screen_utils: convert screen_get_yesno() to an awaitable

src/FileBrowserPage.cxx

@@ -12,10 +12,10 @@
 #include "charset.hxx"
 #include "mpdclient.hxx"
 #include "filelist.hxx"
-#include "screen_utils.hxx"
 #include "screen_client.hxx"
 #include "Command.hxx"
 #include "Options.hxx"
+#include "dialogs/YesNoDialog.hxx"
 #include "ui/Bell.hxx"
 #include "lib/fmt/ToSpan.hxx"
 #include "util/UriUtil.hxx"
@@ -243,8 +243,8 @@ FileBrowserPage::HandleDelete(struct mpdclient &c)
 		snprintf(prompt, sizeof(prompt),
 			 _("Delete playlist %s?"),
 			 Utf8ToLocaleZ{GetUriFilename(mpd_playlist_get_path(playlist))}.c_str());
-		bool confirmed = screen_get_yesno(screen, prompt, false);
-		if (!confirmed)
+
+		if (co_await YesNoDialog{screen, prompt} != YesNoResult::YES)
 			co_return;
 
 		auto *connection = c.GetConnection();

src/dialogs/YesNoDialog.cxx

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright The Music Player Daemon Project
+
+#include "YesNoDialog.hxx"
+#include "ui/Bell.hxx"
+#include "ui/Keys.hxx"
+#include "ui/Options.hxx"
+#include "ui/Window.hxx"
+#include "Styles.hxx"
+#include "i18n.h"
+
+#include <ctype.h>
+
+using std::string_view_literals::operator""sv;
+
+void
+YesNoDialog::OnLeave(const Window window) noexcept
+{
+	noecho();
+	curs_set(0);
+
+	if (ui_options.enable_colors)
+		window.SetBackgroundStyle(Style::STATUS);
+}
+
+void
+YesNoDialog::OnCancel() noexcept
+{
+	SetResult(YesNoResult::CANCEL);
+}
+
+void
+YesNoDialog::Paint(const Window window) const noexcept
+{
+	if (ui_options.enable_colors)
+		window.SetBackgroundStyle(Style::INPUT);
+
+	SelectStyle(window, Style::STATUS_ALERT);
+	window.String({0, 0}, prompt);
+	window.String(" ["sv);
+	window.String(YES_TRANSLATION);
+	window.Char('/');
+	window.String(NO_TRANSLATION);
+	window.String("] "sv);
+
+	SelectStyle(window, Style::INPUT);
+	window.ClearToEol();
+
+	echo();
+	curs_set(1);
+}
+
+static constexpr bool
+IsCancelKey(int key) noexcept
+{
+	return key == KEY_CANCEL || key == KEY_SCANCEL ||
+	       key == KEY_CLOSE ||
+	       key == KEY_UNDO ||
+	       key == KEY_CTL('C') ||
+	       key == KEY_CTL('G') ||
+	       key == KEY_ESCAPE;
+}
+
+bool
+YesNoDialog::OnKey(Window, int key)
+{
+	/* NOTE: if one day a translator decides to use a multi-byte character
+	   for one of the yes/no keys, we'll have to parse it properly */
+
+	key = tolower(key);
+	if (key == YES_TRANSLATION[0]) {
+		Hide();
+		SetResult(YesNoResult::YES);
+	} else if (key == NO_TRANSLATION[0]) {
+		Hide();
+		SetResult(YesNoResult::NO);
+	} else if (IsCancelKey(key)) {
+		Cancel();
+	} else {
+		Bell();
+	}
+
+	return true;
+}

