Added FloatLogSlider

a slider that uses a logarithmic scale. Closes #719

ipywidgets/widgets/__init__.py

@@ -11,7 +11,7 @@
 from .widget_bool import Checkbox, ToggleButton, Valid
 from .widget_button import Button, ButtonStyle
 from .widget_box import Box, HBox, VBox
-from .widget_float import FloatText, BoundedFloatText, FloatSlider, FloatProgress, FloatRangeSlider
+from .widget_float import FloatText, BoundedFloatText, FloatSlider, FloatProgress, FloatRangeSlider, FloatLogSlider
 from .widget_image import Image
 from .widget_int import IntText, BoundedIntText, IntSlider, IntProgress, IntRangeSlider, Play, SliderStyle
 from .widget_color import ColorPicker

ipywidgets/widgets/widget_float.py

@@ -58,6 +58,39 @@ def _validate_max(self, proposal):
             self.value = max
         return max
 
+class _BoundedLogFloat(_Float):
+    max = CFloat(10.0, help="Max value").tag(sync=True)
+    min = CFloat(0.0, help="Min value").tag(sync=True)
+    base = CFloat(2.0, help="Base of val").tag(sync=True)
+
+    @validate('value')
+    def _validate_value(self, proposal):
+        """Cap and floor value"""
+        value = proposal['value']
+        if self.base ** self.min > value or self.base ** self.max < value:
+            value = min(max(value, self.base **  self.min), self.base **  self.max)
+        return value
+
+    @validate('min')
+    def _validate_min(self, proposal):
+        """Enforce min <= value <= max"""
+        min = proposal['value']
+        if min > self.max:
+            raise TraitError('Setting min > max')
+        if min > self.value:
+            self.value = min
+        return min
+
+    @validate('max')
+    def _validate_max(self, proposal):
+        """Enforce min <= value <= max"""
+        max = proposal['value']
+        if max < self.min:
+            raise TraitError('setting max < min')
+        if max < self.value:
+            self.value = max
+        return max
+
 
 @register
 class FloatText(_Float):
@@ -113,10 +146,12 @@ class FloatSlider(_BoundedFloat):
     ----------
     value : float
         position of the slider
+    base : float
+        base of the logarithmic scale. Default is 2
     min : float
-        minimal position of the slider
+        minimal position of the slider in log scale, i.e., actual minimum is base ** min
     max : float
-        maximal position of the slider
+        maximal position of the slider in log scale, i.e., actual maximum is base ** max
     step : float
         step of the trackbar
     description : str
@@ -141,6 +176,46 @@ class FloatSlider(_BoundedFloat):
     continuous_update = Bool(True, help="Update the value of the widget as the user is holding the slider.").tag(sync=True)
     disabled = Bool(False, help="Enable or disable user changes").tag(sync=True)
 
+    style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)
+
+
+@register
+class FloatLogSlider(_BoundedLogFloat):
+    """ Slider/trackbar of logarithmic floating values with the specified range.
+
+    Parameters
+    ----------
+    value : float
+        position of the slider
+    min : float
+        minimal position of the slider
+    max : float
+        maximal position of the slider
+    step : float
+        step of the trackbar
+    description : str
+        name of the slider
+    orientation : {'horizontal', 'vertical'}
+        default is 'horizontal', orientation of the slider
+    readout : {True, False}
+        default is True, display the current value of the slider next to it
+    readout_format : str
+        default is '.2f', specifier for the format function used to represent
+        slider value for human consumption, modeled after Python 3's format
+        specification mini-language (PEP 3101).
+    """
+    _view_name = Unicode('FloatLogSliderView').tag(sync=True)
+    _model_name = Unicode('FloatLogSliderModel').tag(sync=True)
+    step = CFloat(0.1, help="Minimum step to increment the value").tag(sync=True)
+    orientation = CaselessStrEnum(values=['horizontal', 'vertical'],
+        default_value='horizontal', help="Vertical or horizontal.").tag(sync=True)
+    readout = Bool(True, help="Display the current value of the slider next to it.").tag(sync=True)
+    readout_format = NumberFormat(
+        '.2f', help="Format for the readout").tag(sync=True)
+    continuous_update = Bool(True, help="Update the value of the widget as the user is holding the slider.").tag(sync=True)
+    disabled = Bool(False, help="Enable or disable user changes").tag(sync=True)
+    base = CFloat(2., help="Base for the logarithm").tag(sync=True)
+
 
     style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)
 

packages/controls/src/widget_float.ts

@@ -12,13 +12,14 @@ import {
 import * as _ from 'underscore';
 
 import {
-    IntSliderView, IntRangeSliderView, IntTextView
+    IntSliderView, IntRangeSliderView, IntTextView, BaseIntSliderView
 } from './widget_int';
 
 import {
     format
 } from 'd3-format';
 
