Improve clipboard guidance for KDE users

PKGBUILD

@@ -6,6 +6,8 @@ arch=('x86_64')
 url='https://git.mshq.dev/AxiFisk/shinoa'
 license=('custom:unknown')
 depends=('gcc-libs' 'glibc' 'ncurses' 'openssl' 'zlib')
+optdepends=('wl-clipboard: clipboard image paste on Wayland/Plasma'
+            'xclip: clipboard image paste on X11')
 options=(!debug)
 provides=('shinoa')
 conflicts=('shinoa')

README.md

@@ -50,6 +50,12 @@ Or start the app without env vars and enter them interactively when prompted.
 When entered in the TUI, the app now stores `api_id` and `api_hash` in
 `~/.local/share/telegram-tui/config.json` and reuses them on later launches.
 
+Clipboard image sending via `>paste` or `>clip` requires an external clipboard tool:
+- `wl-clipboard` on Wayland or KDE Plasma Wayland
+- `xclip` on X11
+
+Klipper by itself is not a supported image backend for this feature.
+
 To use Telegram test servers instead of production:
 
 ```bash

src/app_auth.cpp

@@ -65,6 +65,36 @@ bool command_exists(const char *command) {
 	return !trim_copy(resolved).empty();
 }
 
+bool is_wayland_session() {
+	return get_env("XDG_SESSION_TYPE") == "wayland";
+}
+
+bool is_kde_session() {
+	const std::string current_desktop = get_env("XDG_CURRENT_DESKTOP");
+	const std::string session_desktop = get_env("XDG_SESSION_DESKTOP");
+	return current_desktop.find("KDE") != std::string::npos ||
+	       current_desktop.find("PLASMA") != std::string::npos ||
+	       session_desktop.find("kde") != std::string::npos ||
+	       session_desktop.find("plasma") != std::string::npos;
+}
+
+std::string missing_clipboard_tool_hint() {
+	if (command_exists("wl-paste") || command_exists("xclip") || command_exists("pngpaste")) {
+		return {};
+	}
+
+	if (is_wayland_session()) {
+		if (is_kde_session()) {
+			return " Install wl-clipboard. Klipper alone is not enough.";
+		}
+		return " Install wl-clipboard.";
+	}
+	if (is_kde_session()) {
+		return " Install xclip or wl-clipboard. Klipper alone is not enough.";
+	}
+	return " Install wl-clipboard or xclip.";
+}
+
 std::string clipboard_capture_command(const std::string &mime_type,
                                       const std::string &destination_path) {
 	if (command_exists("wl-paste")) {
@@ -580,8 +610,8 @@ bool App::preview_clipboard_photo_message(std::int64_t chat_id, const std::strin
                                           std::optional<std::int64_t> reply_to_message_id) {
 	const auto clipboard_type = detect_clipboard_image_type();
 	if (!clipboard_type.has_value()) {
-		status_line_ =
-		        "Clipboard doesn't contain an image, or no clipboard tool is available.";
+		status_line_ = "Clipboard doesn't contain an image, or no clipboard tool is available." +
+		               missing_clipboard_tool_hint();
 		return false;
 	}