From 8b27efc99f0513efe6a163c0a38f5c0977001669 Mon Sep 17 00:00:00 2001
From: Sergii Liebodkin <s.lebedkin@gmail.com>
Date: Wed, 30 Oct 2024 12:02:23 +0000
Subject: [PATCH] wg_engine: fix cubic splines and circles tesselation quality

Tesseletion factor now depends on scale matix of the shape
---
 src/renderer/wg_engine/tvgWgGeometry.h     | 25 +++++++++++++---------
 src/renderer/wg_engine/tvgWgRenderData.cpp |  7 +++++-
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/renderer/wg_engine/tvgWgGeometry.h b/src/renderer/wg_engine/tvgWgGeometry.h
index 39e5a4b0..48235818 100755
--- a/src/renderer/wg_engine/tvgWgGeometry.h
+++ b/src/renderer/wg_engine/tvgWgGeometry.h
@@ -39,15 +39,17 @@ struct WgVertexBuffer
     float vleng[WG_POINTS_COUNT]; // distance to the first point through all previous points
     size_t vcount{};
     bool closed{};
+    float tscale = 1.0f; // tesselation scale
 
     // callback for external process of polyline
     using onPolylineFn = std::function<void(const WgVertexBuffer& buff)>;
 
     // reset buffer
-    void reset()
+    void reset(float scale)
     {
         vcount = 0;
         closed = false;
+        tscale = scale;
     }
 
     // get the last point with optional index offset from the end
@@ -134,8 +136,8 @@ struct WgVertexBuffer
     {
         // get approx circle length
         float clen = 2.0f * radius * MATH_PI;
-        size_t nsegs = std::max((uint32_t)(clen / 8), 16U);
-        // append circle
+        size_t nsegs = std::max((uint32_t)(clen * tscale / 8), 16U);
+        // append circle^
         Point prev { std::sin(0.0f) * radius, std::cos(0.0f) * radius };
         for (size_t i = 1; i <= nsegs; i++) {
             float t = (2.0f * MATH_PI * i) / nsegs;
@@ -151,8 +153,8 @@ struct WgVertexBuffer
     void appendCubic(const Point& v0, const Point& v1, const Point& v2, const Point& v3)
     {
         // get approx cubic length
-        float clen = length(v0 - v1) + length(v1 - v2) + length(v2 - v3);
-        size_t nsegs = std::max((uint32_t)(clen / 8), 16U);
+        float clen = (length(v0 - v1) + length(v1 - v2) + length(v2 - v3));
+        size_t nsegs = std::max((uint32_t)(clen * tscale / 16), 16U);
         // append cubic
         Bezier bezier{v0, v1, v2, v3};
         for (size_t i = 1; i <= nsegs; i++)
@@ -189,7 +191,7 @@ struct WgVertexBuffer
     void decodePath(const RenderShape& rshape, bool update_dist, onPolylineFn onPolyline)
     {
         // decode path
-        reset();
+        reset(tscale);
         size_t pntIndex = 0;
         for (uint32_t cmdIndex = 0; cmdIndex < rshape.path.cmds.count; cmdIndex++) {
             PathCommand cmd = rshape.path.cmds[cmdIndex];
@@ -198,7 +200,7 @@ struct WgVertexBuffer
                 if (update_dist) updateDistances();
                 if ((onPolyline) && (vcount != 0))
                     onPolyline(*this);
-                reset();
+                reset(tscale);
                 append(rshape.path.pts[pntIndex]);
                 pntIndex++;
             } else if (cmd == PathCommand::LineTo) {
@@ -226,11 +228,13 @@ struct WgVertexBufferInd
     uint32_t ibuff[WG_POINTS_COUNT*16];
     size_t vcount = 0;
     size_t icount = 0;
+    float tscale = 1.0f;
 
     // reset buffer
-    void reset()
+    void reset(float scale)
     {
         icount = vcount = 0;
+        tscale = scale;
     }
 
     // get min and max values of the buffer
@@ -269,7 +273,7 @@ struct WgVertexBufferInd
     {
         // dashed buffer
         WgVertexBuffer dashed;
-        dashed.reset();
+        dashed.reset(tscale);
         // ignore single points polyline
         if (buff.vcount < 2) return;
         const float* dashPattern = rstroke->dashPattern;
@@ -294,7 +298,7 @@ struct WgVertexBufferInd
                 if (index_dash % 2 != 0) {
                     dashed.updateDistances();
                     appendStrokes(dashed, rstroke);
-                    dashed.reset();
+                    dashed.reset(tscale);
                 }
             }
             // update current subline length
@@ -391,6 +395,7 @@ struct WgVertexBufferInd
         if ((rstroke->join == StrokeJoin::Round) || (rstroke->cap == StrokeCap::Round)) {
             // create mesh for circle
             WgVertexBuffer circle;
+            circle.reset(buff.tscale);
             circle.appendCircle(halfWidth);
             // append caps (round)
             if (rstroke->cap == StrokeCap::Round) {
diff --git a/src/renderer/wg_engine/tvgWgRenderData.cpp b/src/renderer/wg_engine/tvgWgRenderData.cpp
index f9c15d93..2eebf159 100755
--- a/src/renderer/wg_engine/tvgWgRenderData.cpp
+++ b/src/renderer/wg_engine/tvgWgRenderData.cpp
@@ -381,8 +381,12 @@ void WgRenderDataShape::updateMeshes(WgContext &context, const RenderShape &rsha
     releaseMeshes(context);
     strokeFirst = rshape.stroke ? rshape.stroke->strokeFirst : false;
 
+    // get object scale
+    float scale = std::max(std::min(length(Point{tr.e11 + tr.e12,tr.e21 + tr.e22}), 8.0f), 1.0f);
+
     // path decoded vertex buffer
     WgVertexBuffer pbuff;
+    pbuff.reset(scale);
     // append shape without strokes
     if (!rshape.stroke) {
         pbuff.decodePath(rshape, false, [&](const WgVertexBuffer& path_buff) {
@@ -451,11 +455,12 @@ void WgRenderDataShape::updateMeshes(WgContext &context, const RenderShape &rsha
 void WgRenderDataShape::proceedStrokes(WgContext context, const RenderStroke* rstroke, float tbeg, float tend, const WgVertexBuffer& buff)
 {
     assert(rstroke);
-    gStrokesGenerator->reset();
+    gStrokesGenerator->reset(buff.tscale);
     // trim -> dash -> stroke
     if ((tbeg != 0.0f) || (tend != 1.0f)) {
         if (tbeg == tend) return;
         WgVertexBuffer trimed_buff;
+        trimed_buff.reset(buff.tscale);
         trimed_buff.trim(buff, tbeg, tend);
         trimed_buff.updateDistances();
         // trim ->dash -> stroke