common: stroke dash offset support added

The feature is supported also in the svg loader.

@Issue: https://github.com/thorvg/thorvg/issues/1591

inc/thorvg.h

@@ -1002,6 +1002,7 @@ public:
      *
      * @param[in] dashPattern The array of consecutive pair values of the dash length and the gap length.
      * @param[in] cnt The length of the @p dashPattern array.
+     * @param[in] offset The shift of the starting point within the repeating dash pattern from which the path's dashing begins.
      *
      * @retval Result::Success When succeed.
      * @retval Result::FailedAllocation An internal error with a memory allocation for an object to be dashed.
@@ -1010,7 +1011,7 @@ public:
      * @note To reset the stroke dash pattern, pass @c nullptr to @p dashPattern and zero to @p cnt.
      * @warning @p cnt must be greater than 1 if the dash pattern is valid.
      */
-    Result stroke(const float* dashPattern, uint32_t cnt) noexcept;
+    Result stroke(const float* dashPattern, uint32_t cnt, float offset = 0.0f) noexcept;
 
     /**
      * @brief Sets the cap style of the stroke in the open sub-paths.
@@ -1170,10 +1171,11 @@ public:
      * @brief Gets the dash pattern of the stroke.
      *
      * @param[out] dashPattern The pointer to the memory, where the dash pattern array is stored.
+     * @param[out] offset The shift of the starting point within the repeating dash pattern.
      *
      * @return The length of the @p dashPattern array.
      */
-    uint32_t strokeDash(const float** dashPattern) const noexcept;
+    uint32_t strokeDash(const float** dashPattern, float* offset = nullptr) const noexcept;
 
     /**
      * @brief Gets the cap style used for stroking the path.

src/lib/sw_engine/tvgSwRenderer.cpp

@@ -132,7 +132,7 @@ struct SwShapeTask : SwTask
                    shape outline below stroke could be full covered by stroke drawing.
                    Thus it turns off antialising in that condition.
                    Also, it shouldn't be dash style. */
-                auto antiAlias = strokeAlpha < 255 || rshape->strokeWidth() <= 2 || rshape->strokeDash(nullptr) > 0 || (rshape->stroke && rshape->stroke->strokeFirst);
+                auto antiAlias = strokeAlpha < 255 || rshape->strokeWidth() <= 2 || rshape->strokeDash(nullptr, nullptr) > 0 || (rshape->stroke && rshape->stroke->strokeFirst);
 
                 if (!shapeGenRle(&shape, rshape, antiAlias)) goto err;
             }

src/lib/sw_engine/tvgSwShape.cpp

@@ -222,9 +222,27 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix* trans
     dash.curOpGap = false;
 
     const float* pattern;
-    dash.cnt = rshape->strokeDash(&pattern);
+    float offset;
+    dash.cnt = rshape->strokeDash(&pattern, &offset);
     if (dash.cnt == 0) return nullptr;
 
+    auto patternLength = 0.0f;
+    uint32_t offIdx = 0;
+    if (fabsf(offset) > FLT_EPSILON) {
+        for (auto i = 0; i < dash.cnt; ++i) patternLength += pattern[i];
+        bool isOdd = dash.cnt % 2;
+        if (isOdd) patternLength *= 2;
+
+        if (offset < 0) offset = patternLength + fmod(offset, patternLength);
+        else offset = fmod(offset, patternLength);
+
+        for (auto i = 0; i < dash.cnt * (1 + isOdd); ++i, ++offIdx) {
+            auto curPattern = pattern[i % dash.cnt];
+            if (offset < curPattern) break;
+            offset -= curPattern;
+        }
+    }
+
     //OPTMIZE ME: Use mempool???
     dash.pattern = const_cast<float*>(pattern);
     dash.outline = static_cast<SwOutline*>(calloc(1, sizeof(SwOutline)));
@@ -271,9 +289,9 @@ static SwOutline* _genDashOutline(const RenderShape* rshape, const Matrix* trans
             }
             case PathCommand::MoveTo: {
                 //reset the dash
-                dash.curIdx = 0;
-                dash.curLen = *dash.pattern;
-                dash.curOpGap = false;
+                dash.curIdx = offIdx % dash.cnt;
+                dash.curLen = dash.pattern[dash.curIdx] - offset;
+                dash.curOpGap = offIdx % 2;
                 dash.ptStart = dash.ptCur = *pts;
                 ++pts;
                 break;
@@ -515,7 +533,7 @@ bool shapeGenStrokeRle(SwShape* shape, const RenderShape* rshape, const Matrix*
     bool ret = true;
 
