Tickets #4137 & #4821: true color support with ncurses and S-Lang color detection

doc/FAQ

@@ -403,47 +403,51 @@ Frequently Asked Questions
    If you get colors, be happy.
 
    If your terminal stays black and white, your terminal doesn't support
-   color.  You might want to upgrade to a terminal which compatible with
+   color.  You might want to upgrade to a terminal which is compatible with
    the ANSI color sequences.
 
    If your terminal goes completely black, see the next question.
 
    More detailed answer:
 
-   Check that your terminal supports color.  color_xterm, rxvt and Linux
-   console do support, most other terminals don't.  You can test color
-   support with following simple C program:
+   Check that your terminal supports color.  Most terminals do. You can
+   test color support with the following command:
 
-    #include <stdio.h>
+        printf "\033[32m Hello color world! \033[m\n"
 
-    int main (void){
-        printf ("\033[32m Hello world! \033[m\n");
-        return 0;
-    }
+   You can test 256 color support with the following command:
 
-   Compile and run it.  If you see "Hello world!" text in green your
-   terminal supports color, otherwise not (however, for color_xterm see
-   also the next question).
+        printf "\033[38;5;120m Hello 256-color world! \033[m\n"
 
-   Check whether you are using Ncurses or the S-Lang library (type
-   "mc -V" to find out).
+   You can test true color support with the following command:
 
-   With S-Lang library you can force color support by setting the
-   environment variable COLORTERM to any value.
+        printf "\033[38;2;0;200;0m Hello true color world! \033[m\n"
 
-   If you use ncurses library, check that your terminfo database
-   supports color.  If not, you should install one of the enhanced
-   terminfo databases included in GNU Midnight Commander source
-   distribution.
+   If you see the text in green, your terminal supports the respective
+   color mode.
 
-   You might want to set the TERM environment variable so that you are
-   using the correct terminfo database or termcap entry.
+   Check that you are using the proper TERM variable for your terminal.
+   If not, set it accordingly. You can use the 'toe -a' command to list
+   all available terminfo entries.
 
-   If you use color_xterm (or rxvt) the correct value might be
-   xterm-color, xtermc or simply xterm.
+   If your terminal supports 256 colors, the correct entry name may be
+   appended with -256color. If your terminal supports true color, it
+   should be appended with -direct, -direct16, or -direct256. All three
+   variants provide both 256-color and true color support simultaneously.
+   The latter two variants make no difference in mc, and they support
+   basic colors including their bright versions along with true color
+   support, in contrast to the -direct variant, which supports only basic
+   8 colors together with true color when used in a skin.
 
-   If you use Linux console the correct value for TERM is linux or
-   console.
+   If there is no 256-color or true-color terminfo variant for your
+   terminal, even though your terminal supports it, send an e-mail to
+   ncurses/terminfo maintainers ([email protected]) and ask them to
+   add one.
+
+   With the S-Lang library (you can check by 'mc -V'), you can force
+   color support by setting the environment variable COLORTERM to any
+   value, and specifically force true color support by setting it to
+   'truecolor'.
 
 4.5 My color_xterm goes completely (or partially) black!
 

lib/skin/common.c

@@ -73,7 +73,7 @@ mc_skin_get_default_name (void)
     if (mc_global.tty.skin != NULL)
         return g_strdup (mc_global.tty.skin);
 
-    // from envirovement variable
+    // from environment variable
     tmp_str = getenv ("MC_SKIN");
     if (tmp_str != NULL)
         return g_strdup (tmp_str);
@@ -164,9 +164,10 @@ mc_skin_init (const gchar *skin_override, GError **mcerror)
     if (is_good_init && mc_skin__default.have_256_colors && !tty_use_256colors (&error))
     {
         mc_propagate_error (mcerror, 0,
-                            _ ("Unable to use '%s' skin with 256 colors support\non non-256 colors "
-                               "terminal.\nDefault skin has been loaded"),
-                            mc_skin__default.name);
+                            _ ("Unable to use '%s' skin with 256 colors support:\n%s\nDefault "
+                               "skin has been loaded"),
+                            mc_skin__default.name, error->message);
+        g_error_free (error);
         mc_skin_try_to_load_default ();
         mc_skin_colors_old_configure (&mc_skin__default);
         (void) mc_skin_ini_file_parse (&mc_skin__default);

