From 75727c5cbe8282aada4d3a8122cd3271a97c263d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 16:48:26 -0600
Subject: [PATCH 1/8] Multiline editing

---
 examples/menu_window.cpp |   7 +-
 examples/prompt.cpp      | 152 +++++++++++++++++++++++++++++----------
 terminal.h               |  92 ++++++++++++++++++++----
 terminal_base.h          |   1 +
 4 files changed, 199 insertions(+), 53 deletions(-)

diff --git a/examples/menu_window.cpp b/examples/menu_window.cpp
index b9e549b0..2f2e4b41 100644
--- a/examples/menu_window.cpp
+++ b/examples/menu_window.cpp
@@ -30,9 +30,10 @@ std::string render(Term::Window &scr, int rows, int cols,
     int y = menuy0 + menuheight + 5;
     scr.print_str(1, y,   "Selected item: " + std::to_string(menupos));
     scr.print_str(1, y+1, "Menu width: " + std::to_string(menuwidth));
-    scr.print_str(1, y+2, "Menu height: " + std::to_string(menuheight));
+    scr.print_str(1, y+2, "Menu height: " + std::to_string(menuheight),
+            0, true);
 
-    return scr.render();
+    return scr.render(1, 1);
 }
 
 int main() {
@@ -45,7 +46,7 @@ int main() {
         int h = 10;
         int w = 10;
         bool on = true;
-        Term::Window scr(1, 1, cols, rows);
+        Term::Window scr(cols, rows);
         while (on) {
             std::cout << render(scr, rows, cols, h, w, pos) << std::flush;
             int key = term.read_key();
diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index 57aeac91..80a138da 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -12,23 +12,71 @@ using Term::cursor_on;
 // abstract way, irrespective of where or how it is rendered.
 struct Model {
     std::string prompt_string; // The string to show as the prompt
-    std::string input; // The current input string in the prompt
+    std::vector<std::string> lines; // The current input string in the prompt as
+            // a vector of lines, without '\n' at the end.
     // The current cursor position in the "input" string, starting from (1,1)
     size_t cursor_col, cursor_row;
 };
 
-std::string render(const Model &m, int prompt_row, int term_cols) {
-    std::string out;
-    out = cursor_off();
-    out += move_cursor(prompt_row, 1) + m.prompt_string + m.input;
-    size_t last_col = m.prompt_string.size() + m.input.size();
-    for (size_t i=0; i < term_cols-last_col; i++) {
-        out.append(" ");
+std::string concat(const std::vector<std::string> &lines) {
+    std::string s;
+    for (auto &line: lines) {
+        s.append(line + "\n");
     }
-    out.append(move_cursor(prompt_row+m.cursor_row-1,
-        m.prompt_string.size() + m.cursor_col));
-    out.append(cursor_on());
-    return out;
+    return s;
+}
+
+std::vector<std::string> split(const std::string &s) {
+    size_t j = 0;
+    std::vector<std::string> lines;
+    lines.push_back("");
+    if (s[s.size()-1] != '\n') throw std::runtime_error("\\n is required");
+    for (size_t i=0; i<s.size()-1; i++) {
+        if (s[i] == '\n') {
+            j++;
+            lines.push_back("");
+        } else {
+            lines[j].push_back(s[i]);
+        }
+    }
+    return lines;
+}
+
+char32_t U(const std::string &s) {
+    std::u32string s2 = Term::utf8_to_utf32(s);
+    if (s2.size() != 1) throw std::runtime_error("U(s): s not a codepoint.");
+    return s2[0];
+}
+
+void print_left_curly_bracket(Term::Window &scr, int x, int y1, int y2) {
+    int h = y2-y1+1;
+    if (h == 1) {
+        scr.set_char(x, y1, U("]"));
+    } else {
+        scr.set_char(x, y1, U("┐"));
+        for (int j=y1+1; j <= y2-1; j++) {
+            scr.set_char(x, j, U("│"));
+        }
+        scr.set_char(x, y2, U("┘"));
+    }
+}
+
+void render(Term::Window &scr, const Model &m, size_t cols) {
+    scr.clear();
+    print_left_curly_bracket(scr, cols, 1, m.lines.size());
+    scr.print_str(cols-6, m.lines.size(), std::to_string(m.cursor_row) + ","
+            + std::to_string(m.cursor_col));
+    for (size_t j=0; j < m.lines.size(); j++) {
+        if (j == 0) {
+            scr.print_str(1, j+1, m.prompt_string);
+        } else {
+            for (size_t i=0; i < m.prompt_string.size()-1; i++) {
+                scr.set_char(i+1, j+1, '.');
+            }
+        }
+        scr.print_str(m.prompt_string.size()+1, j+1, m.lines[j]);
+    }
+    scr.set_cursor_pos(m.prompt_string.size() + m.cursor_col, m.cursor_row);
 }
 
