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

@@ -771,36 +771,28 @@
             var s, m, t = axis.options.transform || identity,
                 it = axis.options.inverseTransform;
             
+            // precompute how much the axis is scaling a point
+            // in canvas space
             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);
-
-                // data point to canvas coordinate
-                if (t == identity) // slight optimization
-                    axis.p2c = function (p) { return (p - m) * s; };
-                else
-                    axis.p2c = function (p) { return (t(p) - m) * s; };
-                // canvas coordinate to data point
-                if (!it)
-                    axis.c2p = function (c) { return m + c / s; };
-                else
-                    axis.c2p = function (c) { return it(m + c / s); };
+                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 / (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); };
+                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
+                axis.p2c = function (p) { return (p - m) * s; };
+            else
+                axis.p2c = function (p) { return (t(p) - m) * s; };
+            // canvas coordinate to data point
+            if (!it)
+                axis.c2p = function (c) { return m + c / s; };
+            else
+                axis.c2p = function (c) { return it(m + c / s); };
         }
 
         function measureTickLabels(axis) {