description summary="cursor shape manager">
+      This global offers an alternative, optional way to set cursor images. This
+      new way uses enumerated cursors instead of a wl_surface like
+      wl_pointer.set_cursor does.
+
+      Warning! The protocol described in this file is currently in the testing
+      phase. Backward compatible changes may be added together with the
+      corresponding interface version bump. Backward incompatible changes can
+      only be done by creating a new major version of the extension.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy the manager">
+        Destroy the cursor shape manager.
+      </description>
+    </request>
+
+    <request name="get_pointer">
+      <description summary="manage the cursor shape of a pointer device">
+        Obtain a wp_cursor_shape_device_v1 for a wl_pointer object.
+      </description>
+      <arg name="cursor_shape_device" type="new_id" interface="wp_cursor_shape_device_v1"/>
+      <arg name="pointer" type="object" interface="wl_pointer"/>
+    </request>
+
+    <request name="get_tablet_tool_v2">
+      <description summary="manage the cursor shape of a tablet tool device">
+        Obtain a wp_cursor_shape_device_v1 for a zwp_tablet_tool_v2 object.
+      </description>
+      <arg name="cursor_shape_device" type="new_id" interface="wp_cursor_shape_device_v1"/>
+      <arg name="tablet_tool" type="object" interface="zwp_tablet_tool_v2"/>
+    </request>
+  </interface>
+
+  <interface name="wp_cursor_shape_device_v1" version="1">
+    <description summary="cursor shape for a device">
+      This interface advertises the list of supported cursor shapes for a
+      device, and allows clients to set the cursor shape.
+    </description>
+
+    <enum name="shape">
+      <description summary="cursor shapes">
+        This enum describes cursor shapes.
+
+        The names are taken from the CSS W3C specification:
+        https://w3c.github.io/csswg-drafts/css-ui/#cursor
+      </description>
+      <entry name="default" value="1" summary="default cursor"/>
+      <entry name="context_menu" value="2" summary="a context menu is available for the object under the cursor"/>
+      <entry name="help" value="3" summary="help is available for the object under the cursor"/>
+      <entry name="pointer" value="4" summary="pointer that indicates a link or another interactive element"/>
+      <entry name="progress" value="5" summary="progress indicator"/>
+      <entry name="wait" value="6" summary="program is busy, user should wait"/>
+      <entry name="cell" value="7" summary="a cell or set of cells may be selected"/>
+      <entry name="crosshair" value="8" summary="simple crosshair"/>
+      <entry name="text" value="9" summary="text may be selected"/>
+      <entry name="vertical_text" value="10" summary="vertical text may be selected"/>
+      <entry name="alias" value="11" summary="drag-and-drop: alias of/shortcut to something is to be created"/>
+      <entry name="copy" value="12" summary="drag-and-drop: something is to be copied"/>
+      <entry name="move" value="13" summary="drag-and-drop: something is to be moved"/>
+      <entry name="no_drop" value="14" summary="drag-and-drop: the dragged item cannot be dropped at the current cursor location"/>
+      <entry name="not_allowed" value="15" summary="drag-and-drop: the requested action will not be carried out"/>
+      <entry name="grab" value="16" summary="drag-and-drop: something can be grabbed"/>
+      <entry name="grabbing" value="17" summary="drag-and-drop: something is being grabbed"/>
+      <entry name="e_resize" value="18" summary="resizing: the east border is to be moved"/>
+      <entry name="n_resize" value="19" summary="resizing: the north border is to be moved"/>
+      <entry name="ne_resize" value="20" summary="resizing: the north-east corner is to be moved"/>
+      <entry name="nw_resize" value="21" summary="resizing: the north-west corner is to be moved"/>
+      <entry name="s_resize" value="22" summary="resizing: the south border is to be moved"/>
+      <entry name="se_resize" value="23" summary="resizing: the south-east corner is to be moved"/>
+      <entry name="sw_resize" value="24" summary="resizing: the south-west corner is to be moved"/>
+      <entry name="w_resize" value="25" summary="resizing: the west border is to be moved"/>
+      <entry name="ew_resize" value="26" summary="resizing: the east and west borders are to be moved"/>
+      <entry name="ns_resize" value="27" summary="resizing: the north and south borders are to be moved"/>
+      <entry name="nesw_resize" value="28" summary="resizing: the north-east and south-west corners are to be moved"/>
+      <entry name="nwse_resize" value="29" summary="resizing: the north-west and south-east corners are to be moved"/>
+      <entry name="col_resize" value="30" summary="resizing: that the item/column can be resized horizontally"/>
+      <entry name="row_resize" value="31" summary="resizing: that the item/row can be resized vertically"/>
+      <entry name="all_scroll" value="32" summary="something can be scrolled in any direction"/>
+      <entry name="zoom_in" value="33" summary="something can be zoomed in"/>
+      <entry name="zoom_out" value="34" summary="something can be zoomed out"/>
+    </enum>
+
+    <enum name="error">
+      <entry name="invalid_shape" value="1"
+        summary="the specified shape value is invalid"/>
+    </enum>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy the cursor shape device">
+        Destroy the cursor shape device.
+
+        The device cursor shape remains unchanged.
+      </description>
+    </request>
+
+    <request name="set_shape">
+      <description summary="set device cursor to the shape">
+        Sets the device cursor to the specified shape. The compositor will
+        change the cursor image based on the specified shape.
+
+        The cursor actually changes only if the input device focus is one of
+        the requesting client's surfaces. If any, the previous cursor image
+        (surface or shape) is replaced.
+
+        The "shape" argument must be a valid enum entry, otherwise the
+        invalid_shape protocol error is raised.
+
+        This is similar to the wl_pointer.set_cursor and
+        zwp_tablet_tool_v2.set_cursor requests, but this request accepts a
+        shape instead of contents in the form of a surface. Clients can mix
+        set_cursor and set_shape requests.
+
+        The serial parameter must match the latest wl_pointer.enter or
+        zwp_tablet_tool_v2.proximity_in serial number sent to the client.
+        Otherwise the request will be ignored.
+      </description>
+      <arg name="serial" type="uint" summary="serial number of the enter event"/>
+      <arg name="shape" type="uint" enum="shape"/>
+    </request>
+  </interface>
+</protocol>

