osd: add window-switcher custom field (#1670)

Add custom field with subset of printf style formatting
to replace the original field formats.

Example:

    <windowSwitcher preview="no" outlines="no" allWorkspaces="yes">
      <fields>
        <field content="custom" format="foobar %b %3s %-10o %-20W %-10i%t" width="100%" />
      </fields>
    </windowSwitcher>

Mono space font recommended. May need OSD width adjusted

Co-authored-by: @Consolatis (based on work done by them)

docs/labwc-config.5.scd

@@ -243,6 +243,30 @@ this is for compatibility with Openbox.
 
 		- *output* Show output id, if more than one output detected
 
+		- *custom* A printf style config that can replace all the above
+		  fields are:
+			- 'B' - shell type, values [xwayland|xdg-shell]
+			- 'b' - shell type (short form), values [X|W]
+			- 'S' - state of window, values [M|m|F] (3 spaces allocated)
+			        (maximized, minimized, fullscreen)
+			- 's' - state of window (short form), values [M|m|F] (1 space)
+			- 'I' - wm-class/app-id
+			- 'i' - wm-class/app-id trimmed, remove "org." if available
+			- 'W' - workspace name
+			- 'w' - workspace name (if more than 1 ws configured)
+			- 'O' - output name
+			- 'o' - output name (show if more than 1 monitor active)
+			- 'T' - title of window
+			- 't' - title of window (if different than wm-class/app-id)
+		  Recommend using with a mono space font, to keep alignment.
+		- *custom - subset of printf options allowed -- man 3 printf*
+			- random text may be inserted
+			- field length, example "%10" use 10 spaces, even if text uses less
+			- left jusify text, example "%-"
+			- right justify text, example "%" instead of "%-"
+			- example, %-10 would left justify and make room for 10 charaters
+		- Only one custom format allowed now. Future enhancements may allow more than one.
+
 	*width* defines the width of the field expressed as a percentage of
 	the overall window switcher width. The "%" character is required.
 

docs/rc.xml.all

@@ -77,7 +77,22 @@
         <field content="output" width="9%" />
         <field content="identifier" width="30%" />
         <field content="title" width="50%" />
-       </fields>
+      </fields>
+    </windowSwitcher>
+
+    custom format - (introduced in 0.7.2)
+    It allows one to replace all the above "fields" with one line, using a
+    printf style format. For field explanations, "man 5 labwc-config".
+
+    The example below would print "foobar",then type of window (wayland, X),
+    then state of window (M/m/F), then output (shows if more than 1 active),
+    then workspace name, then identifier/app-id, then the window title.
+    Uses 100% of OSD window width.
+
+    <windowSwitcher show="yes" preview="no" outlines="no" allWorkspaces="yes">
+      <fields>
+        <field content="custom" format="foobar %b %3s %-10o %-20W %-10i %t" width="100%" />
+      </fields>
     </windowSwitcher>
   -->
 

include/config/rcxml.h

@@ -15,18 +15,6 @@
 #include "resize_indicator.h"
 #include "theme.h"
 
-enum window_switcher_field_content {
-	LAB_FIELD_NONE = 0,
-	LAB_FIELD_TYPE,
-	LAB_FIELD_IDENTIFIER,
-	LAB_FIELD_TRIMMED_IDENTIFIER,
-	LAB_FIELD_TITLE,
-	LAB_FIELD_WORKSPACE,
-	LAB_FIELD_WIN_STATE,
-	LAB_FIELD_TYPE_SHORT,
-	LAB_FIELD_OUTPUT,
-};
-
 enum view_placement_policy {
 	LAB_PLACE_CENTER = 0,
 	LAB_PLACE_CURSOR,
@@ -53,12 +41,6 @@ struct usable_area_override {
 	struct wl_list link; /* struct rcxml.usable_area_overrides */
 };
 
-struct window_switcher_field {
-	enum window_switcher_field_content content;
-	int width;
-	struct wl_list link; /* struct rcxml.window_switcher.fields */
-};
-
 struct rcxml {
 	/* from command line */
 	char *config_dir;

include/labwc.h

@@ -502,15 +502,6 @@ void server_init(struct server *server);
 void server_start(struct server *server);
 void server_finish(struct server *server);
 
