FR: Allow mixed use of colour modes

[Ingvix]

I'd like to have the possibility to set the colour mode per cell, so you'd have the freedom to use the often custom-defined 8 or 16 colours alongside truecolor. 256-colour mode from the 17th colour onwards isn't too hard to emulate with truecolor as they're not usually set to custom values, but you have no access to the real values of the base colours if you're only able to use the RGB control sequences.

My use cases for this feature would to potentially try to build a termbox-based terminal multiplexer, so to utilise all the host's capabilities, mixed use of the different colour sets would needed. Another idea of mine would be to create a sort of painting program, where the UI elements would use the default colour set, but you would paint with an arbitrary RBG colour if you wished.

[adsr]

Hi @Ingvix, valid point about not knowing what the default terminal colors are while in RGB mode. IMO the use case is still pretty niche to warrant the extra struct field and API function(s). Letting the end-user configure the colors is not a bad solution IMO. I'll leave the issue open for community feedback though.

Here's a (likely buggy) patch if you want to try it:

diff --git a/termbox2.h b/termbox2.h
index 321a9bb..5727f85 100644
--- a/termbox2.h
+++ b/termbox2.h
@@ -426,6 +426,7 @@ struct tb_cell {
     uint32_t ch;   // a Unicode codepoint
     uintattr_t fg; // bitwise foreground attributes
     uintattr_t bg; // bitwise background attributes
+    int output_mode; // output_mode override for this cell
 #ifdef TB_OPT_EGC
     uint32_t *ech; // a grapheme cluster of Unicode codepoints, 0-terminated
     size_t nech;   // num elements in ech, 0 means use ch instead of ech
@@ -511,6 +512,7 @@ int tb_set_cell(int x, int y, uint32_t ch, uintattr_t fg, uintattr_t bg);
 int tb_set_cell_ex(int x, int y, uint32_t *ch, size_t nch, uintattr_t fg,
     uintattr_t bg);
 int tb_extend_cell(int x, int y, uint32_t ch);
+int tb_set_cell_output_mode(int x, int y, int output_mode);
 
 /* Return a pointer to the cell at the specified position.
  *
@@ -2303,9 +2305,9 @@ static int extract_esc_cap(struct tb_event *event);
 static int extract_esc_mouse(struct tb_event *event);
 static int resize_cellbufs(void);
 static void handle_resize(int sig);
-static int send_attr(uintattr_t fg, uintattr_t bg);
+static int send_attr(uintattr_t fg, uintattr_t bg, int output_mode);
 static int send_sgr(uint32_t fg, uint32_t bg, int fg_is_default,
-    int bg_is_default);
+    int bg_is_default, int output_mode);
 static int send_cursor_if(int x, int y);
 static int send_char(int x, int y, uint32_t ch);
 static int send_cluster(int x, int y, uint32_t *ch, size_t nch);
@@ -2434,7 +2436,9 @@ int tb_present(void) {
             if (cell_cmp(back, front) != 0) {
                 cell_copy(front, back);
 
-                send_attr(back->fg, back->bg);
+                int output_mode = back->output_mode > 0 ? back->output_mode : global.output_mode;
+
+                send_attr(back->fg, back->bg, output_mode);
                 if (w > 1 && x >= global.front.width - (w - 1)) {
                     // Not enough room for wide char, send spaces
                     for (i = x; i < global.front.width; i++) {
@@ -2604,6 +2608,27 @@ int tb_set_output_mode(int mode) {
     return TB_ERR;
 }
 
+int tb_set_cell_output_mode(int x, int y, int mode) {
+    int rv;
+    if_not_init_return();
+    struct tb_cell *cell;
+    if_err_return(rv, cellbuf_get(&global.back, x, y, &cell));
+    switch (mode) {
+        case TB_OUTPUT_CURRENT:
+            return cell->output_mode;
+        case TB_OUTPUT_NORMAL:
+        case TB_OUTPUT_256:
+        case TB_OUTPUT_216:
+        case TB_OUTPUT_GRAYSCALE:
+#if TB_OPT_ATTR_W >= 32
+        case TB_OUTPUT_TRUECOLOR:
+#endif
+            cell->output_mode = mode;
+            return TB_OK;
+    }
+    return TB_ERR;
+}
+
 int tb_peek_event(struct tb_event *event, int timeout_ms) {
     if_not_init_return();
     return wait_event(event, timeout_ms);
@@ -3076,7 +3101,7 @@ static int send_init_escape_codes(void) {
 static int send_clear(void) {
     int rv;
 
-    if_err_return(rv, send_attr(global.fg, global.bg));
+    if_err_return(rv, send_attr(global.fg, global.bg, global.output_mode));
     if_err_return(rv,
         bytebuf_puts(&global.out, global.caps[TB_CAP_CLEAR_SCREEN]));
 
