fix(engine): prevent events from stacking up when the search bar is open. Fix #781

espanso-engine/src/event/internal.rs

@@ -85,6 +85,14 @@ pub struct DiscardPreviousEvent {
   pub minimum_source_id: u32,
 }
 
+#[derive(Debug, Clone, PartialEq)]
+pub struct DiscardBetweenEvent {
+  // All Events with a source_id between start_id (included) and end_id (excluded)
+  // will be discarded
+  pub start_id: u32,
+  pub end_id: u32,
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub struct SecureInputEnabledEvent {
   pub app_name: String,

espanso-engine/src/event/mod.rs

@@ -71,6 +71,7 @@ pub enum EventType {
   ImageResolved(internal::ImageResolvedEvent),
   MatchInjected,
   DiscardPrevious(internal::DiscardPreviousEvent),
+  DiscardBetween(internal::DiscardBetweenEvent),
   Undo(internal::UndoEvent),
 
   Disabled,

espanso-engine/src/process/default.rs

@@ -25,11 +25,11 @@ use super::{
     cause::CauseCompensateMiddleware,
     cursor_hint::CursorHintMiddleware,
     delay_modifiers::{DelayForModifierReleaseMiddleware, ModifierStatusProvider},
+    discard::EventsDiscardMiddleware,
     markdown::MarkdownMiddleware,
     match_select::MatchSelectMiddleware,
     matcher::MatcherMiddleware,
     multiplex::MultiplexMiddleware,
-    past_discard::PastEventsDiscardMiddleware,
     render::RenderMiddleware,
   },
   DisableOptions, EnabledStatusProvider, MatchFilter, MatchInfoProvider, MatchProvider,
@@ -73,14 +73,18 @@ impl<'a> DefaultProcessor<'a> {
     Self {
       event_queue: VecDeque::new(),
       middleware: vec![
-        Box::new(PastEventsDiscardMiddleware::new()),
+        Box::new(EventsDiscardMiddleware::new()),
         Box::new(DisableMiddleware::new(disable_options)),
         Box::new(IconStatusMiddleware::new()),
         Box::new(MatcherMiddleware::new(matchers, matcher_options_provider)),
         Box::new(SuppressMiddleware::new(enabled_status_provider)),
         Box::new(ContextMenuMiddleware::new()),
         Box::new(HotKeyMiddleware::new()),
-        Box::new(MatchSelectMiddleware::new(match_filter, match_selector)),
+        Box::new(MatchSelectMiddleware::new(
+          match_filter,
+          match_selector,
+          event_sequence_provider,
+        )),
         Box::new(CauseCompensateMiddleware::new()),
         Box::new(MultiplexMiddleware::new(multiplexer)),
         Box::new(RenderMiddleware::new(renderer)),

espanso-engine/src/process/middleware/discard.rs

@@ -24,42 +24,54 @@ use log::trace;
 use super::super::Middleware;
 use crate::event::{Event, EventType, SourceId};
 
-/// This middleware discards all events that have a source_id smaller than its
-/// configured threshold. This useful to discard past events that might have
-/// been stuck in the event queue for too long.
-pub struct PastEventsDiscardMiddleware {
-  source_id_threshold: RefCell<SourceId>,
+/// This middleware discards all events that have a source_id between
+/// the given maximum and minimum.
+/// This useful to discard past events that might have been stuck in the
+/// event queue for too long, or events generated while the search bar was open.
+pub struct EventsDiscardMiddleware {
+  min_id_threshold: RefCell<SourceId>,
+  max_id_threshold: RefCell<SourceId>,
 }
 
-impl PastEventsDiscardMiddleware {
+impl EventsDiscardMiddleware {
   pub fn new() -> Self {
     Self {
-      source_id_threshold: RefCell::new(0),
+      min_id_threshold: RefCell::new(0),
+      max_id_threshold: RefCell::new(0),
     }
   }
 }
 
-impl Middleware for PastEventsDiscardMiddleware {
+impl Middleware for EventsDiscardMiddleware {
   fn name(&self) -> &'static str {
-    "past_discard"
+    "discard"
   }
 
   fn next(&self, event: Event, _: &mut dyn FnMut(Event)) -> Event {
-    let mut source_id_threshold = self.source_id_threshold.borrow_mut();
+    let mut min_id_threshold = self.min_id_threshold.borrow_mut();
+    let mut max_id_threshold = self.max_id_threshold.borrow_mut();
 
     // Filter out previous events
-    if event.source_id < *source_id_threshold {
+    if event.source_id < *max_id_threshold && event.source_id >= *min_id_threshold {
       trace!("discarding previous event: {:?}", event);
       return Event::caused_by(event.source_id, EventType::NOOP);
     }
 
