Simplify transformation helper function slightly and fix issue 263

that prevented inverse transforms from working correctly.


git-svn-id: https://flot.googlecode.com/svn/trunk@303 1e0a6537-2640-0410-bfb7-f154510ff394

NEWS.txt

@@ -136,6 +136,8 @@ Bug fixes:
 - Fix bug with backwards compatibility for shadowSize = 0 (report and
   suggested fix by aspinak).
 - Adapt examples to skip loading excanvas (fix by Ryley Breiddal).
+- Fix bug that prevent a simple f(x) = -x transform from working
+  correctly (fix by Mike, issue 263).
 
 
 Flot 0.6

jquery.flot.js

@@ -771,11 +771,17 @@
             var s, m, t = axis.options.transform || identity,
                 it = axis.options.inverseTransform;
             
-            if (axis.direction == "x") {
             // precompute how much the axis is scaling a point
             // in canvas space
-                s = axis.scale = plotWidth / (t(axis.max) - t(axis.min));
-                m = t(axis.min);
+            if (axis.direction == "x") {
+                s = axis.scale = plotWidth / Math.abs(t(axis.max) - t(axis.min));
+                m = Math.min(t(axis.max), t(axis.min));
+            }
+            else {
+                s = axis.scale = plotHeight / Math.abs(t(axis.max) - t(axis.min));
+                s = -s;
+                m = Math.max(t(axis.max), t(axis.min));
+            }
 
             // data point to canvas coordinate
             if (t == identity) // slight optimization
@@ -788,20 +794,6 @@
             else
                 axis.c2p = function (c) { return it(m + c / s); };
         }
-            else {
-                s = axis.scale = plotHeight / (t(axis.max) - t(axis.min));
-                m = t(axis.max);
-                
-                if (t == identity)
-                    axis.p2c = function (p) { return (m - p) * s; };
-                else
-                    axis.p2c = function (p) { return (m - t(p)) * s; };
-                if (!it)
-                    axis.c2p = function (c) { return m - c / s; };
-                else
-                    axis.c2p = function (c) { return it(m - c / s); };
-            }
-        }
 
         function measureTickLabels(axis) {
             var opts = axis.options, i, ticks = axis.ticks || [], labels = [],