Add support for background blur

This patch adds a new config option: colors{,2}.blur=no|yes. When
enabled, transparent background are also blurred.

Note that this requires the brand new ext-background-effect-v1
protocol, and specifically, that the compositor implements the blur
effect.

CHANGELOG.md

@@ -78,6 +78,12 @@
 * `[colors-light]` section to `foot.ini`. Replaces `[colors2]`.
 * `XTGETTCAP`: added `query-os-name`, returning the OS foot is
   compiled for (e.g. _'Linux'_) ([#2209][2209]).
+* Preliminary (untested) support for background blur via the new
+  `ext-background-effect-v1` protocol. Enable by setting
+  `colors-{dark,light}.blur=yes`. Foot needs to have been **built**
+  against `wayland-protocols >= 1.45`, and the compositor **must**
+  implement the `ext-background-effect-v1` protocol, **and** the
+  `blur` effect.
 
 [2212]: https://codeberg.org/dnkl/foot/issues/2212
 [2209]: https://codeberg.org/dnkl/foot/issues/2209

config.c

@@ -1576,6 +1576,9 @@ parse_color_theme(struct context *ctx, struct color_theme *theme)
             (int *)&theme->dim_blend_towards);
     }
 
+    else if (streq(key, "blur"))
+        return value_to_bool(ctx, &theme->blur);
+
     else {
         LOG_CONTEXTUAL_ERR("not valid option");
         return false;
@@ -3526,6 +3529,7 @@ config_load(struct config *conf, const char *conf_path,
                 .scrollback_indicator = false,
                 .url = false,
             },
+            .blur = false,
         },
         .initial_color_theme = COLOR_THEME_DARK,
         .cursor = {

config.h

@@ -192,6 +192,8 @@ struct color_theme {
         bool search_box_match:1;
         uint8_t dim;
     } use_custom;
+
+    bool blur;
 };
 
 enum which_color_theme {

doc/foot.ini.5.scd

@@ -1097,6 +1097,14 @@ The default theme used is *colors-dark*, unless
 	
 	Default: _default_
 
+*blur*
+	Boolean. When enabled, foot will blur the background, when it is
+	transparent. This feature requires the compositor to implement the
+	_ext-background-effect-v1_ protocol (and specifically, the _blur_
+	effect).
+	
+	Default: _no_
+
 *dim-blend-towards*
 	Which color to blend towards when "auto" dimming a color (see
 	*dim0*..*dim7* above). One of *black* or *white*. Blending towards

foot-features.c

@@ -28,6 +28,12 @@ const char version_and_features[] =
     " -toplevel-tag"
 #endif
 
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    " +blur"
+#else
+    " -blur"
+#endif
+
 #if !defined(NDEBUG)
     " +assertions"
 #else

meson.build

@@ -188,6 +188,10 @@ if (wayland_protocols.version().version_compare('>=1.43'))
   wl_proto_xml += [wayland_protocols_datadir / 'staging/xdg-toplevel-tag/xdg-toplevel-tag-v1.xml']
   add_project_arguments('-DHAVE_XDG_TOPLEVEL_TAG=1', language: 'c')
 endif
+if (wayland_protocols.version().version_compare('>=1.45'))
+  wl_proto_xml += [wayland_protocols_datadir / 'staging/ext-background-effect/ext-background-effect-v1.xml']
+  add_project_arguments('-DHAVE_EXT_BACKGROUND_EFFECT=1', language: 'c')
+endif
 
 foreach prot : wl_proto_xml
   wl_proto_headers += custom_target(

osc.c

@@ -1458,11 +1458,8 @@ osc_dispatch(struct terminal *term)
 
         case 11:
             term->colors.bg = color;
-            if (!have_alpha) {
+            if (!have_alpha)
-                alpha = term->colors.active_theme == COLOR_THEME_DARK
+                alpha = term_theme_get(term)->alpha;
-                    ? term->conf->colors_dark.alpha
-                    : term->conf->colors_light.alpha;
-            }
 
             const bool changed = term->colors.alpha != alpha;
             term->colors.alpha = alpha;
@@ -1515,10 +1512,7 @@ osc_dispatch(struct terminal *term)
     case 104: {
         /* Reset Color Number 'c' (whole table if no parameter) */
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
 
         if (string[0] == '\0') {
             LOG_DBG("resetting all colors");
@@ -1558,11 +1552,7 @@ osc_dispatch(struct terminal *term)
     case 110: /* Reset default text foreground color */
         LOG_DBG("resetting foreground color");
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
-
         term->colors.fg = theme->fg;
         term_damage_color(term, COLOR_DEFAULT, 0);
         break;
@@ -1570,11 +1560,7 @@ osc_dispatch(struct terminal *term)
     case 111: { /* Reset default text background color */
         LOG_DBG("resetting background color");
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
-
         bool alpha_changed = term->colors.alpha != theme->alpha;
 
         term->colors.bg = theme->bg;
@@ -1593,11 +1579,7 @@ osc_dispatch(struct terminal *term)
     case 112: {
         LOG_DBG("resetting cursor color");
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
-
         term->colors.cursor_fg = theme->cursor.text;
         term->colors.cursor_bg = theme->cursor.cursor;
 
