| Flutter Impeller |

stroke_path_geometry.cc
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "impeller/entity/geometry/stroke_path_geometry.h"
6
7 #include "flutter/display_list/geometry/dl_path.h"
8 #include "impeller/core/buffer_view.h"
9 #include "impeller/core/formats.h"
10 #include "impeller/core/host_buffer.h"
11 #include "impeller/entity/contents/pipelines.h"
12 #include "impeller/entity/geometry/geometry.h"
13 #include "impeller/geometry/constants.h"
14 #include "impeller/geometry/separated_vector.h"
15 #include "impeller/geometry/wangs_formula.h"
16 #include "impeller/tessellator/path_tessellator.h"
17
18 namespace impeller {
19
20 namespace {
21
22 class PositionWriter {
23 public:
24 explicit PositionWriter(std::vector<Point>& points)
25 : points_(points), oversized_() {
26 FML_DCHECK(points_.size() == kPointArenaSize);
27 }
28
29 void AppendVertex(const Point& point) {
30 if (offset_ >= kPointArenaSize) {
31 oversized_.push_back(point);
32 } else {
33 points_[offset_++] = point;
34 }
35 }
36
37 /// @brief Return the number of points used in the arena, followed by
38 /// the number of points allocated in the overized buffer.
39 std::pair<size_t, size_t> GetUsedSize() const {
40 return std::make_pair(offset_, oversized_.size());
41 }
42
43 bool HasOversizedBuffer() const { return !oversized_.empty(); }
44
45 const std::vector<Point>& GetOversizedBuffer() const { return oversized_; }
46
47 private:
48 std::vector<Point>& points_;
49 std::vector<Point> oversized_;
50 size_t offset_ = 0u;
51 };
52
53 } // namespace
54
55 /// StrokePathSegmentReceiver converts path segments (fed by PathTessellator)
56 /// into a vertex strip that covers the outline of the stroked version of the
57 /// path and feeds those vertices, expressed in the form of a vertex strip
58 /// into the supplied PositionWriter.
59 ///
60 /// The general procedure follows the following basic methodology:
61 ///
62 /// Every path segment is represented by a box with two starting vertices
63 /// perpendicular to its start point and two vertices perpendicular to its
64 /// end point, all perpendiculars of length (stroke_width * 0.5).
65 ///
66 /// Joins will connect the ending "box" perpendiculars of the previous segment
67 /// to the starting "box" perpendiculars of the following segment. If the two
68 /// boxes are so aligned that their adjacent perpendiculars are less than a
69 /// threshold distance apart (kJoinPixelThreshold), the join will just be
70 /// elided so that the end of one box becomes the start of the next box.
71 /// If the join process does add decorations, it assumes that the ending
72 /// perpendicular vertices from the prior segment are the last vertices
73 /// added and ensures that it appends the two vertices for the starting
74 /// perpendiculars of the new segment's "box". Thus every join either
75 /// adds nothing and the end perpendiculars of the previous segment become
76 /// the start perpendiculars of the next segment, or it makes sure its
77 /// geometry fills in the gap and ends with the start perpendiculars for the
78 /// new segment.
79 ///
80 /// Prior to the start of an unclosed contour we insert a cap and also the
81 /// starting perpendicular segments for the first segment. Prior to the
82 /// start of a closed contour, we just insert the starting perpendiculars
83 /// for the first segment. Either way, we've initialized the path with the
84 /// starting perpendiculars of the first segment.
85 ///
86 /// After the last segment in an unclosed contour we insert a cap which
87 /// can assume that the last segment has already inserted its closing
88 /// perpendicular segments. After the last segment in a closed contour, we
89 /// insert a join back to the very first segment in that contour.
90 ///
91 /// Connecting any two contours we insert an infinitely thin connecting
92 /// thread by inserting the last point of the previous contour twice and
93 /// then inserting the first point of the next contour twice. This ensures
94 /// that there are no non-empty triangles between the two contours.
95 ///
96 /// Finally, inserting a line segment can assume that the starting
97 /// perpendiculars have already been inserted by the preceding cap, join,
98 /// or prior segment, so all it needs to do is to insert the ending
99 /// perpendiculars which set the process up for the subsequent cap, join,
100 /// or future segment.
101 ///
102 /// Inserting curve segments acts like a series of line segments except
103 /// that the opening perpendicular is taken from the curve rather than the
104 /// direction between the starting point and the first sample point. This
105 /// ensures that any cap or join will be aligned with the curve and not
106 /// tilted by the first approximating segment. The same is true of the
107 /// ending perpendicular which is taken from the curve and not the last
108 /// approximated segment. Between each approximated segment of the curve,
109 /// we insert only Cap::kRound joins so as not to polygonize a curve when
110 /// it turns very sharply. We also skip these joins for any change of
111 /// direction which is smaller than the first sample point of a round join
112 /// for performance reasons.
113 ///
114 /// To facilitate all of that work we maintain variables containing
115 /// SeparatedVector2 values that, by convention, point 90 degrees to the
116 /// right of the given path direction. This facilitates a quick add/subtract
117 /// from the point on the path to insert the necessary perpendicular
118 /// points of a segment's box. These values contain both a unit vector for
119 /// direction and a magnitude for length.
120 ///
121 /// SeparatedVector2 values also allow us to quickly test limits on when to
122 /// include joins by using a simple dot product on the previous and next
123 /// perpendiculars at a given path point which should match the dot product
124 /// of the path's direction itself at the same point since both perpendiculars
125 /// have been rotated identically to the same side of the path.
126 /// The SeparatedVector2 will perform the dot product on the unit-length
127 /// vectors so that the result is exactly the cosine of the angle between the
128 /// segments - also the angle by which the path turned at a given path point.
129 ///
130 /// @see PathTessellator::PathToStrokedSegments
131 class StrokePathSegmentReceiver : public PathAndArcSegmentReceiver {
132 public:
133 StrokePathSegmentReceiver(Tessellator& tessellator,
134 PositionWriter& vtx_builder,
135 const StrokeParameters& stroke,
136 const Scalar scale)
137 : tessellator_(tessellator),
138 vtx_builder_(vtx_builder),
139 half_stroke_width_(stroke.width * 0.5f),
140 maximum_join_cosine_(
141 ComputeMaximumJoinCosine(scale, half_stroke_width_)),
142 minimum_miter_cosine_(ComputeMinimumMiterCosine(stroke.miter_limit)),
143 join_(stroke.join),
144 cap_(stroke.cap),
145 scale_(scale),
146 trigs_(MakeTrigs(tessellator, scale, half_stroke_width_)) {
147 // Trigs ensures that it always contains at least 2 entries.
