3824 - experiment: stop buffering in termbox

Now it's much more apparent why things are slow. You can see each repaint
happening. Already I fixed one performance bug -- in clear-rest-of-screen.

Since this subverts Mu's fake screen there may be bugs.

Another salubrious side effect: I've finally internalized that switching
to raw mode doesn't have to clear the screen. That was just an artifact
of how termbox abstracted operations. Now I can conceive of using termbox
to build a repl as well.

(I was inspired to poke into termbox internals by
http://viewsourcecode.org/snaptoken/kilo and
https://github.com/antirez/linenoise)

3 files changed, 14 insertions, 177 deletions

diff --git a/termbox/termbox.c b/termbox/termbox.c
index e7757f9a..7fff7d7c 100644
--- a/termbox/termbox.c
+++ b/termbox/termbox.c
@@ -23,20 +23,11 @@ extern int wcwidth (wchar_t);
 #include "output.inl"
 #include "input.inl"
 
-struct cellbuf {
-  int width;
-  int height;
-  struct tb_cell *cells;
-};
-
-#define CELL(buf, x, y) (buf)->cells[(y) * (buf)->width + (x)]
 #define IS_CURSOR_HIDDEN(cx, cy) (cx == -1 || cy == -1)
 #define LAST_COORD_INIT -1
 
 static struct termios orig_tios;
 
-static struct cellbuf back_buffer;
-static struct cellbuf front_buffer;
 static struct bytebuffer output_buffer;
 static struct bytebuffer input_buffer;
 
@@ -57,11 +48,6 @@ static uint16_t foreground = TB_WHITE;
 static void write_cursor(int x, int y);
 static void write_sgr(uint16_t fg, uint16_t bg);
 
-static void cellbuf_init(struct cellbuf *buf, int width, int height);
-static void cellbuf_resize(struct cellbuf *buf, int width, int height);
-static void cellbuf_clear(struct cellbuf *buf);
-static void cellbuf_free(struct cellbuf *buf);
-
 static void update_size(void);
 static void update_term_size(void);
 static void send_attr(uint16_t fg, uint16_t bg);
@@ -121,14 +107,8 @@ int tb_init(void)
   bytebuffer_puts(&output_buffer, funcs[T_HIDE_CURSOR]);
   bytebuffer_puts(&output_buffer, funcs[T_ENTER_MOUSE]);
   bytebuffer_puts(&output_buffer, funcs[T_ENTER_BRACKETED_PASTE]);
-  send_clear();
 
   update_term_size();
-  cellbuf_init(&back_buffer, termw, termh);
-  cellbuf_init(&front_buffer, termw, termh);
-  cellbuf_clear(&back_buffer);
-  cellbuf_clear(&front_buffer);
-
   return 0;
 }
 
@@ -151,8 +131,6 @@ void tb_shutdown(void)
   close(winch_fds[0]);
   close(winch_fds[1]);
 
-  cellbuf_free(&back_buffer);
-  cellbuf_free(&front_buffer);
   bytebuffer_free(&output_buffer);
   bytebuffer_free(&input_buffer);
   termw = termh = -1;
@@ -163,65 +141,6 @@ int tb_is_active(void)
   return termw != -1;
 }
 
