From b53eb4f5367920b76ca916f9fdf2210051a5b795 Mon Sep 17 00:00:00 2001
From: Emanuele Giaquinta <e.giaquinta@glauco.it>
Date: Thu, 30 Jun 2016 11:33:42 +0000
Subject: [PATCH 01/11] 24-bit color cube collision avoidance (patch by
 Fengguang Wu)

When the color cube slot is found to be already occupied by a similar
24-bit color, search through the -1, 0, +1 R/G/B indices trying to find
an empty slot, or the oldest used one (which hopefully is no longer in
active use).

This effectively reduces random collisions, hence make it pretty hard to
hit a vim GUI color scheme that cannot be correctly showed in urxvt.
---
 src/command.C | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
 src/rxvt.h    |  8 ++++++-
 2 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/src/command.C b/src/command.C
index c5a3d6dc..caf939d2 100644
--- a/src/command.C
+++ b/src/command.C
@@ -3336,6 +3336,20 @@ rxvt_term::process_osc_seq ()
     }
 }
 
+static unsigned int
+colorcube_index (unsigned int idx_r,
+                 unsigned int idx_g,
+                 unsigned int idx_b)
+{
+  assert (idx_r < Red_levels);
+  assert (idx_g < Green_levels);
+  assert (idx_b < Blue_levels);
+
+  return idx_r * Blue_levels * Green_levels +
+         idx_g * Blue_levels +
+         idx_b;
+}
+
 /*
  * Find the nearest color slot in the hidden color cube,
  * adapt its value to the 24bit RGB color.
@@ -3343,15 +3357,63 @@ rxvt_term::process_osc_seq ()
 unsigned int
 rxvt_term::map_rgb24_color (unsigned int r, unsigned int g, unsigned int b)
 {
-  unsigned int idx_r = (r & 0xff) / (0xff / (Red_levels - 1));
-  unsigned int idx_g = (g & 0xff) / (0xff / (Green_levels - 1));
-  unsigned int idx_b = (b & 0xff) / (0xff / (Blue_levels - 1));
-  unsigned int idx;
+  r &= 0xff;
+  g &= 0xff;
+  b &= 0xff;
+
+  unsigned int color = (r << 16) | (g << 8) | b;
+  unsigned int idx_r = r / (0xff / (Red_levels - 1));
+  unsigned int idx_g = g / (0xff / (Green_levels - 1));
+  unsigned int idx_b = b / (0xff / (Blue_levels - 1));
+  unsigned int idx = colorcube_index (idx_r, idx_g, idx_b);
+
+  // minor issue: could update idx 0 few more times
+  if (rgb24_seqno[idx] == 0
+      && rgb24_color[idx] == 0)
+    goto update;
+
+  if (rgb24_color[idx] == color)
+    return idx + minTermCOLOR24;
+
+  for (int i = idx_r - 1; i <= (signed) idx_r + 1; i++)
+    {
+      if (!IN_RANGE_EXC (i, 0, Red_levels))
+        continue;
+
+      for (int j = idx_g - 1; j <= (signed) idx_g + 1; j++)
+        {
+          if (!IN_RANGE_EXC (j, 0, Green_levels))
+            continue;
+
+          for (int k = idx_b - 1; k <= (signed) idx_b + 1; k++)
+            {
+              if (!IN_RANGE_EXC (k, 0, Blue_levels))
+                continue;
+
+              unsigned int index = colorcube_index (i, j, k);
+
+              // minor issue: could update index 0 few more times
+              if (rgb24_seqno[index] == 0
+                  && rgb24_color[index] == 0)
+                {
+                  idx = index;
+                  goto update;
+                }
+
+              if (rgb24_color[index] == color)
+                return index + minTermCOLOR24;
+
+              if (IN_RANGE_INC (rgb24_seqno[idx], rgb24_seqno[index], 0x7fff))
+                idx = index;
+            }
+        }
+    }
 
-  idx = minTermCOLOR24 + idx_r * Blue_levels * Green_levels +
-                         idx_g * Blue_levels +
-                         idx_b;
+update:
+  rgb24_color[idx] = color;
+  rgb24_seqno[idx] = ++rgb24_sequence;
 
+  idx += minTermCOLOR24;
   pix_colors_focused [idx].free (this);
   pix_colors_focused [idx].set (this, rgba (r * 0x0101,
                                             g * 0x0101,
diff --git a/src/rxvt.h b/src/rxvt.h
index 8c190253..d10e6a4f 100644
--- a/src/rxvt.h
+++ b/src/rxvt.h
@@ -372,6 +372,8 @@ struct mouse_event
 # define Blue_levels     4
 #endif
 
+#define RGB24_CUBE_SIZE (Red_levels * Green_levels * Blue_levels)
+
 #if defined (NO_MOUSE_REPORT) && !defined (NO_MOUSE_REPORT_SCROLLBAR)
 # define NO_MOUSE_REPORT_SCROLLBAR 1
 #endif
@@ -577,7 +579,7 @@ enum colour_list {
 #endif
   minTermCOLOR24,
   maxTermCOLOR24 = minTermCOLOR24 +
-                   (Red_levels * Green_levels * Blue_levels) - 1,
+                   RGB24_CUBE_SIZE - 1,
 #ifndef NO_CURSORCOLOR
   Color_cursor,
   Color_cursor2,
@@ -1272,6 +1274,10 @@ struct rxvt_term : zero_initialized, rxvt_vars, rxvt_screen
   void           *chunk;
   size_t          chunk_size;
 
+  uint32_t        rgb24_color[RGB24_CUBE_SIZE];   // the 24-bit color value
+  uint16_t        rgb24_seqno[RGB24_CUBE_SIZE];   // which one is older?
+  uint16_t        rgb24_sequence;
+
   static vector<rxvt_term *> termlist; // a vector of all running rxvt_term's
 
 #if ENABLE_FRILLS || ISO_14755
-- 
2.13.0