config: add <core><promptCommand>

...to enable configuration of the action prompt command.

Also set some better defaults for labnag.

The new default command is:

    labnag \
        --message '%m' \
        --button-dismiss '%n' \
        --button-dismiss '%y' \
        --background '%b' \
        --text '%t' \
        --border '%t' \
        --border-bottom '%t' \
        --button-background '%b' \
        --button-text '%t' \
        --border-bottom-size 1 \
        --button-border-size 3 \
        --timeout 0

...where the conversion specifiers are defined as follows:

    %m: the `<prompt>` message option
    %n: _("No")
    %y: _("Yes")
    %b: osd.bg.color
    %t: osd.label.text.color

This config options also enables the use of a different dialog client, for
example like this:

    <core>
      <promptCommand>zenity --question --text="%m"</promptCommand>
    </core>

include/action-prompt-command.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LABWC_ACTION_PROMPT_COMMAND_H
+#define LABWC_ACTION_PROMPT_COMMAND_H
+
+struct buf;
+struct action;
+struct theme;
+
+void action_prompt_command(struct buf *buf, const char *format,
+	struct action *action, struct theme *theme);
+
+#endif /* LABWC_ACTION_PROMPT_COMMAND_H */

include/action.h

@@ -23,6 +23,8 @@ struct action {
 
 struct action *action_create(const char *action_name);
 
+const char *action_get_str(struct action *action, const char *key,
+	const char *default_value);
 bool action_is_valid(struct action *action);
 bool action_is_show_menu(struct action *action);
 

include/common/buf.h

@@ -50,6 +50,17 @@ void buf_expand_shell_variables(struct buf *s);
  */
 void buf_add_fmt(struct buf *s, const char *fmt, ...);
 
+/**
+ * buf_add_hex_color - add rgb color as hex string to C string buffer
+ * @s: buffer
+ * @color: rgb color to be added
+ *
+ * For example:
+ *   - With the input 'red' (defined as red[4] = { 1.0f, 0.0f, 0.0f, 1.0f}) the
+ *     string "#ff0000ff" will be written to the buffer.
+ */
+void buf_add_hex_color(struct buf *s, float color[4]);
+
 /**
  * buf_add - add data to C string buffer
  * @s: buffer

include/config/rcxml.h

@@ -74,6 +74,8 @@ struct rcxml {
 	enum lab_placement_policy placement_policy;
 	bool xwayland_persistence;
 	bool primary_selection;
+	char *prompt_command;
+
 	int placement_cascade_offset_x;
 	int placement_cascade_offset_y;