-static void tb_repaint(bool force) {
-  int x,y,w,i;
-  struct tb_cell *back, *front;
-
-  assert(termw != -1);
-
-  /* invalidate cursor position */
-  lastx = LAST_COORD_INIT;
-  lasty = LAST_COORD_INIT;
-
-  if (buffer_size_change_request) {
-    update_size();
-    buffer_size_change_request = 0;
-  }
-
-  for (y = 0; y < front_buffer.height; ++y) {
-    for (x = 0; x < front_buffer.width; ) {
-      back = &CELL(&back_buffer, x, y);
-      front = &CELL(&front_buffer, x, y);
-      w = wcwidth(back->ch);
-      if (w < 1) w = 1;
-      if (!force && memcmp(back, front, sizeof(struct tb_cell)) == 0) {
-        x += w;
-        continue;
-      }
-      memcpy(front, back, sizeof(struct tb_cell));
-      send_attr(back->fg, back->bg);
-      if (w > 1 && x >= front_buffer.width - (w - 1)) {
-        // Not enough room for wide ch, so send spaces
-        for (i = x; i < front_buffer.width; ++i) {
-          send_char(i, y, ' ');
-        }
-      } else {
-        send_char(x, y, back->ch);
-        for (i = 1; i < w; ++i) {
-          front = &CELL(&front_buffer, x + i, y);
-          front->ch = 0;
-          front->fg = back->fg;
-          front->bg = back->bg;
-        }
-      }
-      x += w;
-    }
-  }
-  if (!IS_CURSOR_HIDDEN(cursor_x, cursor_y))
-    write_cursor(cursor_x, cursor_y);
-  bytebuffer_flush(&output_buffer, inout);
-}
-
-void tb_present(void)
-{
-  tb_repaint(false);
-}
-
-void tb_sync(void)
-{
-  tb_repaint(true);
-}
-
 void tb_set_cursor(int cx, int cy)
 {
   assert(termw != -1);
@@ -233,22 +152,15 @@ void tb_set_cursor(int cx, int cy)
   cursor_y = cy;
   if (!IS_CURSOR_HIDDEN(cursor_x, cursor_y))
     write_cursor(cursor_x, cursor_y);
+  bytebuffer_flush(&output_buffer, inout);
 }
 
 void tb_change_cell(int x, int y, uint32_t ch, uint16_t fg, uint16_t bg)
 {
   assert(termw != -1);
-  if ((unsigned)x >= (unsigned)back_buffer.width)
-    return;
-  if ((unsigned)y >= (unsigned)back_buffer.height)
-    return;
-  struct tb_cell c = {ch, fg, bg};
-  CELL(&back_buffer, x, y) = c;
-}
-
-struct tb_cell *tb_cell_buffer()
-{
-  return back_buffer.cells;
+  send_attr(fg, bg);
+  send_char(x, y, ch);
+  bytebuffer_flush(&output_buffer, inout);
 }
 
 int tb_poll_event(struct tb_event *event)
@@ -285,7 +197,7 @@ void tb_clear(void)
     update_size();
     buffer_size_change_request = 0;
   }
-  cellbuf_clear(&back_buffer);
+  send_clear();
 }
 
 void tb_set_clear_attributes(uint16_t fg, uint16_t bg)
@@ -334,56 +246,6 @@ static void write_sgr(uint16_t fg, uint16_t bg) {
   WRITE_LITERAL("m");
 }
 
-static void cellbuf_init(struct cellbuf *buf, int width, int height)
-{
-  buf->cells = (struct tb_cell*)malloc(sizeof(struct tb_cell) * width * height);
-  assert(buf->cells);
-  buf->width = width;
-  buf->height = height;
-}
-
-static void cellbuf_resize(struct cellbuf *buf, int width, int height)
-{
-  if (buf->width == width && buf->height == height)
-    return;
-
-  int oldw = buf->width;
-  int oldh = buf->height;
-  struct tb_cell *oldcells = buf->cells;
-
-  cellbuf_init(buf, width, height);
-  cellbuf_clear(buf);
-
-  int minw = (width < oldw) ? width : oldw;
-  int minh = (height < oldh) ? height : oldh;
-  int i;
-
-  for (i = 0; i < minh; ++i) {
-    struct tb_cell *csrc = oldcells + (i * oldw);
-    struct tb_cell *cdst = buf->cells + (i * width);
-    memcpy(cdst, csrc, sizeof(struct tb_cell) * minw);
-  }
-
-  free(oldcells);
-}
-
-static void cellbuf_clear(struct cellbuf *buf)
-{
-  int i;
-  int ncells = buf->width * buf->height;
-
-  for (i = 0; i < ncells; ++i) {
-    buf->cells[i].ch = ' ';
-    buf->cells[i].fg = foreground;
-    buf->cells[i].bg = background;
-  }
-}
-
-static void cellbuf_free(struct cellbuf *buf)
-{
-  free(buf->cells);
-}
-
 static void get_term_size(int *w, int *h)
 {
   struct winsize sz;
@@ -478,9 +340,6 @@ static void sigwinch_handler(int xxx)
 static void update_size(void)
 {
   update_term_size();
-  cellbuf_resize(&back_buffer, termw, termh);
-  cellbuf_resize(&front_buffer, termw, termh);
-  cellbuf_clear(&front_buffer);
   send_clear();
 }
 