lib/tty/color-internal.c

@@ -155,7 +155,7 @@ parse_256_or_true_color_name (const char *color_name)
                 i = (h[0] << 20) | (h[0] << 16) | (h[1] << 12) | (h[1] << 8) | (h[2] << 4) | h[2];
             else
                 i = (h[0] << 20) | (h[1] << 16) | (h[2] << 12) | (h[3] << 8) | (h[4] << 4) | h[5];
-            return (1 << 24) | i;
+            return FLAG_TRUECOLOR | i;
         }
     }
 
@@ -178,7 +178,7 @@ tty_color_get_name_by_index (int idx)
             return color_table[i].name;
 
     // Create and return the strings in "colorNNN" or "#rrggbb" format.
-    if ((idx >= 16 && idx < 256) || (idx & (1 << 24)) != 0)
+    if ((idx >= 16 && idx < 256) || (idx & FLAG_TRUECOLOR) != 0)
     {
         char name[9];
 
@@ -241,3 +241,37 @@ tty_attr_get_bits (const char *attrs)
 }
 
 /* --------------------------------------------------------------------------------------------- */
+
+int
+convert_256color_to_truecolor (int color)
+{
+    int r, g, b;
+
+    // Invalid color
+    if (color > 255)
+        return 0;
+
+    if (color >= 232)  // Gray scale
+        r = g = b = (color - 231) * 10 + 8;
+    else if (color >= 16)  // 6x6x6 color cube
+    {
+        color -= 16;
+
+        r = (color / (6 * 6) % 6);
+        r = r > 0 ? r * 40 + 55 : 0;
+
+        g = (color / 6 % 6);
+        g = g > 0 ? g * 40 + 55 : 0;
+
+        b = (color % 6);
+        b = b > 0 ? b * 40 + 55 : 0;
+    }
+    else  // We don't convert basic 16 colors as they are terminal-dependent and user-configurable
+        return color;
+
+    color = FLAG_TRUECOLOR | (r << 16) | (g << 8) | b;
+
+    return color;
+}
+
+/* --------------------------------------------------------------------------------------------- */

lib/tty/color-internal.h

@@ -18,6 +18,9 @@
 
 /*** typedefs(not structures) and defined constants **********************************************/
 
+#define FLAG_TRUECOLOR   (1 << 24)
+#define COLORS_TRUECOLOR (1 << 24)
+
 /*** enums ***************************************************************************************/
 
 typedef enum
@@ -44,12 +47,14 @@ typedef struct
 
 extern gboolean use_colors;
 extern gboolean mc_tty_color_disable;
+extern gboolean need_convert_256color;
 
 /*** declarations of public functions ************************************************************/
 
 const char *tty_color_get_name_by_index (int idx);
 int tty_color_get_index_by_name (const char *color_name);
 int tty_attr_get_bits (const char *attrs);
+int convert_256color_to_truecolor (int color);
 
 void tty_color_init_lib (gboolean disable, gboolean force);
 void tty_color_deinit_lib (void);

lib/tty/color-ncurses.c

@@ -38,6 +38,7 @@
 
 #include "lib/global.h"
 
+#include "tty.h"
 #include "tty-ncurses.h"
 #include "color.h"  // variables
 #include "color-internal.h"
@@ -53,6 +54,7 @@
 /*** file scope variables ************************************************************************/
 
 static GHashTable *mc_tty_color_color_pair_attrs = NULL;
+static int overlay_colors = 0;
 
 /* --------------------------------------------------------------------------------------------- */
 /*** file scope functions ************************************************************************/
@@ -127,6 +129,10 @@ tty_color_init_lib (gboolean disable, gboolean force)
         use_colors = TRUE;
         start_color ();
         use_default_colors ();
+
+        // Extended color mode detection routines must first be called before loading any skin
+        tty_use_256colors (NULL);
+        tty_use_truecolors (NULL);
     }
 
     mc_tty_color_color_pair_attrs = g_hash_table_new_full (
@@ -179,8 +185,9 @@ tty_color_try_alloc_lib_pair (tty_color_lib_pair_t *mc_color_pair)
         ibg = mc_color_pair->bg;
         attr = mc_color_pair->attr;
 
