Degrade gracefully when failing to receive cursor position report

Follow up the cursor position report query with a primary device
attribute one.  When that one arrives, any cursor position response
must have arrived too. This allows us to prevent a hang on terminals
that only support primary device attribute.

doc_src/terminal-compatibility.rst

@@ -210,7 +210,7 @@ Optional Commands
        and the second parameter is the column number.
        Both start at 1.
 
-       This is required for terminals that either
+       This is used inside terminals that either
 
        - implement the OSC 133 :ref:`click_events <term-compat-osc-133>` feature.
        - advertise the :ref:`indn <term-compat-indn>` capability via :ref:`XTGETTCAP <term-compat-xtgettcap>`
@@ -284,8 +284,8 @@ Optional Commands
        ``\e]133;A; click_events=1\x07``
      -
      - Mark prompt start (OSC 133), with kitty's ``click_events`` extension.
-       If ``click_events`` is implemented,
-       the :ref:`cursor position reporting <term-compat-cursor-position-report>` feature is required.
+       The ``click_events`` extension enables mouse clicks to move the cursor or select pager items,
+       assuming that :ref:`cursor position reporting <term-compat-cursor-position-report>` is available.
      - FinalTerm, kitty
    * - ``\e]133;C; cmdline_url= Pt \x07``
      -

src/input_common.rs

@@ -756,14 +756,26 @@ pub fn function_set_status(&mut self, status: bool) {
 }
 
 #[derive(Clone, Eq, PartialEq)]
-pub enum CursorPositionQuery {
+pub enum CursorPositionQueryKind {
     MouseLeft(ViewportPosition),
     ScrollbackPush,
 }
 
+#[derive(Clone, Eq, PartialEq)]
+pub struct CursorPositionQuery {
+    pub kind: CursorPositionQueryKind,
+    pub result: Option<ViewportPosition>,
+}
+
+impl CursorPositionQuery {
+    pub fn new(kind: CursorPositionQueryKind) -> Self {
+        Self { kind, result: None }
+    }
+}
+
 #[derive(Eq, PartialEq)]
 pub enum TerminalQuery {
-    PrimaryDeviceAttribute,
+    Initial,
     CursorPosition(CursorPositionQuery),
 }
 

src/reader.rs

@@ -87,8 +87,8 @@
 };
 use crate::input::init_input;
 use crate::input_common::{
-    stop_query, CharEvent, CharInputStyle, CursorPositionQuery, ImplicitEvent, InputData,
-    QueryResponseEvent, ReadlineCmd, TerminalQuery,
+    stop_query, CharEvent, CharInputStyle, CursorPositionQuery, CursorPositionQueryKind,
+    ImplicitEvent, InputData, QueryResponseEvent, ReadlineCmd, TerminalQuery,
 };
 use crate::io::IoChain;
 use crate::key::ViewportPosition;
@@ -276,7 +276,7 @@ pub(crate) fn initial_query(
                 query_capabilities_via_dcs(out.by_ref(), vars);
             }
             out.write_command(QueryPrimaryDeviceAttribute);
-            Some(TerminalQuery::PrimaryDeviceAttribute)
+            Some(TerminalQuery::Initial)
         };
         RefCell::new(query)
     });
@@ -1548,7 +1548,12 @@ pub fn request_cursor_position(&mut self, out: &mut Outputter, q: CursorPosition
         let mut query = self.blocking_query();
         assert!(query.is_none());
         *query = Some(TerminalQuery::CursorPosition(q));
-        out.write_command(QueryCursorPosition);
+        {
+            out.begin_buffering();
+            out.write_command(QueryCursorPosition);
+            out.write_command(QueryPrimaryDeviceAttribute);
+            out.end_buffering();
+        }
         drop(query);
         self.save_screen_state();
     }
@@ -2560,19 +2565,16 @@ fn handle_char_event(&mut self, injected_event: Option<CharEvent>) -> ControlFlo
                     FLOG!(reader, "Mouse left click", position);
                     self.request_cursor_position(
                         &mut Outputter::stdoutput().borrow_mut(),
-                        CursorPositionQuery::MouseLeft(position),
+                        CursorPositionQuery::new(CursorPositionQueryKind::MouseLeft(position)),
                     );
                 }
             },
             CharEvent::QueryResponse(query_result) => {
-                let maybe_query = self.blocking_query();
-                let query = &maybe_query;
+                let mut maybe_query = self.blocking_query();
+                let query = &mut maybe_query;
                 use QueryResponseEvent::*;
-                let query = match (&**query, query_result) {
-                    (
-                        Some(TerminalQuery::PrimaryDeviceAttribute),
-                        PrimaryDeviceAttributeResponse,
-                    ) => {
+                let query = match (&mut **query, query_result) {
+                    (Some(TerminalQuery::Initial), PrimaryDeviceAttributeResponse) => {
                         if get_kitty_keyboard_capability() == Capability::Unknown {
                             set_kitty_keyboard_capability(
                                 reader_save_screen_state,
@@ -2584,15 +2586,28 @@ fn handle_char_event(&mut self, injected_event: Option<CharEvent>) -> ControlFlo
                     (
                         Some(TerminalQuery::CursorPosition(cursor_pos_query)),
                         CursorPositionResponse(cursor_pos),
+                    ) => {
+                        cursor_pos_query.result = Some(cursor_pos);
+                        maybe_query
+                    }
+                    (
+                        Some(TerminalQuery::CursorPosition(cursor_pos_query)),
+                        PrimaryDeviceAttributeResponse,
                     ) => {
                         let cursor_pos_query = cursor_pos_query.clone();
                         drop(maybe_query);
-                        match cursor_pos_query {
-                            CursorPositionQuery::MouseLeft(click_position) => {
-                                self.mouse_left_click(cursor_pos, click_position);
+                        use CursorPositionQueryKind::*;
+                        let cursor_pos = cursor_pos_query.result;
+                        match cursor_pos_query.kind {
+                            MouseLeft(click_position) => {
+                                if let Some(cursor_pos) = cursor_pos {
+                                    self.mouse_left_click(cursor_pos, click_position);
+                                }
                             }
-                            CursorPositionQuery::ScrollbackPush => {
-                                self.screen.push_to_scrollback(cursor_pos.y);
+                            ScrollbackPush => {
+                                if let Some(cursor_pos) = cursor_pos {
+                                    self.screen.push_to_scrollback(cursor_pos.y);
+                                }
                             }
                         };
                         self.blocking_query()
@@ -3908,12 +3923,12 @@ fn handle_readline_command(&mut self, c: ReadlineCmd) {
                     drop(query);
                     self.request_cursor_position(
                         &mut Outputter::stdoutput().borrow_mut(),
-                        CursorPositionQuery::ScrollbackPush,
+                        CursorPositionQuery::new(CursorPositionQueryKind::ScrollbackPush),
                     );
                     return;
                 };
                 match query {
-                    TerminalQuery::PrimaryDeviceAttribute => panic!(),
+                    TerminalQuery::Initial => panic!(),
                     TerminalQuery::CursorPosition(_) => {
                         // TODO: re-queue it I guess.
                         FLOG!(