common: move&fix trimming wrapping logic

The logic of interpretation of trimming start and
end values has been moved to the sw_engine,
so the values provided by the user are not modified.
No logical changes in the interpretation alg.

For pairs of trim's start/end values where the distance
between begin and end is >= 1, the entire stroke should
be drawn, but instead, nothing or only part is drawn. Fixed.

Stroke trim docs fixed.

inc/thorvg.h

@@ -1040,7 +1040,7 @@ public:
     /**
      * @brief Sets the trim of the stroke along the defined path segment, allowing control over which part of the stroke is visible.
      *
-     * The values of the arguments @p begin, @p end, and @p offset are in the range of 0.0 to 1.0, representing the beginning of the path and the end, respectively.
+     * If the values of the arguments @p begin and @p end exceed the 0-1 range, they are wrapped around in a manner similar to angle wrapping, effectively treating the range as circular.
      *
      * @param[in] begin Specifies the start of the segment to display along the path.
      * @param[in] end Specifies the end of the segment to display along the path.

src/bindings/capi/thorvg_capi.h

@@ -1511,7 +1511,7 @@ TVG_API Tvg_Result tvg_shape_get_stroke_miterlimit(const Tvg_Paint* paint, float
 /*!
 * \brief Sets the trim of the stroke along the defined path segment, allowing control over which part of the stroke is visible.
 *
-* The values of the arguments @p begin, @p end, and @p offset are in the range of 0.0 to 1.0, representing the beginning of the path and the end, respectively.
+* If the values of the arguments @p begin and @p end exceed the 0-1 range, they are wrapped around in a manner similar to angle wrapping, effectively treating the range as circular.
 *
 * \param[in] paint A Tvg_Paint pointer to the shape object.
 * \param[in] begin Specifies the start of the segment to display along the path.

src/renderer/sw_engine/tvgSwShape.cpp

@@ -244,10 +244,10 @@ static void _dashMoveTo(SwDashStroke& dash, uint32_t offIdx, float offset, const
 }
 
 
-static void _trimPattern(SwDashStroke* dash, const RenderShape* rshape, float length)
+static void _trimPattern(SwDashStroke* dash, const RenderShape* rshape, float length, float trimBegin, float trimEnd)
 {
-    auto begin = length * rshape->stroke->trim.begin;
+    auto begin = length * trimBegin;
-    auto end = length * rshape->stroke->trim.end;
+    auto end = length * trimEnd;
 
     //default
     if (end > begin) {
@@ -340,6 +340,8 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix& trans
     auto offset = 0.0f;
     dash.cnt = rshape->strokeDash((const float**)&dash.pattern, &offset);
     auto simultaneous = rshape->stroke->trim.simultaneous;
+    float trimBegin = 0.0f, trimEnd = 1.0f;
+    if (trimmed) rshape->stroke->strokeTrim(trimBegin, trimEnd);
 
     if (dash.cnt == 0) {
         if (trimmed) dash.pattern = (float*)malloc(sizeof(float) * 4);
@@ -371,7 +373,7 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix& trans
 
     //must begin with moveTo
     if (cmds[0] == PathCommand::MoveTo) {
-        if (trimmed) _trimPattern(&dash, rshape, _outlineLength(rshape, 0, 0, simultaneous));
+        if (trimmed) _trimPattern(&dash, rshape, _outlineLength(rshape, 0, 0, simultaneous), trimBegin, trimEnd);
         _dashMoveTo(dash, offIdx, offset, pts);
         cmds++;
         pts++;
@@ -386,7 +388,7 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix& trans
             case PathCommand::MoveTo: {
                 if (trimmed) {
                     if (simultaneous) {
-                        _trimPattern(&dash, rshape, _outlineLength(rshape, pts - startPts, cmds - startCmds, true));
+                        _trimPattern(&dash, rshape, _outlineLength(rshape, pts - startPts, cmds - startCmds, true), trimBegin, trimEnd);
                         _dashMoveTo(dash, offIdx, offset, pts);
                     } else _dashMoveTo(dash, pts);
                 } else _dashMoveTo(dash, offIdx, offset, pts);

src/renderer/tvgRender.h

@@ -23,6 +23,7 @@
 #ifndef _TVG_RENDER_H_
 #define _TVG_RENDER_H_
 
+#include <math.h>
 #include "tvgCommon.h"
 #include "tvgArray.h"
 #include "tvgLock.h"
@@ -155,6 +156,32 @@ struct RenderStroke
         trim = rhs.trim;
     }
 
+    bool strokeTrim(float& begin, float& end) const
+    {
+        begin = trim.begin;
+        end = trim.end;
+
+        if (fabsf(end - begin) > 1.0f) {
+            begin = 0.0f;
+            end = 1.0f;
+            return false;
+        }
+
+        auto loop = true;
+
+        if (begin > 1.0f && end > 1.0f) loop = false;
+        if (begin < 0.0f && end < 0.0f) loop = false;
+        if (begin >= 0.0f && begin <= 1.0f && end >= 0.0f  && end <= 1.0f) loop = false;
+
+        if (begin > 1.0f) begin -= 1.0f;
+        if (begin < 0.0f) begin += 1.0f;
+        if (end > 1.0f) end -= 1.0f;
+        if (end < 0.0f) end += 1.0f;
+
+        if ((loop && begin < end) || (!loop && begin > end)) std::swap(begin, end);
+        return true;
+    }
+
     ~RenderStroke()
     {
         free(dashPattern);
@@ -199,7 +226,7 @@ struct RenderShape
     {
         if (!stroke) return false;
         if (stroke->trim.begin == 0.0f && stroke->trim.end == 1.0f) return false;
-        if (stroke->trim.begin == 1.0f && stroke->trim.end == 0.0f) return false;
+        if (fabsf(stroke->trim.end - stroke->trim.begin) > 1.0f) return false;
         return true;
     }
 

src/renderer/tvgShape.h

@@ -217,23 +217,6 @@ struct Shape::Impl
         if (tvg::equal(rs.stroke->trim.begin, begin) && tvg::equal(rs.stroke->trim.end, end) &&
             rs.stroke->trim.simultaneous == simultaneous) return;
 
-        auto loop = true;
-
-        if (begin > 1.0f && end > 1.0f) loop = false;
-        if (begin < 0.0f && end < 0.0f) loop = false;
-        if (begin >= 0.0f && begin <= 1.0f && end >= 0.0f  && end <= 1.0f) loop = false;
-
-        if (begin > 1.0f) begin -= 1.0f;
-        if (begin < 0.0f) begin += 1.0f;
-        if (end > 1.0f) end -= 1.0f;
-        if (end < 0.0f) end += 1.0f;
-
-        if ((loop && begin < end) || (!loop && begin > end)) {
-            auto tmp = begin;
-            begin = end;
-            end = tmp;
-        }
-
         rs.stroke->trim.begin = begin;
         rs.stroke->trim.end = end;
         rs.stroke->trim.simultaneous = simultaneous;