paint.js

/*
    paint.js

    a paint editor for Snap!
    inspired by the Scratch paint editor.
 
    written by Kartik Chandra
    Copyright (C) 2014 by Kartik Chandra
  
    This file is part of Snap!.
 
    Snap! is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of
    the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.


    toc
    ---
    the following list shows the order in which all constructors are
    defined. Use this list to locate code in this document:

        PaintEditorMorph
        PaintColorPickerMorph
        PaintCanvasMorph


    credits
    -------
    Nathan Dinsmore contributed a fully working prototype,
    Nathan's brilliant flood-fill tool has been more or less
    directly imported into this paint implementation.

    Jens Mönig has contributed icons and bugfixes and says he has probably
    introduced many other bugs in that process. :-)


    revision history
    ----------------
    May 10 - first full release (Kartik)
    May 14 - bugfixes, Snap integration (Jens)
    May 16 - flat design adjustments (Jens)
    July 12 - pipette tool, code formatting adjustments (Jens)
    September 16 - flood fill freeze fix (Kartik)
    Jan 08 - mouse leave dragging fix (Kartik)
    Feb 11 - dynamically adjust to stage dimensions (Jens)
    Apr 30 - localizations (Manuel)

 */

/*global Point, Rectangle, DialogBoxMorph, fontHeight, AlignmentMorph,
 FrameMorph, PushButtonMorph, Color, SymbolMorph, newCanvas, Morph, TextMorph,
 CostumeIconMorph, IDE_Morph, Costume, SpriteMorph, nop, Image, WardrobeMorph,
 TurtleIconMorph, localize, MenuMorph, InputFieldMorph, SliderMorph,
 ToggleMorph, ToggleButtonMorph, BoxMorph, modules, radians,
 MorphicPreferences, getDocumentPositionOf, StageMorph
 */

// Global stuff ////////////////////////////////////////////////////////

modules.paint = '2014-May-02';

// Declarations

var PaintEditorMorph;
var PaintCanvasMorph;
var PaintColorPickerMorph;

// PaintEditorMorph //////////////////////////

// A complete paint editor

PaintEditorMorph.prototype = new DialogBoxMorph();
PaintEditorMorph.prototype.constructor = PaintEditorMorph;
PaintEditorMorph.uber = DialogBoxMorph.prototype;

PaintEditorMorph.prototype.padding = 10;

function PaintEditorMorph() {
    this.init();
}

PaintEditorMorph.prototype.init = function () {
    // additional properties:
    this.paper = null; // paint canvas
    this.oncancel = null;

    // initialize inherited properties:
    PaintEditorMorph.uber.init.call(this);

    // override inherited properties:
    this.labelString = "Paint Editor";
    this.createLabel();

    // build contents:
    this.buildContents();
};

PaintEditorMorph.prototype.buildContents = function () {
    var myself = this;

    this.paper = new PaintCanvasMorph(function () {return myself.shift; });
    this.paper.setExtent(StageMorph.prototype.dimensions);

    this.addBody(new AlignmentMorph('row', this.padding));
    this.controls = new AlignmentMorph('column', this.padding);
    this.controls.alignment = 'left';

    this.edits = new AlignmentMorph('row', this.padding);
    this.buildEdits();
    this.controls.add(this.edits);

    this.body.color = this.color;

    this.body.add(this.controls);
    this.body.add(this.paper);

    this.toolbox = new BoxMorph();
    this.toolbox.color = SpriteMorph.prototype.paletteColor.lighter(8);
    this.toolbox.borderColor = this.toolbox.color.lighter(40);
    if (MorphicPreferences.isFlat) {
        this.toolbox.edge = 0;
    }

    this.buildToolbox();
    this.controls.add(this.toolbox);

    this.propertiesControls = {
        colorpicker: null,
        penSizeSlider: null,
        penSizeField: null,
        primaryColorButton: null,
        primaryColorViewer: null,
        constrain: null
    };
    this.populatePropertiesMenu();

    this.addButton("ok", "OK");
    this.addButton("cancel", "Cancel");

    this.refreshToolButtons();
    this.fixLayout();
    this.drawNew();
};