cursor-shape.c

@@ -7,7 +7,7 @@
 const char *
 cursor_shape_to_string(enum cursor_shape shape)
 {
-    static const char *const table[] = {
+    static const char *const table[CURSOR_SHAPE_COUNT] = {
         [CURSOR_SHAPE_NONE] = NULL,
         [CURSOR_SHAPE_HIDDEN] = "hidden",
         [CURSOR_SHAPE_LEFT_PTR] = "left_ptr",
@@ -27,3 +27,26 @@ cursor_shape_to_string(enum cursor_shape shape)
     xassert(shape <= ALEN(table));
     return table[shape];
 }
+
+#if defined(HAVE_CURSOR_SHAPE)
+enum wp_cursor_shape_device_v1_shape
+cursor_shape_to_server_shape(enum cursor_shape shape)
+{
+    static const enum wp_cursor_shape_device_v1_shape table[CURSOR_SHAPE_COUNT] = {
+        [CURSOR_SHAPE_LEFT_PTR] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_DEFAULT,
+        [CURSOR_SHAPE_TEXT] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_TEXT,
+        [CURSOR_SHAPE_TEXT_FALLBACK] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_TEXT,
+        [CURSOR_SHAPE_TOP_LEFT_CORNER] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_NW_RESIZE,
+        [CURSOR_SHAPE_TOP_RIGHT_CORNER] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_NE_RESIZE,
+        [CURSOR_SHAPE_BOTTOM_LEFT_CORNER] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_SW_RESIZE,
+        [CURSOR_SHAPE_BOTTOM_RIGHT_CORNER] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_SE_RESIZE,
+        [CURSOR_SHAPE_LEFT_SIDE] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_W_RESIZE,
+        [CURSOR_SHAPE_RIGHT_SIDE] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_E_RESIZE,
+        [CURSOR_SHAPE_TOP_SIDE] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_N_RESIZE,
+        [CURSOR_SHAPE_BOTTOM_SIDE] = WP_CURSOR_SHAPE_DEVICE_V1_SHAPE_S_RESIZE,
+    };
+
+    xassert(shape <= ALEN(table));
+    return table[shape];
+}
+#endif

cursor-shape.h

@@ -1,10 +1,14 @@
 #pragma once
 
+#if defined(HAVE_CURSOR_SHAPE)
+#include <cursor-shape-v1.h>
+#endif
+
 enum cursor_shape {
     CURSOR_SHAPE_NONE,
     CURSOR_SHAPE_CUSTOM,
-
     CURSOR_SHAPE_HIDDEN,
+
     CURSOR_SHAPE_LEFT_PTR,
     CURSOR_SHAPE_TEXT,
     CURSOR_SHAPE_TEXT_FALLBACK,
@@ -16,6 +20,13 @@ enum cursor_shape {
     CURSOR_SHAPE_RIGHT_SIDE,
     CURSOR_SHAPE_TOP_SIDE,
     CURSOR_SHAPE_BOTTOM_SIDE,
+
+    CURSOR_SHAPE_COUNT,
 };
 