148 FML_DCHECK(trigs_.size() >= 2);
149 FML_DCHECK(trigs_[0].cos == 1.0f); // Angle == 0 degrees
150 FML_DCHECK(trigs_[0].sin == 0.0f);
151 FML_DCHECK(trigs_.end()[-1].cos == 0.0f); // Angle == 90 degrees
152 FML_DCHECK(trigs_.end()[-1].sin == 1.0f);
153 }
154
155 protected:
156 // |SegmentReceiver|
157 void BeginContour(Point origin, bool will_be_closed) override {
158 if (has_prior_contour_ && origin != last_point_) {
159 // We only append these extra points if we have had a prior contour.
160 vtx_builder_.AppendVertex(last_point_);
161 vtx_builder_.AppendVertex(last_point_);
162 vtx_builder_.AppendVertex(origin);
163 vtx_builder_.AppendVertex(origin);
164 }
165 has_prior_contour_ = true;
166 has_prior_segment_ = false;
167 contour_needs_cap_ = !will_be_closed;
168 last_point_ = origin;
169 origin_point_ = origin;
170 }
171
172 // |SegmentReceiver|
173 void RecordLine(Point p1, Point p2) override {
174 if (p2 != p1) {
175 SeparatedVector2 current_perpendicular = PerpendicularFromPoints(p1, p2);
176
177 HandlePreviousJoin(current_perpendicular);
178 AppendVertices(p2, current_perpendicular);
179
180 last_perpendicular_ = current_perpendicular;
181 last_point_ = p2;
182 }
183 }
184
185 // |SegmentReceiver|
186 void RecordQuad(Point p1, Point cp, Point p2) override {
187 RecordCurve<PathTessellator::Quad>({p1, cp, p2});
188 }
189
190 // |SegmentReceiver|
191 void RecordConic(Point p1, Point cp, Point p2, Scalar weight) override {
192 RecordCurve<PathTessellator::Conic>({p1, cp, p2, weight});
193 }
194
195 // |SegmentReceiver|
196 void RecordCubic(Point p1, Point cp1, Point cp2, Point p2) override {
197 RecordCurve<PathTessellator::Cubic>({p1, cp1, cp2, p2});
198 }
199
200 // Utility implementation of |SegmentReceiver| Record<Curve> methods
201 template <typename Curve>
202 inline void RecordCurve(const Curve& curve) {
203 std::optional<Point> start_direction = curve.GetStartDirection();
204 std::optional<Point> end_direction = curve.GetEndDirection();
205
206 // The Prune receiver should have eliminated any empty curves, so any
207 // curve we see should have both start and end direction.
208 FML_DCHECK(start_direction.has_value() && end_direction.has_value());
209
210 // In order to keep the compiler/lint happy we check for values anyway.
211 if (start_direction.has_value() && end_direction.has_value()) {
212 // We now know the curve cannot be degenerate.
213 SeparatedVector2 start_perpendicular =
214 PerpendicularFromUnitDirection(-start_direction.value());
215 SeparatedVector2 end_perpendicular =
216 PerpendicularFromUnitDirection(end_direction.value());
217
218 // We join the previous segment to this one with a normal join
219 // The join will append the perpendicular at the start of this
220 // curve as well.
221 HandlePreviousJoin(start_perpendicular);
222
223 Scalar count =
224 std::ceilf(curve.SubdivisionCount(scale_ * half_stroke_width_));
225
226 Point prev = curve.p1;
227 SeparatedVector2 prev_perpendicular = start_perpendicular;
228
229 // Handle all intermediate curve points up to but not including the end.
230 for (int i = 1; i < count; i++) {
231 Point cur = curve.Solve(i / count);
232 SeparatedVector2 cur_perpendicular = PerpendicularFromPoints(prev, cur);
233 RecordCurveSegment(prev_perpendicular, cur, cur_perpendicular);
234 prev = cur;
235 prev_perpendicular = cur_perpendicular;
236 }
237
238 RecordCurveSegment(prev_perpendicular, curve.p2, end_perpendicular);
239
240 last_perpendicular_ = end_perpendicular;
241 last_point_ = curve.p2;
242 }
243 }
244
245 void RecordCurveSegment(const SeparatedVector2& prev_perpendicular,
246 const Point cur,
247 const SeparatedVector2& cur_perpendicular) {
248 if (prev_perpendicular.GetAlignment(cur_perpendicular) < trigs_[1].cos) {
249 // We only connect 2 curved segments if their change in direction
250 // is faster than a single sample of a round join.
251 AppendVertices(cur, prev_perpendicular);
252 AddJoin(Join::kRound, cur, prev_perpendicular, cur_perpendicular);
253 }
254 AppendVertices(cur, cur_perpendicular);
255 }
256
257 // |SegmentReceiver|
258 void EndContour(Point origin, bool with_close) override {
259 FML_DCHECK(origin == origin_point_);
260 if (!has_prior_segment_) {
261 // Empty contour, fill in an axis aligned "cap box" at the origin.
262 FML_DCHECK(last_point_ == origin);
263 // kButt wouldn't fill anything so it defers to kSquare by convention.
264 Cap cap = (cap_ == Cap::kButt) ? Cap::kSquare : cap_;
265 Vector2 perpendicular = {-half_stroke_width_, 0};
266 AddCap(cap, origin, perpendicular, true);
267 if (cap == Cap::kRound) {
268 // Only round caps need the perpendicular between them to connect.
269 AppendVertices(origin, perpendicular);
270 }
271 AddCap(cap, origin, perpendicular, false);
272 } else if (with_close) {
273 // Closed contour, join back to origin.
