From: "Nikita V. Youshchenko" <yoush@cs.msu.su>
Date: Sat, 02 Nov 2002 17:57:13 +0300
Subject: A bug in Xaw/StripChart.c causes incorrect scale lines in xload window

Recently I tried to run xload on a high loaded server (load was more
than 10), and discovered that if window size is rather small, scale
lines are drawn incorrectly (upper than needed).

This is caused by a bug in Xaw/StripChart.c.
It draws lines with fixed integer steps. Than means that if window
height is 39 pixels, and 10 lines should be drawn to split view into 11
equal parts, lines will be drawn at 3, 6, 9, ,.., 30. So the bottom part
height will be 9 pixels while other parts height will be 2 pixels.

This patch makes part heights differ no more than by 1 pixel.

Debian bug#167448 <http://bugs.debian.org/167448>

Index: libXaw-X11R7.0-1.0.1/src/StripChart.c
===================================================================
--- libXaw-X11R7.0-1.0.1.orig/src/StripChart.c	2005-12-30 14:50:24.000000000 -0500
+++ libXaw-X11R7.0-1.0.1/src/StripChart.c	2006-02-26 19:09:07.000000000 -0500
@@ -373,12 +373,12 @@
  * the returned value is identical to the initial value of next and data is
  * unchanged.  Otherwise keeps half a window's worth of data.  If data is
  * changed, then w->strip_chart.max_value is updated to reflect the
- * largest data point
+ * largest data point.
  */
-static int 
+static int
 repaint_window(StripChartWidget w, int left, int width)
 {
-    int i, j;
+    int i, j, k;
     int next = w->strip_chart.interval;
     int scale = w->strip_chart.scale;
     int scalewidth = 0;
@@ -423,8 +423,10 @@
 	}
 
 	/* Draw graph reference lines */
+	k = XtHeight(w) % w->strip_chart.scale;
 	for (i = 1; i < w->strip_chart.scale; i++) {
-	    j = i * ((int)XtHeight(w) / w->strip_chart.scale);
+	    j = i * (XtHeight(w) / w->strip_chart.scale) +
+		((i * k + w->strip_chart.scale/2) / w->strip_chart.scale);
 	    XDrawLine(dpy, win, w->strip_chart.hiGC, left, j, scalewidth, j);
 	}
     }
@@ -446,7 +448,7 @@
 MoveChart(StripChartWidget w, Bool blit)
 {
     double old_max;
-    int left, i, j;
+    int left, i, j, k;
     int next = w->strip_chart.interval;
 
     if (!XtIsRealized((Widget)w))
@@ -495,8 +497,10 @@
 
     /* Draw graph reference lines */
     left = j;
+    k = XtHeight(w) % w->strip_chart.scale;
     for (i = 1; i < w->strip_chart.scale; i++) {
-	j = i * (XtHeight(w) / w->strip_chart.scale);
+	j = i * (XtHeight(w) / w->strip_chart.scale) +
+	    ((i * k + w->strip_chart.scale/2) / w->strip_chart.scale);
 	XDrawLine(XtDisplay((Widget)w), XtWindow((Widget)w),
 		  w->strip_chart.hiGC, left, j, XtWidth(w), j);
     }
@@ -557,23 +561,26 @@
     StripChartWidget w = (StripChartWidget)widget;
     XPoint *points;
     Cardinal size;
-    int i;
+    int i, k;
 
     if (w->strip_chart.scale <= 1) {
 	XtFree((char *)w->strip_chart.points);
 	w->strip_chart.points = NULL;
 	return;
     }
-    
+
     size = sizeof(XPoint) * (w->strip_chart.scale - 1);
 
     points = (XPoint *)XtRealloc((XtPointer)w->strip_chart.points, size);
     w->strip_chart.points = points;
 
     /* Draw graph reference lines into clip mask */
-
+    k = XtHeight(w) % w->strip_chart.scale;
     for (i = 1; i < w->strip_chart.scale; i++) {
 	points[i - 1].x = 0;
-	points[i - 1].y = XtHeight(w) / w->strip_chart.scale;
+	points[i - 1].y = i * (XtHeight(w) / w->strip_chart.scale) +
+	    ((i * k + w->strip_chart.scale/2) / w->strip_chart.scale);
     }
+    for (i = w->strip_chart.scale - 1; i > 1; i--)
+	points[i - 1].y -= points[i - 2].y;
 }