 const char *cursor_shape_to_string(enum cursor_shape shape);
+
+#if defined(HAVE_CURSOR_SHAPE)
+enum wp_cursor_shape_device_v1_shape cursor_shape_to_server_shape(
+    enum cursor_shape shape);
+#endif

meson.build

@@ -170,6 +170,12 @@ else
   fractional_scale = false
 endif
 
+# TODO: check wayland-protocols version
+wl_proto_xml += [wayland_protocols_datadir + '/unstable/tablet/tablet-unstable-v2.xml',  # required by cursor-shape-v1
+                 'cursor-shape-v1.xml',  # TODO: use wayland-protocols
+                ]
+add_project_arguments('-DHAVE_CURSOR_SHAPE', language: 'c')
+
 foreach prot : wl_proto_xml
   wl_proto_headers += custom_target(
     prot.underscorify() + '-client-header',

render.c

@@ -31,6 +31,7 @@
 #include "box-drawing.h"
 #include "char32.h"
 #include "config.h"
+#include "cursor-shape.h"
 #include "grid.h"
 #include "hsl.h"
 #include "ime.h"
@@ -4259,35 +4260,46 @@ render_xcursor_update(struct seat *seat)
     if (seat->pointer.shape == CURSOR_SHAPE_HIDDEN) {
         /* Hide cursor */
         wl_surface_attach(seat->pointer.surface.surf, NULL, 0, 0);
+        wl_pointer_set_cursor(
+            seat->wl_pointer, seat->pointer.serial, seat->pointer.surface.surf,
+            0, 0);
         wl_surface_commit(seat->pointer.surface.surf);
         return;
     }
 
     xassert(seat->pointer.cursor != NULL);
 
-    const float scale = seat->pointer.scale;
+#if defined(HAVE_CURSOR_SHAPE)
-    struct wl_cursor_image *image = seat->pointer.cursor->images[0];
+    if (seat->pointer.shape_device != NULL) {
-    struct wl_buffer *buf = wl_cursor_image_get_buffer(image);
+        wp_cursor_shape_device_v1_set_shape(
+            seat->pointer.shape_device,
+            seat->pointer.serial,
+            cursor_shape_to_server_shape(seat->pointer.shape));
+    } else
+#endif
+    {
+        const int scale = seat->pointer.scale;
+        struct wl_cursor_image *image = seat->pointer.cursor->images[0];
 
-    wayl_surface_scale_explicit_width_height(
+        wl_surface_attach(
-        seat->mouse_focus->window,
+            seat->pointer.surface.surf, wl_cursor_image_get_buffer(image), 0, 0);
-        &seat->pointer.surface, image->width, image->height, scale);
 
-    wl_surface_attach(seat->pointer.surface.surf, buf, 0, 0);
+        wl_pointer_set_cursor(
+            seat->wl_pointer, seat->pointer.serial,
+            seat->pointer.surface.surf,
+            image->hotspot_x / scale, image->hotspot_y / scale);
 
-    wl_pointer_set_cursor(
+        wl_surface_damage_buffer(
-        seat->wl_pointer, seat->pointer.serial,
+            seat->pointer.surface.surf, 0, 0, INT32_MAX, INT32_MAX);
-        seat->pointer.surface.surf,
-        image->hotspot_x / scale, image->hotspot_y / scale);
 
-    wl_surface_damage_buffer(
+        wl_surface_set_buffer_scale(seat->pointer.surface.surf, scale);
-        seat->pointer.surface.surf, 0, 0, INT32_MAX, INT32_MAX);
 
-    xassert(seat->pointer.xcursor_callback == NULL);
+        xassert(seat->pointer.xcursor_callback == NULL);
-    seat->pointer.xcursor_callback = wl_surface_frame(seat->pointer.surface.surf);
+        seat->pointer.xcursor_callback = wl_surface_frame(seat->pointer.surface.surf);
-    wl_callback_add_listener(seat->pointer.xcursor_callback, &xcursor_listener, seat);
+        wl_callback_add_listener(seat->pointer.xcursor_callback, &xcursor_listener, seat);
 
-    wl_surface_commit(seat->pointer.surface.surf);
+        wl_surface_commit(seat->pointer.surface.surf);
+    }
 }
 
 static void
@@ -4452,6 +4464,7 @@ render_xcursor_set(struct seat *seat, struct terminal *term, enum cursor_shape s
     if (seat->pointer.shape == shape)
         return true;
 
+    /* TODO: skip this when using server-side cursors */
     if (shape != CURSOR_SHAPE_HIDDEN) {
         const char *const xcursor = cursor_shape_to_string(shape);
         const char *const fallback =

wayland.c

@@ -14,6 +14,10 @@
 #include <wayland-cursor.h>
 #include <xkbcommon/xkbcommon-compose.h>
 