274 FML_DCHECK(origin == origin_point_);
275 FML_DCHECK(last_point_ == origin);
276 AddJoin(join_, origin, last_perpendicular_, origin_perpendicular_);
277
278 last_perpendicular_ = origin_perpendicular_;
279 last_point_ = origin;
280 } else {
281 AddCap(cap_, last_point_, last_perpendicular_.GetVector(), false);
282 }
283 has_prior_segment_ = false;
284 }
285
286 // |PathAndArcSegmentReceiver|
287 void RecordArc(const Arc& arc,
288 const Point center,
289 const Size radii) override {
290 Tessellator::Trigs trigs =
291 tessellator_.GetTrigsForDeviceRadius(scale_ * radii.MaxDimension());
292 Arc::Iteration iterator = arc.ComputeIterations(trigs.GetSteps(), false);
293
294 SeparatedVector2 prev_perpendicular =
295 PerpendicularFromUnitDirection({-iterator.start.y, iterator.start.x});
296 HandlePreviousJoin(prev_perpendicular);
297
298 for (size_t i = 0u; i < iterator.quadrant_count; i++) {
299 Arc::Iteration::Quadrant quadrant = iterator.quadrants[i];
300 for (size_t j = quadrant.start_index; j < quadrant.end_index; j++) {
301 Vector2 direction = trigs[j] * quadrant.axis;
302 Point cur = center + direction * radii;
303 SeparatedVector2 cur_perpendicular =
304 PerpendicularFromUnitDirection({-direction.y, direction.x});
305 RecordCurveSegment(prev_perpendicular, cur, cur_perpendicular);
306 prev_perpendicular = cur_perpendicular;
307 }
308 }
309
310 SeparatedVector2 end_perpendicular =
311 PerpendicularFromUnitDirection({-iterator.end.y, iterator.end.x});
312 Point end = center + iterator.end * radii;
313 RecordCurveSegment(prev_perpendicular, end, end_perpendicular);
314
315 last_perpendicular_ = end_perpendicular;
316 last_point_ = end;
317 }
318
319 private:
320 Tessellator& tessellator_;
321 PositionWriter& vtx_builder_;
322 const Scalar half_stroke_width_;
323 const Scalar maximum_join_cosine_;
324 const Scalar minimum_miter_cosine_;
325 const Join join_;
326 const Cap cap_;
327 const Scalar scale_;
328 const Tessellator::Trigs trigs_;
329
330 SeparatedVector2 origin_perpendicular_;
331 Point origin_point_;
332 SeparatedVector2 last_perpendicular_;
333 Point last_point_;
334 bool has_prior_contour_ = false;
335 bool has_prior_segment_ = false;
336 bool contour_needs_cap_ = false;
337
338 static Tessellator::Trigs MakeTrigs(Tessellator& tessellator,
339 Scalar scale,
340 Scalar half_stroke_width) {
341 return tessellator.GetTrigsForDeviceRadius(scale * half_stroke_width);
342 }
343
344 // Half of the allowed distance between the ends of the perpendiculars.
345 static constexpr Scalar kJoinPixelThreshold = 0.25f;
346
347 /// Determine the cosine of the angle where the ends of 2 vectors that are
348 /// each as long as half of the stroke width, differ by less than the
349 /// kJoinPixelThreshold.
350 ///
351 /// Any angle between 2 segments in the path for which the cosine of that
352 /// angle is greater than this return value, do not need any kind of join
353 /// geometry. The angle between the segments can be quickly computed by
354 /// the dot product of their direction vectors.
355 static Scalar ComputeMaximumJoinCosine(Scalar scale,
356 Scalar half_stroke_width) {
357 // Consider 2 perpendicular vectors, each pointing to the same side of
358 // two adjacent path segment "boxes". If they are identical, then there
359 // is no turn at that point on the path and we do not need to decorate
360 // that gap with any join geometry. If they differ, there will be a gap
361 // between them that must be decorated and the cosine of the angle of
362 // that gap will be their Dot product (with +1 meaning that there is
363 // no turn and therefore no decoration needed). We need to find the
364 // cosine of the angle between them where we start to care about adding
365 // the join geometry.
366 //
367 // Consider the right triangle where one side is the line bisecting the
368 // two perpendiculars, starting from the common point on the path and
369 // ending at the line that joins them. The hypotenuse of that triangle
370 // is one of the perpendiculars, whose length is (scale * half_width).
371 // The other non-hypotenuse side is kJoinPixelThreshold. This
372 // triangle establishes the equation:
373 // ||bisector|| ^ 2 + kJoinThreshold ^ 2 == ||hypotenuse|| ^ 2
374 // and the cosine of the angle between the perpendicular and the bisector
375 // will be (||bisector|| / ||hypotenuse||).
376 // The cosine between the perpendiculars which can be compared to the
377 // will be the cosine of double that angle.
378 Scalar hypotenuse = scale * half_stroke_width;
379 if (hypotenuse <= kJoinPixelThreshold) {
380 // The line geometry is too small to register the docorations. Return
381 // a cosine value small enough to never qualify to add join decorations.
382 return -1.1f;
383 }
384 Scalar bisector = std::sqrt(hypotenuse * hypotenuse -
385 kJoinPixelThreshold * kJoinPixelThreshold);
386 Scalar half_cosine = bisector / hypotenuse;
387 Scalar cosine = 2.0f * half_cosine * half_cosine - 1;
388 return cosine;
389 }
390
391 /// Determine the cosine of the angle between 2 segments on the path where
392 /// the miter limit will be exceeded if their outer stroked outlines are
393 /// joined at their intersection. The miter limit is expressed as a multiple
394 /// of the stroke width and since it is dependent on lines offset from the
395 /// path by that same stroke width, the angle is based just on the miter
396 /// limit itself.
397 ///
398 /// Any angle between 2 segments in the path for which the cosine of that
399 /// angle is less than this return value would result in an intersection
400 /// point that is further than the miter limit would allow. The angle
401 /// between the segments can be quickly computed by the dot product of
402 /// their direction vectors.
403 static Scalar ComputeMinimumMiterCosine(Scalar miter_limit) {
404 if (miter_limit <= 1.0f) {
405 // Miter limits less than 1.0 are impossible to meet since the miter
406 // join will always be at least as long as half the line width, so they
407 // essentially eliminate all miters. We return a degenerate cosine
408 // value so that the join routine never adds a miter.
409 return 1.1f;
410 }
411 // We enter the join routine with a point on the path shared between
412 // two segments that must be joined and 2 perpendicular values that
413 // locate the sides of the old and new segment "boxes" relative to
414 // that point. We can think of the miter as a diamond starting at the
415 // point on the path, extending outwards by those 2 perpendicular
416 // lines, and then continuing perpendicular to those perpendiculars
417 // to a common intersection point out in the distance. If you then
418 // consider the line that extends from the path point to the far
419 // intersection point, that divides the diamond into 2 right triangles
420 // (they are right triangles due to the right angle turn we take at
421 // the ends of the path perpendiculars). If we want to know the angle
422 // at which we reach the miter limit we can assume maximum extension
423 // which places the dividing line (the hypotenuse) at a multiple of the
424 // line width which is the length of one of those segment perpendiculars.
425 // This means that the near bisected angle has a cosine of the ratio
426 // of one of the near edges (length of half the line width) with the
427 // miter length (miter_limit times half the line width). The ratio of
428 // those is (1 / miter_limit).
