continue lines off the edge toward invalid log values

Author: alexcjohnson

src/constants/numerical.js

@@ -49,6 +49,12 @@ module.exports = {
      */
     ALMOST_EQUAL: 1 - 1e-6,
 
+    /*
+     * If we're asked to clip a non-positive log value, how far off-screen
+     * do we put it?
+     */
+    LOG_CLIP: 10,
+
     /*
      * not a number, but for displaying numbers: the "minus sign" symbol is
      * wider than the regular ascii dash "-"

src/plots/cartesian/set_convert.js

@@ -21,6 +21,7 @@ var ensureNumber = Lib.ensureNumber;
 var numConstants = require('../../constants/numerical');
 var FP_SAFE = numConstants.FP_SAFE;
 var BADNUM = numConstants.BADNUM;
+var LOG_CLIP = numConstants.LOG_CLIP;
 
 var constants = require('./constants');
 var axisIds = require('./axis_ids');
@@ -59,20 +60,15 @@ module.exports = function setConvert(ax, fullLayout) {
 
     var axLetter = (ax._id || 'x').charAt(0);
 
-    // clipMult: how many axis lengths past the edge do we render?
-    // for panning, 1-2 would suffice, but for zooming more is nice.
-    // also, clipping can affect the direction of lines off the edge...
-    var clipMult = 10;
-
     function toLog(v, clip) {
         if(v > 0) return Math.log(v) / Math.LN10;
 
         else if(v <= 0 && clip && ax.range && ax.range.length === 2) {
-            // clip NaN (ie past negative infinity) to clipMult axis
+            // clip NaN (ie past negative infinity) to LOG_CLIP axis
             // length past the negative edge
             var r0 = ax.range[0],
                 r1 = ax.range[1];
-            return 0.5 * (r0 + r1 - 3 * clipMult * Math.abs(r0 - r1));
+            return 0.5 * (r0 + r1 - 2 * LOG_CLIP * Math.abs(r0 - r1));
         }
 
         else return BADNUM;

src/traces/scatter/line_points.js

@@ -9,7 +9,11 @@
 
 'use strict';
 
-var BADNUM = require('../../constants/numerical').BADNUM;
+var numConstants = require('../../constants/numerical');
+var BADNUM = numConstants.BADNUM;
+var LOG_CLIP = numConstants.LOG_CLIP;
+var LOG_CLIP_PLUS = LOG_CLIP + 0.5;
+var LOG_CLIP_MINUS = LOG_CLIP - 0.5;
 var Lib = require('../../lib');
 var segmentsIntersect = Lib.segmentsIntersect;
 var constrain = Lib.constrain;
@@ -19,6 +23,10 @@ var constants = require('./constants');
 module.exports = function linePoints(d, opts) {
     var xa = opts.xaxis;
     var ya = opts.yaxis;
+    var xLog = xa.type === 'log';
+    var yLog = ya.type === 'log';
+    var xLen = xa._length;
+    var yLen = ya._length;
     var connectGaps = opts.connectGaps;
     var baseTolerance = opts.baseTolerance;
     var shape = opts.shape;
@@ -59,7 +67,25 @@ module.exports = function linePoints(d, opts) {
         if(!di) return false;
         var x = xa.c2p(di.x);
         var y = ya.c2p(di.y);
-        if(x === BADNUM || y === BADNUM) return false;
+
+        // if non-positive log values, set them VERY far off-screen
+        // so the line looks essentially straight from the previous point.
+        if(x === BADNUM) {
+            if(xLog) x = xa.c2p(di.x, true);
+            if(x === BADNUM) return false;
+            // If BOTH were bad log values, make the line follow a constant
+            // exponent rather than a constant slope
+            if(yLog && y === BADNUM) {
+                x *= Math.abs(xa._m * yLen * (xa._m > 0 ? LOG_CLIP_PLUS : LOG_CLIP_MINUS) /
+                    (ya._m * xLen * (ya._m > 0 ? LOG_CLIP_PLUS : LOG_CLIP_MINUS)));
+            }
+            x *= 1000;
+        }
+        if(y === BADNUM) {
+            if(yLog) y = ya.c2p(di.y, true);
+            if(y === BADNUM) return false;
+            y *= 1000;
+        }
         return [x, y];
     }
 