 std::string prompt(const Terminal &term, const std::string &prompt_string,
@@ -40,6 +88,7 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
 
     Model m;
     m.prompt_string = prompt_string;
+    m.lines.push_back("");
     m.cursor_col = 1;
     m.cursor_row = 1;
 
@@ -47,31 +96,38 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
     // changes will be forgotten once a command is submitted.
     std::vector<std::string> hist = history;
     size_t history_pos = hist.size();
-    hist.push_back(m.input); // Push back empty input
+    hist.push_back(concat(m.lines)); // Push back empty input
 
+    Term::Window scr(cols, 1);
     int key;
-    std::cout << render(m, row, cols) << std::flush;
+    render(scr, m, cols);
+    std::cout << scr.render(1, row) << std::flush;
     while ((key = term.read_key()) != Key::ENTER) {
         if (  (key >= 'a' && key <= 'z') ||
               (key >= 'A' && key <= 'Z') ||
               (!iscntrl(key) && key < 128)  ) {
-            std::string before = m.input.substr(0, m.cursor_col-1);
+            std::string before = m.lines[m.cursor_row-1].substr(0,
+                    m.cursor_col-1);
             std::string newchar; newchar.push_back(key);
-            std::string after = m.input.substr(m.cursor_col-1);
-            m.input = before + newchar + after;
+            std::string after = m.lines[m.cursor_row-1].substr(m.cursor_col-1);
+            m.lines[m.cursor_row-1] = before + newchar + after;
             m.cursor_col++;
         } else if (key == CTRL_KEY('d')) {
-            if (m.input.size() == 0) {
-                m.input.push_back(CTRL_KEY('d'));
-                break;
+            if (m.lines.size() == 1 && m.lines[m.cursor_row-1].size() == 0) {
+                m.lines[m.cursor_row-1].push_back(CTRL_KEY('d'));
+                std::cout << "\n" << std::flush;
+                history.push_back(m.lines[0]);
+                return m.lines[0];
             }
         } else {
             switch (key) {
                 case Key::BACKSPACE:
                     if (m.cursor_col > 1) {
-                        std::string before = m.input.substr(0, m.cursor_col-2);
-                        std::string after = m.input.substr(m.cursor_col-1);
-                        m.input = before + after;
+                        std::string before = m.lines[m.cursor_row-1].substr(0,
+                                m.cursor_col-2);
+                        std::string after = m.lines[m.cursor_row-1]
+                                .substr(m.cursor_col-1);
+                        m.lines[m.cursor_row-1] = before + after;
                         m.cursor_col--;
                     }
                     break;
@@ -81,7 +137,7 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                     }
                     break;
                 case Key::ARROW_RIGHT:
-                    if (m.cursor_col <= m.input.size()) {
+                    if (m.cursor_col <= m.lines[m.cursor_row-1].size()) {
                         m.cursor_col++;
                     }
                     break;
@@ -89,31 +145,51 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                     m.cursor_col = 1;
                     break;
                 case Key::END:
-                    m.cursor_col = m.input.size()+1;
+                    m.cursor_col = m.lines[m.cursor_row-1].size()+1;
                     break;
                 case Key::ARROW_UP:
                     if (history_pos > 0) {
-                        hist[history_pos] = m.input;
+                        hist[history_pos] = concat(m.lines);
                         history_pos--;
-                        m.input = hist[history_pos];
-                        m.cursor_col = m.input.size()+1;
+                        m.lines = split(hist[history_pos]);
+                        m.cursor_row = 1;
+                        m.cursor_col = m.lines[0].size()+1;
+                        scr.set_h(m.lines.size());
                     }
                     break;
                 case Key::ARROW_DOWN:
                     if (history_pos < hist.size()-1) {
-                        hist[history_pos] = m.input;
+                        hist[history_pos] = concat(m.lines);
                         history_pos++;
-                        m.input = hist[history_pos];
-                        m.cursor_col = m.input.size()+1;
+                        m.lines = split(hist[history_pos]);
+                        m.cursor_row = 1;
+                        m.cursor_col = m.lines[0].size()+1;
+                        scr.set_h(m.lines.size());
                     }
                     break;
+                case ALT_KEY('n'):
+                case Key::ALT_ENTER:
+                    std::string before = m.lines[m.cursor_row-1].substr(0,
+                            m.cursor_col-1);
+                    std::string after = m.lines[m.cursor_row-1]
+                            .substr(m.cursor_col-1);
+                    m.lines[m.cursor_row-1] = before;
+                    m.lines.push_back(after);
+                    m.cursor_col = after.size()+1;
+                    m.cursor_row++;
+                    scr.set_h(scr.get_h()+1);
             }
         }
-        std::cout << render(m, row, cols) << std::flush;
+        render(scr, m, cols);
+        std::cout << scr.render(1, row) << std::flush;
+        // FIXME: this is a hack
+        if (key == Key::ALT_ENTER || key == ALT_KEY('n')) {
+            if (row+(int)scr.get_h()-1 > rows) row--;
+        }
     }
     std::cout << "\n" << std::flush;
-    history.push_back(m.input);
-    return m.input;
+    history.push_back(concat(m.lines));
+    return concat(m.lines);
 }
 