-    // Update the minimum threshold
+    // Update the thresholds
     if let EventType::DiscardPrevious(m_event) = &event.etype {
       trace!(
-        "updating minimum source id threshold for events to: {}",
+        "updating discard max_id_threshold threshold for events to: {}",
         m_event.minimum_source_id
       );
-      *source_id_threshold = m_event.minimum_source_id;
+      *max_id_threshold = m_event.minimum_source_id;
+    } else if let EventType::DiscardBetween(m_event) = &event.etype {
+      trace!(
+        "updating discard thresholds for events to: max={} min={}",
+        m_event.end_id,
+        m_event.start_id
+      );
+      *max_id_threshold = m_event.end_id;
+      *min_id_threshold = m_event.start_id;
     }
 
     event

espanso-engine/src/process/middleware/match_select.rs

@@ -20,7 +20,13 @@
 use log::{debug, error};
 
 use super::super::Middleware;
-use crate::event::{internal::MatchSelectedEvent, Event, EventType};
+use crate::{
+  event::{
+    internal::{DiscardBetweenEvent, MatchSelectedEvent},
+    Event, EventType,
+  },
+  process::EventSequenceProvider,
+};
 
 pub trait MatchFilter {
   fn filter_active(&self, matches_ids: &[i32]) -> Vec<i32>;
@@ -33,13 +39,19 @@ pub trait MatchSelector {
 pub struct MatchSelectMiddleware<'a> {
   match_filter: &'a dyn MatchFilter,
   match_selector: &'a dyn MatchSelector,
+  event_sequence_provider: &'a dyn EventSequenceProvider,
 }
 
 impl<'a> MatchSelectMiddleware<'a> {
-  pub fn new(match_filter: &'a dyn MatchFilter, match_selector: &'a dyn MatchSelector) -> Self {
+  pub fn new(
+    match_filter: &'a dyn MatchFilter,
+    match_selector: &'a dyn MatchSelector,
+    event_sequence_provider: &'a dyn EventSequenceProvider,
+  ) -> Self {
     Self {
       match_filter,
       match_selector,
+      event_sequence_provider,
     }
   }
 }
@@ -49,7 +61,7 @@ impl<'a> Middleware for MatchSelectMiddleware<'a> {
     "match_select"
   }
 
-  fn next(&self, event: Event, _: &mut dyn FnMut(Event)) -> Event {
+  fn next(&self, event: Event, dispatch: &mut dyn FnMut(Event)) -> Event {
     if let EventType::MatchesDetected(m_event) = event.etype {
       let matches_ids: Vec<i32> = m_event.matches.iter().map(|m| m.id).collect();
 
@@ -75,22 +87,40 @@ impl<'a> Middleware for MatchSelectMiddleware<'a> {
           }
         }
         _ => {
+          let start_event_id = self.event_sequence_provider.get_next_id();
+
           // Multiple matches, we need to ask the user which one to use
-          if let Some(selected_id) = self.match_selector.select(&valid_ids, m_event.is_search) {
-            let m = m_event.matches.into_iter().find(|m| m.id == selected_id);
-            if let Some(m) = m {
-              Event::caused_by(
-                event.source_id,
-                EventType::MatchSelected(MatchSelectedEvent { chosen: m }),
-              )
+          let next_event =
+            if let Some(selected_id) = self.match_selector.select(&valid_ids, m_event.is_search) {
+              let m = m_event.matches.into_iter().find(|m| m.id == selected_id);
+              if let Some(m) = m {
+                Event::caused_by(
+                  event.source_id,
+                  EventType::MatchSelected(MatchSelectedEvent { chosen: m }),
+                )
+              } else {
+                error!("MatchSelectMiddleware could not find the correspondent match");
+                Event::caused_by(event.source_id, EventType::NOOP)
+              }
             } else {
-              error!("MatchSelectMiddleware could not find the correspondent match");
+              debug!("MatchSelectMiddleware did not receive any match selection");
               Event::caused_by(event.source_id, EventType::NOOP)
-            }
-          } else {
-            debug!("MatchSelectMiddleware did not receive any match selection");
-            Event::caused_by(event.source_id, EventType::NOOP)
-          }
+            };
+
+          let end_event_id = self.event_sequence_provider.get_next_id();
+
+          // We want to prevent espanso from "stacking up" events while the search bar is open,
+          // therefore we filter out all events that were generated while the search bar was open.
+          // See also: https://github.com/federico-terzi/espanso/issues/781
+          dispatch(Event::caused_by(
+            event.source_id,
+            EventType::DiscardBetween(DiscardBetweenEvent {
+              start_id: start_event_id,
+              end_id: end_event_id,
+            }),
+          ));
+
+          next_event
         }
       };
     }

espanso-engine/src/process/middleware/mod.rs

@@ -23,6 +23,7 @@ pub mod context_menu;
 pub mod cursor_hint;
 pub mod delay_modifiers;
 pub mod disable;
+pub mod discard;
 pub mod exit;
 pub mod hotkey;
 pub mod icon_status;
@@ -31,7 +32,6 @@ pub mod markdown;
 pub mod match_select;
 pub mod matcher;
 pub mod multiplex;
-pub mod past_discard;
 pub mod render;
 pub mod search;
 pub mod suppress;