From 8422d2715c8a95875737a475ae8a7c6905deebea Mon Sep 17 00:00:00 2001
From: Joachim Wiberg <troglobit@gmail.com>
Date: Mon, 15 Dec 2025 20:52:16 +0100
Subject: [PATCH] initctl: fix flickering in 'top' and handle smaller screens

Drop clear screen to fix flickering in 'initctl top' output.  Also, make
sure to not garble the display if the the terminal is too small.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
---
 src/cgutil.c | 55 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 35 insertions(+), 20 deletions(-)

diff --git a/src/cgutil.c b/src/cgutil.c
index 34af0eab..40ae1b95 100644
--- a/src/cgutil.c
+++ b/src/cgutil.c
@@ -40,8 +40,9 @@
 #include "initctl.h"
 #include "log.h"
 
-#define CDIM plain ? "" : "\e[2m"
-#define CRST plain ? "" : "\e[0m"
+#define CDIM   plain ? "" : "\e[2m"
+#define CRST   plain ? "" : "\e[0m"
+#define CLREOL plain ? "" : "\e[K"		/* Clear to end of line */
 
 #define NONE " "
 #define PIPE plain ? "| " : "│ "
@@ -421,25 +422,24 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 	struct stat st;
 	struct cg *cg;
 	char buf[512];
-	int rc = 0;
 	FILE *fp;
 	int i, n;
 	int num;
 
-	if (pos >= ttrows)
-		return 0;
+	if (pos >= ttrows - 1)
+		return pos;
 
 	if (-1 == lstat(path, &st))
-		return 1;
+		return pos;
 
 	if ((st.st_mode & S_IFMT) != S_IFDIR) {
 		errno = ENOTDIR;
-		return -1;
+		return pos;
 	}
 
 	fp = fopenf("r", "%s/cgroup.procs", path);
 	if (!fp)
-		return -1;
+		return pos;
 	num = 0;
 	while (fgets(buf, sizeof(buf), fp))
 		num++;
@@ -468,7 +468,10 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 			break;
 		}
 
-		puts(row);
+		printf("%s%s\n", row, CLREOL);
+		pos++;
+		if (pos >= ttrows - 1)
+			goto out;
 	}
 
 	if (num > 0) {
@@ -520,19 +523,18 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 					strlcat(row, CRST, sizeof(row));
 				}
 
-				puts(row);
+				printf("%s%s\n", row, CLREOL);
+				pos++;
 
 				free(cmdline);
-			}
 
-			if (mode == 1) {
-				pos += i;
-				if (pos >= ttrows)
+				if (pos >= ttrows - 1)
 					break;
 			}
 		}
 	}
 
+out:
 	fclose(fp);
 
 	n = scandir(path, &namelist, cgroup_filter, alphasort);
@@ -541,6 +543,9 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 			char *nm = namelist[i]->d_name;
 			char prefix[80];
 
+			if (pos >= ttrows - 1)
+				break;
+
 			snprintf(buf, sizeof(buf), "%s/%s", path, nm);
 			switch (mode) {
 			case 1:
@@ -577,9 +582,10 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 			strlcat(row, nm,   rplen);
 			strlcat(row, "/ ", rplen);
 
-			puts(row);
+			printf("%s%s\n", row, CLREOL);
+			pos++;
 
-			rc += cgroup_tree(buf, prefix, mode, pos + i);
+			pos = cgroup_tree(buf, prefix, mode, pos);
 
 			free(namelist[i]);
 		}
@@ -587,7 +593,7 @@ int cgroup_tree(char *path, char *pfx, int mode, int pos)
 		free(namelist);
 	}
 
-	return rc;
+	return pos;
 }
 
 int show_cgps(char *arg)
@@ -606,13 +612,22 @@ int show_cgps(char *arg)
 
 static void cgtop(uev_t *w, void *arg, int events)
 {
+	int lines;
+
 	(void)w;
 	(void)events;
 
-	fputs("\e[2J\e[1;1H", stdout);
-	if (heading)
+	/* Move cursor to home instead of clearing screen to avoid flicker */
+	fputs("\e[H", stdout);
+	lines = 0;
+	if (heading) {
 		print_header(" VmSIZE     RSS   VmLIB  %%MEM  %%CPU  GROUP");
-	cgroup_tree(arg, NULL, 1, 0);
+		lines = 1;
+	}
+	cgroup_tree(arg, NULL, 1, lines);
+	/* Clear from cursor to end of screen to remove leftover lines */
+	fputs("\e[J", stdout);
+	fflush(stdout);
 }
 
 static void cleanup(void)