src/dialogs/YesNoDialog.hxx

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright The Music Player Daemon Project
+
+#pragma once
+
+#include "ModalDialog.hxx"
+#include "co/AwaitableHelper.hxx"
+
+#include <cstdint>
+#include <string_view>
+
+enum class YesNoResult : int8_t {
+	CANCEL = -1,
+	NO = false,
+	YES = true,
+};
+
+/**
+ * A #ModalDialog that asks the user a yes/no question.
+ *
+ * This dialog is supposed to be awaited from a coroutine using
+ * co_await.  It suspends the caller while waiting for user input.
+ */
+class YesNoDialog final : public ModalDialog {
+	const std::string_view prompt;
+
+	std::coroutine_handle<> continuation;
+
+	bool ready = false;
+	YesNoResult result;
+
+	using Awaitable = Co::AwaitableHelper<YesNoDialog, false>;
+	friend Awaitable;
+
+public:
+	/**
+	 * @param _prompt the human-readable prompt to be displayed
+	 * (including question mark if desired); the pointed-by memory
+	 * is owned by the caller and must remain valid during the
+	 * lifetime of this dialog
+	 */
+	YesNoDialog(ModalDock &_dock, std::string_view _prompt) noexcept
+		:ModalDialog(_dock), prompt(_prompt)
+	{
+		Show();
+	}
+
+	~YesNoDialog() noexcept {
+		Hide();
+	}
+
+	/**
+	 * Await completion of this dialog.
+	 *
+	 * @return a YesNoResult
+	 */
+	Awaitable operator co_await() noexcept {
+		return *this;
+	}
+
+private:
+	void SetResult(YesNoResult _result) noexcept {
+		result = _result;
+		ready = true;
+
+		if (continuation)
+			continuation.resume();
+	}
+
+	bool IsReady() const noexcept {
+		return ready;
+	}
+
+	YesNoResult TakeValue() noexcept {
+		return result;
+	}
+
+public:
+	/* virtual methodds from Modal */
+	void OnLeave(Window window) noexcept override;
+	void OnCancel() noexcept override;
+	void Paint(Window window) const noexcept override;
+	bool OnKey(Window window, int key) override;
+};

src/dialogs/meson.build

@@ -1,9 +1,11 @@
 dialogs = static_library(
   'dialogs',
   'ModalDialog.cxx',
+  'YesNoDialog.cxx',
   include_directories: inc,
   dependencies: [
     ui_dep,
+    intl_dep,
   ],
 )
 

src/save_playlist.cxx

@@ -9,7 +9,9 @@
 #include "charset.hxx"
 #include "mpdclient.hxx"
 #include "Completion.hxx"
+#include "screen.hxx"
 #include "screen_utils.hxx"
+#include "dialogs/YesNoDialog.hxx"
 #include "co/InvokeTask.hxx"
 
 #include <mpd/client.h>
@@ -89,8 +91,14 @@ playlist_save(ScreenManager &screen, struct mpdclient &c,
 			char prompt[256];
 			snprintf(prompt, sizeof(prompt),
 				 _("Replace %s?"), filename.c_str());
-			bool replace = screen_get_yesno(screen, prompt, false);
-			if (!replace)
+
+			if (co_await YesNoDialog{screen, prompt} != YesNoResult::YES)
+				co_return;
+
+			/* obtain a new connection pointer after
+			   resuming this coroutine */
+			connection = c.GetConnection();
+			if (connection == nullptr)
 				co_return;
 
 			if (!mpd_run_rm(connection, filename_utf8.c_str()) ||

src/screen_utils.cxx

@@ -75,25 +75,6 @@ screen_getch(ScreenManager &screen, const char *prompt) noexcept
 	return key;
 }
 
-bool
-screen_get_yesno(ScreenManager &screen, const char *_prompt, bool def) noexcept
-{
-	/* NOTE: if one day a translator decides to use a multi-byte character
-	   for one of the yes/no keys, we'll have to parse it properly */
-
-	char prompt[256];
-	snprintf(prompt, sizeof(prompt),
-		 "%s [%s/%s] ", _prompt,
-		 YES_TRANSLATION, NO_TRANSLATION);
-	int key = tolower(screen_getch(screen, prompt));
-	if (key == YES_TRANSLATION[0])
-		return true;
-	else if (key == NO_TRANSLATION[0])
-		return false;
-	else
-		return def;
-}
-
 std::string
 screen_readln(ScreenManager &screen, const char *prompt,
 	      const char *value,

src/screen_utils.hxx

@@ -13,16 +13,6 @@ class ScreenManager;
 int
 screen_getch(ScreenManager &screen, const char *prompt) noexcept;
 
-/**
- * display a prompt, wait for the user to press a key, and compare it with
- * the default keys for "yes" and "no" (and their upper-case pendants).
- *
- * @returns true, if the user pressed the key for "yes"; false, if the user
- *	    pressed the key for "no"; def otherwise
- */
-bool
-screen_get_yesno(ScreenManager &screen, const char *prompt, bool def) noexcept;
-
 std::string
 screen_read_password(ScreenManager &screen, const char *prompt) noexcept;