message_scroll: Move state flags to new module message_scroll_state.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

tools/test-js-with-node

@@ -125,6 +125,7 @@ EXEMPT_FILES = make_set(
         "web/src/message_lists.js",
         "web/src/message_live_update.js",
         "web/src/message_scroll.js",
+        "web/src/message_scroll_state.ts",
         "web/src/message_util.js",
         "web/src/message_view_header.js",
         "web/src/message_viewport.js",

web/src/hotkey.js

@@ -27,7 +27,7 @@ import * as list_util from "./list_util";
 import * as message_edit from "./message_edit";
 import * as message_edit_history from "./message_edit_history";
 import * as message_lists from "./message_lists";
-import * as message_scroll from "./message_scroll";
+import * as message_scroll_state from "./message_scroll_state";
 import * as narrow from "./narrow";
 import * as narrow_state from "./narrow_state";
 import * as navigate from "./navigate";
@@ -958,33 +958,33 @@ export function process_hotkey(e, hotkey) {
     switch (event_name) {
         case "down_arrow":
         case "vim_down":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.down(true); // with_centering
             return true;
         case "up_arrow":
         case "vim_up":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.up();
             return true;
         case "home":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.to_home();
             return true;
         case "end":
         case "G_end":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.to_end();
             return true;
         case "page_up":
         case "vim_page_up":
         case "shift_spacebar":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.page_up();
             return true;
         case "page_down":
         case "vim_page_down":
         case "spacebar":
-            message_scroll.mark_keyboard_triggered_current_scroll();
+            message_scroll_state.set_keyboard_triggered_current_scroll(true);
             navigate.page_down();
             return true;
         case "copy_with_c":

web/src/message_scroll.js

@@ -4,6 +4,7 @@ import _ from "lodash";
 import * as compose_banner from "./compose_banner";
 import * as message_fetch from "./message_fetch";
 import * as message_lists from "./message_lists";
+import * as message_scroll_state from "./message_scroll_state";
 import * as message_viewport from "./message_viewport";
 import * as narrow_state from "./narrow_state";
 import * as unread from "./unread";
@@ -12,22 +13,6 @@ import * as unread_ui from "./unread_ui";
 
 let actively_scrolling = false;
 
-// Tracks whether the next scroll that will complete is initiated by
-// code, not the user, and thus should avoid moving the selected
-// message.
-let update_selection_on_next_scroll = true;
-
-export function suppress_selection_update_on_next_scroll() {
-    update_selection_on_next_scroll = false;
-}
-
-// Whether a keyboard shortcut is triggering a message feed scroll event.
-let keyboard_triggered_current_scroll = false;
-
-export function mark_keyboard_triggered_current_scroll() {
-    keyboard_triggered_current_scroll = true;
-}
-
 let hide_scroll_to_bottom_timer;
 export function hide_scroll_to_bottom() {
     const $show_scroll_to_bottom_button = $("#scroll-to-bottom-button-container");
@@ -94,10 +79,10 @@ export function scroll_finished() {
         }
     }
 
-    if (update_selection_on_next_scroll) {
+    if (message_scroll_state.update_selection_on_next_scroll) {
         message_viewport.keep_pointer_in_view();
     } else {
-        update_selection_on_next_scroll = true;
+        message_scroll_state.set_update_selection_on_next_scroll(true);
     }
 
     if (message_viewport.at_top()) {
@@ -125,10 +110,10 @@ function scroll_finish() {
 
     // Don't present the "scroll to bottom" widget if the current
     // scroll was triggered by the keyboard.
-    if (!keyboard_triggered_current_scroll) {
+    if (!message_scroll_state.keyboard_triggered_current_scroll) {
         show_scroll_to_bottom_button();
     }
-    keyboard_triggered_current_scroll = false;
+    message_scroll_state.set_keyboard_triggered_current_scroll(false);
 
     clearTimeout(scroll_timer);
     scroll_timer = setTimeout(scroll_finished, 100);

web/src/message_scroll_state.ts

@@ -0,0 +1,15 @@
+// Tracks whether the next scroll that will complete is initiated by
+// code, not the user, and thus should avoid moving the selected
+// message.
+export let update_selection_on_next_scroll = true;
+
+export function set_update_selection_on_next_scroll(value: boolean): void {
+    update_selection_on_next_scroll = value;
+}
+
+// Whether a keyboard shortcut is triggering a message feed scroll event.
+export let keyboard_triggered_current_scroll = false;
+
+export function set_keyboard_triggered_current_scroll(value: boolean): void {
+    keyboard_triggered_current_scroll = value;
+}

web/src/message_viewport.js

@@ -2,7 +2,7 @@ import $ from "jquery";
 
 import * as blueslip from "./blueslip";
 import * as message_lists from "./message_lists";
-import * as message_scroll from "./message_scroll";
+import * as message_scroll_state from "./message_scroll_state";
 import * as popover_menus from "./popover_menus";
 import * as rows from "./rows";
 import * as util from "./util";
@@ -156,7 +156,7 @@ export function set_message_position(message_top, message_height, viewport_info,
 
     const new_scroll_top = message_top - message_offset;
 
-    message_scroll.suppress_selection_update_on_next_scroll();
+    message_scroll_state.set_update_selection_on_next_scroll(false);
     scrollTop(new_scroll_top);
 }
 
@@ -334,7 +334,7 @@ export function stop_auto_scrolling() {
 }
 
 export function system_initiated_animate_scroll(scroll_amount) {
-    message_scroll.suppress_selection_update_on_next_scroll();
+    message_scroll_state.set_update_selection_on_next_scroll(false);
     const viewport_offset = scrollTop();
     in_stoppable_autoscroll = true;
     $scroll_container.animate({
@@ -346,7 +346,7 @@ export function system_initiated_animate_scroll(scroll_amount) {
 }
 
 export function user_initiated_animate_scroll(scroll_amount) {
-    message_scroll.suppress_selection_update_on_next_scroll();
+    message_scroll_state.set_update_selection_on_next_scroll(false);
     in_stoppable_autoscroll = false; // defensive
 
     const viewport_offset = scrollTop();