From b7c9e8ca23dee372ddf8ad5d1e845950ec15a2e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Janouch?= <p.janouch@gmail.com>
Date: Fri, 15 Jan 2016 03:49:24 +0100
Subject: [PATCH] degesch: make backlog limit configurable

---
 NEWS      |  2 ++
 degesch.c | 45 ++++++++++++++++++++++++++++++++++-----------
 2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/NEWS b/NEWS
index ebe7f7f..dc455df 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,8 @@
 
  * degesch: added a basic last.fm "now playing" plugin
 
+ * degesch: backlog limit was made configurable
+
  * Various bugfixes
 
 
diff --git a/degesch.c b/degesch.c
index 92669fd..0886df2 100644
--- a/degesch.c
+++ b/degesch.c
@@ -88,9 +88,6 @@ enum
 /// Some arbitrary limit for the history file
 #define HISTORY_LIMIT 10000
 
-/// How many lines of backlog to store in memory
-#define BACKLOG_LIMIT 1000
-
 /// Characters that separate words
 #define WORD_BREAKING_CHARS " \f\n\r\t\v"
 
@@ -1547,6 +1544,7 @@ struct app_context
 	// TODO: make buffer names fully unique like weechat does
 	struct str_map buffers_by_name;     ///< Buffers by name
 
+	unsigned backlog_limit;             ///< Limit for buffer lines
 	time_t last_displayed_msg_time;     ///< Time of last displayed message
 
 	// Terminal:
@@ -1616,6 +1614,8 @@ app_context_init (struct app_context *self)
 	str_map_init (&self->buffers_by_name);
 	self->buffers_by_name.key_xfrm = tolower_ascii_strxfrm;
 
+	// So that we don't lose the logo shortly after startup
+	self->backlog_limit = 1000;
 	self->last_displayed_msg_time = time (NULL);
 
 	char *encoding = nl_langinfo (CODESET);
@@ -1701,6 +1701,7 @@ on_config_show_all_prefixes_change (struct config_item *item)
 	refresh_prompt (ctx);
 }
 
+static void on_config_backlog_limit_change (struct config_item *item);
 static void on_config_attribute_change (struct config_item *item);
 static void on_config_logging_change (struct config_item *item);
 
@@ -1903,6 +1904,12 @@ static struct config_schema g_config_behaviour[] =
 	// You can use the -r switch, however that makes `less` very confused
 	// about line wrapping, and the result is suboptimal.
 
+	{ .name      = "backlog_limit",
+	  .comment   = "Maximum number of lines stored in the backlog",
+	  .type      = CONFIG_ITEM_INTEGER,
+	  .validate  = config_validate_nonnegative,
+	  .default_  = "1000",
+	  .on_change = on_config_backlog_limit_change },
 	{ .name      = "backlog_helper",
 	  .comment   = "Shell command to display a buffer's history",
 	  .type      = CONFIG_ITEM_STRING,
@@ -2991,6 +2998,29 @@ formatter_flush (struct formatter *self, FILE *stream, bool raw_attributes)
 
 // --- Buffers -----------------------------------------------------------------
 
+static void
+buffer_pop_excess_lines (struct app_context *ctx, struct buffer *self)
+{
+	int to_delete = (int) self->lines_count - (int) ctx->backlog_limit;
+	while (to_delete-- > 0 && self->lines)
+	{
+		struct buffer_line *excess = self->lines;
+		LIST_UNLINK_WITH_TAIL (self->lines, self->lines_tail, excess);
+		buffer_line_destroy (excess);
+		self->lines_count--;
+	}
+}
+
+static void
+on_config_backlog_limit_change (struct config_item *item)
+{
+	struct app_context *ctx = item->user_data;
+	ctx->backlog_limit = MAX (item->value.integer, INT_MAX);
+
+	LIST_FOR_EACH (struct buffer, iter, ctx->buffers)
+		buffer_pop_excess_lines (ctx, iter);
+}
+
 static void
 buffer_update_time (struct app_context *ctx, time_t now)
 {
@@ -3114,14 +3144,6 @@ log_formatter (struct app_context *ctx,
 	if (!buffer)
 		buffer = ctx->global_buffer;
 
-	if (buffer->lines_count >= BACKLOG_LIMIT)
-	{
-		struct buffer_line *popped = buffer->lines;
-		LIST_UNLINK_WITH_TAIL (buffer->lines, buffer->lines_tail, popped);
-		buffer_line_destroy (popped);
-		buffer->lines_count--;
-	}
-
 	struct buffer_line *line = buffer_line_new ();
 	line->flags = flags;
 	line->when = time (NULL);
@@ -3130,6 +3152,7 @@ log_formatter (struct app_context *ctx,
 	line->formatter = xmalloc (sizeof *line->formatter);
 	*line->formatter = *f;
 
+	buffer_pop_excess_lines (ctx, buffer);
 	LIST_APPEND_WITH_TAIL (buffer->lines, buffer->lines_tail, line);
 	buffer->lines_count++;