429 Scalar half_cosine = 1 / miter_limit;
430 Scalar cosine = 2.0f * half_cosine * half_cosine - 1;
431 return cosine;
432 }
433
434 inline SeparatedVector2 PerpendicularFromPoints(const Point from,
435 const Point to) const {
436 return PerpendicularFromUnitDirection((to - from).Normalize());
437 }
438
439 inline SeparatedVector2 PerpendicularFromUnitDirection(
440 const Vector2 direction) const {
441 return SeparatedVector2(Vector2{-direction.y, direction.x},
442 half_stroke_width_);
443 }
444
445 inline void AppendVertices(const Point curve_point, Vector2 offset) {
446 vtx_builder_.AppendVertex(curve_point + offset);
447 vtx_builder_.AppendVertex(curve_point - offset);
448 }
449
450 inline void AppendVertices(const Point curve_point,
451 SeparatedVector2 perpendicular) {
452 return AppendVertices(curve_point, perpendicular.GetVector());
453 }
454
455 inline void HandlePreviousJoin(SeparatedVector2 new_perpendicular) {
456 FML_DCHECK(has_prior_contour_);
457 if (has_prior_segment_) {
458 AddJoin(join_, last_point_, last_perpendicular_, new_perpendicular);
459 } else {
460 has_prior_segment_ = true;
461 Vector2 perpendicular_vector = new_perpendicular.GetVector();
462 if (contour_needs_cap_) {
463 AddCap(cap_, last_point_, perpendicular_vector, true);
464 }
465 // Start the new segment's "box" at the shared "last_point_" with
466 // the new perpendicular vector.
467 AppendVertices(last_point_, perpendicular_vector);
468 origin_perpendicular_ = new_perpendicular;
469 }
470 }
471
472 // Adds a cap to an endpoint of a contour. The location points to the
473 // centerline of the stroke. The perpendicular points clockwise to the
474 // direction the path is traveling and is the length of half of the
475 // stroke width.
476 //
477 // If contour_start is true, then the cap is being added prior to the first
478 // segment at the beginning of a contour and assumes that no points have
479 // been added for this contour yet and also that the caller will add the
480 // two points that start the segment's "box" when this method returns.
481 //
482 // If contour_start is false, then the cap is being added after the last
483 // segment at the end of a contour and assumes that the caller has already
484 // added the two segments that define the end of the "box" for the last
485 // path segment.
486 void AddCap(Cap cap,
487 Point path_point,
488 Vector2 perpendicular,
489 bool contour_start) {
490 switch (cap) {
491 case Cap::kButt:
492 break;
493 case Cap::kRound: {
494 Point along(perpendicular.y, -perpendicular.x);
495 if (contour_start) {
496 // Start with a single point at the far end of the round cap.
497 vtx_builder_.AppendVertex(path_point - along);
498
499 // Iterate from the last non-quadrant value in the trigs vector
500 // (trigs.back() == (1, 0)) down to, but not including, the first
501 // entry (which is (0, 1)).
502 for (size_t i = trigs_.size() - 2u; i > 0u; --i) {
503 Point center = path_point - along * trigs_[i].sin;
504 Vector2 offset = perpendicular * trigs_[i].cos;
505
506 AppendVertices(center, offset);
507 }
508 } else {
509 // Iterate from the first non-quadrant value in the trigs vector
510 // (trigs[0] == (0, 1)) up to, but not including, the last entry
511 // (which is (0, 1)).
512 size_t end = trigs_.size() - 1u;
513 for (size_t i = 1u; i < end; ++i) {
514 Point center = path_point + along * trigs_[i].sin;
515 Vector2 offset = perpendicular * trigs_[i].cos;
516
517 AppendVertices(center, offset);
518 }
519
520 // End with a single point at the far end of the round cap.
521 vtx_builder_.AppendVertex(path_point + along);
522 }
523 break;
524 }
525 case Cap::kSquare: {
526 Point along(perpendicular.y, -perpendicular.x);
527 Point square_center = contour_start //
528 ? path_point - along //
529 : path_point + along;
530 AppendVertices(square_center, perpendicular);
531 break;
532 }
533 }
534 }
535
536 void AddJoin(Join join,
537 Point path_point,
538 SeparatedVector2 old_perpendicular,
539 SeparatedVector2 new_perpendicular) {
540 Scalar cosine = old_perpendicular.GetAlignment(new_perpendicular);
541 if (cosine >= maximum_join_cosine_) {
542 // If the perpendiculars are closer than a pixel to each other, then
543 // no need to add any further points, we don't even need to start
544 // the new segment's "box", we can just let it connect back to the
545 // prior segment's "box end" directly.
546 return;
547 }
548 // All cases of this switch will fall through into the code that starts
549 // the new segment's "box" down below which is good enough to bevel join
550 // the segments should they individually decide that they don't need any
551 // other decorations to bridge the gap.
552 switch (join) {
553 case Join::kBevel:
554 // Just fall through to the bevel operation after the switch.
555 break;
556
557 case Join::kMiter: {
558 if (cosine >= minimum_miter_cosine_) {
559 Point miter_vector =
560 (old_perpendicular.GetVector() + new_perpendicular.GetVector()) /
561 (cosine + 1);
562 if (old_perpendicular.Cross(new_perpendicular) < 0) {
563 vtx_builder_.AppendVertex(path_point + miter_vector);
564 } else {
565 vtx_builder_.AppendVertex(path_point - miter_vector);
566 }
567 }
568 // Else just fall through to bevel operation after the switch.
569 break;
570 } // end of case Join::kMiter
571
572 case Join::kRound: {
573 if (cosine >= trigs_[1].cos) {
574 // If rotating by the first (non-quadrant) entry in trigs takes
575 // us too far then we don't need to fill in anything. Just fall
576 // through to the bevel operation after the switch.
577 break;
578 }
579 if (cosine < -trigs_[1].cos) {
580 // This is closer to a 180 degree turn than the last trigs entry
581 // can distinguish. Since we are going to generate all of the
582 // sample points of the entire round join anyway, it is faster to
583 // generate them using a round cap operation. Additionally, it
584 // avoids math issues in the code below that stem from the
585 // calculations being performed on a pair of vectors that are
586 // nearly opposite each other.
587 AddCap(Cap::kRound, path_point, old_perpendicular.GetVector(), false);
588 // The bevel operation following the switch statement will set
589 // us up to start drawing the following segment.
590 break;
591 }
592 // We want to set up the from and to vectors to facilitate a
593 // clockwise angular fill from one to the other. We might generate
594 // a couple fewer points by iterating counter-clockwise in some
595 // cases so that we always go from the old to new perpendiculars,
596 // but there is a lot of code to duplicate below for just a small
597 // change in whether we negate the trigs and expect the a.Cross(b)
598 // values to be > or < 0.
599 Vector2 from_vector, to_vector;
600 bool begin_end_crossed;
601 Scalar turning = old_perpendicular.Cross(new_perpendicular);
602 if (turning > 0) {
603 // Clockwise path turn, since our prependicular vectors point to
604 // the right of the path we need to fill in the "back side" of the
605 // turn, so we fill from -old to -new perpendicular which also
606 // has a clockwise turn.
