From fa126c8c7e00ee089af5f86ad6922d8257156425 Mon Sep 17 00:00:00 2001
From: Andy Spencer <andy753421@gmail.com>
Date: Mon, 20 Apr 2015 04:46:48 +0000
Subject: [PATCH] Add residual tracking in wm-wmii

This prevents extra space caused by
floating point round-off while tiling.
---
 util.c    |  8 ++++++++
 util.h    |  2 ++
 wm-wmii.c | 12 ++++++------
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/util.c b/util.c
index b589fd3..52bcf95 100644
--- a/util.c
+++ b/util.c
@@ -126,6 +126,14 @@ list_t *list_sort(list_t *list, int rev, int (*func)(void *a, void*b))
 }
 
 /* Misc */
+int residual(float num, float *state)
+{
+	float f = num + *state;
+	int   i = (int)(f+0.5);
+	*state = f - i;
+	return i;
+}
+
 int str2num(char *str, int def)
 {
 	char *end = NULL;
diff --git a/util.h b/util.h
index bc23ecd..16fe41e 100644
--- a/util.h
+++ b/util.h
@@ -58,6 +58,8 @@ list_t *list_find(list_t *list, void *data);
 list_t *list_sort(list_t *list, int rev, int (*func)(void*,void*));
 
 /* Misc */
+int residual(float num, float *state);
+
 int str2num(char *str, int def);
 
 int warn(char *fmt, ...);
diff --git a/wm-wmii.c b/wm-wmii.c
index e31f074..506cced 100644
--- a/wm-wmii.c
+++ b/wm-wmii.c
@@ -617,13 +617,15 @@ static void wm_update_cols(dpy_t *dpy)
 	int mx=0, my=0; // Maximum usable size (screen size minus margins)
 	int       sy=0; // Stack size (height of focused stack window)
 
+	float rx=0, ry=0; // Residuals for floating point round off
+
 	/* Scale horizontally */
 	x  = dpy->geom->x;
 	mx = dpy->geom->w - (list_length(dpy->cols)+1)*margin;
 	for (list_t *lcol = dpy->cols; lcol; lcol = lcol->next)
 		tx += COL(lcol)->width;
 	for (list_t *lcol = dpy->cols; lcol; lcol = lcol->next)
-		COL(lcol)->width *= (float)mx / tx;
+		COL(lcol)->width = residual(COL(lcol)->width * (float)mx/tx, &rx);
 
 	/* Scale each column vertically */
 	win_t *focus = get_focus();
@@ -645,13 +647,11 @@ static void wm_update_cols(dpy_t *dpy)
 			}
 			win->h = ROW(lrow)->height;
 			state_t state = ST_SHOW;
-			int height = 0;
 			switch (col->layout) {
 			case SPLIT:
-				sys_move(win, x+margin, y+margin,
-					col->width, win->h * ((float)my / ty));
-				height = win->h;
-				y += height + margin;
+				sys_move(win, x+margin, y+margin, col->width,
+					residual(win->h * ((float)my/ty), &ry));
+				y += win->h + margin;
 				break;
 			case STACK:
 				if (lrow->next && ROW(lrow->next)->win == col->row->win) {
-- 
2.43.2