Fix bug #1077600 -> correct mirroring and no drifting of origin

diff --git a/src/seltrans.cpp b/src/seltrans.cpp
index cfc784dac6c24e19def0abe7e01a1c1fa5f9cbdf..9c874c242cb666d8d2b07f18c92deb0e7b1846bd 100644 (file)
--- a/src/seltrans.cpp
+++ b/src/seltrans.cpp
@@ -1338,22 +1338,17 @@ void Inkscape::SelTrans::stretch(SPSelTransHandle const &handle, NR::Point &pt,
         return;
     }
 
-    //Get two corners of the new bbox
-    NR::Point p1 = _approximate_bbox->min() * (NR::translate(-scale_origin) * NR::Matrix(s) * NR::translate(scale_origin));
-    NR::Point p2 = _approximate_bbox->max() * (NR::translate(-scale_origin) * NR::Matrix(s) * NR::translate(scale_origin));
-
-    //Find the corners at the lower-left and upper-right, as required by get_scale_transform_with_stroke
-    NR::Point new_bbox_min = NR::Point(std::min(p1[NR::X], p2[NR::X]), std::min(p1[NR::Y], p2[NR::Y]));
-    NR::Point new_bbox_max = NR::Point(std::max(p1[NR::X], p2[NR::X]), std::max(p1[NR::Y], p2[NR::Y]));
+    NR::Point new_bbox_min = _approximate_bbox->min() * (NR::translate(-scale_origin) * NR::Matrix(s) * NR::translate(scale_origin));
+    NR::Point new_bbox_max = _approximate_bbox->max() * (NR::translate(-scale_origin) * NR::Matrix(s) * NR::translate(scale_origin));
 
     int transform_stroke = false;
     gdouble strokewidth = 0;
-        
+
     if ( _snap_bbox_type != SPItem::GEOMETRIC_BBOX) {
         transform_stroke = prefs_get_int_attribute ("options.transform", "stroke", 1);
         strokewidth = _strokewidth;
     }
-        
+
     NR::Matrix scaler = get_scale_transform_with_stroke (*_approximate_bbox, strokewidth, transform_stroke,
                     new_bbox_min[NR::X], new_bbox_min[NR::Y], new_bbox_max[NR::X], new_bbox_max[NR::Y]);
 
@@ -1376,13 +1371,8 @@ void Inkscape::SelTrans::scale(NR::Point &pt, guint state)
             s[i] = 1e-9;
     }
     
-    //Get two corners of the new bbox
-    NR::Point p1 = _approximate_bbox->min() * (NR::translate(-_origin) * NR::Matrix(s) * NR::translate(_origin));
-    NR::Point p2 = _approximate_bbox->max() * (NR::translate(-_origin) * NR::Matrix(s) * NR::translate(_origin));
-
-    //Find the corners at the lower-left and upper-right, as required by get_scale_transform_with_stroke
-    NR::Point new_bbox_min = NR::Point(std::min(p1[NR::X], p2[NR::X]), std::min(p1[NR::Y], p2[NR::Y]));
-    NR::Point new_bbox_max = NR::Point(std::max(p1[NR::X], p2[NR::X]), std::max(p1[NR::Y], p2[NR::Y]));
+    NR::Point new_bbox_min = _approximate_bbox->min() * (NR::translate(-_origin) * NR::Matrix(s) * NR::translate(_origin));
+    NR::Point new_bbox_max = _approximate_bbox->max() * (NR::translate(-_origin) * NR::Matrix(s) * NR::translate(_origin));
     
     int transform_stroke = false;
     gdouble strokewidth = 0;

diff --git a/src/sp-item-transform.cpp b/src/sp-item-transform.cpp
index 10eba684885302e37b62c971a14a2a53c567ec8c..2ad7758a46262720130862ae94502e9f73cb1ae0 100644 (file)
--- a/src/sp-item-transform.cpp
+++ b/src/sp-item-transform.cpp
@@ -114,25 +114,43 @@ get_scale_transform_with_stroke (NR::Rect &bbox_param, gdouble strokewidth, bool
         return (p2o * direct * o2n); // can't solve the equation: one of the dimensions is equal to stroke width, so return the straightforward scaler
     }
 