@@ -79,16 +105,16 @@ module.exports = function linePoints(d, opts) {
     var latestXFrac, latestYFrac;
     // if we're off-screen, increase tolerance over baseTolerance
     function getTolerance(pt, nextPt) {
-        var xFrac = pt[0] / xa._length;
-        var yFrac = pt[1] / ya._length;
+        var xFrac = pt[0] / xLen;
+        var yFrac = pt[1] / yLen;
         var offScreenFraction = Math.max(0, -xFrac, xFrac - 1, -yFrac, yFrac - 1);
         if(offScreenFraction && (latestXFrac !== undefined) &&
             crossesViewport(xFrac, yFrac, latestXFrac, latestYFrac)
         ) {
             offScreenFraction = 0;
         }
         if(offScreenFraction && nextPt &&
-            crossesViewport(xFrac, yFrac, nextPt[0] / xa._length, nextPt[1] / ya._length)
+            crossesViewport(xFrac, yFrac, nextPt[0] / xLen, nextPt[1] / yLen)
         ) {
             offScreenFraction = 0;
         }
@@ -114,10 +140,10 @@ module.exports = function linePoints(d, opts) {
     // if both are outside there will be 0 or 2 intersections
     // (or 1 if it's right at a corner - we'll treat that like 0)
     // returns an array of intersection pts
-    var xEdge0 = -xa._length * maxScreensAway;
-    var xEdge1 = xa._length * (1 + maxScreensAway);
-    var yEdge0 = -ya._length * maxScreensAway;
-    var yEdge1 = ya._length * (1 + maxScreensAway);
+    var xEdge0 = -xLen * maxScreensAway;
+    var xEdge1 = xLen * (1 + maxScreensAway);
+    var yEdge0 = -yLen * maxScreensAway;
+    var yEdge1 = yLen * (1 + maxScreensAway);
     var edges = [
         [xEdge0, yEdge0, xEdge1, yEdge0],
         [xEdge1, yEdge0, xEdge1, yEdge1],
@@ -261,8 +287,8 @@ module.exports = function linePoints(d, opts) {
     }
 
     function addPt(pt) {
-        latestXFrac = pt[0] / xa._length;
-        latestYFrac = pt[1] / ya._length;
+        latestXFrac = pt[0] / xLen;
+        latestYFrac = pt[1] / yLen;
         // Are we more than maxScreensAway off-screen any direction?
         // if so, clip to this box, but in such a way that on-screen
         // drawing is unchanged

test/image/baselines/log_lines_fills.png

@@ -0,0 +1,33 @@
+{
+    "data": [{
+        "x": [-1, 1.5, 2, 0, 1, 3, 4, 5, 6, 1, -1, -1, 3, 3, 0, 7, 7, -1, -1],
+        "y": [-1, 1.5, 1, -1, -1, 1, 1, 0, 2, 2, 0, 2, 3, 4, 5, 6, -2, -2, -1],
+        "mode": "markers+lines", "fill": "toself"
+    }, {
+        "x": [-1, 1.5, 2, 0, 1, 3, 4, 5, 6, 1, -1, -1, 3, 3, 0, 7, 7, -1, -1],
+        "y": [-1, 1.5, 1, -1, -1, 1, 1, 0, 2, 2, 0, 2, 3, 4, 5, 6, -2, -2, -1],
+        "mode": "markers+lines", "fill": "toself", "xaxis": "x2"
+    }, {
+        "x": [-1, 1.5, 2, 0, 1, 3, 4, 5, 6, 1, -1, -1, 3, 3, 0, 7, 7, -1, -1],
+        "y": [-1, 1.5, 1, -1, -1, 1, 1, 0, 2, 2, 0, 2, 3, 4, 5, 6, -2, -2, -1],
+        "mode": "markers+lines", "fill": "toself", "yaxis": "y2"
+    }, {
+        "x": [-1, 1.5, 2, 0, 1, 3, 4, 5, 6, 1, -1, -1, 3, 3, 0, 7, 7, -1, -1],
+        "y": [-1, 1.5, 1, -1, -1, 1, 1, 0, 2, 2, 0, 2, 3, 4, 5, 6, -2, -2, -1],
+        "mode": "markers+lines", "fill": "toself", "xaxis": "x2", "yaxis": "y2"
+    }, {
+        "x": [0.01, 0.1], "y": [0.01, 0.1],
+        "mode": "markers", "xaxis": "x2", "yaxis": "y2"
+    }],
+    "layout": {
+        "width": 800,
+        "height": 600,
+        "xaxis": {"title": "linear"},
+        "xaxis2": {"title": "log", "type": "log"},
+        "yaxis": {"title": "linear"},
+        "yaxis2": {"title": "log", "type": "log"},
+        "grid": {"columns": 2, "rows": 2},
+        "showlegend": false,
+        "title": "Lines to invalid log values"
+    }
+}