PaintEditorMorph.prototype.buildToolbox = function () {
    var tools = {
            brush:
                "Paintbrush tool\n(free draw)",
            rectangle:
                "Stroked Rectangle\n(shift: square)",
            circle:
                "Stroked Ellipse\n(shift: circle)",
            eraser:
                "Eraser tool",
            crosshairs:
                "Set the rotation center",

            line:
                "Line tool\n(shift: vertical/horizontal)",
            rectangleSolid:
                "Filled Rectangle\n(shift: square)",
            circleSolid:
                "Filled Ellipse\n(shift: circle)",
            paintbucket:
                "Fill a region",
            pipette:
                "Pipette tool\n(pick a color anywhere)"
        },
        myself = this,
        left = this.toolbox.left(),
        top = this.toolbox.top(),
        padding = 2,
        inset = 5,
        x = 0,
        y = 0;

    Object.keys(tools).forEach(function (tool) {
        var btn = myself.toolButton(tool, tools[tool]);
        btn.setPosition(new Point(
            left + x,
            top + y
        ));
        x += btn.width() + padding;
        if (tool === "crosshairs") {
            x = 0;
            y += btn.height() + padding;
            myself.paper.drawcrosshair();
        }
        myself.toolbox[tool] = btn;
        myself.toolbox.add(btn);
    });

    this.toolbox.bounds = this.toolbox.fullBounds().expandBy(inset * 2);
    this.toolbox.drawNew();
};

PaintEditorMorph.prototype.buildEdits = function () {
    var paper = this.paper;

    this.edits.add(this.pushButton(
        "undo",
        function () {paper.undo(); }
    ));

    this.edits.add(this.pushButton(
        "clear",
        function () {paper.clearCanvas(); }
    ));
    this.edits.fixLayout();
};

PaintEditorMorph.prototype.openIn = function (world, oldim, oldrc, callback) {
    // Open the editor in a world with an optional image to edit
    this.oldim = oldim;
    this.oldrc = oldrc.copy();
    this.callback = callback || nop;

    this.processKeyUp = function () {
        this.shift = false;
        this.propertiesControls.constrain.refresh();
    };

    this.processKeyDown = function () {
        this.shift = this.world().currentKey === 16;
        this.propertiesControls.constrain.refresh();
    };

    //merge oldim:
    if (this.oldim) {
        this.paper.centermerge(this.oldim, this.paper.paper);
        this.paper.rotationCenter =
            this.oldrc.add(
                new Point(
                    (this.paper.paper.width - this.oldim.width) / 2,
                    (this.paper.paper.height - this.oldim.height) / 2
                )
            );
        this.paper.drawNew();
    }

    this.key = 'paint';
    this.popUp(world);
};

PaintEditorMorph.prototype.fixLayout = function () {
    var oldFlag = Morph.prototype.trackChanges;

    this.changed();
    oldFlag = Morph.prototype.trackChanges;
    Morph.prototype.trackChanges = false;

    if (this.paper) {
        this.paper.buildContents();
        this.paper.drawNew();
    }
    if (this.controls) {this.controls.fixLayout(); }
    if (this.body) {this.body.fixLayout(); }
    PaintEditorMorph.uber.fixLayout.call(this);

    Morph.prototype.trackChanges = oldFlag;
    this.changed();
};

PaintEditorMorph.prototype.refreshToolButtons = function () {
    this.toolbox.children.forEach(function (toggle) {
        toggle.refresh();
    });
};

PaintEditorMorph.prototype.ok = function () {
    this.callback(
        this.paper.paper,
        this.paper.rotationCenter
    );
    this.destroy();
};

PaintEditorMorph.prototype.cancel = function () {
    if (this.oncancel) {this.oncancel(); }
    this.destroy();
};

PaintEditorMorph.prototype.populatePropertiesMenu = function () {
    var c = this.controls,
        myself = this,
        pc = this.propertiesControls,
        alpen = new AlignmentMorph("row", this.padding);

    pc.primaryColorViewer = new Morph();
    pc.primaryColorViewer.setExtent(new Point(180, 50));
    pc.primaryColorViewer.color = new Color(0, 0, 0);
    pc.colorpicker = new PaintColorPickerMorph(
        new Point(180, 100),
        function (color) {
            var ni = newCanvas(pc.primaryColorViewer.extent()),
                ctx = ni.getContext("2d"),
                i,
                j;
            myself.paper.settings.primarycolor = color;
            if (color === "transparent") {
                for (i = 0; i < 180; i += 5) {
                    for (j = 0; j < 15; j += 5) {
                        ctx.fillStyle =
                            ((j + i) / 5) % 2 === 0 ?
                                            "rgba(0, 0, 0, 0.2)" :
                                            "rgba(0, 0, 0, 0.5)";
                        ctx.fillRect(i, j, 5, 5);