+#if defined(HAVE_CURSOR_SHAPE)
+#include <cursor-shape-v1.h>
+#endif
+
 #include <tllist.h>
 
 #define LOG_MODULE "wayland"
@@ -209,6 +213,11 @@ seat_destroy(struct seat *seat)
     if (seat->data_device != NULL)
         wl_data_device_release(seat->data_device);
 
+#if defined(HAVE_CURSOR_SHAPE)
+    if (seat->pointer.shape_device != NULL)
+        wp_cursor_shape_device_v1_destroy(seat->pointer.shape_device);
+#endif
+
     if (seat->wl_keyboard != NULL)
         wl_keyboard_release(seat->wl_keyboard);
     if (seat->wl_pointer != NULL)
@@ -316,9 +325,22 @@ seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
 
             seat->wl_pointer = wl_seat_get_pointer(wl_seat);
             wl_pointer_add_listener(seat->wl_pointer, &pointer_listener, seat);
+
+#if defined(HAVE_CURSOR_SHAPE)
+            if (seat->wayl->cursor_shape_manager != NULL) {
+                xassert(seat->pointer.shape_device == NULL);
+                seat->pointer.shape_device = wp_cursor_shape_manager_v1_get_pointer(
+                    seat->wayl->cursor_shape_manager, seat->wl_pointer);
+            }
+#endif
         }
     } else {
         if (seat->wl_pointer != NULL) {
+#if defined(HAVE_CURSOR_SHAPE)
+            wp_cursor_shape_device_v1_destroy(seat->pointer.shape_device);
+            seat->pointer.shape_device = NULL;
+#endif
+
             wl_pointer_release(seat->wl_pointer);
             wl_surface_destroy(seat->pointer.surface.surf);
 
@@ -1167,6 +1189,17 @@ handle_global(void *data, struct wl_registry *registry,
     }
 #endif
 
+#if defined(HAVE_CURSOR_SHAPE)
+    else if (strcmp(interface, wp_cursor_shape_manager_v1_interface.name) == 0) {
+        const uint32_t required = 1;
+        if (!verify_iface_version(interface, version, required))
+            return;
+
+        wayl->cursor_shape_manager = wl_registry_bind(
+            wayl->registry, name, &wp_cursor_shape_manager_v1_interface, required);
+    }
+#endif
+
 #if defined(FOOT_IME_ENABLED) && FOOT_IME_ENABLED
     else if (strcmp(interface, zwp_text_input_manager_v3_interface.name) == 0) {
         const uint32_t required = 1;
@@ -1401,6 +1434,15 @@ wayl_init(struct fdm *fdm, struct key_binding_manager *key_binding_manager,
         LOG_WARN("fractional scaling not available");
     }
 
+#if defined(HAVE_CURSOR_SHAPE)
+    if (wayl->cursor_shape_manager == NULL) {
+#else
+    if (true) {
+#endif
+        LOG_WARN("no server-side cursors available, "
+                 "falling back to client-side cursors");
+    }
+
     if (presentation_timings && wayl->presentation == NULL) {
         LOG_ERR("presentation time interface not implemented by compositor");
         goto out;
@@ -1495,6 +1537,10 @@ wayl_destroy(struct wayland *wayl)
     if (wayl->viewporter != NULL)
         wp_viewporter_destroy(wayl->viewporter);
 #endif
+#if defined(HAVE_CURSOR_SHAPE)
+    if (wayl->cursor_shape_manager != NULL)
+        wp_cursor_shape_manager_v1_destroy(wayl->cursor_shape_manager);
+#endif
 #if defined(HAVE_XDG_ACTIVATION)
     if (wayl->xdg_activation != NULL)
         xdg_activation_v1_destroy(wayl->xdg_activation);

wayland.h

@@ -146,12 +146,18 @@ struct seat {
     struct {
         uint32_t serial;
 
+        /* Client-side cursor */
         struct wayl_surface surface;
         struct wl_cursor_theme *theme;
         struct wl_cursor *cursor;
+
+        /* Server-side cursor */
+#if defined(HAVE_CURSOR_SHAPE)
+        struct wp_cursor_shape_device_v1 *shape_device;
+#endif
+
         float scale;
         bool hidden;
-
         enum cursor_shape shape;
         struct wl_callback *xcursor_callback;
         bool xcursor_pending;
@@ -426,6 +432,10 @@ struct wayland {
     struct xdg_activation_v1 *xdg_activation;
 #endif
 
+#if defined(HAVE_CURSOR_SHAPE)
+    struct wp_cursor_shape_manager_v1 *cursor_shape_manager;
+#endif
+
     bool presentation_timings;
     struct wp_presentation *presentation;
     uint32_t presentation_clock_id;