From 6809b92e34bb038f8e0486dcd7dd471384aafccb Mon Sep 17 00:00:00 2001
From: Kirill Bulatov <kirill@zed.dev>
Date: Wed, 10 Jan 2024 10:16:09 +0200
Subject: [PATCH] Disable synthetic drag on drag and drop

Otherwise, conflicting MouseMove events are generated and page regions start to flicker.
---
 crates/gpui/src/platform/mac/window.rs | 27 +++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/crates/gpui/src/platform/mac/window.rs b/crates/gpui/src/platform/mac/window.rs
index 2beac528c1..6d03a3b5cd 100644
--- a/crates/gpui/src/platform/mac/window.rs
+++ b/crates/gpui/src/platform/mac/window.rs
@@ -338,6 +338,7 @@ struct MacWindowState {
     ime_state: ImeState,
     // Retains the last IME Text
     ime_text: Option<String>,
+    external_files_dragged: bool,
 }
 
 impl MacWindowState {
@@ -567,6 +568,7 @@ impl MacWindow {
                 previous_modifiers_changed_event: None,
                 ime_state: ImeState::None,
                 ime_text: None,
+                external_files_dragged: false,
             })));
 
             (*native_window).set_ivar(
@@ -1223,15 +1225,20 @@ extern "C" fn handle_view_event(this: &Object, _: Sel, native_event: id) {
                     ..
                 },
             ) => {
-                lock.synthetic_drag_counter += 1;
-                let executor = lock.executor.clone();
-                executor
-                    .spawn(synthetic_drag(
-                        weak_window_state,
-                        lock.synthetic_drag_counter,
-                        event.clone(),
-                    ))
-                    .detach();
+                // Synthetic drag is used for selecting long buffer contents while buffer is being scrolled.
+                // External file drag and drop is able to emit its own synthetic mouse events which will conflict
+                // with these ones.
+                if !lock.external_files_dragged {
+                    lock.synthetic_drag_counter += 1;
+                    let executor = lock.executor.clone();
+                    executor
+                        .spawn(synthetic_drag(
+                            weak_window_state,
+                            lock.synthetic_drag_counter,
+                            event.clone(),
+                        ))
+                        .detach();
+                }
             }
 
             InputEvent::MouseMove(_) if !(is_active || lock.kind == WindowKind::PopUp) => return,
@@ -1675,6 +1682,7 @@ extern "C" fn dragging_entered(this: &Object, _: Sel, dragging_info: id) -> NSDr
         let paths = external_paths_from_event(dragging_info);
         InputEvent::FileDrop(FileDropEvent::Entered { position, paths })
     }) {
+        window_state.lock().external_files_dragged = true;
         NSDragOperationCopy
     } else {
         NSDragOperationNone
@@ -1697,6 +1705,7 @@ extern "C" fn dragging_updated(this: &Object, _: Sel, dragging_info: id) -> NSDr
 extern "C" fn dragging_exited(this: &Object, _: Sel, _: id) {
     let window_state = unsafe { get_window_state(this) };
     send_new_event(&window_state, InputEvent::FileDrop(FileDropEvent::Exited));
+    window_state.lock().external_files_dragged = false;
 }
 
 extern "C" fn perform_drag_operation(this: &Object, _: Sel, dragging_info: id) -> BOOL {