-/* Updates onscreen display 'alt-tab' buffer */
-void osd_update(struct server *server);
-/* Closes the OSD */
-void osd_finish(struct server *server);
-/* Moves preview views back into their original stacking order and state */
-void osd_preview_restore(struct server *server);
-/* Notify OSD about a destroying view */
-void osd_on_view_destroy(struct view *view);
-
 /*
  * wlroots "input inhibitor" extension (required for swaylock) blocks
  * any client other than the requesting client from receiving events

include/osd.h

@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LABWC_OSD_H
+#define LABWC_OSD_H
+
+#include <stdbool.h>
+#include <wayland-server-core.h>
+
+/* TODO: add field with keyboard layout? */
+enum window_switcher_field_content {
+	LAB_FIELD_NONE = 0,
+	LAB_FIELD_TYPE,
+	LAB_FIELD_TYPE_SHORT,
+	LAB_FIELD_IDENTIFIER,
+	LAB_FIELD_TRIMMED_IDENTIFIER,
+	LAB_FIELD_TITLE,
+	LAB_FIELD_TITLE_SHORT,
+	LAB_FIELD_WORKSPACE,
+	LAB_FIELD_WORKSPACE_SHORT,
+	LAB_FIELD_WIN_STATE,
+	LAB_FIELD_WIN_STATE_ALL,
+	LAB_FIELD_OUTPUT,
+	LAB_FIELD_OUTPUT_SHORT,
+	LAB_FIELD_CUSTOM,
+
+	LAB_FIELD_COUNT
+};
+
+struct window_switcher_field {
+	enum window_switcher_field_content content;
+	int width;
+	char *format;
+	struct wl_list link; /* struct rcxml.window_switcher.fields */
+};
+
+struct buf;
+struct view;
+struct server;
+
+/* Updates onscreen display 'alt-tab' buffer */
+void osd_update(struct server *server);
+
+/* Closes the OSD */
+void osd_finish(struct server *server);
+
+/* Moves preview views back into their original stacking order and state */
+void osd_preview_restore(struct server *server);
+
+/* Notify OSD about a destroying view */
+void osd_on_view_destroy(struct view *view);
+
+/* Used by osd.c internally to render window switcher fields */
+void osd_field_get_content(struct window_switcher_field *field,
+	struct buf *buf, struct view *view);
+
+/* Used by rcxml.c when parsing the config */
+struct window_switcher_field *osd_field_create(void);
+void osd_field_arg_from_xml_node(struct window_switcher_field *field,
+	const char *nodename, const char *content);
+bool osd_field_validate(struct window_switcher_field *field);
+void osd_field_free(struct window_switcher_field *field);
+
+#endif // LABWC_OSD_H

src/action.c

@@ -16,6 +16,7 @@
 #include "debug.h"
 #include "labwc.h"
 #include "menu/menu.h"
+#include "osd.h"
 #include "output-virtual.h"
 #include "placement.h"
 #include "regions.h"

