levelBar: Factor out bar drawing

Split drawing logic from Slider to BarLevel subclass.
This changes part of the theme css from -slider- to -barlevel-.

https://bugzilla.gnome.org/show_bug.cgi?id=790280.

js/ui/barLevel.js

@@ -0,0 +1,131 @@
+/* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
+
+const Atk = imports.gi.Atk;
+const Cairo = imports.cairo;
+const Clutter = imports.gi.Clutter;
+const Lang = imports.lang;
+const St = imports.gi.St;
+const Signals = imports.signals;
+
+var BarLevel = new Lang.Class({
+    Name: "BarLevel",
+
+    _init(value, params) {
+        if (isNaN(value))
+            // Avoid spreading NaNs around
+            throw TypeError('The bar level value must be a number');
+        this._value = Math.max(Math.min(value, 1), 0);
+        this._barLevelWidth = 0;
+
+        if (params == undefined)
+            params = {}
+
+        this.actor = new St.DrawingArea({ styleClass: params['styleClass'] || 'barlevel',
+                                          can_focus: params['canFocus'] || false,
+                                          reactive: params['reactive'] || false,
+                                          accessible_role: params['accessibleRole'] || Atk.Role.LEVEL_BAR });
+        this.actor.connect('repaint', this._barLevelRepaint.bind(this));
+        this.actor.connect('allocation-changed', (actor, box) => {
+            this._barLevelWidth = box.get_width();
+        });
+
+        this._customAccessible = St.GenericAccessible.new_for_actor(this.actor);
+        this.actor.set_accessible(this._customAccessible);
+
+        this._customAccessible.connect('get-current-value', this._getCurrentValue.bind(this));
+        this._customAccessible.connect('get-minimum-value', this._getMinimumValue.bind(this));
+        this._customAccessible.connect('get-maximum-value', this._getMaximumValue.bind(this));
+        this._customAccessible.connect('set-current-value', this._setCurrentValue.bind(this));
+
+        this.connect('value-changed', this._valueChanged.bind(this));
+    },
+
+    setValue(value) {
+        if (isNaN(value))
+            throw TypeError('The bar level value must be a number');
+
+        this._value = Math.max(Math.min(value, 1), 0);
+        this.actor.queue_repaint();
+    },
+
+    _barLevelRepaint(area) {
+        let cr = area.get_context();
+        let themeNode = area.get_theme_node();
+        let [width, height] = area.get_surface_size();
+
+        let barLevelHeight = themeNode.get_length('-barlevel-height');
+        let barLevelBorderRadius = Math.min(width, barLevelHeight) / 2;
+        let fgColor = themeNode.get_foreground_color();
+
+        let barLevelColor = themeNode.get_color('-barlevel-background-color');
+        let barLevelActiveColor = themeNode.get_color('-barlevel-active-background-color');
+
+        let barLevelBorderWidth = themeNode.get_length('-barlevel-border-width');
+        let barLevelBorderColor = themeNode.get_color('-barlevel-border-color');
+        let barLevelActiveBorderColor = themeNode.get_color('-barlevel-active-border-color');
+
+        const TAU = Math.PI * 2;
+
+        let endX = barLevelBorderRadius + (width - 2 * barLevelBorderRadius) * this._value;
+
+        /* background bar */
+        cr.arc(width - barLevelBorderRadius - barLevelBorderWidth, height / 2, barLevelBorderRadius, TAU * 3 / 4, TAU * 1 / 4);
+        cr.lineTo(endX, (height + barLevelHeight) / 2);
+        cr.lineTo(endX, (height - barLevelHeight) / 2);
+        cr.lineTo(width - barLevelBorderRadius - barLevelBorderWidth, (height - barLevelHeight) / 2);
+        Clutter.cairo_set_source_color(cr, barLevelColor);
+        cr.fillPreserve();
+        Clutter.cairo_set_source_color(cr, barLevelBorderColor);
+        cr.setLineWidth(barLevelBorderWidth);
+        cr.stroke();
+
+        /* normal progress bar */
+        cr.arc(barLevelBorderRadius + barLevelBorderWidth, height / 2, barLevelBorderRadius, TAU * 1 / 4, TAU * 3 / 4);
+        cr.lineTo(endX, (height - barLevelHeight) / 2);
+        cr.lineTo(endX, (height + barLevelHeight) / 2);
+        cr.lineTo(barLevelBorderRadius + barLevelBorderWidth, (height + barLevelHeight) / 2);
+        Clutter.cairo_set_source_color(cr, barLevelActiveColor);
+        cr.fillPreserve();
+        Clutter.cairo_set_source_color(cr, barLevelActiveBorderColor);
+        cr.setLineWidth(barLevelBorderWidth);
+        cr.stroke();
+
+        /* end progress bar arc */
+        Clutter.cairo_set_source_color(cr, barLevelActiveColor);
+        cr.arc(endX, height / 2, barLevelBorderRadius, TAU * 3 / 4, TAU * 1 / 4);
+        cr.lineTo(Math.floor(endX), (height + barLevelHeight) / 2);
+        cr.lineTo(Math.floor(endX), (height - barLevelHeight) / 2);
+        cr.lineTo(endX, (height - barLevelHeight) / 2);
+        cr.fillPreserve();
+        cr.setLineWidth(barLevelBorderWidth);
+        cr.stroke();
+
+        cr.$dispose();
+    },
+
+    _getCurrentValue(actor) {
+        return this._value;
+    },
+
+    _getMinimumValue(actor) {
+        return 0;
+    },
+
+    _getMaximumValue(actor) {
+        return 1;
+    },
+
+    _setCurrentValue(actor, value) {
+        this._value = value;
+    },
+
+    _valueChanged(barLevel, value, property) {
+        this._customAccessible.notify("accessible-value");
+    },
+
+    get value() {
+        return this._value;
+    }
+});
+
+Signals.addSignalMethods(BarLevel.prototype);