LibLine: Correctly display suggestions on multiline prompts

Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/f20becf71b8
Pull-request: https://github.com/SerenityOS/serenity/pull/2660

Libraries/LibLine/Editor.cpp

@@ -56,7 +56,7 @@ Editor::Editor(Configuration configuration)
         m_num_columns = ws.ws_col;
         m_num_lines = ws.ws_row;
     }
-    m_suggestion_display = make<XtermSuggestionDisplay>(m_num_lines, m_num_columns);
+    m_suggestion_display = make<XtermSuggestionDisplay>(m_num_lines, m_num_columns, m_cached_prompt_metrics);
 }
 
 Editor::~Editor()
@@ -304,6 +304,7 @@ auto Editor::get_line(const String& prompt) -> Result<String, Editor::Error>
 
         if (m_finish) {
             m_finish = false;
+            reposition_cursor(true);
             printf("\n");
             fflush(stdout);
             auto string = line();
@@ -950,6 +951,12 @@ void Editor::recalculate_origin()
 }
 void Editor::cleanup()
 {
+    auto current_buffer_metrics = actual_rendered_string_metrics(buffer_view());
+    auto new_lines = current_prompt_metrics().lines_with_addition(current_buffer_metrics, m_num_columns);
+    auto shown_lines = num_lines();
+    if (new_lines < shown_lines)
+        m_extra_forward_lines = max(shown_lines - new_lines, m_extra_forward_lines);
+
     VT::move_relative(-m_extra_forward_lines, m_pending_chars.size() - m_chars_inserted_in_the_middle);
     auto current_line = cursor_line();
 
@@ -1105,14 +1112,22 @@ void Editor::strip_styles(bool strip_anchored)
     m_refresh_needed = true;
 }
 
-void Editor::reposition_cursor()
+void Editor::reposition_cursor(bool to_end)
 {
-    m_drawn_cursor = m_cursor;
+    auto cursor = m_cursor;
+    auto saved_cursor = m_cursor;
+    if (to_end)
+        cursor = m_buffer.size();
+
+    m_cursor = cursor;
+    m_drawn_cursor = cursor;
 
     auto line = cursor_line() - 1;
     auto column = offset_in_line();
 
     VT::move_absolute(line + m_origin_row, column + m_origin_column);
+
+    m_cursor = saved_cursor;
 }
 
 void VT::move_absolute(u32 row, u32 col)
@@ -1307,7 +1322,7 @@ void VT::clear_to_end_of_line()
     fflush(stdout);
 }
 
-Editor::StringMetrics Editor::actual_rendered_string_metrics(const StringView& string) const
+StringMetrics Editor::actual_rendered_string_metrics(const StringView& string) const
 {
     size_t length { 0 };
     StringMetrics metrics;
@@ -1331,7 +1346,7 @@ Editor::StringMetrics Editor::actual_rendered_string_metrics(const StringView& s
     return metrics;
 }
 
-Editor::StringMetrics Editor::actual_rendered_string_metrics(const Utf32View& view) const
+StringMetrics Editor::actual_rendered_string_metrics(const Utf32View& view) const
 {
     size_t length { 0 };
     StringMetrics metrics;
@@ -1557,7 +1572,7 @@ void Editor::readjust_anchored_styles(size_t hint_index, ModificationKind modifi
     }
 }
 
-size_t Editor::StringMetrics::lines_with_addition(const StringMetrics& offset, size_t column_width) const
+size_t StringMetrics::lines_with_addition(const StringMetrics& offset, size_t column_width) const
 {
     size_t lines = 0;
 

Libraries/LibLine/Editor.h

@@ -41,6 +41,7 @@
 #include <LibCore/Notifier.h>
 #include <LibCore/Object.h>
 #include <LibLine/Span.h>
+#include <LibLine/StringMetrics.h>
 #include <LibLine/Style.h>
 #include <LibLine/SuggestionDisplay.h>
 #include <LibLine/SuggestionManager.h>
@@ -104,20 +105,6 @@ public:
     const Vector<String>& history() const { return m_history; }
 
     void register_character_input_callback(char ch, Function<bool(Editor&)> callback);
-    struct StringMetrics {
-        Vector<size_t> line_lengths;
-        size_t total_length { 0 };
-        size_t max_line_length { 0 };
-
-        size_t lines_with_addition(const StringMetrics& offset, size_t column_width) const;
-        void reset()
-        {
-            line_lengths.clear();
-            total_length = 0;
-            max_line_length = 0;
-            line_lengths.append(0);
-        }
-    };
     StringMetrics actual_rendered_string_metrics(const StringView&) const;
     StringMetrics actual_rendered_string_metrics(const Utf32View&) const;
 
