From 4db3087c4591d789d966de4bb0f001983422469f Mon Sep 17 00:00:00 2001
From: Mira Grudzinska <m.grudzinska@samsung.com>
Date: Sat, 23 Oct 2021 14:27:04 +0200
Subject: [PATCH] svg_loader: gradient transformation properly applied

The final gradient transformation depends on the coordinate system.
It can not be applied during an svg loading. The transformation matrix
has to be passed via api for further gradient processing.
---
 src/loaders/svg/tvgSvgSceneBuilder.cpp | 85 +++++++++++++++-----------
 1 file changed, 49 insertions(+), 36 deletions(-)

diff --git a/src/loaders/svg/tvgSvgSceneBuilder.cpp b/src/loaders/svg/tvgSvgSceneBuilder.cpp
index dd9a2eca..e62cc957 100644
--- a/src/loaders/svg/tvgSvgSceneBuilder.cpp
+++ b/src/loaders/svg/tvgSvgSceneBuilder.cpp
@@ -69,29 +69,44 @@ static inline bool _isGroupType(SvgNodeType type)
 }
 
 
+static void _transformMultiply(const Matrix* mBBox, Matrix* gradTransf)
+{
+    gradTransf->e13 = gradTransf->e13 * mBBox->e11 + mBBox->e13;
+    gradTransf->e12 *= mBBox->e11;
+    gradTransf->e11 *= mBBox->e11;
+
+    gradTransf->e23 = gradTransf->e23 * mBBox->e22 + mBBox->e23;
+    gradTransf->e22 *= mBBox->e22;
+    gradTransf->e21 *= mBBox->e22;
+}
+
+
 static unique_ptr<LinearGradient> _applyLinearGradientProperty(SvgStyleGradient* g, const Shape* vg, float rx, float ry, float rw, float rh, int opacity)
 {
     Fill::ColorStop* stops;
     int stopCount = 0;
     auto fillGrad = LinearGradient::gen();
 
-    g->linear->x1 = g->linear->x1 * rw + rx;
-    g->linear->y1 = g->linear->y1 * rh + ry;
-    g->linear->x2 = g->linear->x2 * rw + rx;
-    g->linear->y2 = g->linear->y2 * rh + ry;
+    bool isTransform = (g->transform ? true : false);
+    Matrix finalTransform = {1, 0, 0, 0, 1, 0, 0, 0, 1};
+    if (isTransform) finalTransform = *g->transform;
 
-    if (g->transform) {
-        //Calc start point
-        auto x = g->linear->x1;
-        g->linear->x1 = x * g->transform->e11 + g->linear->y1 * g->transform->e12 + g->transform->e13;
-        g->linear->y1 = x * g->transform->e21 + g->linear->y1 * g->transform->e22 + g->transform->e23;
-
-        //Calc end point
-        x = g->linear->x2;
-        g->linear->x2 = x * g->transform->e11 + g->linear->y2 * g->transform->e12 + g->transform->e13;
-        g->linear->y2 = x * g->transform->e21 + g->linear->y2 * g->transform->e22 + g->transform->e23;
+    if (g->userSpace) {
+        g->linear->x1 = g->linear->x1 * rw;
+        g->linear->y1 = g->linear->y1 * rh;
+        g->linear->x2 = g->linear->x2 * rw;
+        g->linear->y2 = g->linear->y2 * rh;
+    } else {
+        Matrix m = {rw, 0, rx, 0, rh, ry, 0, 0, 1};
+        if (isTransform) _transformMultiply(&m, &finalTransform);
+        else {
+            finalTransform = m;
+            isTransform = true;
+        }
     }
 
+    if (isTransform) fillGrad->transform(finalTransform);
+
     fillGrad->linear(g->linear->x1, g->linear->y1, g->linear->x2, g->linear->y2);
     fillGrad->spread(g->spread);
 
@@ -125,32 +140,30 @@ static unique_ptr<RadialGradient> _applyRadialGradientProperty(SvgStyleGradient*
 {
     Fill::ColorStop *stops;
     int stopCount = 0;
-    float radius;
     auto fillGrad = RadialGradient::gen();
 
-    radius = sqrtf(powf(rw, 2.0f) + powf(rh, 2.0f)) / sqrtf(2.0f);
-    if (!g->userSpace) {
-         //That is according to Units in here
-         //https://www.w3.org/TR/2015/WD-SVG2-20150915/coords.html
-        int min = static_cast<int>((rh > rw) ? rw : rh);
-        radius = sqrtf(pow(min, 2) + pow(min, 2)) / sqrtf(2.0f);
+    bool isTransform = (g->transform ? true : false);
+    Matrix finalTransform = {1, 0, 0, 0, 1, 0, 0, 0, 1};
+    if (isTransform) finalTransform = *g->transform;
+
+    if (g->userSpace) {
+        //The radius scalling is done according to the Units section:
+        //https://www.w3.org/TR/2015/WD-SVG2-20150915/coords.html
+        g->radial->cx = g->radial->cx * rw;
+        g->radial->cy = g->radial->cy * rh;
+        g->radial->r = g->radial->r * sqrtf(powf(rw, 2.0f) + powf(rh, 2.0f)) / sqrtf(2.0f);
+        g->radial->fx = g->radial->fx * rw;
+        g->radial->fy = g->radial->fy * rh;
+    } else {
+        Matrix m = {rw, 0, rx, 0, rh, ry, 0, 0, 1};
+        if (isTransform) _transformMultiply(&m, &finalTransform);
+        else {
+            finalTransform = m;
+            isTransform = true;
+        }
     }
 
-    g->radial->cx = g->radial->cx * rw + rx;
-    g->radial->cy = g->radial->cy * rh + ry;
-    g->radial->r = g->radial->r * radius;
-    g->radial->fx = g->radial->fx * rw + rx;
-    g->radial->fy = g->radial->fy * rh + ry;
-
-    //TODO: Radial gradient transformation - all tests possible after rx/ry implementation
-    if (g->transform) {
-        auto cx = g->radial->cx * g->transform->e11 + g->radial->cy * g->transform->e12 + g->transform->e13;
-        g->radial->cy = g->radial->cx * g->transform->e21 + g->radial->cy * g->transform->e22 + g->transform->e23;
-        g->radial->cx = cx;
-
-        auto sx = sqrtf(powf(g->transform->e11, 2.0f) + powf(g->transform->e21, 2.0f));
-        g->radial->r *= sx;
-    }
+    if (isTransform) fillGrad->transform(finalTransform);
 
     //TODO: Tvg is not support to focal
     //if (g->radial->fx != 0 && g->radial->fy != 0) {