[dia] [transform] Group::move_handle() improvements

[Hans Breuer <hans src gnome org>]

commit 1ddc5cda623bad74e81d9810973a23a67d706719
Author: Hans Breuer <hans breuer org>
Date:   Sun Aug 25 13:45:40 2013 +0200

    [transform] Group::move_handle() improvements
    
    Group handles are only used for scaling of the group content.
    The group position is supposed to be scale-invariant. With this
    changes the handles behave as intended as long as there is no
    rotation within the matrix.
    In the rotation case the drawing might get skewed (acceptable
    effect not specially handled elsewhere) and the size/position
    of the group change (no idea how to properly avoid this yet).

 lib/group.c |   81 +++++++++++++++++++++++++---------------------------------
 1 files changed, 35 insertions(+), 46 deletions(-)
---
diff --git a/lib/group.c b/lib/group.c
index c341f80..11550eb 100644
--- a/lib/group.c
+++ b/lib/group.c
@@ -217,12 +217,8 @@ group_move_handle(Group *group, Handle *handle, Point *to, ConnectionPoint *cp,
   DiaObject *obj = &group->object;
   Rectangle *bb = &obj->bounding_box;
   /* top and left handles are also changing the objects position */
-  Point pos = obj->position;
-  /* only flies, when the top left handle is the position */
-  gboolean also_move = (   group->resize_handles[0].pos.x == pos.x 
-                        && group->resize_handles[0].pos.y == pos.y);
   Point top_left = { bb->left, bb->top };
-  Point delta;
+  Point delta = { 0.0, 0.0 };
   /* before and after width and height */
   real w0, h0, w1, h1;
   
@@ -232,9 +228,9 @@ group_move_handle(Group *group, Handle *handle, Point *to, ConnectionPoint *cp,
   w0 = w1 = bb->right - bb->left;
   h0 = h1 = bb->bottom - bb->top;
 
-  /* Movement vs. scaling is still a bit bogus, e.g. if the object list
-   * position happens to be near a different than top-left handle we might
-   * only resize and not move the given handle at all.
+  /* Movement and scaling only work as intended with no active rotation.
+   * For rotated group we should either translate the handle positions
+   * or we might rotate the horizontal and vertical scale ...
    */
   switch(handle->id) {
   case HANDLE_RESIZE_NW:
@@ -243,20 +239,27 @@ group_move_handle(Group *group, Handle *handle, Point *to, ConnectionPoint *cp,
     w1 = w0 - delta.x;
     h1 = h0 - delta.y;
     break;
-  case HANDLE_RESIZE_NE:
-    w1 = to->x - pos.x;
-    /* fall through */
   case HANDLE_RESIZE_N:
     delta.y = to->y - top_left.y;
     h1 = h0 - delta.y;
     break;
-  case HANDLE_RESIZE_SW:
-    h1 = to->y - pos.y;
-    /* fall through */
+  case HANDLE_RESIZE_NE:
+    delta.y = to->y - top_left.y;
+    w1 = to->x - top_left.x;
+    h1 = h0 - delta.y;
+    break;
   case HANDLE_RESIZE_W:
     delta.x = to->x - top_left.x;
     w1 = w0 - delta.x;
     break;
+  case HANDLE_RESIZE_E:
+    w1 = to->x - top_left.x;
+    break;
+  case HANDLE_RESIZE_SW:
+    delta.x = to->x - top_left.x;
+    w1 = w0 - delta.x;
+    h1 = to->y - top_left.y;
+    break;
   case HANDLE_RESIZE_SE:
     w1 = to->x - top_left.x;
     h1 = to->y - top_left.y;
@@ -264,50 +267,36 @@ group_move_handle(Group *group, Handle *handle, Point *to, ConnectionPoint *cp,
   case HANDLE_RESIZE_S:
     h1 = to->y - top_left.y;
     break;
-  case HANDLE_RESIZE_E:
-    w1 = to->x - top_left.x;
-    break;
   default:
     g_warning("group_move_handle() called with wrong handle-id\n");
   }
 
-  if (also_move)
-    group_objects_move_delta(group, &delta);
   if (!group->matrix) {
     group->matrix = g_new0 (DiaMatrix, 1);
     group->matrix->xx = 1.0;
     group->matrix->yy = 1.0;
   }
 
-  /* The resizing is in the destination coordinate system, translate
-   * it to respective object scaling. BEWARE: this is not completely
-   * reversible, so we probably should deliver some extra undo information.
+  /* The resizing is in the diagram coordinate system, translate
+   * it to respective object offset. BEWARE: this is not completely
+   * reversible, so we might need to deliver some extra undo information.
    */
   {
-    DiaMatrix inv = *group->matrix;
-    real sx0, sx;
-    real sy0, sy;
-    real angle;
-
-    inv.x0 = w0/2;
-    inv.y0 = h0/2;
-    if (cairo_matrix_invert ((cairo_matrix_t *)&inv) != CAIRO_STATUS_SUCCESS)
-      g_warning ("Group::move_handle() matrix invert");
-
-    dia_matrix_get_angle_and_scales (group->matrix, &angle, &sx0, &sy0);
-
-    cairo_matrix_transform_distance ((cairo_matrix_t *)&inv, &w0, &h0);
-    cairo_matrix_transform_distance ((cairo_matrix_t *)&inv, &w1, &h1);
-    /* with angle of 45 degree (+x*90) the below does not work out, because
-     * transformed height or width becomes zero so convert to even scale */
-    if ((fabs(w0) < 1e-3) || (fabs(h0) < 1e-3)) {
-      sx = sy = sqrt(w1*w1 + h1*h1) / sqrt(w0*w0 + h0*h0);
-    } else {
-      sx = w1/w0;
-      sy = h1/h0;
-    }
-
-    dia_matrix_set_angle_and_scales (group->matrix, angle, sx0 * sx, sy0 * sy);
+    DiaMatrix mat;
+
+    delta.x += group->matrix->x0;
+    delta.y += group->matrix->y0;
+    group->matrix->x0 = group->matrix->y0 = 0.0;
+    /* it's just another matrix transform */
+    mat.xx = w1/w0;
+    mat.yy = h1/h0;
+    /* no rotation via handles */
+    mat.yx = mat.xy = 0.0;
+    
+    dia_matrix_multiply (group->matrix, group->matrix, &mat);
+    /* restore complete offset */
+    group->matrix->x0 = delta.x;
+    group->matrix->y0 = delta.y;
   }
   group_update_data(group);