From 467bc3713790ae920e3d289102d2bd75b40ba9ee Mon Sep 17 00:00:00 2001
From: Alexander Iljin <ajsoft@yandex.ru>
Date: Fri, 20 Jan 2017 00:55:29 +0300
Subject: [PATCH] charts.lines: add flip-y-axis

---
 lines/lines-tests.factor | 11 +++++++++++
 lines/lines.factor       |  9 +++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/lines/lines-tests.factor b/lines/lines-tests.factor
index 9721703d48..d548eab506 100644
--- a/lines/lines-tests.factor
+++ b/lines/lines-tests.factor
@@ -220,6 +220,17 @@ IN: charts.lines.tests
     drawable-chunks [ { } like ] map
 ] unit-test
 
+{ 0 } [ -10 10 middle ] unit-test
+{ 15 } [ 10 20 middle ] unit-test
+{ -81/2 } [ -50 -31 middle ] unit-test
+
+{
+    { { { 0 300 } { 1 200 } { 2 150 } { 3 100 } { 4 0 } } }
+} [
+    { { { 0 0 } { 1 100 } { 2 150 } { 3 200 } { 4 300 } } }
+    { 0 300 } flip-y-axis
+] unit-test
+
 { { } }
 [ { } { } clip-data ] unit-test
 
diff --git a/lines/lines.factor b/lines/lines.factor
index da0946863f..4b885c142c 100644
--- a/lines/lines.factor
+++ b/lines/lines.factor
@@ -206,6 +206,11 @@ SYMBOL: elt
         monotonic-split-slice
     ] 2keep (drawable-chunks) ;
 
+: middle ( min max -- middle ) dupd swap - 2 / + ;
+
+: flip-y-axis ( chunks ymin,ymax -- chunks )
+    first2 middle 2 * '[ [ first2 _ swap - 2array ] map ] map ;
+
 PRIVATE>
 
 : draw-line ( seq -- )
@@ -228,6 +233,6 @@ M: line draw-gadget*
     dup parent>> dup chart? [
         chart-axes swap
         [ color>> gl-color ] [ data>> ] bi
-        dupd clip-data swap second drawable-chunks
-        [ [ draw-line ] each ] unless-empty
+        dupd clip-data swap second [ drawable-chunks ] keep
+        flip-y-axis [ [ draw-line ] each ] unless-empty
     ] [ 2drop ] if ;