607 from_vector = -old_perpendicular.GetVector();
608 to_vector = -new_perpendicular.GetVector();
609 // Despite the fact that we are using the negative vectors, they
610 // are in the right "order" so we can connect directly from the
611 // prior segment's "box" and directly to the following segment's.
612 begin_end_crossed = false;
613 } else {
614 // Countercockwise path turn, we need to reverse the order of the
615 // perpendiculars to achieve a clockwise angular fill, and since
616 // both vectors are pointing to the right, the vectors themselves
617 // are "turning outside" the widened path.
618 from_vector = new_perpendicular.GetVector();
619 to_vector = old_perpendicular.GetVector();
620 // We are reversing the direction of traversal with respect to
621 // the old segment's and new segment's boxes so we should append
622 // extra segments to cross back and forth.
623 begin_end_crossed = true;
624 }
625 FML_DCHECK(from_vector.Cross(to_vector) > 0);
626
627 if (begin_end_crossed) {
628 vtx_builder_.AppendVertex(path_point + from_vector);
629 }
630
631 // We only need to trace back to the common center point on every
632 // other circular vertex we add. This generates a "corrugated"
633 // path that visits the center once for every pair of edge vertices.
634 bool visit_center = false;
635
636 // The sum of the vectors points in the direction halfway between
637 // them. Since we only need its direction, this is enough without
638 // having to adjust for the length to get the exact midpoint of
639 // the curve we have to draw.
640 Point middle_vector = (from_vector + to_vector);
641
642 // Iterate through trigs until we reach a full quadrant's rotation
643 // or until we pass the halfway point (middle_vector). We start at
644 // position 1 because the first value is (0, 1) and just repeats
645 // the from_vector, and we choose the end here as the last value
646 // rather than the end of the vector because it is (1, 0) and that
647 // would just repeat the to_vector. The end variable will be updated
648 // in the first loop if we stop short of a full quadrant.
649 size_t end = trigs_.size() - 1u;
650 for (size_t i = 1u; i < end; ++i) {
651 Point p = trigs_[i] * from_vector;
652 if (p.Cross(middle_vector) <= 0) {
653 // We've traversed far enough to pass the halfway vector, stop
654 // here and drop out to traverse backwards from the to_vector.
655 // Record the stopping point in the end variable as we will use
656 // it to backtrack in the next loop.
657 end = i;
658 break;
659 }
660 if (visit_center) {
661 vtx_builder_.AppendVertex(path_point);
662 visit_center = false;
663 } else {
664 visit_center = true;
665 }
666 vtx_builder_.AppendVertex(path_point + p);
667 }
668
669 // The end variable points to the last trigs entry we decided not to
670 // use, so a pre-decrement here moves us onto the trigs we actually
671 // want to use (stopping before we use 0 which is the no rotation
672 // vector).
673 while (--end > 0u) {
674 Point p = -trigs_[end] * to_vector;
675 if (visit_center) {
676 vtx_builder_.AppendVertex(path_point);
677 visit_center = false;
678 } else {
679 visit_center = true;
680 }
681 vtx_builder_.AppendVertex(path_point + p);
682 }
683
684 if (begin_end_crossed) {
685 vtx_builder_.AppendVertex(path_point + to_vector);
686 }
687 break;
688 } // end of case Join::kRound
689 } // end of switch
690 // All joins need a final segment that is perpendicular to the shared
691 // path point along the new perpendicular direction, and this also
692 // provides a bevel join for all cases that decided no further
693 // decoration was warranted.
694 AppendVertices(path_point, new_perpendicular);
695 }
696 };
697
698 // Private for benchmarking and debugging
699 std::vector<Point> StrokeSegmentsGeometry::GenerateSolidStrokeVertices(
700 Tessellator& tessellator,
701 const PathSource& source,
702 const StrokeParameters& stroke,
703 Scalar scale) {
704 std::vector<Point> points(4096);
705 PositionWriter vtx_builder(points);
706 StrokePathSegmentReceiver receiver(tessellator, vtx_builder, stroke, scale);
707 PathTessellator::PathToStrokedSegments(source, receiver);
708 auto [arena, extra] = vtx_builder.GetUsedSize();
709 FML_DCHECK(extra == 0u);
710 points.resize(arena);
711 return points;
712 }
713
714 StrokeSegmentsGeometry::StrokeSegmentsGeometry(const StrokeParameters& stroke)
715 : stroke_(stroke) {}
716
717 StrokeSegmentsGeometry::~StrokeSegmentsGeometry() = default;
718
719 Scalar StrokeSegmentsGeometry::GetStrokeWidth() const {
720 return stroke_.width;
721 }
722
723 Scalar StrokeSegmentsGeometry::GetMiterLimit() const {
724 return stroke_.miter_limit;
725 }
726
727 Cap StrokeSegmentsGeometry::GetStrokeCap() const {
728 return stroke_.cap;
729 }
730
731 Join StrokeSegmentsGeometry::GetStrokeJoin() const {
732 return stroke_.join;
733 }
734
735 Scalar StrokeSegmentsGeometry::ComputeAlphaCoverage(
736 const Matrix& transform) const {
737 return Geometry::ComputeStrokeAlphaCoverage(transform, stroke_.width);
738 }
739
740 GeometryResult StrokeSegmentsGeometry::GetPositionBuffer(
741 const ContentContext& renderer,
742 const Entity& entity,
743 RenderPass& pass) const {
744 if (stroke_.width < 0.0) {
745 return {};
746 }
747 Scalar max_basis = entity.GetTransform().GetMaxBasisLengthXY();
748 if (max_basis == 0) {
749 return {};
750 }
751
752 Scalar min_size = kMinStrokeSize / max_basis;
753 StrokeParameters adjusted_stroke = stroke_;
754 adjusted_stroke.width = std::max(stroke_.width, min_size);
755
756 auto& host_buffer = renderer.GetTransientsBuffer();
757 auto scale = entity.GetTransform().GetMaxBasisLengthXY();
758 auto& tessellator = renderer.GetTessellator();
759
760 PositionWriter position_writer(tessellator.GetStrokePointCache());
761 StrokePathSegmentReceiver receiver(tessellator, position_writer,
762 adjusted_stroke, scale);
763 Dispatch(receiver, tessellator, scale);
764
765 const auto [arena_length, oversized_length] = position_writer.GetUsedSize();
766 if (!position_writer.HasOversizedBuffer()) {
767 BufferView buffer_view =
768 host_buffer.Emplace(tessellator.GetStrokePointCache().data(),