     //Dash Style Stroke
-    if (rshape->strokeDash(nullptr) > 0) {
+    if (rshape->strokeDash(nullptr, nullptr) > 0) {
         shapeOutline = _genDashOutline(rshape, transform);
         if (!shapeOutline) return false;
         freeOutline = true;

src/lib/tvgRender.h

@@ -137,6 +137,7 @@ struct RenderStroke
     Fill *fill = nullptr;
     float* dashPattern = nullptr;
     uint32_t dashCnt = 0;
+    float dashOffset = 0.0f;
     StrokeCap cap = StrokeCap::Square;
     StrokeJoin join = StrokeJoin::Bevel;
     float miterlimit = 4.0f;
@@ -200,10 +201,11 @@ struct RenderShape
         return stroke->fill;
     }
 
-    uint32_t strokeDash(const float** dashPattern) const
+    uint32_t strokeDash(const float** dashPattern, float* offset) const
     {
         if (!stroke) return 0;
         if (dashPattern) *dashPattern = stroke->dashPattern;
+        if (offset) *offset = stroke->dashOffset;
         return stroke->dashCnt;
     }
 

src/lib/tvgShape.cpp

@@ -340,7 +340,7 @@ const Fill* Shape::strokeFill() const noexcept
 }
 
 
-Result Shape::stroke(const float* dashPattern, uint32_t cnt) noexcept
+Result Shape::stroke(const float* dashPattern, uint32_t cnt, float offset) noexcept
 {
     if ((cnt == 1) || (!dashPattern && cnt > 0) || (dashPattern && cnt == 0)) {
         return Result::InvalidArguments;
@@ -349,15 +349,15 @@ Result Shape::stroke(const float* dashPattern, uint32_t cnt) noexcept
     for (uint32_t i = 0; i < cnt; i++)
         if (dashPattern[i] < FLT_EPSILON) return Result::InvalidArguments;
 
-    if (!pImpl->strokeDash(dashPattern, cnt)) return Result::FailedAllocation;
+    if (!pImpl->strokeDash(dashPattern, cnt, offset)) return Result::FailedAllocation;
 
     return Result::Success;
 }
 
 
-uint32_t Shape::strokeDash(const float** dashPattern) const noexcept
+uint32_t Shape::strokeDash(const float** dashPattern, float* offset) const noexcept
 {
-    return pImpl->rs.strokeDash(dashPattern);
+    return pImpl->rs.strokeDash(dashPattern, offset);
 }
 
 

src/lib/tvgShapeImpl.h

@@ -269,7 +269,7 @@ struct Shape::Impl
         return Result::Success;
     }
 
-    bool strokeDash(const float* pattern, uint32_t cnt)
+    bool strokeDash(const float* pattern, uint32_t cnt, float offset)
     {
         //Reset dash
         if (!pattern && cnt == 0) {
@@ -290,6 +290,7 @@ struct Shape::Impl
             }
         }
         rs.stroke->dashCnt = cnt;
+        rs.stroke->dashOffset = offset;
         flag |= RenderUpdateFlag::Stroke;
 
         return true;
@@ -338,6 +339,7 @@ struct Shape::Impl
             dup->rs.stroke = new RenderStroke();
             dup->rs.stroke->width = rs.stroke->width;
             dup->rs.stroke->dashCnt = rs.stroke->dashCnt;
+            dup->rs.stroke->dashOffset = rs.stroke->dashOffset;
             dup->rs.stroke->cap = rs.stroke->cap;
             dup->rs.stroke->join = rs.stroke->join;
             dup->rs.stroke->strokeFirst = rs.stroke->strokeFirst;

src/loaders/svg/tvgSvgLoader.cpp

@@ -952,6 +952,12 @@ static void _handleStrokeDashArrayAttr(SvgLoaderData* loader, SvgNode* node, con
     _parseDashArray(loader, value, &node->style->stroke.dash);
 }
 
