From c4b45efb9aa79554f591f2156c291bde8dce3b6c Mon Sep 17 00:00:00 2001
From: Stefan Jahn <stefan@gruft.de>
Date: Sat, 26 Nov 2022 21:22:50 +0100
Subject: [PATCH] Removed off-by-one error in zoomed histogram

---
 histogram.cc | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/histogram.cc b/histogram.cc
index 2e68c20..bebfde2 100644
--- a/histogram.cc
+++ b/histogram.cc
@@ -19,7 +19,7 @@ GtkWidget *histogram_da = NULL;
 int histogram[3][HISTOGRAM_WIDTH];	// 6* hist_width min, max, min , max.....
 int histogram_max;				// max vlaue
 int histogram_zoom_start = 0;           // first zoom value
-int histogram_zoom_stop = HISTOGRAM_WIDTH; // second zoom value
+int histogram_zoom_stop = HISTOGRAM_WIDTH-1; // second zoom value
 int histogram_x;                        // current mouse x-coordinate 
 int histogram_pressed_x;                // window x-coordinate when pressing a button
 int histogram_released_x;               // window x-coordinate when releasing a button
@@ -68,9 +68,10 @@ void cb_histogramda_draw(GtkWidget *area, cairo_t *cr, int w, int h, gpointer da
 		}
 		gdk_cairo_set_source_rgba(cr, &color);
 
-		int histogram_width = histogram_zoom_stop - histogram_zoom_start;
+		int histogram_width = histogram_zoom_stop - histogram_zoom_start + 1;
+		int histogram_scale = histogram_width - 1 > 0 ? histogram_width - 1 : 1;
     	for (int i = 0; i < histogram_width; i++) {
-	  px = HISTOGRAM_MARGIN + ((clientw-HISTOGRAM_MARGIN*2) * i) / histogram_width;
+	  px = HISTOGRAM_MARGIN + ((clientw-HISTOGRAM_MARGIN*2) * i) / histogram_scale;
 	  py2 = (clienth-HISTOGRAM_MARGIN) - ((clienth-HISTOGRAM_MARGIN*2) * log10(histogram[chan][histogram_zoom_start+i]+1) / log10(histogram_max));
 
     		if (i == 0) cairo_move_to(cr, px, py2);
@@ -183,7 +184,7 @@ void cb_histogramda_btnpress (GtkWidget *widget, gpointer data) {
   } else {
     histogram_zoomed = 0;
     histogram_zoom_start = 0;
-    histogram_zoom_stop = HISTOGRAM_WIDTH;
+    histogram_zoom_stop = HISTOGRAM_WIDTH-1;
   }
 };
 
@@ -202,13 +203,13 @@ void cb_histogramda_btnrelease (GtkWidget *widget, gpointer data) {
       // translate first coordinate
       histogram_zoom_start = (histogram_pressed_x - HISTOGRAM_MARGIN) * HISTOGRAM_WIDTH / (clientw - HISTOGRAM_MARGIN*2);
       if (histogram_zoom_start < 0) histogram_zoom_start = 0;
-      if (histogram_zoom_start > HISTOGRAM_WIDTH) histogram_zoom_start = HISTOGRAM_WIDTH;
+      if (histogram_zoom_start >= HISTOGRAM_WIDTH) histogram_zoom_start = HISTOGRAM_WIDTH-1;
 
       // translate second coordinate
       histogram_zoom_stop = (histogram_released_x - HISTOGRAM_MARGIN) * HISTOGRAM_WIDTH / (clientw - HISTOGRAM_MARGIN*2) + 1;
       // limit the values
       if (histogram_zoom_stop < 0) histogram_zoom_stop = 0;
-      if (histogram_zoom_stop > HISTOGRAM_WIDTH) histogram_zoom_stop = HISTOGRAM_WIDTH;
+      if (histogram_zoom_stop >= HISTOGRAM_WIDTH) histogram_zoom_stop = HISTOGRAM_WIDTH-1;
 
       // exchange the values if necessary
       if (histogram_zoom_start > histogram_zoom_stop) {