LibLine: Recalculate the origin on resize

Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/4bf14715a1b
Pull-request: https://github.com/SerenityOS/serenity/pull/8142
Issue: https://github.com/SerenityOS/serenity/issues/287
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibLine/Editor.cpp

@@ -598,6 +598,27 @@ void Editor::resized()
     m_previous_num_columns = m_num_columns;
     get_terminal_size();
 
+    if (!m_has_origin_reset_scheduled) {
+        // Reset the origin, but make sure it doesn't blow up if we can't read it
+        if (set_origin(false)) {
+            handle_resize_event(false);
+        } else {
+            deferred_invoke([this](auto&) { handle_resize_event(true); });
+            m_has_origin_reset_scheduled = true;
+        }
+    }
+}
+
+void Editor::handle_resize_event(bool reset_origin)
+{
+    m_has_origin_reset_scheduled = false;
+    if (reset_origin && !set_origin(false)) {
+        m_has_origin_reset_scheduled = true;
+        return deferred_invoke([this](auto&) { handle_resize_event(true); });
+    }
+
+    set_origin(m_origin_row, 1);
+
     reposition_cursor(true);
     m_suggestion_display->redisplay(m_suggestion_manager, m_num_lines, m_num_columns);
     reposition_cursor();
@@ -1751,7 +1772,7 @@ Editor::VTState Editor::actual_rendered_string_length_step(StringMetrics& metric
     return state;
 }
 
-Vector<size_t, 2> Editor::vt_dsr()
+Result<Vector<size_t, 2>, Editor::Error> Editor::vt_dsr()
 {
     char buf[16];
 
@@ -1783,7 +1804,7 @@ Vector<size_t, 2> Editor::vt_dsr()
     } while (more_junk_to_read);
 
     if (m_input_error.has_value())
-        return { 1, 1 };
+        return m_input_error.value();
 
     fputs("\033[6n", stderr);
     fflush(stderr);
@@ -1813,15 +1834,11 @@ Vector<size_t, 2> Editor::vt_dsr()
                 continue;
             }
             dbgln("Error while reading DSR: {}", strerror(errno));
-            m_input_error = Error::ReadFailure;
-            finish();
-            return { 1, 1 };
+            return Error::ReadFailure;
         }
         if (nread == 0) {
-            m_input_error = Error::Empty;
-            finish();
             dbgln("Terminal DSR issue; received no response");
-            return { 1, 1 };
+            return Error::Empty;
         }
 
         switch (state) {
@@ -1897,7 +1914,7 @@ Vector<size_t, 2> Editor::vt_dsr()
 
     if (has_error)
         dbgln("Terminal DSR issue, couldn't parse DSR response");
-    return { row, col };
+    return Vector<size_t, 2> { row, col };
 }
 
 String Editor::line(size_t up_to_index) const

Userland/Libraries/LibLine/Editor.h

@@ -266,10 +266,11 @@ private:
     void try_update_once();
     void handle_interrupt_event();
     void handle_read_event();
+    void handle_resize_event(bool reset_origin);
 
     void ensure_free_lines_from_origin(size_t count);
 
-    Vector<size_t, 2> vt_dsr();
+    Result<Vector<size_t, 2>, Error> vt_dsr();
     void remove_at_index(size_t);
 
     enum class ModificationKind {
@@ -360,10 +361,18 @@ private:
         return current_prompt_metrics().offset_with_addition(buffer_metrics, m_num_columns);
     }
 
-    void set_origin()
+    bool set_origin(bool quit_on_error = true)
     {
         auto position = vt_dsr();
-        set_origin(position[0], position[1]);
+        if (!position.is_error()) {
+            set_origin(position.value()[0], position.value()[1]);
+            return true;
+        }
+        if (quit_on_error && position.is_error()) {
+            m_input_error = position.error();
+            finish();
+        }
+        return false;
     }
 
     void set_origin(int row, int col)
@@ -423,6 +432,7 @@ private:
     // Exact position before our prompt in the terminal.
     size_t m_origin_row { 0 };
     size_t m_origin_column { 0 };
+    bool m_has_origin_reset_scheduled { false };
 
     OwnPtr<SuggestionDisplay> m_suggestion_display;