769 arena_length * sizeof(Point), alignof(Point));
770
771 return GeometryResult{.type = PrimitiveType::kTriangleStrip,
772 .vertex_buffer =
773 {
774 .vertex_buffer = buffer_view,
775 .vertex_count = arena_length,
776 .index_type = IndexType::kNone,
777 },
778 .transform = entity.GetShaderTransform(pass),
779 .mode = GeometryResult::Mode::kPreventOverdraw};
780 }
781 const std::vector<Point>& oversized_data =
782 position_writer.GetOversizedBuffer();
783 BufferView buffer_view = host_buffer.Emplace(
784 /*buffer=*/nullptr, //
785 (arena_length + oversized_length) * sizeof(Point), //
786 alignof(Point) //
787 );
788 memcpy(buffer_view.GetBuffer()->OnGetContents() +
789 buffer_view.GetRange().offset, //
790 tessellator.GetStrokePointCache().data(), //
791 arena_length * sizeof(Point) //
792 );
793 memcpy(buffer_view.GetBuffer()->OnGetContents() +
794 buffer_view.GetRange().offset + arena_length * sizeof(Point), //
795 oversized_data.data(), //
796 oversized_data.size() * sizeof(Point) //
797 );
798 buffer_view.GetBuffer()->Flush(buffer_view.GetRange());
799
800 return GeometryResult{.type = PrimitiveType::kTriangleStrip,
801 .vertex_buffer =
802 {
803 .vertex_buffer = buffer_view,
804 .vertex_count = arena_length + oversized_length,
805 .index_type = IndexType::kNone,
806 },
807 .transform = entity.GetShaderTransform(pass),
808 .mode = GeometryResult::Mode::kPreventOverdraw};
809 }
810
811 GeometryResult::Mode StrokeSegmentsGeometry::GetResultMode() const {
812 return GeometryResult::Mode::kPreventOverdraw;
813 }
814
815 std::optional<Rect> StrokeSegmentsGeometry::GetStrokeCoverage(
816 const Matrix& transform,
817 const Rect& path_bounds) const {
818 if (path_bounds.IsEmpty()) {
819 return std::nullopt;
820 }
821
822 Scalar max_radius = 0.5;
823 if (stroke_.cap == Cap::kSquare) {
824 max_radius = max_radius * kSqrt2;
825 }
826 if (stroke_.join == Join::kMiter) {
827 max_radius = std::max(max_radius, stroke_.miter_limit * 0.5f);
828 }
829 Scalar max_basis = transform.GetMaxBasisLengthXY();
830 if (max_basis == 0) {
831 return {};
832 }
833 // Use the most conervative coverage setting.
834 Scalar min_size = kMinStrokeSize / max_basis;
835 max_radius *= std::max(stroke_.width, min_size);
836 return path_bounds.Expand(max_radius).TransformBounds(transform);
837 }
838
839 StrokePathSourceGeometry::StrokePathSourceGeometry(
840 const StrokeParameters& parameters)
841 : StrokeSegmentsGeometry(parameters) {}
842
843 std::optional<Rect> StrokePathSourceGeometry::GetCoverage(
844 const Matrix& transform) const {
845 return GetStrokeCoverage(transform, GetSource().GetBounds());
846 }
847
848 void StrokePathSourceGeometry::Dispatch(PathAndArcSegmentReceiver& receiver,
849 Tessellator& tessellator,
850 Scalar scale) const {
851 PathTessellator::PathToStrokedSegments(GetSource(), receiver);
852 }
853
854 StrokePathGeometry::StrokePathGeometry(const flutter::DlPath& path,
855 const StrokeParameters& parameters)
856 : StrokePathSourceGeometry(parameters), path_(path) {}
857
858 const PathSource& StrokePathGeometry::GetSource() const {
859 return path_;
860 }
861
862 ArcStrokeGeometry::ArcStrokeGeometry(const Arc& arc,
863 const StrokeParameters& parameters)
864 : StrokeSegmentsGeometry(parameters), arc_(arc) {}
865
866 std::optional<Rect> ArcStrokeGeometry::GetCoverage(
867 const Matrix& transform) const {
868 return GetStrokeCoverage(transform, arc_.GetTightArcBounds());
869 }
870
871 void ArcStrokeGeometry::Dispatch(PathAndArcSegmentReceiver& receiver,
872 Tessellator& tessellator,
873 Scalar scale) const {
874 Point center = arc_.GetOvalCenter();
875 Size radii = arc_.GetOvalSize() * 0.5f;
876
877 auto trigs =
878 tessellator.GetTrigsForDeviceRadius(scale * radii.MaxDimension());
879 Arc::Iteration iterator =
880 arc_.ComputeIterations(trigs.GetSteps(), /*simplify_360=*/false);
881 Point start = center + iterator.start * radii;
882 bool include_center = arc_.IncludeCenter();
883
884 receiver.BeginContour(start, include_center);
885 receiver.RecordArc(arc_, center, radii);
886 if (include_center) {
887 Point end = center + iterator.end * radii;
888 receiver.RecordLine(end, center);
889 receiver.RecordLine(center, start);
890 }
891 receiver.EndContour(start, include_center);
892 }
893
894 StrokeDiffRoundRectGeometry::StrokeDiffRoundRectGeometry(
895 const RoundRect& outer,
896 const RoundRect& inner,
897 const StrokeParameters& parameters)
898 : StrokePathSourceGeometry(parameters), source_(outer, inner) {}
899
900 const PathSource& StrokeDiffRoundRectGeometry::GetSource() const {
901 return source_;
902 }
903
904 StrokeDashedLineGeometry::StrokeDashedLineGeometry(
905 Point p0,
906 Point p1,
907 Scalar on_length,
908 Scalar off_length,
909 const StrokeParameters& parameters)
910 : StrokePathSourceGeometry(parameters),
911 source_(p0, p1, on_length, off_length) {}
912
913 const PathSource& StrokeDashedLineGeometry::GetSource() const {
914 return source_;
915 }
916
917 } // namespace impeller
buffer_view
BufferView buffer_view
Definition: blit_command_gles.cc:154
buffer_view.h
impeller::ArcStrokeGeometry::Dispatch
void Dispatch(PathAndArcSegmentReceiver &receiver, Tessellator &tessellator, Scalar scale) const override
Definition: stroke_path_geometry.cc:871
impeller::ArcStrokeGeometry::ArcStrokeGeometry
ArcStrokeGeometry(const Arc &arc, const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:862
impeller::ArcStrokeGeometry::GetCoverage
std::optional< Rect > GetCoverage(const Matrix &transform) const override
Definition: stroke_path_geometry.cc:866
impeller::ContentContext
Definition: content_context.h:138
impeller::ContentContext::GetTransientsBuffer
HostBuffer & GetTransientsBuffer() const
Retrieve the currnent host buffer for transient storage.
Definition: content_context.h:297
impeller::ContentContext::GetTessellator
Tessellator & GetTessellator() const
Definition: content_context.cc:935
impeller::Entity
Definition: entity.h:26
impeller::Entity::GetShaderTransform
Matrix GetShaderTransform(const RenderPass &pass) const
Definition: entity.cc:48
impeller::Entity::GetTransform
const Matrix & GetTransform() const
Get the global transform matrix for this Entity.