                    }
                }
            } else {
                ctx.fillStyle = color.toString();
                ctx.fillRect(0, 0, 180, 15);
            }
            ctx.strokeStyle = "black";
            ctx.lineWidth = Math.min(myself.paper.settings.linewidth, 20);
            ctx.beginPath();
            ctx.lineCap = "round";
            ctx.moveTo(20, 30);
            ctx.lineTo(160, 30);
            ctx.stroke();
            pc.primaryColorViewer.image = ni;
            pc.primaryColorViewer.changed();
        }
    );
    pc.colorpicker.action(new Color(0, 0, 0));

    pc.penSizeSlider = new SliderMorph(0, 20, 5, 5);
    pc.penSizeSlider.orientation = "horizontal";
    pc.penSizeSlider.setHeight(15);
    pc.penSizeSlider.setWidth(150);
    pc.penSizeSlider.action = function (num) {
        if (pc.penSizeField) {
            pc.penSizeField.setContents(num);
        }
        myself.paper.settings.linewidth = num;
        pc.colorpicker.action(myself.paper.settings.primarycolor);
    };
    pc.penSizeField = new InputFieldMorph("5", true, null, false);
    pc.penSizeField.contents().minWidth = 20;
    pc.penSizeField.setWidth(25);
    pc.penSizeField.accept = function () {
        var val = parseFloat(pc.penSizeField.getValue());
        pc.penSizeSlider.value = val;
        pc.penSizeSlider.drawNew();
        pc.penSizeSlider.updateValue();
        this.setContents(val);
        myself.paper.settings.linewidth = val;
        this.world().keyboardReceiver = myself;
        pc.colorpicker.action(myself.paper.settings.primarycolor);
    };
    alpen.add(pc.penSizeSlider);
    alpen.add(pc.penSizeField);
    alpen.color = myself.color;
    alpen.fixLayout();
    pc.penSizeField.drawNew();
    pc.constrain = new ToggleMorph(
        "checkbox",
        this,
        function () {myself.shift = !myself.shift; },
        "Constrain proportions of shapes?\n(you can also hold shift)",
        function () {return myself.shift; }
    );
    c.add(pc.colorpicker);
    //c.add(pc.primaryColorButton);
    c.add(pc.primaryColorViewer);
    c.add(new TextMorph(localize("Brush size")));
    c.add(alpen);
    c.add(pc.constrain);
};

PaintEditorMorph.prototype.toolButton = function (icon, hint) {
    var button, myself = this;

    button = new ToggleButtonMorph(
        null,
        this,
        function () { // action
            myself.paper.currentTool = icon;
            myself.paper.toolChanged(icon);
            myself.refreshToolButtons();
            if (icon === 'pipette') {
                myself.getUserColor();
            }
        },
        new SymbolMorph(icon, 18),
        function () {return myself.paper.currentTool === icon; }
    );

    button.hint = hint;
    button.drawNew();
    button.fixLayout();
    return button;
};

PaintEditorMorph.prototype.pushButton = function (title, action, hint) {
    return new PushButtonMorph(
        this,
        action,
        title,
        null,
        hint
    );
};

PaintEditorMorph.prototype.getUserColor = function () {
    var myself = this,
        world = this.world(),
        hand = world.hand,
        posInDocument = getDocumentPositionOf(world.worldCanvas),
        mouseMoveBak = hand.processMouseMove,
        mouseDownBak = hand.processMouseDown,
        mouseUpBak = hand.processMouseUp;

    hand.processMouseMove = function (event) {
        var color;
        hand.setPosition(new Point(
            event.pageX - posInDocument.x,
            event.pageY - posInDocument.y
        ));
        color = world.getGlobalPixelColor(hand.position());
        color.a = 255;
        myself.propertiesControls.colorpicker.action(color);
    };

    hand.processMouseDown = nop;

    hand.processMouseUp = function () {
        myself.paper.currentTool = 'brush';
        myself.paper.toolChanged('brush');
        myself.refreshToolButtons();
        hand.processMouseMove = mouseMoveBak;
        hand.processMouseDown = mouseDownBak;
        hand.processMouseUp = mouseUpBak;
    };
};