@@ -1613,11 +1595,7 @@ osc_dispatch(struct terminal *term)
     case 117: {
         LOG_DBG("resetting selection background color");
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
-
         term->colors.selection_bg = theme->selection_bg;
         break;
     }
@@ -1625,11 +1603,7 @@ osc_dispatch(struct terminal *term)
     case 119: {
         LOG_DBG("resetting selection foreground color");
 
-        const struct color_theme *theme =
+        const struct color_theme *theme = term_theme_get(term);
-            term->colors.active_theme == COLOR_THEME_DARK
-                ? &term->conf->colors_dark
-                : &term->conf->colors_light;
-
         term->colors.selection_fg = theme->selection_fg;
         break;
     }

render.c

@@ -312,9 +312,7 @@ color_dim(const struct terminal *term, uint32_t color)
         }
     }
 
-    const struct color_theme *theme = term->colors.active_theme == COLOR_THEME_DARK
+    const struct color_theme *theme = term_theme_get(term);
-        ? &conf->colors_dark
-        : &conf->colors_light;
 
     return color_blend_towards(
         color,

terminal.c

@@ -4809,3 +4809,11 @@ term_theme_toggle(struct terminal *term)
     term_damage_margins(term);
     render_refresh(term);
 }
+
+const struct color_theme *
+term_theme_get(const struct terminal *term)
+{
+    return term->colors.active_theme == COLOR_THEME_DARK
+        ? &term->conf->colors_dark
+        : &term->conf->colors_light;
+}

terminal.h

@@ -997,6 +997,7 @@ void term_send_size_notification(struct terminal *term);
 void term_theme_switch_to_dark(struct terminal *term);
 void term_theme_switch_to_light(struct terminal *term);
 void term_theme_toggle(struct terminal *term);
+const struct color_theme *term_theme_get(const struct terminal *term);
 
 static inline void term_reset_grapheme_state(struct terminal *term)
 {

tests/test-config.c

@@ -774,6 +774,8 @@ test_section_colors_dark(void)
                    &conf.colors_dark.table[i]);
     }
 
+    test_boolean(&ctx, &parse_section_colors, "blur", &conf.colors_dark.blur);
+
     test_invalid_key(&ctx, &parse_section_colors_dark, "256");
 
     /* TODO: alpha (float in range 0-1, converted to uint16_t) */
@@ -853,6 +855,8 @@ test_section_colors_light(void)
                    &conf.colors_light.table[i]);
     }
 
+    test_boolean(&ctx, &parse_section_colors, "blur", &conf.colors_light.blur);
+
     test_invalid_key(&ctx, &parse_section_colors_light, "256");
 
     /* TODO: alpha (float in range 0-1, converted to uint16_t) */

wayland.c

@@ -1196,6 +1196,27 @@ static const struct zxdg_toplevel_decoration_v1_listener xdg_toplevel_decoration
     .configure = &xdg_toplevel_decoration_configure,
 };
 
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+static void
+ext_background_capabilities(
+    void *data,
+    struct ext_background_effect_manager_v1 *ext_background_effect_manager_v1,
+    uint32_t flags)
+{
+    struct wayland *wayl = data;
+
+    wayl->have_background_blur =
+        !!(flags & EXT_BACKGROUND_EFFECT_MANAGER_V1_CAPABILITY_BLUR);
+
+    LOG_DBG("compositor supports background blur: %s",
+            wayl->have_background_blur ? "yes" : "no");
+}
+
+static const struct ext_background_effect_manager_v1_listener background_manager_listener = {
+    .capabilities = &ext_background_capabilities,
+};
+#endif  /* HAVE_EXT_BACKGROUND_EFFECT */
+
 static bool
 fdm_repeat(struct fdm *fdm, int fd, int events, void *data)
 {
@@ -1558,6 +1579,20 @@ handle_global(void *data, struct wl_registry *registry,
             wayl->registry, name, &xdg_toplevel_tag_manager_v1_interface, required);
     }
 #endif
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    else if (streq(interface, ext_background_effect_manager_v1_interface.name)) {
+        const uint32_t required = 1;
+        if (!verify_iface_version(interface, version, required))
+            return;
+
+        wayl->background_effect_manager = wl_registry_bind(
+            wayl->registry, name,
+            &ext_background_effect_manager_v1_interface, required);
+
+        ext_background_effect_manager_v1_add_listener(
+            wayl->background_effect_manager, &background_manager_listener, wayl);
+    }
+#endif
 
 #if defined(FOOT_IME_ENABLED) && FOOT_IME_ENABLED
     else if (streq(interface, zwp_text_input_manager_v3_interface.name)) {
@@ -1572,6 +1607,7 @@ handle_global(void *data, struct wl_registry *registry,
             seat_add_text_input(&it->item);
     }
 #endif
+
 }
 
 static void
@@ -1885,6 +1921,10 @@ wayl_destroy(struct wayland *wayl)
     if (wayl->toplevel_tag_manager != NULL)
         xdg_toplevel_tag_manager_v1_destroy(wayl->toplevel_tag_manager);
 #endif
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    if (wayl->background_effect_manager != NULL)
+        ext_background_effect_manager_v1_destroy(wayl->background_effect_manager);
+#endif
 
     if (wayl->color_management.img_description != NULL)
         wp_image_description_v1_destroy(wayl->color_management.img_description);
@@ -1989,8 +2029,6 @@ wayl_win_init(struct terminal *term, const char *token)
         goto out;
     }
 
