Created stream_color.js.

This is a pure refactoring that mostly just moves code from
subs.js to the new stream_color.js and updates module references
accordingly.  In order to prevent introducing some exports,
update_stream_color was given an additional "sub" parameter
and update_stream_sidebar_swatch_color was given an "id"
parameter.

Killed off unused initial_color_fetch var.

(imported from commit b7644ce67f50d31fb46f564d758d661eea776aa6)

static/js/stream_color.js

@@ -0,0 +1,184 @@
+var stream_color = (function () {
+
+var exports = {};
+
+exports.default_color = "#c2c2c2";
+// Auto-assigned colors should be from the default palette so it's easy to undo
+// changes, so if that pallete changes, change these colors.
+var stream_assignment_colors = ["#76ce90", "#fae589", "#a6c7e5", "#e79ab5",
+                                "#bfd56f", "#f4ae55", "#b0a5fd", "#addfe5",
+                                "#f5ce6e", "#c2726a", "#94c849", "#bd86e5",
+                                "#ee7e4a", "#a6dcbf", "#95a5fd", "#53a063",
+                                "#9987e1", "#e4523d", "#c2c2c2", "#4f8de4",
+                                "#c6a8ad", "#e7cc4d", "#c8bebf", "#a47462"];
+
+// Clone stream_assignement_colors
+var available_colors = stream_assignment_colors.slice(0);
+
+// Classes which could be returned by get_color_class.
+exports.color_classes = 'dark_background';
+
+exports.pick_color = function () {
+    if (available_colors.length === 0) {
+        // We've used all the palette colors, so start re-using them.
+        return stream_assignment_colors[exports.subscribed_streams().length
+                                        % stream_assignment_colors.length];
+    }
+
+    return available_colors[0];
+};
+
+exports.mark_color_used = function (color) {
+    var i;
+    for (i = 0; i < available_colors.length; ++i) {
+        if (available_colors[i] === color) {
+            available_colors.splice(i, 1);
+            return;
+        }
+    }
+};
+
+function update_table_stream_color(table, stream_name, color) {
+    var color_class = exports.get_color_class(color);
+    function fixup(elem) {
+        elem.css("background-color", color)
+            .removeClass(exports.color_classes)
+            .addClass(color_class);
+    }
+
+    var stream_labels = $("#floating_recipient_bar").add(table).find(".stream_label");
+    _.each(stream_labels, function (label) {
+        if ($(label).text() === stream_name) {
+            fixup($(label).parent("td").parent("tr").prev("tr")
+                          .nextUntil(".bookend_tr")
+                          .children(".messagebox_colorblock,.message_header_colorblock"));
+        }
+    });
+}
+
+function update_stream_sidebar_swatch_color(id, color) {
+    $("#stream_sidebar_swatch_" + id).css('background-color', color);
+}
+
+function update_historical_message_color(stream_name, color) {
+    update_table_stream_color($(".focused_table"), stream_name, color);
+    if ($(".focused_table").attr("id") !== "#zhome") {
+        update_table_stream_color($("#zhome"), stream_name, color);
+    }
+}
+
+var stream_color_palette = [
+    ['a47462', 'c2726a', 'e4523d', 'e7664d', 'ee7e4a', 'f4ae55'],
+    ['76ce90', '53a063', '94c849', 'bfd56f', 'fae589', 'f5ce6e'],
+    ['a6dcbf', 'addfe5', 'a6c7e5', '4f8de4', '95a5fd', 'b0a5fd'],
+    ['c2c2c2', 'c8bebf', 'c6a8ad', 'e79ab5', 'bd86e5', '9987e1']
+];
+
+var subscriptions_table_colorpicker_options = {
+    clickoutFiresChange: true,
+    showPalette: true,
+    palette: stream_color_palette
+};
+
+exports.set_colorpicker_color = function (colorpicker, color) {
+    colorpicker.spectrum(_.extend(subscriptions_table_colorpicker_options,
+                         {color: color}));
+};
+
+exports.update_stream_color = function (sub, stream_name, color, opts) {
+    opts = _.defaults({}, opts, {update_historical: false});
+    sub.color = color;
+    var id = parseInt(sub.id, 10);
+    // The swatch in the subscription row header.
+    $("#subscription_" + id + " .color_swatch").css('background-color', color);
+    // The swatch in the color picker.
+    exports.set_colorpicker_color($("#subscription_" + id + " .colorpicker"), color);
+
+    if (opts.update_historical) {
+        update_historical_message_color(stream_name, color);
+    }
+    update_stream_sidebar_swatch_color(sub.id, color);
+    tab_bar.colorize_tab_bar();
+};
+
+function picker_do_change_color (color) {
+    var stream_name = $(this).attr('stream_name');
+    var hex_color = color.toHexString();
+    subs.set_color(stream_name, hex_color);
+}
+subscriptions_table_colorpicker_options.change = picker_do_change_color;
+
+exports.sidebar_popover_colorpicker_options = {
+    clickoutFiresChange: true,
+    showPaletteOnly: true,
+    showPalette: true,
+    flat: true,
+    palette: stream_color_palette,
+    change: picker_do_change_color
+};
+
+exports.sidebar_popover_colorpicker_options_full = {
+    clickoutFiresChange: true,
+    showPalette: true,
+    flat: true,
+    cancelText: "",
+    chooseText: "choose",
+    palette: stream_color_palette,
+    change: picker_do_change_color
+};
+
+var lightness_threshold;
+$(function () {
+    // sRGB color component for dark label text.
+    // 0x33 to match the color #333333 set by Bootstrap.
+    var label_color = 0x33;
+    var lightness = colorspace.luminance_to_lightness(
+        colorspace.sRGB_to_linear(label_color));
+
+    // Compute midpoint lightness between that and white (100).
+    lightness_threshold = (lightness + 100) / 2;
+});
+
+// From a background color (in format "#fff" or "#ffffff")
+// pick a CSS class (or empty string) to determine the
+// text label color etc.
+//
+// It would be better to work with an actual data structure
+// rather than a hex string, but we have to deal with values
+// already saved on the server, etc.
+//
+// This gets called on every message, so cache the results.
+exports.get_color_class = _.memoize(function (color) {
+    var match, i, lightness, channel = [0, 0, 0], mult = 1;
+
+    match = /^#([\da-fA-F]{2})([\da-fA-F]{2})([\da-fA-F]{2})$/.exec(color);
+    if (!match) {
+        // 3-digit shorthand; Spectrum gives this e.g. for pure black.
+        // Multiply each digit by 16+1.
+        mult = 17;
+
+        match = /^#([\da-fA-F])([\da-fA-F])([\da-fA-F])$/.exec(color);
+        if (!match) {
+            // Can't understand color.
+            return '';
+        }
+    }
+
+    // CSS colors are specified in the sRGB color space.
+    // Convert to linear intensity values.
+    for (i=0; i<3; i++) {
+        channel[i] = colorspace.sRGB_to_linear(mult * parseInt(match[i+1], 16));
+    }
+
+    // Compute perceived lightness as CIE L*.
+    lightness = colorspace.luminance_to_lightness(
+        colorspace.rgb_luminance(channel));
+
+    // Determine if we're past the midpoint between the
+    // dark and light label lightness.
+    return (lightness < lightness_threshold) ? 'dark_background' : '';
+});
+
+return exports;
+
+}());