// AdvancedColorPickerMorph //////////////////

// A large hsl color picker

PaintColorPickerMorph.prototype = new Morph();
PaintColorPickerMorph.prototype.constructor = PaintColorPickerMorph;
PaintColorPickerMorph.uber = Morph.prototype;

function PaintColorPickerMorph(extent, action) {
    this.init(extent, action);
}

PaintColorPickerMorph.prototype.init = function (extent, action) {
    this.setExtent(extent || new Point(200, 100));
    this.action = action || nop;
    this.drawNew();
};

PaintColorPickerMorph.prototype.drawNew = function () {
    var x = 0,
        y = 0,
        can = newCanvas(this.extent()),
        ctx = can.getContext("2d"),
        colorselection,
        r;
    for (x = 0; x < this.width(); x += 1) {
        for (y = 0; y < this.height() - 20; y += 1) {
            ctx.fillStyle = "hsl(" +
                (360 * x / this.width()) +
                "," +
                "100%," +
                (y * 100 / (this.height() - 20)) +
                "%)";
            ctx.fillRect(x, y, 1, 1);
        }
    }
    for (x = 0; x < this.width(); x += 1) {
        r = Math.floor(255 * x / this.width());
        ctx.fillStyle = "rgb(" + r + ", " + r + ", " + r + ")";
        ctx.fillRect(x, this.height() - 20, 1, 10);
    }
    colorselection = ["black", "white", "gray"];
    for (x = 0; x < colorselection.length; x += 1) {
        ctx.fillStyle = colorselection[x];
        ctx.fillRect(
            x * this.width() / colorselection.length,
            this.height() - 10,
            this.width() / colorselection.length,
            10
        );
    }
    for (x = this.width() * 2 / 3; x < this.width(); x += 2) {
        for (y = this.height() - 10; y < this.height(); y += 2) {
            if ((x + y) / 2 % 2 === 0) {
                ctx.fillStyle = "#DDD";
                ctx.fillRect(x, y, 2, 2);
            }
        }
    }
    this.image = can;
};

PaintColorPickerMorph.prototype.mouseDownLeft = function (pos) {
    if ((pos.subtract(this.position()).x > this.width() * 2 / 3) &&
            (pos.subtract(this.position()).y > this.height() - 10)) {
        this.action("transparent");
    } else {
        this.action(this.getPixelColor(pos));
    }
};

PaintColorPickerMorph.prototype.mouseMove =
    PaintColorPickerMorph.prototype.mouseDownLeft;

// PaintCanvasMorph ///////////////////////////
/*
    A canvas which reacts to drag events to
    modify its image, based on a 'tool' property.
*/

PaintCanvasMorph.prototype = new Morph();
PaintCanvasMorph.prototype.constructor = PaintCanvasMorph;
PaintCanvasMorph.uber = Morph.prototype;

function PaintCanvasMorph(shift) {
    this.init(shift);
}

PaintCanvasMorph.prototype.init = function (shift) {
    this.rotationCenter = new Point(240, 180);
    this.dragRect = null;
    this.previousDragPoint = null;
    this.currentTool = "brush";
    this.dragRect = new Rectangle();
    // rectangle with origin being the starting drag position and
    // corner being the current drag position
    this.mask = newCanvas(this.extent()); // Temporary canvas
    this.paper = newCanvas(this.extent()); // Actual canvas
    this.erasermask = newCanvas(this.extent()); // eraser memory
    this.background = newCanvas(this.extent()); // checkers
    this.settings = {
        "primarycolor": new Color(0, 0, 0, 255), // usually fill color
        "secondarycolor": new Color(0, 0, 0, 255), // (unused)
        "linewidth": 3 // stroke width
    };
    this.brushBuffer = [];
    this.undoBuffer = [];
    this.isShiftPressed = shift || function () {
        var key = this.world().currentKey;
        return (key === 16);
    };
    this.buildContents();
};