diff --git a/termbox/termbox.h b/termbox/termbox.h
index c6cda6e1..a86bc6ca 100644
--- a/termbox/termbox.h
+++ b/termbox/termbox.h
@@ -9,18 +9,12 @@ extern "C" {
 /*** 1. Controlling the screen. */
 
 /* The screen is a 2D array of cells. */
-struct tb_cell {
-  uint32_t ch;  /* unicode character */
-  uint16_t fg;  /* foreground color (0-255) and attributes */
-  uint16_t bg;  /* background color (0-255) and attributes */
-};
 
-/* Names for some colors in tb_cell.fg and tb_cell.bg. */
+/* Names for some colors. */
 #define TB_BLACK 232
 #define TB_WHITE 255
 
-/* Colors in tb_cell can be combined using bitwise-OR with multiple
- * of the following attributes. */
+/* Some attributes of screen cells that can be combined with colors using bitwise-OR. */
 #define TB_BOLD      0x0100
 #define TB_UNDERLINE 0x0200
 #define TB_REVERSE   0x0400
@@ -44,34 +38,17 @@ int tb_is_active(void);
 int tb_width(void);
 int tb_height(void);
 
-/* Update the screen with internal state. Most methods below modify just the
- * internal state of the screen. Changes won't be visible until you call
- * tb_present(). */
-void tb_present(void);
-
-/* Variant of tb_present() that always refreshes the entire screen. */
-void tb_sync(void);
-
-/* Returns a pointer to the internal screen state: a 1D array of cells in
- * raster order. You'll need to call tb_width() and tb_height() for the
- * array's dimensions. The array stays valid until tb_clear() or tb_present()
- * are called. */
-struct tb_cell *tb_cell_buffer();
-
-/* Clear the internal screen state using either TB_DEFAULT or the
- * color/attributes set by tb_set_clear_attributes(). */
+/* Clear the screen. */
 void tb_clear(void);
 void tb_set_clear_attributes(uint16_t fg, uint16_t bg);
 
-/* Move the cursor. Upper-left character is (0, 0).
- */
+/* Move the cursor. Upper-left character is (0, 0). */
 void tb_set_cursor(int cx, int cy);
 /* To hide the cursor, call tb_set_cursor(TB_HIDE_CURSOR, TB_HIDE_CURSOR).
  * Cursor starts out hidden. */
 #define TB_HIDE_CURSOR -1
 
-/* Modify a specific cell of the screen. Don't forget to call tb_present() to
- * commit your changes. */
+/* Modify a specific cell of the screen. */
 void tb_change_cell(int x, int y, uint32_t ch, uint16_t fg, uint16_t bg);
 
 /*** 2. Controlling keyboard events. */
diff --git a/termbox/x.cc b/termbox/x.cc
index 73373818..5c7fb0a6 100644
--- a/termbox/x.cc
+++ b/termbox/x.cc
@@ -2,10 +2,11 @@
 #include"termbox.h"
 
 int main() {
-  tb_event event;
   tb_init();
-  tb_poll_event(&event);
+  tb_clear();
+  tb_change_cell(0, 0, 'a', TB_WHITE, TB_BLACK);
+  tb_event x;
+  tb_poll_event(&x);
   tb_shutdown();
-  std::cerr << (int)event.type << '\n';
   return 0;
 }