-    gdouble ratio_x = (w1 - r0) / (w0 - r0);
-    gdouble ratio_y = (h1 - r0) / (h0 - r0);
-    NR::Matrix direct_constant_r = NR::Matrix (NR::scale(ratio_x, ratio_y));
+    // Flip when the width or height changes sign
+    int flip_x = ((w1 < 0) == (w0 < 0)) ? 1 : -1;
+    int flip_y = ((h1 < 0) == (h0 < 0)) ? 1 : -1;
+    
+    // w1 and h1 can be negative, but if so then e.g. w1-r0 won't make sense
+    // therefore we should use fabs() all over the place
+    gdouble ratio_x = (fabs(w1) - fabs(r0)) / (fabs(w0) - fabs(r0));
+    gdouble ratio_y = (fabs(h1) - fabs(r0)) / (fabs(h0) - fabs(r0));    
+    
+    NR::Matrix direct_constant_r = NR::Matrix (NR::scale(flip_x * ratio_x, flip_y*ratio_y));
 
     if (transform_stroke && r0 != 0 && r0 != NR_HUGE) { // there's stroke, and we need to scale it
         // These coefficients are obtained from the assumption that scaling applies to the
         // non-stroked "shape proper" and that stroke scale is scaled by the expansion of that
         // matrix
-        gdouble A = -(w0 *h0) + r0*(w0 + h0);
-        gdouble B = -(w1 + h1) * r0*r0;
-        gdouble C = w1 * h1 * r0*r0;
+        // In fact, we're trying to solve this equation:
+        // r1 = r0 * sqrt (((w1-r0)/(w0-r0))*((h1-r1)/(h0-r0)))
+        // To make sense of this, the operant of the sqrt() should
+        // be positive, hence all the fabs() below
+        // (w1 and h1 will be negative when mirroring, w0 and h0 will probably never be negative)
+        gdouble A = -fabs(w0*h0) + fabs(r0)*(fabs(w0) + fabs(h0));
+        gdouble B = -(fabs(w1) + fabs(h1)) * r0*r0;
+        gdouble C = fabs(w1 * h1 * r0*r0);
         if (B*B - 4*A*C > 0) {
             gdouble r1 = (-B - sqrt (B*B - 4*A*C))/(2*A);
             //gdouble r2 = (-B + sqrt (B*B - 4*A*C))/(2*A);
             //std::cout << "r0" << r0 << " r1" << r1 << " r2" << r2 << "\n";
-            gdouble scale_x = (w1 - r1)/(w0 - r0);
-            gdouble scale_y = (h1 - r1)/(h0 - r0);
-            scale *= NR::scale(scale_x, scale_y);
-            unbudge *= NR::translate (-0.5 * (r0 * scale_x - r1), -0.5 * (r0 * scale_y - r1));
+            //
+            // I think r1 will always be positive if r0 is (mathematical proof?)
+            // but if w1 becomes negative, then the scale will be wrong if we just do  
+            // gdouble scale_x = (w1 - r1)/(w0 - r0);
+            // gdouble scale_y = (h1 - r1)/(h0 - r0);
+            // So let's do it like this: Calculate the absolute scale
+            gdouble scale_x = (fabs(w1) - fabs(r1))/(fabs(w0) - fabs(r0));
+            gdouble scale_y = (fabs(h1) - fabs(r1))/(fabs(h0) - fabs(r0));
+            scale *= NR::scale(flip_x*scale_x, flip_y*scale_y);
+            unbudge *= NR::translate (-flip_x * 0.5 * (fabs(r0) * scale_x - fabs(r1)), -flip_y * 0.5 * (fabs(r0) * scale_y - fabs(r1)));
         } else {
             scale *= direct;
         }
@@ -141,7 +159,7 @@ get_scale_transform_with_stroke (NR::Rect &bbox_param, gdouble strokewidth, bool
             scale *= direct;
         } else {// nonscaling strokewidth
             scale *= direct_constant_r;
-            unbudge *= NR::translate (0.5 * r0 * (1 - ratio_x), 0.5 * r0 * (1 - ratio_y));
+            unbudge *= NR::translate (flip_x * 0.5 * fabs(r0) * (1 - ratio_x), flip_y * 0.5 * fabs(r0) * (1 - ratio_y));
         }
     }
 

diff --git a/src/sp-shape.cpp b/src/sp-shape.cpp
index 8d9b2296ac8ed70e31c6a151f8ff842ea3360abe..a0c26e8f55d0078a5fab049138901c3e6c653b85 100644 (file)
--- a/src/sp-shape.cpp
+++ b/src/sp-shape.cpp
@@ -1025,10 +1025,6 @@ static void sp_shape_snappoints(SPItem const *item, SnapPointsIter p)
         *p = bp->c(3) * i2d;
         bp++;
     }
-    
-    // Additionaly, add the center for snapping
-    *p = shape->getCenter();
-    
 }