PaintCanvasMorph.prototype.cacheUndo = function () {
    var cachecan = newCanvas(this.extent());
    this.merge(this.paper, cachecan);
    this.undoBuffer.push(cachecan);
};

PaintCanvasMorph.prototype.undo = function () {
    if (this.undoBuffer.length > 0) {
        this.paper = newCanvas(this.extent());
        this.mask.width = this.mask.width + 1 - 1;
        this.merge(this.undoBuffer.pop(), this.paper);
        this.drawNew();
        this.changed();
    }
};

PaintCanvasMorph.prototype.merge = function (a, b) {
    b.getContext("2d").drawImage(a, 0, 0);
};

PaintCanvasMorph.prototype.centermerge = function (a, b) {
    b.getContext("2d").drawImage(
        a,
        (b.width - a.width) / 2,
        (b.height - a.height) / 2
    );
};

PaintCanvasMorph.prototype.clearCanvas = function () {
    this.buildContents();
    this.drawNew();
    this.changed();
};

PaintCanvasMorph.prototype.toolChanged = function (tool) {
    this.mask = newCanvas(this.extent());
    if (tool === "crosshairs") {
        this.drawcrosshair();
    }
    this.drawNew();
    this.changed();
};

PaintCanvasMorph.prototype.drawcrosshair = function (context) {
    var ctx = context || this.mask.getContext("2d"),
        rp = this.rotationCenter;

    ctx.lineWidth = 1;
    ctx.strokeStyle = 'black';
    ctx.clearRect(0, 0, this.mask.width, this.mask.height);

    // draw crosshairs:
    ctx.globalAlpha = 0.5;

    // circle around center:
    ctx.fillStyle = 'white';
    ctx.beginPath();
    ctx.arc(
        rp.x,
        rp.y,
        20,
        radians(0),
        radians(360),
        false
    );
    ctx.closePath();
    ctx.fill();
    ctx.stroke();

    ctx.beginPath();
    ctx.arc(
        rp.x,
        rp.y,
        10,
        radians(0),
        radians(360),
        false
    );
    ctx.stroke();

    // horizontal line:
    ctx.beginPath();
    ctx.moveTo(0, rp.y);
    ctx.lineTo(this.mask.width, rp.y);
    ctx.stroke();

    // vertical line:
    ctx.beginPath();
    ctx.moveTo(rp.x, 0);
    ctx.lineTo(rp.x, this.mask.height);
    ctx.stroke();

    this.drawNew();
    this.changed();
};

PaintCanvasMorph.prototype.floodfill = function (sourcepoint) {
    var width = this.paper.width,
        height = this.paper.height,
        ctx = this.paper.getContext("2d"),
        img = ctx.getImageData(0, 0, width, height),
        data = img.data,
        stack = [Math.round(sourcepoint.y) * width + sourcepoint.x],
        currentpoint,
        read,
        sourcecolor,
        checkpoint;
    read = function (p) {
        var d = p * 4;
        return [data[d], data[d + 1], data[d + 2], data[d + 3]];
    };
    sourcecolor = read(stack[0]);
    checkpoint = function (p) {
        return p[0] === sourcecolor[0] &&
            p[1] === sourcecolor[1] &&
            p[2] === sourcecolor[2] &&
            p[3] === sourcecolor[3];
    };

    // if already filled, abort
    if (sourcecolor[3] === 0 &&
            this.settings.primarycolor === "transparent") {
        return;
    }
    if (sourcecolor[0] === this.settings.primarycolor.r &&
            sourcecolor[1] === this.settings.primarycolor.g &&
            sourcecolor[2] === this.settings.primarycolor.b &&
            sourcecolor[3] === this.settings.primarycolor.a) {
        return;
    }
    if (sourcecolor[3] === 0 && this.settings.primarycolor.a === 0) {
        return;
    }

    while (stack.length > 0) {
        currentpoint = stack.pop();
        if (checkpoint(read(currentpoint))) {
            if (currentpoint % width > 1) {
                stack.push(currentpoint + 1);
                stack.push(currentpoint - 1);
            }
            if (currentpoint > 0 && currentpoint < height * width) {
                stack.push(currentpoint + width);
                stack.push(currentpoint - width);
            }
        }
        if (this.settings.primarycolor === "transparent") {
            data[currentpoint * 4 + 3] = 0;
        } else {
            data[currentpoint * 4] = this.settings.primarycolor.r;
            data[currentpoint * 4 + 1] = this.settings.primarycolor.g;
            data[currentpoint * 4 + 2] = this.settings.primarycolor.b;
            data[currentpoint * 4 + 3] = this.settings.primarycolor.a;
        }
    }
    ctx.putImageData(img, 0, 0);
    this.drawNew();
    this.changed();
};