+static void _handleStrokeDashOffsetAttr(SvgLoaderData* loader, SvgNode* node, const char* value)
+{
+    node->style->stroke.flags = (node->style->stroke.flags | SvgStrokeFlags::DashOffset);
+    node->style->stroke.dash.offset = _toFloat(loader->svgParse, value, SvgParserLengthType::Horizontal);
+}
+
 static void _handleStrokeWidthAttr(SvgLoaderData* loader, SvgNode* node, const char* value)
 {
     node->style->stroke.flags = (node->style->stroke.flags | SvgStrokeFlags::Width);
@@ -1108,6 +1114,7 @@ static constexpr struct
     STYLE_DEF(stroke-linecap, StrokeLineCap, SvgStyleFlags::StrokeLineCap),
     STYLE_DEF(stroke-opacity, StrokeOpacity, SvgStyleFlags::StrokeOpacity),
     STYLE_DEF(stroke-dasharray, StrokeDashArray, SvgStyleFlags::StrokeDashArray),
+    STYLE_DEF(stroke-dashoffset, StrokeDashOffset, SvgStyleFlags::StrokeDashOffset),
     STYLE_DEF(transform, Transform, SvgStyleFlags::Transform),
     STYLE_DEF(clip-path, ClipPath, SvgStyleFlags::ClipPath),
     STYLE_DEF(mask, Mask, SvgStyleFlags::Mask),
@@ -2773,6 +2780,9 @@ static void _styleInherit(SvgStyleProperty* child, const SvgStyleProperty* paren
             }
         }
     }
+    if (!(child->stroke.flags & SvgStrokeFlags::DashOffset)) {
+        child->stroke.dash.offset = parent->stroke.dash.offset;
+    }
     if (!(child->stroke.flags & SvgStrokeFlags::Cap)) {
         child->stroke.cap = parent->stroke.cap;
     }
@@ -2839,13 +2849,15 @@ static void _styleCopy(SvgStyleProperty* to, const SvgStyleProperty* from)
             }
         }
     }
+    if (from->stroke.flags & SvgStrokeFlags::DashOffset) {
+        to->stroke.dash.offset = from->stroke.dash.offset;
+    }
     if (from->stroke.flags & SvgStrokeFlags::Cap) {
         to->stroke.cap = from->stroke.cap;
     }
     if (from->stroke.flags & SvgStrokeFlags::Join) {
         to->stroke.join = from->stroke.join;
     }
-
     if (from->stroke.flags & SvgStrokeFlags::Miterlimit) {
         to->stroke.miterlimit = from->stroke.miterlimit;
     }

src/loaders/svg/tvgSvgLoaderCommon.h

@@ -100,7 +100,8 @@ enum class SvgStrokeFlags
     Cap = 0x20,
     Join = 0x40,
     Dash = 0x80,
-    Miterlimit = 0x100
+    Miterlimit = 0x100,
+    DashOffset = 0x200
 };
 
 constexpr bool operator &(SvgStrokeFlags a, SvgStrokeFlags b)
@@ -139,7 +140,8 @@ enum class SvgStyleFlags
     MaskType = 0x4000,
     Display = 0x8000,
     PaintOrder = 0x10000,
-    StrokeMiterlimit = 0x20000
+    StrokeMiterlimit = 0x20000,
+    StrokeDashOffset = 0x40000,
 };
 
 constexpr bool operator &(SvgStyleFlags a, SvgStyleFlags b)
@@ -423,6 +425,7 @@ struct SvgPaint
 struct SvgDash
 {
     Array<float> array;
+    float offset;
 };
 
 struct SvgStyleGradient
@@ -469,7 +472,6 @@ struct SvgStyleStroke
     StrokeJoin join;
     float miterlimit;
     SvgDash dash;
-    int dashCount;
 };
 
 struct SvgStyleProperty

src/loaders/svg/tvgSvgSceneBuilder.cpp

@@ -349,7 +349,7 @@ static void _applyProperty(SvgLoaderData& loaderData, SvgNode* node, Shape* vg,
     vg->stroke(style->stroke.join);
     vg->strokeMiterlimit(style->stroke.miterlimit);
     if (style->stroke.dash.array.count > 0) {
-        vg->stroke(style->stroke.dash.array.data, style->stroke.dash.array.count);
+        vg->stroke(style->stroke.dash.array.data, style->stroke.dash.array.count, style->stroke.dash.offset);
     }
 
     //If stroke property is nullptr then do nothing