-        // In legacy color mode, change bright colors into bold
-        if (!tty_use_256colors (NULL) && !tty_use_truecolors (NULL))
+        // If we have 8 indexed colors only, change foreground bright colors into bold and
+        // background bright colors to basic colors
+        if (COLORS <= 8 || (tty_use_truecolors (NULL) && overlay_colors <= 8))
         {
             if (ifg >= 8 && ifg < 16)
             {
@@ -191,11 +198,31 @@ tty_color_try_alloc_lib_pair (tty_color_lib_pair_t *mc_color_pair)
             if (ibg >= 8 && ibg < 16)
             {
                 ibg &= 0x07;
-                // attr | = A_BOLD | A_REVERSE ;
             }
         }
 
+        // Shady trick: if we don't have the exact color, because it is overlaid by backwards
+        // compatibility indexed values, just borrow one degree of red. The user won't notice :)
+        if ((ifg & FLAG_TRUECOLOR) != 0)
+        {
+            ifg &= ~FLAG_TRUECOLOR;
+            if (ifg != 0 && ifg <= overlay_colors)
+                ifg += (1 << 16);
+        }
+
+        if ((ibg & FLAG_TRUECOLOR) != 0)
+        {
+            ibg &= ~FLAG_TRUECOLOR;
+            if (ibg != 0 && ibg <= overlay_colors)
+                ibg += (1 << 16);
+        }
+
+#if NCURSES_VERSION_PATCH >= 20170401 && defined(NCURSES_EXT_COLORS) && defined(NCURSES_EXT_FUNCS) \
+    && defined(HAVE_NCURSES_WIDECHAR)
+        init_extended_pair (mc_color_pair->pair_index, ifg, ibg);
+#else
         init_pair (mc_color_pair->pair_index, ifg, ibg);
+#endif
         mc_tty_color_save_attr (mc_color_pair->pair_index, attr);
     }
 }
@@ -231,17 +258,56 @@ tty_use_256colors (GError **error)
 {
     (void) error;
 
-    return (COLORS == 256);
+    overlay_colors = tty_tigetnum ("CO", NULL);
+
+    if (COLORS == 256 || (COLORS > 256 && overlay_colors == 256))
+        return TRUE;
+
+    if (tty_use_truecolors (NULL))
+    {
+        need_convert_256color = TRUE;
+        return TRUE;
+    }
+
+    g_set_error (error, MC_ERROR, -1,
+                 _ ("\nIf your terminal supports 256 colors, you need to set your TERM\n"
+                    "environment variable to match your terminal, perhaps using\n"
+                    "a *-256color or *-direct256 variant. Use the 'toe -a'\n"
+                    "command to list all available variants on your system.\n"));
+    return FALSE;
 }
 
 /* --------------------------------------------------------------------------------------------- */
 
 gboolean
 tty_use_truecolors (GError **error)
 {
-    // Not yet supported in ncurses
-    g_set_error (error, MC_ERROR, -1, _ ("True color not supported with ncurses."));
+    // Low level true color is supported since ncurses 6.0 patch 20170401 preceding release
+    // of ncurses 6.1. It needs ABI 6 or higher.
+#if !(NCURSES_VERSION_PATCH >= 20170401 && defined(NCURSES_EXT_COLORS)                             \
+      && defined(NCURSES_EXT_FUNCS) && defined(HAVE_NCURSES_WIDECHAR))
+    g_set_error (error, MC_ERROR, -1,
+                 _ ("For true color support, you need version 6.1 or later of the ncurses\n"
+                    "library with wide character and ABI 6 or higher support.\n"
+                    "Please upgrade your system.\n"));
     return FALSE;
+#else
+    // We support only bool RGB cap configuration (8:8:8 bits), but the other variants are so rare
+    // that we don't need to bother.
+    if (!(tty_tigetflag ("RGB", NULL) && COLORS == COLORS_TRUECOLOR))
+    {
+        g_set_error (
+            error, MC_ERROR, -1,
+            _ ("\nIf your terminal supports true colors, you need to set your TERM\n"
+               "environment variable to a *-direct256, *-direct16, or *-direct variant.\n"
+               "Use the 'toe -a' command to list all available variants on your system.\n"));
+        return FALSE;
+    }
+
+    overlay_colors = tty_tigetnum ("CO", NULL);
+
+    return TRUE;
+#endif
 }
 