src/config/rcxml.c

@@ -30,6 +30,7 @@
 #include "config/tablet.h"
 #include "config/rcxml.h"
 #include "labwc.h"
+#include "osd.h"
 #include "regions.h"
 #include "view.h"
 #include "window-rules.h"
@@ -187,7 +188,7 @@ static void
 fill_window_switcher_field(char *nodename, char *content)
 {
 	if (!strcasecmp(nodename, "field.fields.windowswitcher")) {
-		current_field = znew(*current_field);
+		current_field = osd_field_create();
 		wl_list_append(&rc.window_switcher.fields, &current_field->link);
 		return;
 	}
@@ -197,39 +198,8 @@ fill_window_switcher_field(char *nodename, char *content)
 		/* intentionally left empty */
 	} else if (!current_field) {
 		wlr_log(WLR_ERROR, "no <field>");
-	} else if (!strcmp(nodename, "content")) {
-		if (!strcmp(content, "type")) {
-			current_field->content = LAB_FIELD_TYPE;
-		} else if (!strcmp(content, "identifier")) {
-			current_field->content = LAB_FIELD_IDENTIFIER;
-		} else if (!strcmp(content, "app_id")) {
-			wlr_log(WLR_ERROR, "window-switcher field 'app_id' is deprecated");
-			current_field->content = LAB_FIELD_IDENTIFIER;
-		} else if (!strcmp(content, "trimmed_identifier")) {
-			current_field->content = LAB_FIELD_TRIMMED_IDENTIFIER;
-		} else if (!strcmp(content, "title")) {
-			current_field->content = LAB_FIELD_TITLE;
-		} else if (!strcmp(content, "workspace")) {
-			current_field->content = LAB_FIELD_WORKSPACE;
-		} else if (!strcmp(content, "state")) {
-			current_field->content = LAB_FIELD_WIN_STATE;
-		} else if (!strcmp(content, "type_short")) {
-			current_field->content = LAB_FIELD_TYPE_SHORT;
-		} else if (!strcmp(content, "output")) {
-			current_field->content = LAB_FIELD_OUTPUT;
-		} else {
-			wlr_log(WLR_ERROR, "bad windowSwitcher field '%s'", content);
-		}
-	} else if (!strcmp(nodename, "width") && !strchr(content, '%')) {
-		wlr_log(WLR_ERROR, "Removing invalid field, %s='%s' misses"
-			" trailing %%", nodename, content);
-		wl_list_remove(&current_field->link);
-		zfree(current_field);
-	} else if (!strcmp(nodename, "width")) {
-		current_field->width = atoi(content);
 	} else {
-		wlr_log(WLR_ERROR, "Unexpected data in field parser: %s=\"%s\"",
-			nodename, content);
+		osd_field_arg_from_xml_node(current_field, nodename, content);
 	}
 }
 
@@ -1516,6 +1486,16 @@ validate(void)
 	}
 
 	validate_actions();
+
+	/* OSD fields */
+	struct window_switcher_field *field, *field_tmp;
+	wl_list_for_each_safe(field, field_tmp, &rc.window_switcher.fields, link) {
+		if (!osd_field_validate(field)) {
+			wlr_log(WLR_ERROR, "Deleting invalid window switcher field %p", field);
+			wl_list_remove(&field->link);
+			osd_field_free(field);
+		}
+	}
 }
 
 void
@@ -1645,7 +1625,7 @@ rcxml_finish(void)
 	struct window_switcher_field *field, *field_tmp;
 	wl_list_for_each_safe(field, field_tmp, &rc.window_switcher.fields, link) {
 		wl_list_remove(&field->link);
-		zfree(field);
+		osd_field_free(field);
 	}
 
 	struct window_rule *rule, *rule_tmp;

src/desktop.c

@@ -7,6 +7,7 @@
 #include "labwc.h"
 #include "layers.h"
 #include "node.h"
+#include "osd.h"
 #include "ssd.h"
 #include "view.h"
 #include "window-rules.h"

src/input/keyboard.c

@@ -11,6 +11,7 @@
 #include "input/key-state.h"
 #include "labwc.h"
 #include "menu/menu.h"
+#include "osd.h"
 #include "regions.h"
 #include "view.h"
 #include "workspaces.h"

src/meson.build

@@ -12,6 +12,7 @@ labwc_sources = files(
   'main.c',
   'node.c',
   'osd.c',
+  'osd_field.c',
   'output.c',
   'output-virtual.c',
   'overlay.c',

src/osd.c

@@ -14,39 +14,13 @@
 #include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
-#include "theme.h"
 #include "node.h"
+#include "osd.h"
+#include "theme.h"
 #include "view.h"
 #include "window-rules.h"
 #include "workspaces.h"
 