-    wayl_win_alpha_changed(win);
-
     wl_surface_add_listener(win->surface.surf, &surface_listener, win);
 
     if (wayl->fractional_scale_manager != NULL && wayl->viewporter != NULL) {
@@ -2003,6 +2041,16 @@ wayl_win_init(struct terminal *term, const char *token)
             win->fractional_scale, &fractional_scale_listener, win);
     }
 
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    if (wayl->background_effect_manager != NULL) {
+        win->surface.background_effect =
+            ext_background_effect_manager_v1_get_background_effect(
+                wayl->background_effect_manager, win->surface.surf);
+    }
+#endif
+
+    wayl_win_alpha_changed(win);
+
     win->xdg_surface = xdg_wm_base_get_xdg_surface(wayl->shell, win->surface.surf);
     xdg_surface_add_listener(win->xdg_surface, &xdg_surface_listener, win);
 
@@ -2207,7 +2255,12 @@ wayl_win_destroy(struct wl_window *win)
         free(it->item);
 
         tll_remove(win->xdg_tokens, it);
-}
+    }
+
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    if (win->surface.background_effect != NULL)
+        ext_background_effect_surface_v1_destroy(win->surface.background_effect);
+#endif
 
     if (win->surface.color_management != NULL)
         wp_color_management_surface_v1_destroy(win->surface.color_management);
@@ -2447,16 +2500,16 @@ void
 wayl_win_alpha_changed(struct wl_window *win)
 {
     struct terminal *term = win->term;
+    struct wayland *wayl = term->wl;
 
     /*
      * When fullscreened, transparency is disabled (see render.c).
      * Update the opaque region to match.
      */
-    bool is_opaque = term->colors.alpha == 0xffff || win->is_fullscreen;
+    const bool is_opaque = term->colors.alpha == 0xffff || win->is_fullscreen;
 
     if (is_opaque) {
-        struct wl_region *region = wl_compositor_create_region(
+        struct wl_region *region = wl_compositor_create_region(wayl->compositor);
-            term->wl->compositor);
 
         if (region != NULL) {
             wl_region_add(region, 0, 0, INT32_MAX, INT32_MAX);
@@ -2465,6 +2518,38 @@ wayl_win_alpha_changed(struct wl_window *win)
         }
     } else
         wl_surface_set_opaque_region(win->surface.surf, NULL);
+
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    if (term_theme_get(term)->blur) {
+        if (wayl->have_background_blur) {
+            xassert(win->surface.background_effect != NULL);
+
+            if (is_opaque) {
+                /* No transparency, disable blur */
+                LOG_DBG("disabling background blur");
+                ext_background_effect_surface_v1_set_blur_region(
+                    win->surface.background_effect, NULL);
+            } else {
+                /* We have transparency, enable blur if user has enabled it */
+                struct wl_region *region = wl_compositor_create_region(wayl->compositor);
+                if (region != NULL) {
+                    LOG_DBG("enabling background blur");
+
+                    wl_region_add(region, 0, 0, INT32_MAX, INT32_MAX);
+                    ext_background_effect_surface_v1_set_blur_region(
+                        win->surface.background_effect, region);
+                    wl_region_destroy(region);
+                }
+            }
+        } else {
+            static bool have_warned = false;
+            if (!have_warned) {
+                LOG_WARN("background blur requested, but compositor does not support it");
+                have_warned = true;
+            }
+        }
+    }
+#endif /* HAVE_EXT_BACKGROUND_EFFECT */
 }
 
 static void

wayland.h

@@ -26,6 +26,9 @@
 #if defined(HAVE_XDG_TOPLEVEL_TAG)
  #include <xdg-toplevel-tag-v1.h>
 #endif
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+ #include <ext-background-effect-v1.h>
+#endif
 
 #include <fcft/fcft.h>
 #include <tllist.h>
@@ -62,6 +65,10 @@ struct wayl_surface {
     struct wl_surface *surf;
     struct wp_viewport *viewport;
     struct wp_color_management_surface_v1 *color_management;
+
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    struct ext_background_effect_surface_v1 *background_effect;
+#endif
 };
 
 struct wayl_sub_surface {
@@ -488,6 +495,10 @@ struct wayland {
 #if defined(HAVE_XDG_TOPLEVEL_TAG)
     struct xdg_toplevel_tag_manager_v1 *toplevel_tag_manager;
 #endif
+#if defined(HAVE_EXT_BACKGROUND_EFFECT)
+    struct ext_background_effect_manager_v1 *background_effect_manager;
+    bool have_background_blur;
+#endif
 
 #if defined(FOOT_IME_ENABLED) && FOOT_IME_ENABLED
     struct zwp_text_input_manager_v3 *text_input_manager;