Definition: entity.cc:44
impeller::Geometry::ComputeStrokeAlphaCoverage
static Scalar ComputeStrokeAlphaCoverage(const Matrix &entity, Scalar stroke_width)
Compute an alpha value to simulate lower coverage of fractional pixel strokes.
Definition: geometry.cc:149
impeller::PathAndArcSegmentReceiver
A |SegmentReceiver| that also accepts Arc segments for optimal handling. A path or |PathSource| will ...
Definition: stroke_path_geometry.h:20
impeller::PathAndArcSegmentReceiver::RecordArc
virtual void RecordArc(const Arc &arc, const Point center, const Size radii)=0
impeller::PathSource
Definition: path_source.h:55
impeller::PathTessellator::SegmentReceiver::RecordLine
virtual void RecordLine(Point p1, Point p2)=0
impeller::PathTessellator::SegmentReceiver::EndContour
virtual void EndContour(Point origin, bool with_close)=0
impeller::PathTessellator::SegmentReceiver::BeginContour
virtual void BeginContour(Point origin, bool will_be_closed)=0
impeller::PathTessellator::PathToStrokedSegments
static void PathToStrokedSegments(const PathSource &source, SegmentReceiver &receiver)
Definition: path_tessellator.cc:290
impeller::RenderPass
Render passes encode render commands directed as one specific render target into an underlying comman...
Definition: render_pass.h:30
impeller::StrokeDashedLineGeometry::GetSource
const PathSource & GetSource() const override
Definition: stroke_path_geometry.cc:913
impeller::StrokeDashedLineGeometry::StrokeDashedLineGeometry
StrokeDashedLineGeometry(Point p0, Point p1, Scalar on_length, Scalar off_length, const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:904
impeller::StrokeDiffRoundRectGeometry::StrokeDiffRoundRectGeometry
StrokeDiffRoundRectGeometry(const RoundRect &outer, const RoundRect &inner, const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:894
impeller::StrokeDiffRoundRectGeometry::GetSource
const PathSource & GetSource() const override
Definition: stroke_path_geometry.cc:900
impeller::StrokePathGeometry::StrokePathGeometry
StrokePathGeometry(const flutter::DlPath &path, const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:854
impeller::StrokePathGeometry::GetSource
const PathSource & GetSource() const override
Definition: stroke_path_geometry.cc:858
impeller::StrokePathSegmentReceiver
Definition: stroke_path_geometry.cc:131
impeller::StrokePathSegmentReceiver::RecordCurve
void RecordCurve(const Curve &curve)
Definition: stroke_path_geometry.cc:202
impeller::StrokePathSegmentReceiver::BeginContour
void BeginContour(Point origin, bool will_be_closed) override
Definition: stroke_path_geometry.cc:157
impeller::StrokePathSegmentReceiver::RecordArc
void RecordArc(const Arc &arc, const Point center, const Size radii) override
Definition: stroke_path_geometry.cc:287
impeller::StrokePathSegmentReceiver::EndContour
void EndContour(Point origin, bool with_close) override
Definition: stroke_path_geometry.cc:258
impeller::StrokePathSegmentReceiver::RecordQuad
void RecordQuad(Point p1, Point cp, Point p2) override
Definition: stroke_path_geometry.cc:186
impeller::StrokePathSegmentReceiver::StrokePathSegmentReceiver
StrokePathSegmentReceiver(Tessellator &tessellator, PositionWriter &vtx_builder, const StrokeParameters &stroke, const Scalar scale)
Definition: stroke_path_geometry.cc:133
impeller::StrokePathSegmentReceiver::RecordConic
void RecordConic(Point p1, Point cp, Point p2, Scalar weight) override
Definition: stroke_path_geometry.cc:191
impeller::StrokePathSegmentReceiver::RecordCubic
void RecordCubic(Point p1, Point cp1, Point cp2, Point p2) override
Definition: stroke_path_geometry.cc:196
impeller::StrokePathSegmentReceiver::RecordCurveSegment
void RecordCurveSegment(const SeparatedVector2 &prev_perpendicular, const Point cur, const SeparatedVector2 &cur_perpendicular)
Definition: stroke_path_geometry.cc:245
impeller::StrokePathSegmentReceiver::RecordLine
void RecordLine(Point p1, Point p2) override
Definition: stroke_path_geometry.cc:173
impeller::StrokePathSourceGeometry
An abstract Geometry base class that produces fillable vertices representing the stroked outline from...
Definition: stroke_path_geometry.h:94
impeller::StrokePathSourceGeometry::GetSource
virtual const PathSource & GetSource() const =0
impeller::StrokePathSourceGeometry::GetCoverage
std::optional< Rect > GetCoverage(const Matrix &transform) const override
Definition: stroke_path_geometry.cc:843
impeller::StrokePathSourceGeometry::StrokePathSourceGeometry
StrokePathSourceGeometry(const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:839
impeller::StrokePathSourceGeometry::Dispatch
void Dispatch(PathAndArcSegmentReceiver &receiver, Tessellator &tessellator, Scalar scale) const override
Definition: stroke_path_geometry.cc:848
impeller::StrokeSegmentsGeometry
An abstract Geometry base class that produces fillable vertices representing the stroked outline of t...
Definition: stroke_path_geometry.h:35
impeller::StrokeSegmentsGeometry::Dispatch
virtual void Dispatch(PathAndArcSegmentReceiver &receiver, Tessellator &tessellator, Scalar scale) const =0
impeller::StrokeSegmentsGeometry::GetStrokeJoin
Join GetStrokeJoin() const
Definition: stroke_path_geometry.cc:731
impeller::StrokeSegmentsGeometry::GetStrokeWidth
Scalar GetStrokeWidth() const
Definition: stroke_path_geometry.cc:719
impeller::StrokeSegmentsGeometry::GetMiterLimit
Scalar GetMiterLimit() const
Definition: stroke_path_geometry.cc:723
impeller::StrokeSegmentsGeometry::ComputeAlphaCoverage
Scalar ComputeAlphaCoverage(const Matrix &transform) const override
Definition: stroke_path_geometry.cc:735
impeller::StrokeSegmentsGeometry::GetStrokeCap
Cap GetStrokeCap() const
Definition: stroke_path_geometry.cc:727
impeller::StrokeSegmentsGeometry::GetStrokeCoverage
std::optional< Rect > GetStrokeCoverage(const Matrix &transform, const Rect &segment_bounds) const
Definition: stroke_path_geometry.cc:815
impeller::StrokeSegmentsGeometry::StrokeSegmentsGeometry
StrokeSegmentsGeometry(const StrokeParameters &parameters)
Definition: stroke_path_geometry.cc:714
impeller::StrokeSegmentsGeometry::~StrokeSegmentsGeometry
~StrokeSegmentsGeometry() override
impeller::Tessellator::Trigs
Definition: tessellator.h:48
impeller::Tessellator::Trigs::end
std::vector< Trig >::iterator end() const
Definition: tessellator.h:55
impeller::Tessellator::Trigs::size
size_t size() const
Definition: tessellator.h:53
impeller::Tessellator::Trigs::GetSteps
size_t GetSteps() const
Definition: tessellator.h:58
impeller::Tessellator
A utility that generates triangles of the specified fill type given a polyline. This happens on the C...
