diff --git a/canvas.go b/canvas.go index 4177785..548e445 100644 --- a/canvas.go +++ b/canvas.go @@ -42,6 +42,8 @@ type drawState struct { } font *Font fontSize float32 + lineJoin lineJoin + lineEnd lineEnd /* The current transformation matrix. The current clipping region. @@ -53,6 +55,17 @@ type drawState struct { */ } +type lineJoin uint8 +type lineEnd uint8 + +const ( + Miter = iota + Bevel + Round + Square + Butt +) + // New creates a new canvas with the given viewport coordinates. // While all functions on the canvas use the top left point as // the origin, since GL uses the bottom left coordinate, the @@ -208,6 +221,11 @@ func (cv *Canvas) SetFont(font *Font, size float32) { cv.state.fontSize = size } +// SetLineJoin sets the style of line joints for rendering a path with Stroke +func (cv *Canvas) SetLineJoin(join lineJoin) { + cv.state.lineJoin = join +} + // Save saves the current draw state to a stack func (cv *Canvas) Save() { cv.stateStack = append(cv.stateStack, cv.state) diff --git a/paths.go b/paths.go index 93195ea..60969bc 100644 --- a/paths.go +++ b/paths.go @@ -30,7 +30,6 @@ func (cv *Canvas) LineTo(x, y float32) { } func (cv *Canvas) Arc(x, y, radius, startAngle, endAngle float32, anticlockwise bool) { - step := 6 / radius startAngle = fmath.Mod(startAngle, math.Pi*2) if startAngle < 0 { startAngle += math.Pi * 2 @@ -45,7 +44,7 @@ func (cv *Canvas) Arc(x, y, radius, startAngle, endAngle float32, anticlockwise startAngle += math.Pi * 2 startAngle, endAngle = endAngle, startAngle } - for a := startAngle; a < endAngle; a += step { + for a := startAngle; a < endAngle; a += 0.1 { s, c := fmath.Sincos(a) cv.LineTo(x+radius*c, y+radius*s) } @@ -112,40 +111,8 @@ func (cv *Canvas) Stroke() { l0x0f, l0y0f, l0x1f, l0y1f, l0x3f, l0y3f, l0x0f, l0y0f, l0x3f, l0y3f, l0x2f, l0y2f) - // miter joints if p.attach { - p2 := p.next - - v2 := p1.Sub(p2).Norm() - v3 := lm.Vec2{v2[1], -v2[0]}.MulF(cv.state.stroke.lineWidth * 0.5) - //v2 = v2.MulF(cv.state.stroke.lineWidth * 0.5) - - l1p0 := p2.Sub(v3) - l1p1 := p1.Sub(v3) - l1p2 := p2.Add(v3) - l1p3 := p1.Add(v3) - - l1x1f, l1y1f := cv.vecToGL(l1p1) - l1x3f, l1y3f := cv.vecToGL(l1p3) - - ip0 := lineIntersection(l0p0, l0p1, l1p1, l1p0) - ip1 := lineIntersection(l0p2, l0p3, l1p3, l1p2) - - ix0f, iy0f := cv.vecToGL(ip0) - ix1f, iy1f := cv.vecToGL(ip1) - - tris = append(tris, - l0x1f, l0y1f, ix0f, iy0f, l1x1f, l1y1f, - l0x1f, l0y1f, l1x1f, l1y1f, l1x3f, l1y3f, - l0x1f, l0y1f, l1x3f, l1y3f, ix1f, iy1f, - l0x1f, l0y1f, ix1f, iy1f, l0x3f, l0y3f) - - // todo this is an ugly hack... - tris = append(tris, - l0x1f, l0y1f, ix0f, iy0f, l1x1f, l1y1f, - l0x1f, l0y1f, l1x1f, l1y1f, l0x3f, l0y3f, - l0x1f, l0y1f, l0x3f, l0y3f, ix1f, iy1f, - l0x1f, l0y1f, ix1f, iy1f, l1x3f, l1y3f) + tris = cv.lineJoint(p, p0, p1, p.next, l0p0, l0p1, l0p2, l0p3, tris) } p0 = p1 @@ -169,6 +136,64 @@ func (cv *Canvas) Stroke() { gli.StencilFunc(gl_EQUAL, 0, 0xFF) } +func (cv *Canvas) lineJoint(p pathPoint, p0, p1, p2, l0p0, l0p1, l0p2, l0p3 lm.Vec2, tris []float32) []float32 { + v2 := p1.Sub(p2).Norm() + v3 := lm.Vec2{v2[1], -v2[0]}.MulF(cv.state.stroke.lineWidth * 0.5) + + l0x1f, l0y1f := cv.vecToGL(l0p1) + l0x3f, l0y3f := cv.vecToGL(l0p3) + + switch cv.state.lineJoin { + case Miter: + l1p0 := p2.Sub(v3) + l1p1 := p1.Sub(v3) + l1p2 := p2.Add(v3) + l1p3 := p1.Add(v3) + + l1x1f, l1y1f := cv.vecToGL(l1p1) + l1x3f, l1y3f := cv.vecToGL(l1p3) + + ip0 := lineIntersection(l0p0, l0p1, l1p1, l1p0) + ip1 := lineIntersection(l0p2, l0p3, l1p3, l1p2) + + cxf, cyf := cv.vecToGL(p1) + ix0f, iy0f := cv.vecToGL(ip0) + ix1f, iy1f := cv.vecToGL(ip1) + + tris = append(tris, + cxf, cyf, l0x1f, l0y1f, ix0f, iy0f, + cxf, cyf, ix0f, iy0f, l1x1f, l1y1f, + cxf, cyf, l1x3f, l1y3f, ix1f, iy1f, + cxf, cyf, ix1f, iy1f, l0x3f, l0y3f) + case Bevel: + l1p1 := p1.Sub(v3) + l1p3 := p1.Add(v3) + + l1x1f, l1y1f := cv.vecToGL(l1p1) + l1x3f, l1y3f := cv.vecToGL(l1p3) + + cxf, cyf := cv.vecToGL(p1) + + tris = append(tris, + cxf, cyf, l0x1f, l0y1f, l1x1f, l1y1f, + cxf, cyf, l1x3f, l1y3f, l0x3f, l0y3f) + case Round: + cxf, cyf := cv.vecToGL(p1) + + radius := cv.state.stroke.lineWidth * 0.5 + step := 6 / radius + p0x, p0y := cv.vecToGL(lm.Vec2{p1[0], p1[1] + radius}) + for angle := step; angle <= math.Pi*2+step; angle += 0.1 { + s, c := fmath.Sincos(angle) + p1x, p1y := cv.vecToGL(lm.Vec2{p1[0] + s*radius, p1[1] + c*radius}) + tris = append(tris, cxf, cyf, p0x, p0y, p1x, p1y) + p0x, p0y = p1x, p1y + } + } + + return tris +} + func lineIntersection(a0, a1, b0, b1 lm.Vec2) lm.Vec2 { va := a1.Sub(a0) vb := b1.Sub(b0)