-static const char *
-get_formatted_app_id(struct view *view)
-{
-	char *s = (char *)view_get_string_prop(view, "app_id");
-	if (!s) {
-		return NULL;
-	}
-	return s;
-}
-
-static const char *
-get_trimmed_app_id(char *s)
-{
-	if (!s) {
-		return NULL;
-	}
-	/* remove the first two nodes of 'org.' strings */
-	if (!strncmp(s, "org.", 4)) {
-		char *p = s + 4;
-		p = strchr(p, '.');
-		if (p) {
-			return ++p;
-		}
-	}
-	return s;
-}
-
 static void
 destroy_osd_nodes(struct output *output)
 {
@@ -225,63 +199,6 @@ preview_cycled_view(struct view *view)
 	wlr_scene_node_raise_to_top(osd_state->preview_node);
 }
 
-static const char *
-get_type(struct view *view)
-{
-	switch (view->type) {
-	case LAB_XDG_SHELL_VIEW:
-		return "[xdg-shell]";
-#if HAVE_XWAYLAND
-	case LAB_XWAYLAND_VIEW:
-		return "[xwayland]";
-#endif
-	}
-	return "";
-}
-
-static const char *
-get_type_short(struct view *view)
-{
-	switch (view->type) {
-	case LAB_XDG_SHELL_VIEW:
-		return "[W]";
-#if HAVE_XWAYLAND
-	case LAB_XWAYLAND_VIEW:
-		return "[X]";
-#endif
-	}
-	return "";
-}
-
-static const char *
-get_app_id(struct view *view)
-{
-	switch (view->type) {
-	case LAB_XDG_SHELL_VIEW:
-		return get_formatted_app_id(view);
-#if HAVE_XWAYLAND
-	case LAB_XWAYLAND_VIEW:
-		return view_get_string_prop(view, "class");
-#endif
-	}
-	return "";
-}
-
-static const char *
-get_title_if_different(struct view *view)
-{
-	/*
-	 * XWayland clients return WM_CLASS for 'app_id' so we don't need a
-	 * special case for that here.
-	 */
-	const char *identifier = view_get_string_prop(view, "app_id");
-	const char *title = view_get_string_prop(view, "title");
-	if (!identifier) {
-		return title;
-	}
-	return (!title || !strcmp(identifier, title)) ? NULL : title;
-}
-
 static void
 render_osd(struct server *server, cairo_t *cairo, int w, int h,
 		bool show_workspace, const char *workspace_name,
@@ -374,50 +291,8 @@ render_osd(struct server *server, cairo_t *cairo, int w, int h,
 				+ theme->osd_window_switcher_item_padding_y
 				+ theme->osd_window_switcher_item_active_border_width);
 
-			switch (field->content) {
-			case LAB_FIELD_TYPE:
-				buf_add(&buf, get_type(*view));
-				break;
-			case LAB_FIELD_TYPE_SHORT:
-				buf_add(&buf, get_type_short(*view));
-				break;
-			case LAB_FIELD_WORKSPACE:
-				buf_add(&buf, (*view)->workspace->name);
-				break;
-			case LAB_FIELD_WIN_STATE:
-				if ((*view)->maximized) {
-					buf_add(&buf, "M");
-				} else if ((*view)->minimized) {
-					buf_add(&buf, "m");
-				} else if ((*view)->fullscreen) {
-					buf_add(&buf, "F");
-				} else {
-					buf_add(&buf, " ");
-				}
-				break;
-			case LAB_FIELD_OUTPUT:
-				if (wl_list_length(&server->outputs) > 1 &&
-						output_is_usable((*view)->output)) {
-					buf_add(&buf, (*view)->output->wlr_output->name);
-				} else {
-					buf_add(&buf, " ");
-				}
-				break;
-			case LAB_FIELD_IDENTIFIER:
-				buf_add(&buf, get_app_id(*view));
-				break;
-			case LAB_FIELD_TRIMMED_IDENTIFIER:
-				{
-					char *s = (char *)get_app_id(*view);
-					buf_add(&buf, get_trimmed_app_id(s));
-					break;
-				}
-			case LAB_FIELD_TITLE:
-				buf_add(&buf, get_title_if_different(*view));
-				break;
-			default:
-				break;
-			}
+			osd_field_get_content(field, &buf, *view);
+
 			int field_width = (available_width - (nr_fields + 1)
 				* theme->osd_window_switcher_item_padding_x)
 				* field->width / 100.0;