 /* --------------------------------------------------------------------------------------------- */

lib/tty/color-slang.c

@@ -38,6 +38,7 @@
 #include "lib/global.h"
 #include "lib/util.h"  // whitespace()
 
+#include "tty.h"
 #include "tty-slang.h"
 #include "color.h"  // variables
 #include "color-internal.h"
@@ -61,7 +62,10 @@ has_colors (gboolean disable, gboolean force)
 {
     mc_tty_color_disable = disable;
 
-    if (force || (getenv ("COLORTERM") != NULL))
+    // S-Lang enables color if the setaf/setab/setf/setb terminfo capabilities are set or
+    // the COLORTERM environment variable is set
+
+    if (force)
         SLtt_Use_Ansi_Colors = 1;
 
     if (!mc_tty_color_disable)
@@ -132,6 +136,10 @@ tty_color_init_lib (gboolean disable, gboolean force)
     if (has_colors (disable, force) && !disable)
     {
         use_colors = TRUE;
+
+        // Extended color mode detection routines must first be called before loading any skin
+        tty_use_256colors (NULL);
+        tty_use_truecolors (NULL);
     }
 }
 
@@ -214,15 +222,27 @@ tty_set_normal_attrs (void)
 gboolean
 tty_use_256colors (GError **error)
 {
-    gboolean ret;
+    int colors, overlay_colors;
 
-    ret = (SLtt_Use_Ansi_Colors && SLtt_tgetnum ((char *) "Co") == 256);
+    colors = tty_tigetnum ("colors", "Co");
+    overlay_colors = tty_tigetnum ("CO", NULL);
 
-    if (!ret)
-        g_set_error (error, MC_ERROR, -1,
-                     _ ("Your terminal doesn't even seem to support 256 colors."));
+    if (SLtt_Use_Ansi_Colors && (colors == 256 || (colors > 256 && overlay_colors == 256)))
+        return TRUE;
+
+    if (tty_use_truecolors (NULL))
+    {
+        need_convert_256color = TRUE;
+        return TRUE;
+    }
+
+    g_set_error (error, MC_ERROR, -1,
+                 _ ("\nIf your terminal supports 256 colors, you need to set your TERM\n"
+                    "environment variable to match your terminal, perhaps using\n"
+                    "a *-256color or *-direct256 variant. Use the 'toe -a'\n"
+                    "command to list all available variants on your system.\n"));
 
-    return ret;
+    return FALSE;
 }
 
 /* --------------------------------------------------------------------------------------------- */
@@ -245,11 +265,15 @@ tty_use_truecolors (GError **error)
     /* Duplicate slang's check so that we can pop up an error message
        rather than silently use wrong colors. */
     colorterm = getenv ("COLORTERM");
-    if (colorterm == NULL
-        || (strcmp (colorterm, "truecolor") != 0 && strcmp (colorterm, "24bit") != 0))
+    if (!((tty_tigetflag ("RGB", NULL) && tty_tigetnum ("colors", "Co") == COLORS_TRUECOLOR)
+          || (colorterm != NULL
+              && (strcmp (colorterm, "truecolor") == 0 || strcmp (colorterm, "24bit") == 0))))
     {
         g_set_error (error, MC_ERROR, -1,
-                     _ ("Set COLORTERM=truecolor if your terminal really supports true colors."));
+                     _ ("\nIf your terminal supports true colors, you need to set your TERM\n"
+                        "environment variable to a *-direct256, *-direct16, or *-direct variant.\n"
+                        "Use the 'toe -a' command to list all available variants on your system.\n"
+                        "Alternatively, you can set COLORTERM=truecolor.\n"));
         return FALSE;
     }