@@ -313,7 +300,7 @@ private:
     bool should_break_token(Vector<u32, 1024>& buffer, size_t index);
 
     void recalculate_origin();
-    void reposition_cursor();
+    void reposition_cursor(bool to_end = false);
 
     struct CodepointRange {
         size_t start { 0 };

Libraries/LibLine/StringMetrics.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, The SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <AK/Vector.h>
+
+namespace Line {
+
+struct StringMetrics {
+    Vector<size_t> line_lengths;
+    size_t total_length { 0 };
+    size_t max_line_length { 0 };
+
+    size_t lines_with_addition(const StringMetrics& offset, size_t column_width) const;
+    void reset()
+    {
+        line_lengths.clear();
+        total_length = 0;
+        max_line_length = 0;
+        line_lengths.append(0);
+    }
+};
+
+}

Libraries/LibLine/SuggestionDisplay.h

@@ -28,6 +28,7 @@
 
 #include <AK/Forward.h>
 #include <AK/String.h>
+#include <LibLine/StringMetrics.h>
 #include <LibLine/SuggestionManager.h>
 #include <stdlib.h>
 
@@ -61,9 +62,10 @@ protected:
 
 class XtermSuggestionDisplay : public SuggestionDisplay {
 public:
-    XtermSuggestionDisplay(size_t lines, size_t columns)
+    XtermSuggestionDisplay(size_t lines, size_t columns, const StringMetrics& prompt_metrics)
         : m_num_lines(lines)
         , m_num_columns(columns)
+        , m_prompt_metrics(prompt_metrics)
     {
     }
     virtual ~XtermSuggestionDisplay() override { }
@@ -92,7 +94,7 @@ private:
     size_t m_num_lines { 0 };
     size_t m_num_columns { 0 };
     size_t m_prompt_lines_at_suggestion_initiation { 0 };
-    size_t m_prompt_length { 0 };
+    const StringMetrics& m_prompt_metrics;
 
     struct PageRange {
         size_t start;

Libraries/LibLine/XtermSuggestionDisplay.cpp

@@ -52,7 +52,11 @@ void XtermSuggestionDisplay::display(const SuggestionManager& manager)
     VT::restore_cursor();
 
     auto spans_entire_line { false };
-    auto max_line_count = (m_prompt_length + longest_suggestion_length + m_num_columns - 1) / m_num_columns;
+    Vector<size_t> lines;
+    for (size_t i = 0; i < m_prompt_lines_at_suggestion_initiation - 1; ++i)
+        lines.append(0);
+    lines.append(longest_suggestion_length);
+    auto max_line_count = StringMetrics { move(lines) }.lines_with_addition({ { 0 } }, m_num_columns);
     if (longest_suggestion_length >= m_num_columns - 2) {
         spans_entire_line = true;
         // We should make enough space for the biggest entry in
@@ -126,9 +130,9 @@ void XtermSuggestionDisplay::display(const SuggestionManager& manager)
 
         if (spans_entire_line) {
             num_printed += m_num_columns;
-            fprintf(stderr, "%s", suggestion.text_string.characters());
+            fprintf(stdout, "%s", suggestion.text_string.characters());
         } else {
-            fprintf(stderr, "%-*s", static_cast<int>(longest_suggestion_byte_length) + 2, suggestion.text_string.characters());
+            fprintf(stdout, "%-*s", static_cast<int>(longest_suggestion_byte_length) + 2, suggestion.text_string.characters());
             num_printed += longest_suggestion_length + 2;
         }
 
@@ -153,6 +157,7 @@ void XtermSuggestionDisplay::display(const SuggestionManager& manager)
 
         if (string.length() > m_num_columns - 1) {
             // This would overflow into the next line, so just don't print an indicator.
+            fflush(stdout);
             return;
         }
 
@@ -160,8 +165,9 @@ void XtermSuggestionDisplay::display(const SuggestionManager& manager)
         VT::apply_style({ Style::Background(Style::XtermColor::Green) });
         fputs(string.characters(), stdout);
         VT::apply_style(Style::reset_style());
-        fflush(stdout);
     }
+
+    fflush(stdout);
 }
 
 bool XtermSuggestionDisplay::cleanup()