1 files changed, 40 insertions, 12 deletions

diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index c4241eed45..be28e08675 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -743,18 +743,21 @@ struct file_buffer {
 // Stuff for diff mode.
 #define DB_COUNT 8     // up to four buffers can be diff'ed
 
-// Each diffblock defines where a block of lines starts in each of the buffers
-// and how many lines it occupies in that buffer.  When the lines are missing
-// in the buffer the df_count[] is zero.  This is all counted in
-// buffer lines.
-// There is always at least one unchanged line in between the diffs.
-// Otherwise it would have been included in the diff above or below it.
-// df_lnum[] + df_count[] is the lnum below the change.  When in one buffer
-// lines have been inserted, in the other buffer df_lnum[] is the line below
-// the insertion and df_count[] is zero.  When appending lines at the end of
-// the buffer, df_lnum[] is one beyond the end!
-// This is using a linked list, because the number of differences is expected
-// to be reasonable small.  The list is sorted on lnum.
+/// Each diffblock defines where a block of lines starts in each of the buffers
+/// and how many lines it occupies in that buffer.  When the lines are missing
+/// in the buffer the df_count[] is zero.  This is all counted in
+/// buffer lines.
+/// There is always at least one unchanged line in between the diffs (unless
+/// linematch is used).  Otherwise it would have been included in the diff above
+/// or below it.
+/// df_lnum[] + df_count[] is the lnum below the change.  When in one buffer
+/// lines have been inserted, in the other buffer df_lnum[] is the line below
+/// the insertion and df_count[] is zero.  When appending lines at the end of
+/// the buffer, df_lnum[] is one beyond the end!
+/// This is using a linked list, because the number of differences is expected
+/// to be reasonable small.  The list is sorted on lnum.
+/// Each diffblock also contains a cached list of inline diff of changes within
+/// the block, used for highlighting.
 typedef struct diffblock_S diff_T;
 struct diffblock_S {
   diff_T *df_next;
@@ -762,6 +765,31 @@ struct diffblock_S {
   linenr_T df_count[DB_COUNT];          // nr of inserted/changed lines
   bool is_linematched;  // has the linematch algorithm ran on this diff hunk to divide it into
                         // smaller diff hunks?
+
+  bool has_changes;     ///< has cached list of inline changes
+  garray_T df_changes;  ///< list of inline changes (diffline_change_T)
+};
+
+/// Each entry stores a single inline change within a diff block. Line numbers
+/// are recorded as relative offsets, and columns are byte offsets, not
+/// character counts.
+/// Ranges are [start,end), with the end being exclusive.
+typedef struct diffline_change_S diffline_change_T;
+struct diffline_change_S {
+  colnr_T dc_start[DB_COUNT];       ///< byte offset of start of range in the line
+  colnr_T dc_end[DB_COUNT];         ///< 1 paste byte offset of end of range in line
+  int dc_start_lnum_off[DB_COUNT];  ///< starting line offset
+  int dc_end_lnum_off[DB_COUNT];    ///< end line offset
+};
+
+/// Describes a single line's list of inline changes. Use diff_change_parse() to
+/// parse this.
+typedef struct diffline_S diffline_T;
+struct diffline_S {
+  diffline_change_T *changes;
+  int num_changes;
+  int bufidx;
+  int lineoff;
 };
 
 #define SNAP_HELP_IDX   0