+
 export
 class FloatModel extends CoreDescriptionModel {
     defaults() {
@@ -69,6 +70,36 @@ class FloatSliderModel extends BoundedFloatModel {
     readout_formatter: any;
 }
 
+export
+class FloatLogSliderModel extends BoundedFloatModel {
+    defaults() {
+        return _.extend(super.defaults(), {
+            _model_name: 'FloatLogSliderModel',
+            _view_name: 'FloatLogSliderView',
+            step: 1.0,
+            orientation: 'horizontal',
+            _range: false,
+            readout: true,
+            readout_format: '.2f',
+            slider_color: null,
+            continuous_update: true,
+            disabled: false,
+            base: 2.,
+        });
+    }
+    initialize(attributes, options) {
+        super.initialize(attributes, options);
+        this.on('change:readout_format', this.update_readout_format, this);
+        this.update_readout_format();
+    }
+
+    update_readout_format() {
+        this.readout_formatter = format(this.get('readout_format'));
+    }
+
+    readout_formatter: any;
+}
+
 export
 class FloatRangeSliderModel extends FloatSliderModel {}
 
@@ -85,6 +116,111 @@ class FloatSliderView extends IntSliderView {
     _parse_value = parseFloat;
 }
 
+
+export
+class FloatLogSliderView extends BaseIntSliderView {
+
+    update(options?) {
+        super.update(options);
+        let min = this.model.get('min');
+        let max = this.model.get('max');
+        let value = this.model.get('value');
+        let base = this.model.get('base');
+
+        let log_value = Math.log( value ) / Math.log( base );
+
+        if(log_value > max) {
+            log_value = max;
+        } else if(log_value < min) {
+            log_value = min;
+        }
+        this.$slider.slider('option', 'value', log_value);
+        this.readout.textContent = this.valueToString(value);
+        if(this.model.get('value') !== value) {
+            this.model.set('value', value, {updated_view: this});
+            this.touch();
+        }
+    }
+
+    /**
+     * Write value to a string
+     */
+    valueToString(value: number): string {
+        let format = this.model.readout_formatter;
+        return format(value);
+    }
+
+    /**
+     * Parse value from a string
+     */
+    stringToValue(text: string): number {
+            return this._parse_value(text);
+    }
+
+    /**
+     * this handles the entry of text into the contentEditable label first, the
+     * value is checked if it contains a parseable value then it is clamped
+     * within the min-max range of the slider finally, the model is updated if
+     * the value is to be changed
+     *
+     * if any of these conditions are not met, the text is reset
+     */
+    handleTextChange() {
+        let value = this.stringToValue(this.readout.textContent);
+        let vmin = this.model.get('min');
+        let vmax = this.model.get('max');
+
+        if (isNaN(value as number)) {
+            this.readout.textContent = this.valueToString(this.model.get('value'));
+        } else {
+            value = Math.max(Math.min(value as number, vmax), vmin);
+
+            if (value !== this.model.get('value')) {
+                this.readout.textContent = this.valueToString(value);
+                this.model.set('value', value, {updated_view: this});
+                this.touch();
+            } else {
+                this.readout.textContent = this.valueToString(this.model.get('value'));
+            }
+        }
+    }
+    /**
+     * Called when the slider value is changing.
+     */
+    handleSliderChange(e, ui) {
+        let base = this.model.get('base');
+        let actual_value = Math.pow(base,this._validate_slide_value(ui.value));
+        this.readout.textContent = this.valueToString(actual_value);
+
+        // Only persist the value while sliding if the continuous_update
+        // trait is set to true.
+        if (this.model.get('continuous_update')) {
+            this.handleSliderChanged(e, ui);
+        }
+    }
+
+    /**
+     * Called when the slider value has changed.
+     *
+     * Calling model.set will trigger all of the other views of the
+     * model to update.
+     */
+    handleSliderChanged(e, ui) {
+        let base = this.model.get('base');
+        let actual_value = Math.pow(base,this._validate_slide_value(ui.value));
+        this.model.set('value', actual_value, {updated_view: this});
+        this.touch();
+    }
+
+        _validate_slide_value(x) {
+        return x;
+    }
+
+    _parse_value = parseFloat;
+
+}
+
+
 export
 class FloatRangeSliderView extends IntRangeSliderView {
     /**