src/osd_field.c

@@ -0,0 +1,365 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <assert.h>
+#include <ctype.h>
+#include <wlr/util/log.h>
+#include "common/mem.h"
+#include "config/rcxml.h"
+#include "view.h"
+#include "workspaces.h"
+#include "labwc.h"
+#include "osd.h"
+
+/* includes '%', terminating 's' and NULL byte, 8 is enough for %-9999s */
+#define LAB_FIELD_SINGLE_FMT_MAX_LEN 8
+static_assert(LAB_FIELD_SINGLE_FMT_MAX_LEN <= 255, "fmt_position is a unsigned char");
+
+/* forward declares */
+typedef void field_conversion_type(struct buf *buf, struct view *view, const char *format);
+struct field_converter {
+	const char fmt_char;
+	field_conversion_type *fn;
+};
+
+static const struct field_converter field_converter[];
+
+/* Internal helpers */
+
+static const char *
+get_app_id_or_class(struct view *view, bool trim)
+{
+	/*
+	 * XWayland clients return WM_CLASS for 'app_id' so we don't need a
+	 * special case for that here.
+	 */
+	const char *identifier = view_get_string_prop(view, "app_id");
+
+	/* remove the first two nodes of 'org.' strings */
+	if (trim && identifier && !strncmp(identifier, "org.", 4)) {
+		char *p = (char *)identifier + 4;
+		p = strchr(p, '.');
+		if (p) {
+			return ++p;
+		}
+	}
+	return identifier;
+}
+
+static const char *
+get_type(struct view *view, bool short_form)
+{
+	switch (view->type) {
+	case LAB_XDG_SHELL_VIEW:
+		return short_form ? "[W]" : "[xdg-shell]";
+#if HAVE_XWAYLAND
+	case LAB_XWAYLAND_VIEW:
+		return short_form ? "[X]" : "[xwayland]";
+#endif
+	}
+	return "???";
+}
+
+static const char *
+get_title(struct view *view)
+{
+	return view_get_string_prop(view, "title");
+}
+
+static const char *
+get_title_if_different(struct view *view)
+{
+	const char *identifier = get_app_id_or_class(view, /*trim*/ false);
+	const char *title = get_title(view);
+	if (!identifier) {
+		return title;
+	}
+	return (!title || !strcmp(identifier, title)) ? NULL : title;
+}
+
+/* Field handlers */
+static void
+field_set_type(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: B (backend) */
+	buf_add(buf, get_type(view, /*short_form*/ false));
+}
+
+static void
+field_set_type_short(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: b (backend) */
+	buf_add(buf, get_type(view, /*short_form*/ true));
+}
+
+static void
+field_set_workspace(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: W */
+	buf_add(buf, view->workspace->name);
+}
+
+static void
+field_set_workspace_short(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: w */
+	if (wl_list_length(&rc.workspace_config.workspaces) > 1) {
+		buf_add(buf, view->workspace->name);
+	}
+}
+
+static void
+field_set_win_state(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: s */
+	if (view->maximized) {
+		buf_add(buf, "M");
+	} else if (view->minimized) {
+		buf_add(buf, "m");
+	} else if (view->fullscreen) {
+		buf_add(buf, "F");
+	} else {
+		buf_add(buf, " ");
+	}
+}
+
+static void
+field_set_win_state_all(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: S */
+	buf_add(buf, view->minimized ? "m" : " ");
+	buf_add(buf, view->maximized ? "M" : " ");
+	buf_add(buf, view->fullscreen ? "F" : " ");
+	/* TODO: add always-on-top and omnipresent ? */
+}
+
+static void
+field_set_output(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: O */
+	if (output_is_usable(view->output)) {
+		buf_add(buf, view->output->wlr_output->name);
+	}
+}
+
+static void
