sw_engine: revised the trimpath dash line logic

Support the TrimPath modes (individual/simultaneous)
internally in the engine to handle them efficiently.

src/loaders/lottie/tvgLottieBuilder.cpp

@@ -897,7 +897,7 @@ static void _updateTrimpath(TVG_UNUSED LottieGroup* parent, LottieObject** child
         end = (length * end) + pbegin;
     }
 
-    P(ctx->propagator)->strokeTrim(begin, end);
+    P(ctx->propagator)->strokeTrim(begin, end, false);
 
     //TODO: individual or simultaenous mode
 }

src/renderer/sw_engine/tvgSwShape.cpp

@@ -105,6 +105,7 @@ static void _dashLineTo(SwDashStroke& dash, const Point* to, const Matrix* trans
 
     if (mathZero(len)) {
         _outlineMoveTo(*dash.outline, &dash.ptCur, transform);
+    //draw the current line fully
     } else if (len < dash.curLen) {
         dash.curLen -= len;
         if (!dash.curOpGap) {
@@ -114,6 +115,7 @@ static void _dashLineTo(SwDashStroke& dash, const Point* to, const Matrix* trans
             }
             _outlineLineTo(*dash.outline, to, transform);
         }
+    //draw the current line partially
     } else {
         while (len - dash.curLen > 0.0001f) {
             Line left, right;
@@ -162,6 +164,7 @@ static void _dashCubicTo(SwDashStroke& dash, const Point* ctrl1, const Point* ct
     Bezier cur = {dash.ptCur, *ctrl1, *ctrl2, *to};
     auto len = bezLength(cur);
 
+    //draw the current line fully
     if (mathZero(len)) {
         _outlineMoveTo(*dash.outline, &dash.ptCur, transform);
     } else if (len < dash.curLen) {
@@ -173,6 +176,7 @@ static void _dashCubicTo(SwDashStroke& dash, const Point* ctrl1, const Point* ct
             }
             _outlineCubicTo(*dash.outline, ctrl1, ctrl2, to, transform);
         }
+    //draw the current line partially
     } else {
         while ((len - dash.curLen) > 0.0001f) {
             Bezier left, right;
@@ -222,7 +226,15 @@ static void _dashClose(SwDashStroke& dash, const Matrix* transform)
 }
 
 
-static void _dashMoveTo(SwDashStroke& dash, uint32_t offIdx, float offset, const Point* pts, const Matrix* transform)
+static void _dashMoveTo(SwDashStroke& dash, const Point* pts)
+{
+    dash.ptCur = *pts;
+    dash.ptStart = *pts;
+    dash.move = true;
+}
+
+
+static void _dashMoveTo(SwDashStroke& dash, uint32_t offIdx, float offset, const Point* pts)
 {
     dash.curIdx = offIdx % dash.cnt;
     dash.curLen = dash.pattern[dash.curIdx] - offset;
@@ -257,7 +269,7 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix* trans
 
         //default
         if (end > begin) {
-            if (begin > 0) dash.cnt += 4;
+            if (begin > 0.0f) dash.cnt += 4;
             else dash.cnt += 2;
         //looping
         } else dash.cnt += 3;
@@ -275,7 +287,7 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix* trans
             dash.pattern[0] = 0;     //zero dash to start with a space.
             dash.pattern[1] = begin;
             dash.pattern[2] = end - begin;
-            dash.pattern[3] = length - (end - begin);
+            dash.pattern[3] = length - end;
         }
 
         trimmed = true;
@@ -304,14 +316,22 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix* trans
 
     dash.outline = mpoolReqDashOutline(mpool, tid);
 
-    while (cmdCnt-- > 0) {
+    //must begin with moveTo
+    if (cmds[0] == PathCommand::MoveTo) {
+        _dashMoveTo(dash, offIdx, offset, pts);
+        cmds++;
+        pts++;
+    }
+
+    while (--cmdCnt > 0) {
         switch (*cmds) {
             case PathCommand::Close: {
                 _dashClose(dash, transform);
                 break;
             }
             case PathCommand::MoveTo: {
-                _dashMoveTo(dash, offIdx, offset, pts, transform);
+                if (rshape->stroke->trim.individual) _dashMoveTo(dash, pts);
+                else _dashMoveTo(dash, offIdx, offset, pts);
                 ++pts;
                 break;
             }
@@ -349,13 +369,19 @@ static float _outlineLength(const RenderShape* rshape)
 
     const Point* close = nullptr;
     auto length = 0.0f;
+    auto slength = 0.0f;
+    auto simutaneous = !rshape->stroke->trim.individual;
 
     //Compute the whole length
     while (cmdCnt-- > 0) {
         switch (*cmds) {
             case PathCommand::Close: {
                 length += mathLength(pts - 1, close);
-                ++pts;
+                //retrieve the max length of the shape if the simultaneous mode.
+                if (simutaneous && slength < length) {
+                    slength = length;
+                    length = 0.0f;
+                }
                 break;
             }
             case PathCommand::MoveTo: {
@@ -376,7 +402,8 @@ static float _outlineLength(const RenderShape* rshape)
         }
         ++cmds;
     }
-    return length;
+    if (simutaneous && slength > length) return slength;
+    else return length;
 }
 
 

src/renderer/tvgRender.h

@@ -161,6 +161,7 @@ struct RenderStroke
     struct {
         float begin = 0.0f;
         float end = 1.0f;
+        bool individual = false;
     } trim;
 
     ~RenderStroke()

src/renderer/tvgShape.h

@@ -203,7 +203,7 @@ struct Shape::Impl
         return true;
     }
 
-    bool strokeTrim(float begin, float end)
+    bool strokeTrim(float begin, float end, bool individual)
     {
         if (!rs.stroke) {
             if (begin == 0.0f && end == 1.0f) return true;
@@ -214,6 +214,7 @@ struct Shape::Impl
 
         rs.stroke->trim.begin = begin;
         rs.stroke->trim.end = end;
+        rs.stroke->trim.individual = individual;
         flag |= RenderUpdateFlag::Stroke;
 
         return true;