PaintCanvasMorph.prototype.mouseDownLeft = function (pos) {
    this.cacheUndo();
    this.dragRect.origin = pos.subtract(this.bounds.origin);
    this.dragRect.corner = pos.subtract(this.bounds.origin);
    this.previousDragPoint = this.dragRect.corner.copy();
    if (this.currentTool === 'crosshairs') {
        this.rotationCenter = pos.subtract(this.bounds.origin);
        this.drawcrosshair();
        return;
    }
    if (this.currentTool === "paintbucket") {
        return this.floodfill(pos.subtract(this.bounds.origin));
    }
    if (this.settings.primarycolor === "transparent" &&
            this.currentTool !== "crosshairs") {
        this.erasermask = newCanvas(this.extent());
        this.merge(this.paper, this.erasermask);
    }
};

PaintCanvasMorph.prototype.mouseMove = function (pos) {
    if (this.currentTool === "paintbucket") {
        return;
    }

    var relpos = pos.subtract(this.bounds.origin),
        mctx = this.mask.getContext("2d"),
        pctx = this.paper.getContext("2d"),
        x = this.dragRect.origin.x, // original drag X
        y = this.dragRect.origin.y, // original drag y
        p = relpos.x,               // current drag x
        q = relpos.y,               // current drag y
        w = (p - x) / 2,            // half the rect width
        h = (q - y) / 2,            // half the rect height
        i,                          // iterator number
        width = this.paper.width;

    mctx.save();
    function newW() {
        return Math.max(Math.abs(w), Math.abs(h)) * (w / Math.abs(w));
    }
    function newH() {
        return Math.max(Math.abs(w), Math.abs(h)) * (h / Math.abs(h));
    }
    this.brushBuffer.push([p, q]);
    mctx.lineWidth = this.settings.linewidth;
    mctx.clearRect(0, 0, this.bounds.width(), this.bounds.height()); // mask

    this.dragRect.corner = relpos.subtract(this.dragRect.origin); // reset crn

    if (this.settings.primarycolor === "transparent" &&
            this.currentTool !== "crosshairs") {
        this.merge(this.erasermask, this.mask);
        pctx.clearRect(0, 0, this.bounds.width(), this.bounds.height());
        mctx.globalCompositeOperation = "destination-out";
    } else {
        mctx.fillStyle = this.settings.primarycolor.toString();
        mctx.strokeStyle = this.settings.primarycolor.toString();
    }
    switch (this.currentTool) {
    case "rectangle":
        if (this.isShiftPressed()) {
            mctx.strokeRect(x, y, newW() * 2, newH() * 2);
        } else {
            mctx.strokeRect(x, y, w * 2, h * 2);
        }
        break;
    case "rectangleSolid":
        if (this.isShiftPressed()) {
            mctx.fillRect(x, y, newW() * 2, newH() * 2);
        } else {
            mctx.fillRect(x, y, w * 2, h * 2);
        }
        break;
    case "brush":
        mctx.lineCap = "round";
        mctx.lineJoin = "round";
        mctx.beginPath();
        mctx.moveTo(this.brushBuffer[0][0], this.brushBuffer[0][1]);
        for (i = 0; i < this.brushBuffer.length; i += 1) {
            mctx.lineTo(this.brushBuffer[i][0], this.brushBuffer[i][1]);
        }
        mctx.stroke();
        break;
    case "line":
        mctx.beginPath();
        mctx.moveTo(x, y);
        if (this.isShiftPressed()) {
            if (Math.abs(h) > Math.abs(w)) {
                mctx.lineTo(x, q);
            } else {
                mctx.lineTo(p, y);
            }
        } else {
            mctx.lineTo(p, q);
        }
        mctx.stroke();
        break;
    case "circle":
    case "circleSolid":
        mctx.beginPath();
        if (this.isShiftPressed()) {
            mctx.arc(
                x,
                y,
                new Point(x, y).distanceTo(new Point(p, q)),
                0,
                Math.PI * 2,
                false
            );
        } else {
            for (i = 0; i < width; i += 1) {
                mctx.lineTo(
                    i,
                    (2 * h) * Math.sqrt(2 - Math.pow(
                        (i - x) / (2 * w),
                        2
                    )) + y
                );
            }
            for (i = width; i > 0; i -= 1) {
                mctx.lineTo(
                    i,
                    -1 * (2 * h) * Math.sqrt(2 - Math.pow(
                        (i - x) / (2 * w),
                        2
                    )) + y
                );
            }
        }
        mctx.closePath();
        if (this.currentTool === "circleSolid") {
            mctx.fill();
        } else {
            if (this.currentTool === "circle") {
                mctx.stroke();
            }
        }
        break;
    case "crosshairs":
        this.rotationCenter = relpos.copy();
        this.drawcrosshair(mctx);
        break;
    case "eraser":
        this.merge(this.paper, this.mask);
        mctx.save();
        mctx.globalCompositeOperation = "destination-out";
        mctx.beginPath();
        mctx.moveTo(this.brushBuffer[0][0], this.brushBuffer[0][1]);
        for (i = 0; i < this.brushBuffer.length; i += 1) {
            mctx.lineTo(this.brushBuffer[i][0], this.brushBuffer[i][1]);
        }
        mctx.stroke();
        mctx.restore();
        this.paper = newCanvas(this.extent());
        this.merge(this.mask, this.paper);
        break;
    default:
        nop();
    }
    this.previousDragPoint = relpos;
    this.drawNew();
    this.changed();
    mctx.restore();
};

