Expose minreducedwidth and minreducedheight to API

src/plots/layout_attributes.js

@@ -228,6 +228,20 @@ module.exports = {
                 'between the plotting area and the axis lines'
             ].join(' ')
         },
+        minreducedwidth: {
+            valType: 'number',
+            min: 0,
+            dflt: 64,
+            editType: 'plot',
+            description: 'Minimum width of the plot with automargin applied.'
+        },
+        minreducedheight: {
+            valType: 'number',
+            min: 0,
+            dflt: 64,
+            editType: 'plot',
+            description: 'Minimum height of the plot with automargin applied.'
+        },
         autoexpand: {
             valType: 'boolean',
             dflt: true,

src/plots/plots.js

@@ -1512,6 +1512,8 @@ plots.supplyLayoutGlobalDefaults = function(layoutIn, layoutOut, formatObj) {
     coerce('margin.b');
     coerce('margin.pad');
     coerce('margin.autoexpand');
+    coerce('margin.minreducedwidth');
+    coerce('margin.minreducedheight');
 
     if(layoutIn.width && layoutIn.height) plots.sanitizeMargins(layoutOut);
 
@@ -1861,10 +1863,6 @@ function initMargins(fullLayout) {
 var MIN_SPECIFIED_WIDTH = 2;
 var MIN_SPECIFIED_HEIGHT = 2;
 
-// could be exposed as an option - the smallest we will allow automargin to shrink a larger plot
-var MIN_REDUCED_WIDTH = 64;
-var MIN_REDUCED_HEIGHT = 64;
-
 /**
  * autoMargin: called by components that may need to expand the margins to
  * be rendered on-plot.
@@ -1889,13 +1887,13 @@ plots.autoMargin = function(gd, id, o) {
     var minFinalWidth = Lib.constrain(
         width - margin.l - margin.r,
         MIN_SPECIFIED_WIDTH,
-        MIN_REDUCED_WIDTH
+        margin.minreducedwidth
     );
 
     var minFinalHeight = Lib.constrain(
         height - margin.t - margin.b,
         MIN_SPECIFIED_HEIGHT,
-        MIN_REDUCED_HEIGHT
+        margin.minreducedheight
     );
 
     var maxSpaceW = Math.max(0, width - minFinalWidth);
@@ -2032,13 +2030,13 @@ plots.doAutoMargin = function(gd) {
     var minFinalWidth = Lib.constrain(
         width - margin.l - margin.r,
         MIN_SPECIFIED_WIDTH,
-        MIN_REDUCED_WIDTH
+        margin.minreducedwidth
     );
 
     var minFinalHeight = Lib.constrain(
         height - margin.t - margin.b,
         MIN_SPECIFIED_HEIGHT,
-        MIN_REDUCED_HEIGHT
+        margin.minreducedheight
     );
 
     var maxSpaceW = Math.max(0, width - minFinalWidth);

test/image/mocks/z-automargin-minreducedheight.json

@@ -0,0 +1,55 @@
+{
+    "data": [{
+            "name": "< D E A T H >",
+            "marker": { "color": "red" },
+            "x": [
+                "Antonio Vivaldi",
+                "Johann Sebastian Bach",
+                "Wolfgang Amadeus Mozart",
+                "Ludwig van Beethoven"
+            ],
+            "y": [
+                "1741",
+                "1750",
+                "1791",
+                "1827"
+            ]
+    },
+    {
+        "name": "< B I R T H >",
+        "marker": { "color": "blue" },
+        "x": [
+            "Antonio Vivaldi",
+            "Johann Sebastian Bach",
+            "Wolfgang Amadeus Mozart",
+            "Ludwig van Beethoven"
+        ],
+        "y": [
+            "1678",
+            "1685",
+            "1756",
+            "1770"
+        ]
+    }],
+    "layout": {
+        "title": {
+            "text": "Longest and shortest<br>names and time periods"
+        },
+        "width": 240,
+        "height": 300,
+        "margin": {
+            "t": 80,
+            "b": 20,
+            "l": 20,
+            "r": 20,
+            "minreducedheight": 55
+        },
+        "yaxis": {
+            "type": "date",
+            "automargin": true
+        },
+        "xaxis": {
+            "automargin": true
+        }
+    }
+}

test/image/mocks/z-automargin-minreducedwidth.json

@@ -0,0 +1,56 @@
+{
+    "data": [{
+            "name": "< D E A T H >",
+            "marker": { "color": "red" },
+            "y": [
+                "Antonio Vivaldi but even longer",
+                "Johann Sebastian Bach but even longer",
+                "Wolfgang Amadeus Mozart but even longer",
+                "Ludwig van Beethoven but even longer"
+            ],
+            "x": [
+                "1741",
+                "1750",
+                "1791",
+                "1827"
+            ]
+    },
+    {
+        "name": "< B I R T H >",
+        "marker": { "color": "blue" },
+        "y": [
+            "Antonio Vivaldi but even longer",
+            "Johann Sebastian Bach but even longer",
+            "Wolfgang Amadeus Mozart but even longer",
+            "Ludwig van Beethoven but even longer"
+        ],
+        "x": [
+            "1678",
+            "1685",
+            "1756",
+            "1770"
+        ]
+    }],
+    "layout": {
+        "showlegend": false,
+        "title": {
+            "text": "Longest and shortest<br>names and time periods"
+        },
+        "width": 240,
+        "height": 200,
+        "margin": {
+            "t": 80,
+            "b": 20,
+            "l": 20,
+            "r": 20,
+            "minreducedwidth": 55
+        },
+        "xaxis": {
+            "type": "date",
+            "automargin": true
+        },
+        "yaxis": {
+            "automargin": true
+        }
+    }
+}