 int main() {
@@ -125,21 +201,21 @@ int main() {
         std::cout << "  * Features:" << std::endl;
         std::cout << "    - Editing (Keys: Left, Right, Home, End, Backspace)" << std::endl;
         std::cout << "    - History (Keys: Up, Down)" << std::endl;
+        std::cout << "    - Multi-line editing (use Alt-Enter or Alt-N to add a new line)" << std::endl;
         // TODO:
-        //std::cout << "    - Multi-line editing (use Alt-Enter to add a new line)" << std::endl;
         //std::cout << "    - Syntax highlighting" << std::endl;
         std::vector<std::string> history;
         while (true) {
-            std::string answer = prompt(term, "> ", history);
+            std::string answer = prompt(term, ">>> ", history);
             if (answer.size() == 1 && answer[0] == CTRL_KEY('d')) break;
             std::cout << "Submitted text: " << answer << std::endl;
         }
     } catch(const std::runtime_error& re) {
         std::cerr << "Runtime error: " << re.what() << std::endl;
-        return 2;
+        return 1;
     } catch(...) {
         std::cerr << "Unknown error." << std::endl;
-        return 1;
+        throw;
     }
     return 0;
 }
diff --git a/terminal.h b/terminal.h
index 29c8b187..aeab3517 100644
--- a/terminal.h
+++ b/terminal.h
@@ -101,6 +101,7 @@ std::string cursor_on()
 
 // If an attempt is made to move the cursor out of the window, the result is
 // undefined.
+// TODO: switch col/row
 std::string move_cursor(int row, int col)
 {
     return "\x1b[" + std::to_string(row) + ";" + std::to_string(col) + "H";
@@ -378,6 +379,7 @@ class Terminal: public BaseTerminal {
         }
     }
 
+    // TODO: switch rows, cols
     void get_cursor_position(int& rows, int& cols) const
     {
         char buf[32];
@@ -403,6 +405,7 @@ class Terminal: public BaseTerminal {
     }
 
     // This function takes about 23ms, so it should only be used as a fallback
+    // TODO: switch rows / cols
     void get_term_size_slow(int& rows, int& cols) const
     {
         struct CursorOff {
@@ -553,6 +556,13 @@ std::string utf32_to_utf8(const std::u32string &s)
 }
 
 
+// TODO:
+// * Rename Window to Screen, as it really is a model of the terminal screen,
+// and should only be used once per application. If an application has windows,
+// those should be built on top, and they should render to Screen.
+// * Remember cursor position also (and if it is on or off)
+// * Implement screen diffing (taking another Window instance as an argument in
+// render())
 
