From 957e482f458e62e00714745d871e070140a5b7bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 11 Jun 2020 17:13:32 +0200
Subject: [PATCH] osc: 'Set Color' now updates already rendered cells in
 current grid

Since we don't have the original palette index in already rendered
cells, we compare the color *value*. If it matches, we assume this was
the color index used, and updates the cell's color.

Note that for performance reasons, we only update the current
grid. This is of course wrong, strictly speaking.

However, it is expected that _Set Color_ is used by full-screen
applications using the alternate grid.
---
 CHANGELOG.md |  2 ++
 osc.c        | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 030d6c7b..eb11f45e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,6 +30,8 @@
   double forked.
 * Unicode combining character overflow errors are only logged in when
   debug logging has been enabled.
+* OSC 4 (_Set Color_) now already rendered cells in the **current**
+  grid (_normal_ or _alternate_).
 
 
 ### Deprecated
diff --git a/osc.c b/osc.c
index 42f775b4..5a976100 100644
--- a/osc.c
+++ b/osc.c
@@ -470,7 +470,52 @@ osc_dispatch(struct terminal *term)
                 if (!color_is_valid)
                     continue;
 
-                LOG_DBG("change color definition for #%u to %06x", idx, color);
+                LOG_DBG("change color definition for #%u from %06x to %06x",
+                        idx, term->colors.table[idx], color);
+
+                /*
+                 * Update color of already rendered cells.
+                 *
+                 * Note that we do *not* store the original palette
+                 * index. Therefor, the best we can do is compare
+                 * colors - if they match, assume "our" palette index
+                 * was the one used to render the cell.
+                 *
+                 * There are a couple of cases where this isn't necessarily true:
+                 *  - user has configured the 16 base colors with non-unique colors.
+                 *  - the client has used 24-bit escapes for colors
+                 *
+                 * In general though, if the client configures the
+                 * palette, it is very likely only using index:ed
+                 * coloring (i.e. not 24-bit direct colors), and I
+                 * hope that it is unusual with palettes where all the
+                 * colors aren't unique.
+                 *
+                 * TODO: we should update *both* grids... but that's
+                 * really really slow. Normal usage of this OSC is by
+                 * full-screen applications using the alt screen.
+                 */
+                for (size_t r = 0; r < term->grid->num_rows; r++) {
+                    struct row *row = term->grid->rows[r];
+                    if (row == NULL)
+                        continue;
+
+                    for (size_t c = 0; c < term->grid->num_cols; c++) {
+                        struct cell *cell = &row->cells[c];
+                        if (cell->attrs.have_fg && cell->attrs.fg == term->colors.table[idx]) {
+                            cell->attrs.fg = color;
+                            cell->attrs.clean = 0;
+                            row->dirty = true;
+                        }
+
+                        if (cell->attrs.have_bg && cell->attrs.bg == term->colors.table[idx]) {
+                            cell->attrs.bg = color;
+                            cell->attrs.clean = 0;
+                            row->dirty = true;
+                        }
+                    }
+                }
+
                 term->colors.table[idx] = color;
             }
         }