func (t *textureImpl) draw(xp render.Picture, src2dst *f64.Aff3, sr image.Rectangle, op draw.Op, w, h int, opts *screen.DrawOptions) {
// TODO: honor sr.Max
t.renderMu.Lock()
defer t.renderMu.Unlock()
// For simple copies and scales, the inverse matrix is trivial to compute,
// and we do not need the "Src becomes OutReverse plus Over" dance (see
// below). Thus, draw can be one render.SetPictureTransform call and then
// one render.Composite call, regardless of whether or not op is Src.
if src2dst[1] == 0 && src2dst[3] == 0 {
dstXMin := float64(sr.Min.X)*src2dst[0] + src2dst[2]
dstXMax := float64(sr.Max.X)*src2dst[0] + src2dst[2]
if dstXMin > dstXMax {
// TODO: check if this (and below) works when src2dst[0] < 0.
dstXMin, dstXMax = dstXMax, dstXMin
}
dXMin := int(math.Floor(dstXMin))
dXMax := int(math.Ceil(dstXMax))
dstYMin := float64(sr.Min.Y)*src2dst[4] + src2dst[5]
dstYMax := float64(sr.Max.Y)*src2dst[4] + src2dst[5]
if dstYMin > dstYMax {
// TODO: check if this (and below) works when src2dst[4] < 0.
dstYMin, dstYMax = dstYMax, dstYMin
}
dYMin := int(math.Floor(dstYMin))
dYMax := int(math.Ceil(dstYMax))
render.SetPictureTransform(t.s.xc, t.xp, render.Transform{
f64ToFixed(1 / src2dst[0]), 0, 0,
0, f64ToFixed(1 / src2dst[4]), 0,
0, 0, 1 << 16,
})
render.Composite(t.s.xc, renderOp(op), t.xp, 0, xp,
int16(sr.Min.X), int16(sr.Min.Y), // SrcX, SrcY,
0, 0, // MaskX, MaskY,
int16(dXMin), int16(dYMin), // DstX, DstY,
uint16(dXMax-dXMin), uint16(dYMax-dYMin), // Width, Height,
)
return
}
// The X11/Render transform matrix maps from destination pixels to source
// pixels, so we invert src2dst.
dst2src := inv(src2dst)
render.SetPictureTransform(t.s.xc, t.xp, render.Transform{
f64ToFixed(dst2src[0]), f64ToFixed(dst2src[1]), f64ToFixed(dst2src[2]),
f64ToFixed(dst2src[3]), f64ToFixed(dst2src[4]), f64ToFixed(dst2src[5]),
0, 0, 1 << 16,
})
if op == draw.Src {
// render.Composite visits every dst-space pixel in the rectangle
// defined by its args DstX, DstY, Width, Height. That axis-aligned
// bounding box (AABB) must contain the transformation of the sr
// rectangle in src-space to a quad in dst-space, but it need not be
// the smallest possible AABB.
//
// In any case, for arbitrary src2dst affine transformations, which
// include rotations, this means that a naive render.Composite call
// will affect those pixels inside the AABB but outside the quad. For
// the draw.Src operator, this means that pixels in that AABB can be
// incorrectly set to zero.
//
// Instead, we implement the draw.Src operator as two render.Composite
// calls. The first one (using the PictOpOutReverse operator) clears
// the dst-space quad but leaves pixels outside that quad (but inside
// the AABB) untouched. The second one (using the PictOpOver operator)
// fills in the quad and again does not touch the pixels outside.
//
// What X11/Render calls PictOpOutReverse is also known as dst-out. See
// http://www.w3.org/TR/SVGCompositing/examples/compop-porterduff-examples.png
// for a visualization.
//
// The arguments to this render.Composite call are identical to the
// second one call below, other than the compositing operator.
//
// TODO: the source picture for this call needs to be fully opaque even
// if t.xp isn't.
render.Composite(t.s.xc, render.PictOpOutReverse, t.xp, 0, xp,
int16(sr.Min.X), int16(sr.Min.Y), 0, 0, 0, 0, uint16(w), uint16(h),
)
}
// TODO: tighten the (0, 0)-(w, h) dst rectangle. As it is, we're
// compositing an unnecessarily large number of pixels.
render.Composite(t.s.xc, render.PictOpOver, t.xp, 0, xp,
int16(sr.Min.X), int16(sr.Min.Y), // SrcX, SrcY,
0, 0, // MaskX, MaskY,
0, 0, // DstX, DstY,
uint16(w), uint16(h), // Width, Height,
)
}
func (t *textureImpl) draw(xp render.Picture, src2dst *f64.Aff3, sr image.Rectangle, op draw.Op, w, h int, opts *screen.DrawOptions) {
// TODO: honor sr.Max
// TODO: use a mutex a la https://go-review.googlesource.com/14861, so that
// the render.Xxx calls in this method are effectively one atomic
// operation, in case multiple concurrent Draw(etc, t, etc) calls occur.
// TODO: recognize simple copies or scales, which do not need the "Src
// becomes OutReverse plus Over" dance and can be one simple
// render.Composite(etc, renderOp(op), etc) call, regardless of whether or
// not op is Src.
// The XTransform matrix maps from destination pixels to source
// pixels, so we invert src2dst.
dst2src := inv(src2dst)
render.SetPictureTransform(t.s.xc, t.xp, render.Transform{
f64ToFixed(dst2src[0]), f64ToFixed(dst2src[1]), f64ToFixed(dst2src[2]),
f64ToFixed(dst2src[3]), f64ToFixed(dst2src[4]), f64ToFixed(dst2src[5]),
f64ToFixed(0), f64ToFixed(0), f64ToFixed(1),
})
if op == draw.Src {
// render.Composite visits every dst-space pixel in the rectangle
// defined by its args DstX, DstY, Width, Height. That axis-aligned
// bounding box (AABB) must contain the transformation of the sr
// rectangle in src-space to a quad in dst-space, but it need not be
// the smallest possible AABB.
//
// In any case, for arbitrary src2dst affine transformations, which
// include rotations, this means that a naive render.Composite call
// will affect those pixels inside the AABB but outside the quad. For
// the draw.Src operator, this means that pixels in that AABB can be
// incorrectly set to zero.
//
// Instead, we implement the draw.Src operator as two render.Composite
// calls. The first one (using the PictOpOutReverse operator) clears
// the dst-space quad but leaves pixels outside that quad (but inside
// the AABB) untouched. The second one (using the PictOpOver operator)
// fills in the quad and again does not touch the pixels outside.
//
// What X11/Render calls PictOpOutReverse is also known as dst-out. See
// http://www.w3.org/TR/SVGCompositing/examples/compop-porterduff-examples.png
// for a visualization.
//
// The arguments to this render.Composite call are identical to the
// second one call below, other than the compositing operator.
//
// TODO: the source picture for this call needs to be fully opaque even
// if t.xp isn't.
render.Composite(t.s.xc, render.PictOpOutReverse, t.xp, 0, xp,
int16(sr.Min.X), int16(sr.Min.Y), 0, 0, 0, 0, uint16(w), uint16(h),
)
}
// TODO: tighten the (0, 0)-(w, h) dst rectangle. As it is, we're
// compositing an unnecessarily large number of pixels.
render.Composite(t.s.xc, render.PictOpOver, t.xp, 0, xp,
int16(sr.Min.X), int16(sr.Min.Y), // SrcX, SrcY,
0, 0, // MaskX, MaskY,
0, 0, // DstX, DstY,
uint16(w), uint16(h), // Width, Height,
)
}