diff --git a/src/canvas.js b/src/canvas.js index 780a96c9b..c1d2785e8 100644 --- a/src/canvas.js +++ b/src/canvas.js @@ -59,6 +59,116 @@ function ScratchCanvas(width, height) { return canvas; } +function addContextCurrentTransform(ctx) { + // If the context doesn't expose a `mozCurrentTransform`, add a JS based on. + if (!ctx.mozCurrentTransform) { + // Store the original context + ctx._originalSave = ctx.save; + ctx._originalRestore = ctx.restore; + ctx._originalRotate = ctx.rotate; + ctx._originalScale = ctx.scale; + ctx._originalTranslate = ctx.translate; + ctx._originalTransform = ctx.transform; + + ctx._transformMatrix = [1, 0, 0, 1, 0, 0]; + ctx._transformStack = []; + + Object.defineProperty(ctx, 'mozCurrentTransform', { + get: function getCurrentTransform() { + return this._transformMatrix; + } + }); + + Object.defineProperty(ctx, 'mozCurrentTransformInverse', { + get: function getCurrentTransformInverse() { + // Calculation done using WolframAlpha: + // http://www.wolframalpha.com/input/? + // i=Inverse+{{a%2C+c%2C+e}%2C+{b%2C+d%2C+f}%2C+{0%2C+0%2C+1}} + + var m = this._transformMatrix; + var a = m[0], b = m[1], c = m[2], d = m[3], e = m[4], f = m[5]; + + var ad_bc = a * d - b * c; + var bc_ad = b * c - a * d; + + return [ + d / ad_bc, + b / bc_ad, + c / bc_ad, + a / ad_bc, + (d * e - c * f) / bc_ad, + (b * e - a * f) / ad_bc + ]; + } + }); + + ctx.save = function ctxSave() { + var old = this._transformMatrix; + this._transformStack.push(old); + this._transformMatrix = old.slice(0, 6); + + this._originalSave(); + }; + + ctx.restore = function ctxRestore() { + var prev = this._transformStack.pop(); + if (prev) { + this._transformMatrix = prev; + this._originalRestore(); + } + }; + + ctx.translate = function ctxTranslate(x, y) { + var m = this._transformMatrix; + m[4] = m[0] * x + m[2] * y + m[4]; + m[5] = m[1] * x + m[3] * y + m[5]; + + this._originalTranslate(x, y); + }; + + ctx.scale = function ctxScale(x, y) { + var m = this._transformMatrix; + m[0] = m[0] * x; + m[1] = m[1] * x; + m[2] = m[2] * y; + m[3] = m[3] * y; + + this._originalScale(x, y); + }; + + ctx.transform = function ctxTransform(a, b, c, d, e, f) { + var m = this._transformMatrix; + this._transformMatrix = [ + m[0] * a + m[2] * b, + m[1] * a + m[3] * b, + m[0] * c + m[2] * d, + m[1] * c + m[3] * d, + m[0] * e + m[2] * f + m[4], + m[1] * e + m[3] * f + m[5] + ]; + + ctx._originalTransform(a, b, c, d, e, f); + }; + + ctx.rotate = function ctxRotate(angle) { + var cosValue = Math.cos(angle); + var sinValue = Math.sin(angle); + + var m = this._transformMatrix; + this._transformMatrix = [ + m[0] * cosValue + m[2] * sinValue, + m[1] * cosValue + m[3] * sinValue, + m[0] * (-sinValue) + m[2] * cosValue, + m[1] * (-sinValue) + m[3] * cosValue, + m[4], + m[5] + ]; + + this._originalRotate(angle); + }; + } +} + var CanvasGraphics = (function canvasGraphics() { // Defines the time the executeIRQueue is going to be executing // before it stops and shedules a continue of execution. @@ -73,6 +183,10 @@ var CanvasGraphics = (function canvasGraphics() { this.xobjs = null; this.ScratchCanvas = ScratchCanvas; this.objs = objs; + + if (canvasCtx) { + addContextCurrentTransform(canvasCtx); + } } var LINE_CAP_STYLES = ['butt', 'round', 'square'];