 
 /* Represents a rectangular window, as a 2D array of characters and their
@@ -567,15 +577,15 @@ std::string utf32_to_utf8(const std::u32string &s)
 class Window
 {
 private:
-    size_t x0, y0; // top-left corner of the window on the screen
     size_t w, h; // width and height of the window
+    size_t cursor_x, cursor_y; // current cursor position
     std::vector<char32_t> chars; // the characters in row first order
     std::vector<fg> m_fg;
     std::vector<bg> m_bg;
     std::vector<style> m_style;
 public:
-    Window(size_t x0, size_t y0, size_t w, size_t h)
-        : x0{x0}, y0{y0}, w{w}, h{h}, chars(w*h, ' '),
+    Window(size_t w, size_t h)
+        : w{w}, h{h}, cursor_x{1}, cursor_y{1}, chars(w*h, ' '),
           m_fg(w*h, fg::reset), m_bg(w*h, bg::reset),
           m_style(w*h, style::reset) {}
 
@@ -583,8 +593,12 @@ class Window
         return chars[(y-1)*w+(x-1)];
     }
 
-    void set_char(int x, int y, char32_t c) {
-        chars[(y-1)*w+(x-1)] = c;
+    void set_char(size_t x, size_t y, char32_t c) {
+        if (x >= 1 && y >= 1 && x <= w && y <= h) {
+            chars[(y-1)*w+(x-1)] = c;
+        } else {
+            throw std::runtime_error("set_char(): (x,y) out of bounds");
+        }
     }
 
     fg get_fg(int x, int y) {
@@ -611,17 +625,65 @@ class Window
         m_style[(y-1)*w+(x-1)] = c;
     }
 
-    void print_str(int x, int y, const std::string &s) {
+    void set_cursor_pos(int x, int y) {
+        cursor_x = x;
+        cursor_y = y;
+    }
+
+    size_t get_w() {
+        return w;
+    }
+
+    size_t get_h() {
+        return h;
+    }
+
+    void set_h(size_t new_h) {
+        if (new_h == h) {
+            return;
+        } else if (new_h > h) {
+            int dc = (new_h-h) * w;
+            chars.insert(chars.end(), dc, 'X');
+            m_fg.insert(m_fg.end(), dc, fg::reset);
+            m_bg.insert(m_bg.end(), dc, bg::reset);
+            m_style.insert(m_style.end(), dc, style::reset);
+            h = new_h;
+        } else {
+            std::runtime_error("Shrinking height not implemented.");
+        }
+    }
+
+    void print_str(int x, int y, const std::string &s, int indent=0,
+            bool move_cursor=false) {
         std::u32string s2 = utf8_to_utf32(s);
+        size_t xpos = x;
+        size_t ypos = y;
         for (size_t i=0; i < s2.size(); i++) {
-            size_t xpos = x+i;
-            if (xpos < w) {
-                set_char(xpos, y, s2[i]);
+            if (s2[i] == U'\n') {
+                xpos = x+indent;
+                ypos++;
+                if (xpos <= w && ypos <= h) {
+                    for (int j=0; j < indent; j++) {
+                        set_char(x+j, ypos, '.');
+                    }
+                } else {
+                    // String is out of the window
+                    return;
+                }
             } else {
-                // String is out of the window
-                return;
+                if (xpos <= w && ypos <= h) {
+                    set_char(xpos, y, s2[i]);
+                } else {
+                    // String is out of the window
+                    return;
+                }
+                xpos++;
             }
         }
+        if (move_cursor) {
+            cursor_x = xpos;
+            cursor_y = ypos;
+        }
     }
 
     void fill_fg(int x1, int y1, int x2, int y2, fg color) {
@@ -690,7 +752,11 @@ class Window
         }
     }
 
-    std::string render() {
+    // TODO: add Window/Screen parameter here, to be used like this:
+    // old_scr = scr;
+    // scr.print_str(...)
+    // scr.render(1, 1, old_scr)
+    std::string render(int x0, int y0) {
         std::string out;
         out.append(cursor_off());
         fg current_fg = fg::reset;
@@ -728,10 +794,12 @@ class Window
                 if (update_bg) out.append(color(get_bg(i,j)));
                 codepoint_to_utf8(out, get_char(i,j));
             }
+            if (j < h) out.append("\n");
         }
         if (current_fg != fg::reset) out.append(color(fg::reset));
         if (current_bg != bg::reset) out.append(color(bg::reset));
         if (current_style != style::reset) out.append(color(style::reset));
+        out.append(move_cursor(y0+cursor_y-1, x0+cursor_x-1));
         out.append(cursor_on());
         return out;
     }
diff --git a/terminal_base.h b/terminal_base.h
index fb48a1ad..32267008 100644
--- a/terminal_base.h
+++ b/terminal_base.h
@@ -172,6 +172,7 @@ class BaseTerminal {
 #endif
     }
 