Definition: tessellator.h:37
impeller::Tessellator::GetTrigsForDeviceRadius
Trigs GetTrigsForDeviceRadius(Scalar pixel_radius)
Definition: tessellator.cc:310
formats.h
transform
Matrix transform
Definition: gaussian_blur_filter_contents.cc:214
constants.h
geometry.h
host_buffer.h
impeller
Definition: allocation.cc:12
impeller::Join
Join
An enum that describes ways to join two segments of a path.
Definition: stroke_parameters.h:20
impeller::Join::kRound
@ kRound
impeller::Join::kMiter
@ kMiter
impeller::Join::kBevel
@ kBevel
impeller::PrimitiveType::kTriangleStrip
@ kTriangleStrip
impeller::Vector2
Point Vector2
Definition: point.h:331
impeller::Scalar
float Scalar
Definition: scalar.h:19
impeller::IndexType::kNone
@ kNone
Does not use the index buffer.
impeller::Point
TPoint< Scalar > Point
Definition: point.h:327
impeller::Cap
Cap
An enum that describes ways to decorate the end of a path contour.
Definition: stroke_parameters.h:13
impeller::Cap::kRound
@ kRound
impeller::Cap::kButt
@ kButt
impeller::Cap::kSquare
@ kSquare
impeller::DlPath
flutter::DlPath DlPath
Definition: dl_dispatcher.h:29
impeller::kSqrt2
constexpr float kSqrt2
Definition: constants.h:47
impeller::kPointArenaSize
static constexpr size_t kPointArenaSize
The size of the point arena buffer stored on the tessellator.
Definition: tessellator.h:25
impeller::kMinStrokeSize
static constexpr Scalar kMinStrokeSize
Definition: geometry.h:19
path_tessellator.h
pipelines.h
separated_vector.h
stroke_path_geometry.h
impeller::Arc::Iteration::Quadrant
Definition: arc.h:45
impeller::Arc::Iteration::Quadrant::axis
impeller::Vector2 axis
Definition: arc.h:46
impeller::Arc::Iteration::Quadrant::start_index
size_t start_index
Definition: arc.h:47
impeller::Arc::Iteration::Quadrant::end_index
size_t end_index
Definition: arc.h:48
impeller::Arc::Iteration
Definition: arc.h:42
impeller::Arc::Iteration::end
impeller::Vector2 end
Definition: arc.h:59
impeller::Arc::Iteration::start
impeller::Vector2 start
Definition: arc.h:58
impeller::Arc::Iteration::quadrants
Quadrant quadrants[9]
Definition: arc.h:86
impeller::Arc::Iteration::quadrant_count
size_t quadrant_count
Definition: arc.h:63
impeller::Arc
Definition: arc.h:13
impeller::Arc::ComputeIterations
Iteration ComputeIterations(size_t step_count, bool simplify_360=true) const
Definition: arc.cc:102
impeller::Arc::GetTightArcBounds
Rect GetTightArcBounds() const
Definition: arc.cc:59
impeller::Arc::IncludeCenter
constexpr bool IncludeCenter() const
Definition: arc.h:110
impeller::Arc::GetOvalSize
const Size GetOvalSize() const
Returns the size of the oval bounds.
Definition: arc.h:100
impeller::Arc::GetOvalCenter
const Point GetOvalCenter() const
Returns the center of the oval bounds.
Definition: arc.h:97
impeller::GeometryResult
Definition: geometry.h:21
impeller::GeometryResult::Mode
Mode
Definition: geometry.h:22
impeller::GeometryResult::Mode::kPreventOverdraw
@ kPreventOverdraw
impeller::Matrix
A 4x4 matrix using column-major storage.
Definition: matrix.h:37
impeller::Matrix::GetMaxBasisLengthXY
Scalar GetMaxBasisLengthXY() const
Return the maximum scale applied specifically to either the X axis or Y axis unit vectors (the bases)...
Definition: matrix.h:328
impeller::RoundRect
Definition: round_rect.h:16
impeller::SeparatedVector2
A Vector2, broken down as a separate magnitude and direction. Assumes that the direction given is nor...
Definition: separated_vector.h:21
impeller::SeparatedVector2::GetAlignment
Scalar GetAlignment(const SeparatedVector2 &other) const
Definition: separated_vector.cc:25
impeller::SeparatedVector2::GetVector
Vector2 GetVector() const
Returns the vector representation of the vector.
Definition: separated_vector.cc:17
impeller::StrokeParameters
A structure to store all of the parameters related to stroking a path or basic geometry object.
Definition: stroke_parameters.h:28
impeller::StrokeParameters::cap
Cap cap
Definition: stroke_parameters.h:30
impeller::StrokeParameters::join
Join join
Definition: stroke_parameters.h:31
impeller::StrokeParameters::miter_limit
Scalar miter_limit
Definition: stroke_parameters.h:32
impeller::StrokeParameters::width
Scalar width
Definition: stroke_parameters.h:29
impeller::TPoint< Scalar >
impeller::TPoint::y
Type y
Definition: point.h:31
impeller::TPoint::x
Type x
Definition: point.h:30
impeller::TRect< Scalar >
impeller::TRect::Expand
constexpr TRect< T > Expand(T left, T top, T right, T bottom) const
Returns a rectangle with expanded edges. Negative expansion results in shrinking.
Definition: rect.h:622
impeller::TRect::TransformBounds
constexpr TRect TransformBounds(const Matrix &transform) const
Creates a new bounding box that contains this transformed rectangle.
Definition: rect.h:476
impeller::TRect::IsEmpty
constexpr bool IsEmpty() const
Returns true if either of the width or height are 0, negative, or NaN.
Definition: rect.h:301
impeller::TSize< Scalar >
impeller::TSize::MaxDimension
constexpr Type MaxDimension() const
Definition: size.h:106
start
const size_t start
Definition: tessellator_libtess.cc:62
end
const size_t end
Definition: tessellator_libtess.cc:63
points
std::vector< Point > points
Definition: tessellator_libtess.cc:76
wangs_formula.h