@@ -3774,7 +3799,7 @@ static void handle_resize(int sig) {
     errno = errno_copy;
 }
 
-static int send_attr(uintattr_t fg, uintattr_t bg) {
+static int send_attr(uintattr_t fg, uintattr_t bg, int output_mode) {
     int rv;
 
     if (fg == global.last_fg && bg == global.last_bg) {
@@ -3784,7 +3809,7 @@ static int send_attr(uintattr_t fg, uintattr_t bg) {
     if_err_return(rv, bytebuf_puts(&global.out, global.caps[TB_CAP_SGR0]));
 
     uint32_t cfg, cbg;
-    switch (global.output_mode) {
+    switch (output_mode) {
         default:
         case TB_OUTPUT_NORMAL:
             // The minus 1 below is because our colors are 1-indexed starting
@@ -3868,18 +3893,18 @@ static int send_attr(uintattr_t fg, uintattr_t bg) {
 
     int fg_is_default = (fg & 0xff) == 0;
     int bg_is_default = (bg & 0xff) == 0;
-    if (global.output_mode == TB_OUTPUT_256) {
+    if (output_mode == TB_OUTPUT_256) {
         if (fg & TB_HI_BLACK) fg_is_default = 0;
         if (bg & TB_HI_BLACK) bg_is_default = 0;
     }
 #if TB_OPT_ATTR_W >= 32
-    if (global.output_mode == TB_OUTPUT_TRUECOLOR) {
+    if (output_mode == TB_OUTPUT_TRUECOLOR) {
         fg_is_default = ((fg & 0xffffff) == 0) && ((fg & TB_HI_BLACK) == 0);
         bg_is_default = ((bg & 0xffffff) == 0) && ((bg & TB_HI_BLACK) == 0);
     }
 #endif
 
-    if_err_return(rv, send_sgr(cfg, cbg, fg_is_default, bg_is_default));
+    if_err_return(rv, send_sgr(cfg, cbg, fg_is_default, bg_is_default, output_mode));
 
     global.last_fg = fg;
     global.last_bg = bg;
@@ -3888,7 +3913,7 @@ static int send_attr(uintattr_t fg, uintattr_t bg) {
 }
 
 static int send_sgr(uint32_t cfg, uint32_t cbg, int fg_is_default,
-    int bg_is_default) {
+    int bg_is_default, int output_mode) {
     int rv;
     char nbuf[32];
 
@@ -3896,7 +3921,7 @@ static int send_sgr(uint32_t cfg, uint32_t cbg, int fg_is_default,
         return TB_OK;
     }
 
-    switch (global.output_mode) {
+    switch (output_mode) {
         default:
         case TB_OUTPUT_NORMAL:
             send_literal(rv, "\x1b[");
diff --git a/tests/test_output_mode/expected.ansi b/tests/test_output_mode/expected.ansi
index 466ae50..ded55af 100644
Binary files a/tests/test_output_mode/expected.ansi and b/tests/test_output_mode/expected.ansi differ
diff --git a/tests/test_output_mode/test.php b/tests/test_output_mode/test.php
index cee4897..075b898 100755
--- a/tests/test_output_mode/test.php
+++ b/tests/test_output_mode/test.php
@@ -14,4 +14,11 @@ $test->ffi->tb_set_output_mode($test->defines['TB_OUTPUT_GRAYSCALE']);
 $test->ffi->tb_printf(0, $y++, $fg, 0, "gray");
 $test->ffi->tb_present();
 
+$test->ffi->tb_set_cell_output_mode(2, 1, $test->defines['TB_OUTPUT_TRUECOLOR']);
+$test->ffi->tb_set_cell(2, 1, ord('A'), 0xff0000, 0x8080ff);
+$test->ffi->tb_present();
+
+$test->ffi->tb_printf(0, $y++, $fg + 1, 0, "more gray");
+$test->ffi->tb_present();
+
 $test->screencap();

And an example of setting a specific cell to TB_OUTPUT_TRUECOLOR:

I'll reiterate the patch likely contains multiple bugs. E.g., termbox makes an optimization to avoid repeatedly sending the same cell attributes for adjacent cells. It uses last_bg and last_fg to do this. We'd need to add last_output_mode as well to account for this. Also cell_cmp and cell_copy would probably need to account for mode. As you can see there's a fair bit of complexity involved.

[adsr]

I just remembered you might also be able to achieve this without any modifications to termbox. Set your first output mode, color whatever cells, and call tb_present. Then set the 2nd output mode, color your other cells, and call tb_present again. The original output mode colors will remain until the next resize, at which point you should re-render using the same technique. It's not the cleanest and maybe has edge cases / bugs, but I think you can do this today without any changes to termbox.