+    //TODO: switch rows / cols
     void get_term_size(int& rows, int& cols) const
     {
 #ifdef _WIN32

From 38f6caa731bbba2579c165b4325a960bc7f2f078 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 20:29:56 -0600
Subject: [PATCH 2/8] Extend with ' '

---
 terminal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/terminal.h b/terminal.h
index aeab3517..f24dab37 100644
--- a/terminal.h
+++ b/terminal.h
@@ -643,7 +643,7 @@ class Window
             return;
         } else if (new_h > h) {
             int dc = (new_h-h) * w;
-            chars.insert(chars.end(), dc, 'X');
+            chars.insert(chars.end(), dc, ' ');
             m_fg.insert(m_fg.end(), dc, fg::reset);
             m_bg.insert(m_bg.end(), dc, bg::reset);
             m_style.insert(m_style.end(), dc, style::reset);

From f4cb7e20a7f996fbae0873c91a069132871feb6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 20:44:25 -0600
Subject: [PATCH 3/8] Fix up rows

---
 examples/prompt.cpp | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index 80a138da..8a2f5a8d 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -81,7 +81,7 @@ void render(Term::Window &scr, const Model &m, size_t cols) {
 
 std::string prompt(const Terminal &term, const std::string &prompt_string,
         std::vector<std::string> &history) {
-    int row, col;
+    int row, col, new_row;
     term.get_cursor_position(row, col);
     int rows, cols;
     term.get_term_size(rows, cols);
@@ -103,6 +103,7 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
     render(scr, m, cols);
     std::cout << scr.render(1, row) << std::flush;
     while ((key = term.read_key()) != Key::ENTER) {
+        new_row = row;
         if (  (key >= 'a' && key <= 'z') ||
               (key >= 'A' && key <= 'Z') ||
               (!iscntrl(key) && key < 128)  ) {
@@ -155,6 +156,9 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.cursor_row = 1;
                         m.cursor_col = m.lines[0].size()+1;
                         scr.set_h(m.lines.size());
+                        if (row+(int)scr.get_h()-1 > rows) {
+                            new_row = rows - ((int)scr.get_h()-1);
+                        }
                     }
                     break;
                 case Key::ARROW_DOWN:
@@ -165,6 +169,9 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.cursor_row = 1;
                         m.cursor_col = m.lines[0].size()+1;
                         scr.set_h(m.lines.size());
+                        if (row+(int)scr.get_h()-1 > rows) {
+                            new_row = rows - ((int)scr.get_h()-1);
+                        }
                     }
                     break;
                 case ALT_KEY('n'):
@@ -178,14 +185,14 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                     m.cursor_col = after.size()+1;
                     m.cursor_row++;
                     scr.set_h(scr.get_h()+1);
+                    if (row+(int)scr.get_h()-1 > rows) {
+                        new_row = rows - ((int)scr.get_h()-1);
+                    }
             }
         }
         render(scr, m, cols);
         std::cout << scr.render(1, row) << std::flush;
-        // FIXME: this is a hack
-        if (key == Key::ALT_ENTER || key == ALT_KEY('n')) {
-            if (row+(int)scr.get_h()-1 > rows) row--;
-        }
+        row = new_row;
     }
     std::cout << "\n" << std::flush;
     history.push_back(concat(m.lines));

From ea4652900e95883659d688c80000f8dc3afcfcf9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 21:29:13 -0600
Subject: [PATCH 4/8] Throw the exception

---
 terminal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/terminal.h b/terminal.h
index f24dab37..0b92dee0 100644
--- a/terminal.h
+++ b/terminal.h
@@ -649,7 +649,7 @@ class Window
             m_style.insert(m_style.end(), dc, style::reset);
             h = new_h;
         } else {
-            std::runtime_error("Shrinking height not implemented.");
+            throw std::runtime_error("Shrinking height not implemented.");
         }
     }
 