+field_set_output_short(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: o */
+	if (wl_list_length(&view->server->outputs) > 1 &&
+			output_is_usable(view->output)) {
+		buf_add(buf, view->output->wlr_output->name);
+	}
+}
+
+static void
+field_set_identifier(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: I */
+	buf_add(buf, get_app_id_or_class(view, /*trim*/ false));
+}
+
+static void
+field_set_identifier_trimmed(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: i */
+	buf_add(buf, get_app_id_or_class(view, /*trim*/ true));
+}
+
+static void
+field_set_title(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: T */
+	buf_add(buf, get_title(view));
+}
+
+static void
+field_set_title_short(struct buf *buf, struct view *view, const char *format)
+{
+	/* custom type conversion-specifier: t */
+	buf_add(buf, get_title_if_different(view));
+}
+
+static void
+field_set_custom(struct buf *buf, struct view *view, const char *format)
+{
+	if (!format) {
+		wlr_log(WLR_ERROR, "Missing format for custom window switcher field");
+		return;
+	}
+
+	char fmt[LAB_FIELD_SINGLE_FMT_MAX_LEN];
+	unsigned char fmt_position = 0;
+
+	struct buf field_result;
+	buf_init(&field_result);
+
+	char converted_field[4096];
+
+	for (const char *p = format; *p; p++) {
+		if (!fmt_position) {
+			if (*p == '%') {
+				fmt[fmt_position++] = *p;
+			} else {
+				/*
+				 * Just relay anything not part of a
+				 * format string to the output buffer.
+				 */
+				buf_add_char(buf, *p);
+			}
+			continue;
+		}
+
+		/* Allow string formatting */
+		/* TODO: add . for manual truncating? */
+		/*
+		 * Remove the || *p == '#' section as not used/needed
+		 * change (*p >= '0' && *p <= '9') to isdigit(*p)
+		 * changes by droc12345
+		 */
+		if (*p == '-' || isdigit(*p)) {
+			if (fmt_position >= LAB_FIELD_SINGLE_FMT_MAX_LEN - 2) {
+				/* Leave space for terminating 's' and NULL byte */
+				wlr_log(WLR_ERROR,
+					"single format string length exceeded: '%s'", p);
+			} else {
+				fmt[fmt_position++] = *p;
+			}
+			continue;
+		}
+
+		/* Handlers */
+		for (unsigned char i = 0; i < LAB_FIELD_COUNT; i++) {
+			if (*p != field_converter[i].fmt_char) {
+				continue;
+			}
+
+			/* Generate the actual content*/
+			field_converter[i].fn(&field_result, view, /*format*/ NULL);
+
+			/* Throw it at snprintf to allow formatting / padding */
+			fmt[fmt_position++] = 's';
+			fmt[fmt_position++] = '\0';
+			snprintf(converted_field, sizeof(converted_field),
+				fmt, field_result.buf);
+
+			/* And finally write it to the output buffer */
+			buf_add(buf, converted_field);
+			goto reset_format;
+		}
+
+		wlr_log(WLR_ERROR,
+			"invalid format character found for osd %s: '%c'",
+			format, *p);
+
+reset_format:
+		/* Reset format string and tmp field result buffer */
+		buf_clear(&field_result);
+		fmt_position = 0;
+	}
+	free(field_result.buf);
+}
+
+static const struct field_converter field_converter[LAB_FIELD_COUNT] = {
+	[LAB_FIELD_TYPE]               = { 'B', field_set_type },
+	[LAB_FIELD_TYPE_SHORT]         = { 'b', field_set_type_short },
+	[LAB_FIELD_WIN_STATE_ALL]      = { 'S', field_set_win_state_all },
+	[LAB_FIELD_WIN_STATE]          = { 's', field_set_win_state },
+	[LAB_FIELD_IDENTIFIER]         = { 'I', field_set_identifier },
+	[LAB_FIELD_TRIMMED_IDENTIFIER] = { 'i', field_set_identifier_trimmed },
+	[LAB_FIELD_WORKSPACE]          = { 'W', field_set_workspace },
