From c496046c21dec2ceef5e03a5205ea6d0cc0fde9f Mon Sep 17 00:00:00 2001
From: fvogel <fvogelnew1@free.fr>
Date: Sun, 28 Dec 2014 15:09:46 +0000
Subject: Fixed Bad counting of the total number of vertical pixels in the text
 widget, resulting in small change of the Y scrollbar size. Happened because
 CalculateDisplayLineHeight expects an index at start of a display line, which
 was not always the case.

---
 generic/tkTextDisp.c | 14 ++++++++++++++
 tests/text.test      | 18 ++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index f99ecd8..ae9c341 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -3711,6 +3711,20 @@ TkTextUpdateOneLine(
     }
 
     /*
+     * CalculateDisplayLineHeight _must_ be called (below) with an index at
+     * the beginning of a display line. Force this to happen. This is needed
+     * when TkTextUpdateOneLine is called with a line that is merged with its
+     * previous line: the number of merged logical lines in a display line is
+     * calculated correctly only when CalculateDisplayLineHeight receives
+     * an index at the beginning of a display line. In turn this causes the
+     * merged lines to receive their correct zero pixel height in
+     * TkBTreeAdjustPixelHeight.
+     */
+
+    TkTextFindDisplayLineEnd(textPtr, indexPtr, 0, NULL);
+    linePtr = indexPtr->linePtr;
+
+    /*
      * Iterate through all display-lines corresponding to the single logical
      * line 'linePtr' (and lines merged into this line due to eol elision),
      * adding up the pixel height of each such display line as we go along.
diff --git a/tests/text.test b/tests/text.test
index 6121b85..e75f38a 100644
--- a/tests/text.test
+++ b/tests/text.test
@@ -733,6 +733,24 @@ test text-9.2.46 {TextWidgetCmd procedure, "count" option} -setup {
 } -cleanup {
     destroy .mytop
 } -result {1 3}
+test text-9.2.47 {TextWidgetCmd procedure, "count" option} -setup {
+    .t delete 1.0 end
+    update
+    set res {}
+} -body {
+    for {set i 1} {$i < 25} {incr i} {
+        .t insert end "Line $i\n"
+    }
+    .t tag configure hidden -elide true
+    .t tag add hidden 5.7 11.0
+    update
+    set y1 [lindex [.t yview] 1]
+    .t count -displaylines 5.0 11.0
+    set y2 [lindex [.t yview] 1]
+    .t count -displaylines 5.0 12.0
+    set y3 [lindex [.t yview] 1]
+    list [expr {$y1 == $y2}] [expr {$y1 == $y3}]
+} -result {1 1}
 
 # Newer tags are higher priority
 .t tag configure elide1 -elide 0
-- 
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