PaintCanvasMorph.prototype.mouseClickLeft = function () {
    if (this.currentTool !== "crosshairs") {
        this.merge(this.mask, this.paper);
    }
    this.brushBuffer = [];
};

PaintCanvasMorph.prototype.mouseLeaveDragging
    = PaintCanvasMorph.prototype.mouseClickLeft;

PaintCanvasMorph.prototype.buildContents = function () {
    this.background = newCanvas(this.extent());
    this.paper = newCanvas(this.extent());
    this.mask = newCanvas(this.extent());
    this.erasermask = newCanvas(this.extent());
    var i, j, bkctx = this.background.getContext("2d");
    for (i = 0; i < this.background.width; i += 5) {
        for (j = 0; j < this.background.height; j += 5) {
            if ((i + j) / 5 % 2 === 1) {
                bkctx.fillStyle = "rgba(255, 255, 255, 1)";
            } else {
                bkctx.fillStyle = "rgba(255, 255, 255, 0.3)";
            }
            bkctx.fillRect(i, j, 5, 5);
        }
    }
};

PaintCanvasMorph.prototype.drawNew = function () {
    var can = newCanvas(this.extent());
    this.merge(this.background, can);
    this.merge(this.paper, can);
    this.merge(this.mask, can);
    this.image = can;
    this.drawFrame();
};

PaintCanvasMorph.prototype.drawFrame = function () {
    var context, borderColor;

    context = this.image.getContext('2d');
    if (this.parent) {
        this.color = this.parent.color.lighter(this.contrast * 0.75);
        borderColor = this.parent.color;
    } else {
        borderColor = new Color(120, 120, 120);
    }
    context.fillStyle = this.color.toString();

    // cache my border colors
    this.cachedClr = borderColor.toString();
    this.cachedClrBright = borderColor.lighter(this.contrast)
        .toString();
    this.cachedClrDark = borderColor.darker(this.contrast).toString();
    this.drawRectBorder(context);
};

PaintCanvasMorph.prototype.drawRectBorder
    = InputFieldMorph.prototype.drawRectBorder;

PaintCanvasMorph.prototype.edge
    = InputFieldMorph.prototype.edge;

PaintCanvasMorph.prototype.fontSize
    = InputFieldMorph.prototype.fontSize;

PaintCanvasMorph.prototype.typeInPadding
    = InputFieldMorph.prototype.typeInPadding;

PaintCanvasMorph.prototype.contrast
    = InputFieldMorph.prototype.contrast;