+	[LAB_FIELD_WORKSPACE_SHORT]    = { 'w', field_set_workspace_short },
+	[LAB_FIELD_OUTPUT]             = { 'O', field_set_output },
+	[LAB_FIELD_OUTPUT_SHORT]       = { 'o', field_set_output_short },
+	[LAB_FIELD_TITLE]              = { 'T', field_set_title },
+	[LAB_FIELD_TITLE_SHORT]        = { 't', field_set_title_short },
+	/* fmt_char can never be matched so prevents LAB_FIELD_CUSTOM recursion */
+	[LAB_FIELD_CUSTOM]             = { '\0', field_set_custom },
+};
+
+struct window_switcher_field *
+osd_field_create(void)
+{
+	struct window_switcher_field *field = znew(*field);
+	return field;
+}
+
+void
+osd_field_arg_from_xml_node(struct window_switcher_field *field,
+		const char *nodename, const char *content)
+{
+	if (!strcmp(nodename, "content")) {
+		if (!strcmp(content, "type")) {
+			field->content = LAB_FIELD_TYPE;
+		} else if (!strcmp(content, "type_short")) {
+			field->content = LAB_FIELD_TYPE_SHORT;
+		} else if (!strcmp(content, "app_id")) {
+			wlr_log(WLR_ERROR, "window-switcher field 'app_id' is deprecated");
+			field->content = LAB_FIELD_IDENTIFIER;
+		} else if (!strcmp(content, "identifier")) {
+			field->content = LAB_FIELD_IDENTIFIER;
+		} else if (!strcmp(content, "trimmed_identifier")) {
+			field->content = LAB_FIELD_TRIMMED_IDENTIFIER;
+		} else if (!strcmp(content, "title")) {
+			/* Keep old defaults */
+			field->content = LAB_FIELD_TITLE_SHORT;
+		} else if (!strcmp(content, "workspace")) {
+			field->content = LAB_FIELD_WORKSPACE;
+		} else if (!strcmp(content, "state")) {
+			field->content = LAB_FIELD_WIN_STATE;
+		} else if (!strcmp(content, "output")) {
+			/* Keep old defaults */
+			field->content = LAB_FIELD_OUTPUT_SHORT;
+		} else if (!strcmp(content, "custom")) {
+			field->content = LAB_FIELD_CUSTOM;
+		} else {
+			wlr_log(WLR_ERROR, "bad windowSwitcher field '%s'", content);
+		}
+	} else if (!strcmp(nodename, "format")) {
+		zfree(field->format);
+		field->format = xstrdup(content);
+	} else if (!strcmp(nodename, "width") && !strchr(content, '%')) {
+		wlr_log(WLR_ERROR, "Invalid osd field width: %s, misses trailing %%", content);
+	} else if (!strcmp(nodename, "width")) {
+		field->width = atoi(content);
+	} else {
+		wlr_log(WLR_ERROR, "Unexpected data in field parser: %s=\"%s\"",
+			nodename, content);
+	}
+}
+
+bool
+osd_field_validate(struct window_switcher_field *field)
+{
+	if (field->content == LAB_FIELD_NONE) {
+		wlr_log(WLR_ERROR, "Invalid OSD field: no content set");
+		return false;
+	}
+	if (field->content == LAB_FIELD_CUSTOM && !field->format) {
+		wlr_log(WLR_ERROR, "Invalid OSD field: custom without format");
+		return false;
+	}
+	if (!field->width) {
+		wlr_log(WLR_ERROR, "Invalid OSD field: no width");
+		return false;
+	}
+	return true;
+}
+
+void
+osd_field_get_content(struct window_switcher_field *field,
+		struct buf *buf, struct view *view)
+{
+	if (field->content == LAB_FIELD_NONE) {
+		wlr_log(WLR_ERROR, "Invalid window switcher field type");
+		return;
+	}
+	assert(field->content < LAB_FIELD_COUNT && field_converter[field->content].fn);
+
+	field_converter[field->content].fn(buf, view, field->format);
+}
+
+void
+osd_field_free(struct window_switcher_field *field)
+{
+	zfree(field->format);
+	zfree(field);
+}

src/view.c

@@ -10,6 +10,7 @@
 #include "input/keyboard.h"
 #include "labwc.h"
 #include "menu/menu.h"
+#include "osd.h"
 #include "placement.h"
 #include "regions.h"
 #include "resize_indicator.h"