From e6cbb65eccec66cb901883341faa7871c54e7440 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 21:38:00 -0600
Subject: [PATCH 5/8] Don't shrink

---
 examples/prompt.cpp | 16 ++++++++++------
 terminal.h          |  2 +-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index 8a2f5a8d..a67fa31b 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -155,9 +155,11 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.lines = split(hist[history_pos]);
                         m.cursor_row = 1;
                         m.cursor_col = m.lines[0].size()+1;
-                        scr.set_h(m.lines.size());
-                        if (row+(int)scr.get_h()-1 > rows) {
-                            new_row = rows - ((int)scr.get_h()-1);
+                        if (m.lines.size() > scr.get_h()) {
+                            scr.set_h(m.lines.size());
+                            if (row+(int)scr.get_h()-1 > rows) {
+                                new_row = rows - ((int)scr.get_h()-1);
+                            }
                         }
                     }
                     break;
@@ -168,9 +170,11 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.lines = split(hist[history_pos]);
                         m.cursor_row = 1;
                         m.cursor_col = m.lines[0].size()+1;
-                        scr.set_h(m.lines.size());
-                        if (row+(int)scr.get_h()-1 > rows) {
-                            new_row = rows - ((int)scr.get_h()-1);
+                        if (m.lines.size() > scr.get_h()) {
+                            scr.set_h(m.lines.size());
+                            if (row+(int)scr.get_h()-1 > rows) {
+                                new_row = rows - ((int)scr.get_h()-1);
+                            }
                         }
                     }
                     break;
diff --git a/terminal.h b/terminal.h
index 0b92dee0..a16f15dd 100644
--- a/terminal.h
+++ b/terminal.h
@@ -649,7 +649,7 @@ class Window
             m_style.insert(m_style.end(), dc, style::reset);
             h = new_h;
         } else {
-            throw std::runtime_error("Shrinking height not implemented.");
+            throw std::runtime_error("Shrinking height not supported.");
         }
     }
 

From 3d33d016a922e2d4182f206a46b8a0ccec7c901f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 23:10:57 -0600
Subject: [PATCH 6/8] Simplify new_row

---
 examples/prompt.cpp | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index a67fa31b..253ead3b 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -81,7 +81,7 @@ void render(Term::Window &scr, const Model &m, size_t cols) {
 
 std::string prompt(const Terminal &term, const std::string &prompt_string,
         std::vector<std::string> &history) {
-    int row, col, new_row;
+    int row, col;
     term.get_cursor_position(row, col);
     int rows, cols;
     term.get_term_size(rows, cols);
@@ -103,7 +103,6 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
     render(scr, m, cols);
     std::cout << scr.render(1, row) << std::flush;
     while ((key = term.read_key()) != Key::ENTER) {
-        new_row = row;
         if (  (key >= 'a' && key <= 'z') ||
               (key >= 'A' && key <= 'Z') ||
               (!iscntrl(key) && key < 128)  ) {
@@ -157,9 +156,6 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.cursor_col = m.lines[0].size()+1;
                         if (m.lines.size() > scr.get_h()) {
                             scr.set_h(m.lines.size());
-                            if (row+(int)scr.get_h()-1 > rows) {
-                                new_row = rows - ((int)scr.get_h()-1);
-                            }
                         }
                     }
                     break;
@@ -172,9 +168,6 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                         m.cursor_col = m.lines[0].size()+1;
                         if (m.lines.size() > scr.get_h()) {
                             scr.set_h(m.lines.size());
-                            if (row+(int)scr.get_h()-1 > rows) {
-                                new_row = rows - ((int)scr.get_h()-1);
-                            }
                         }
                     }
                     break;
@@ -189,14 +182,13 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                     m.cursor_col = after.size()+1;
                     m.cursor_row++;
                     scr.set_h(scr.get_h()+1);
-                    if (row+(int)scr.get_h()-1 > rows) {
-                        new_row = rows - ((int)scr.get_h()-1);
-                    }
             }
         }
         render(scr, m, cols);
         std::cout << scr.render(1, row) << std::flush;
-        row = new_row;
+        if (row+(int)scr.get_h()-1 > rows) {
+            row = rows - ((int)scr.get_h()-1);
+        }
     }
     std::cout << "\n" << std::flush;
     history.push_back(concat(m.lines));

From 6f9ab8f4c1b20a63db5d1fb476c71ae8fb74b399 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 23:21:19 -0600
Subject: [PATCH 7/8] up/down arrow

---
 examples/prompt.cpp | 46 +++++++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 16 deletions(-)

diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index 253ead3b..9258b3b7 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -148,26 +148,40 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                     m.cursor_col = m.lines[m.cursor_row-1].size()+1;
                     break;
                 case Key::ARROW_UP:
-                    if (history_pos > 0) {
-                        hist[history_pos] = concat(m.lines);
-                        history_pos--;
-                        m.lines = split(hist[history_pos]);
-                        m.cursor_row = 1;
-                        m.cursor_col = m.lines[0].size()+1;
-                        if (m.lines.size() > scr.get_h()) {
-                            scr.set_h(m.lines.size());
+                    if (m.cursor_row == 1) {
+                        if (history_pos > 0) {
+                            hist[history_pos] = concat(m.lines);
+                            history_pos--;
+                            m.lines = split(hist[history_pos]);
+                            m.cursor_row = 1;
+                            m.cursor_col = m.lines[0].size()+1;
+                            if (m.lines.size() > scr.get_h()) {
+                                scr.set_h(m.lines.size());
+                            }
+                        }
+                    } else {
+                        m.cursor_row--;
+                        if (m.cursor_col > m.lines[m.cursor_row-1].size()+1) {
+                            m.cursor_col = m.lines[m.cursor_row-1].size()+1;
                         }
                     }
                     break;
                 case Key::ARROW_DOWN:
-                    if (history_pos < hist.size()-1) {
-                        hist[history_pos] = concat(m.lines);
-                        history_pos++;
-                        m.lines = split(hist[history_pos]);
-                        m.cursor_row = 1;
-                        m.cursor_col = m.lines[0].size()+1;
-                        if (m.lines.size() > scr.get_h()) {
-                            scr.set_h(m.lines.size());
+                    if (m.cursor_row == m.lines.size()) {
+                        if (history_pos < hist.size()-1) {
+                            hist[history_pos] = concat(m.lines);
+                            history_pos++;
+                            m.lines = split(hist[history_pos]);
+                            m.cursor_row = 1;
+                            m.cursor_col = m.lines[0].size()+1;
+                            if (m.lines.size() > scr.get_h()) {
+                                scr.set_h(m.lines.size());
+                            }
+                        }
+                    } else {
+                        m.cursor_row++;
+                        if (m.cursor_col > m.lines[m.cursor_row-1].size()+1) {
+                            m.cursor_col = m.lines[m.cursor_row-1].size()+1;
                         }
                     }
                     break;

From 9a35db7410b756eb47d7a638e11a9ffaf66ed9ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C4=8Cert=C3=ADk?= <ondrej@certik.us>
Date: Wed, 2 Oct 2019 23:25:02 -0600
Subject: [PATCH 8/8] Update

---
 examples/prompt.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/examples/prompt.cpp b/examples/prompt.cpp
index 9258b3b7..e9d30c8c 100644
--- a/examples/prompt.cpp
+++ b/examples/prompt.cpp
@@ -153,8 +153,10 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                             hist[history_pos] = concat(m.lines);
                             history_pos--;
                             m.lines = split(hist[history_pos]);
-                            m.cursor_row = 1;
-                            m.cursor_col = m.lines[0].size()+1;
+                            m.cursor_row = m.lines.size();
+                            if (m.cursor_col>m.lines[m.cursor_row-1].size()+1) {
+                                m.cursor_col = m.lines[m.cursor_row-1].size()+1;
+                            }
                             if (m.lines.size() > scr.get_h()) {
                                 scr.set_h(m.lines.size());
                             }
@@ -173,7 +175,9 @@ std::string prompt(const Terminal &term, const std::string &prompt_string,
                             history_pos++;
                             m.lines = split(hist[history_pos]);
                             m.cursor_row = 1;
-                            m.cursor_col = m.lines[0].size()+1;
+                            if (m.cursor_col>m.lines[m.cursor_row-1].size()+1) {
+                                m.cursor_col = m.lines[m.cursor_row-1].size()+1;
+                            }
                             if (m.lines.size() > scr.get_h()) {
                                 scr.set_h(m.lines.size());
                             }