[gimp/gimp-2-10] app: improve transform-tools readjustment

[Ell <ell src gnome org>]

commit 581944253c67a6543600a8fccb7f631b51b15702
Author: Ell <ell_se yahoo com>
Date:   Wed Mar 13 05:20:51 2019 -0400

    app: improve transform-tools readjustment
    
    In GimpTransformGridTool, extend the functionality of the
    "Readjust" button, such that if the transformation is already
    adjusted to the view (i.e., when the button is clicked the second
    time), readjust the transformation to the item bounds (as when
    using the tool "normally"), and vice versa.  This allows switching
    back and forth between "normal" mode, and "adjusted-to-view" mode.
    
    Additionally, disable readjustment when the current transforamtion
    is invalid, and show an error when readjustment results in an
    invalid transformation.
    
    (cherry picked from commit a3fa3b6181fc9edbc7ca2e0e102ae79566f42d33)

 app/tools/gimptransformgridtool.c | 132 +++++++++++++++++++++++++++++++++-----
 1 file changed, 115 insertions(+), 17 deletions(-)
---
diff --git a/app/tools/gimptransformgridtool.c b/app/tools/gimptransformgridtool.c
index ac227e44e9..13679420b7 100644
--- a/app/tools/gimptransformgridtool.c
+++ b/app/tools/gimptransformgridtool.c
@@ -56,6 +56,9 @@
 #include "gimp-intl.h"
 
 
+#define EPSILON 1e-6
+
+
 #define RESPONSE_RESET    1
 #define RESPONSE_READJUST 2
 
@@ -169,6 +172,11 @@ static void      gimp_transform_grid_tool_show_active_item   (GimpTransformGridT
 static UndoInfo * undo_info_new  (void);
 static void       undo_info_free (UndoInfo *info);
 
+static gboolean   trans_info_equal  (const TransInfo  trans_info1,
+                                     const TransInfo  trans_info2);
+static gboolean   trans_infos_equal (const TransInfo *trans_infos1,
+                                     const TransInfo *trans_infos2);
+
 
 G_DEFINE_TYPE (GimpTransformGridTool, gimp_transform_grid_tool, GIMP_TYPE_TRANSFORM_TOOL)
 
@@ -857,15 +865,15 @@ gimp_transform_grid_tool_get_undo_desc (GimpTransformTool *tr_tool)
       result = GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->get_undo_desc (
         tg_tool);
     }
-  else if (! memcmp (tg_tool->trans_infos[GIMP_TRANSFORM_BACKWARD],
-                     tg_tool->init_trans_info, sizeof (TransInfo)))
+  else if (trans_info_equal (tg_tool->trans_infos[GIMP_TRANSFORM_BACKWARD],
+                             tg_tool->init_trans_info))
     {
       tg_tool->trans_info = tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD];
       result = GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->get_undo_desc (
         tg_tool);
     }
-  else if (! memcmp (tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD],
-                     tg_tool->init_trans_info, sizeof (TransInfo)))
+  else if (trans_info_equal (tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD],
+                             tg_tool->init_trans_info))
     {
       gchar *desc;
 
@@ -1237,6 +1245,7 @@ gimp_transform_grid_tool_response (GimpToolGui           *gui,
 {
   GimpTool                 *tool       = GIMP_TOOL (tg_tool);
   GimpTransformTool        *tr_tool    = GIMP_TRANSFORM_TOOL (tg_tool);
+  GimpTransformOptions     *tr_options = GIMP_TRANSFORM_TOOL_GET_OPTIONS (tg_tool);
   GimpTransformGridOptions *tg_options = GIMP_TRANSFORM_GRID_TOOL_GET_OPTIONS (tg_tool);
   GimpDisplay              *display    = tool->display;
 
@@ -1266,11 +1275,19 @@ gimp_transform_grid_tool_response (GimpToolGui           *gui,
       break;
 
     case RESPONSE_READJUST:
-      if (GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->readjust)
+      if (GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->readjust       &&
+          GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->matrix_to_info &&
+          tr_tool->transform_valid)
         {
-          gboolean direction_linked;
+          TransInfo old_trans_infos[2];
+          gboolean  direction_linked;
+          gboolean  transform_valid;
+
+          /*  save the current transformation info  */
+          memcpy (old_trans_infos, tg_tool->trans_infos,
+                  sizeof (old_trans_infos));
 
-          /*  readjust the transformation info  */
+          /*  readjust the transformation info to view  */
           GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->readjust (tg_tool);
 
           /*  recalculate the tool's transformation matrix, preserving the
@@ -1281,8 +1298,63 @@ gimp_transform_grid_tool_response (GimpToolGui           *gui,
           gimp_transform_tool_recalc_matrix (tr_tool, display);
           tg_options->direction_linked = direction_linked;
 
-          /*  push the new info to the undo stack  */
-          gimp_transform_grid_tool_push_internal_undo (tg_tool);
+          transform_valid = tr_tool->transform_valid;
+
+          /*  if the resulting transformation is invalid, or if the
+           *  transformation info is already adjusted to view ...
+           */
+          if (! transform_valid ||
+              trans_infos_equal (old_trans_infos, tg_tool->trans_infos))
+            {
+              /*  ... readjust the transformation info to the item bounds  */
+              GimpMatrix3 transform = tr_tool->transform;
+
+              if (tr_options->direction == GIMP_TRANSFORM_BACKWARD)
+                gimp_matrix3_invert (&transform);
+
+              memcpy (tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD],
+                      tg_tool->init_trans_info,
+                      sizeof (TransInfo));
+              memcpy (tg_tool->trans_infos[GIMP_TRANSFORM_BACKWARD],
+                      tg_tool->init_trans_info,
+                      sizeof (TransInfo));
+
+              GIMP_TRANSFORM_GRID_TOOL_GET_CLASS (tg_tool)->matrix_to_info (
+                tg_tool, &transform);
+
+              /*  recalculate the tool's transformation matrix  */
+              direction_linked             = tg_options->direction_linked;
+              tg_options->direction_linked = FALSE;
+              gimp_transform_tool_recalc_matrix (tr_tool, display);
+              tg_options->direction_linked = direction_linked;
+
+              if (! tr_tool->transform_valid ||
+                  ! trans_infos_equal (old_trans_infos, tg_tool->trans_infos))
+                {
+                  transform_valid = tr_tool->transform_valid;
+                }
+            }
+
+          if (transform_valid)
+            {
+              /*  push the new info to the undo stack  */
+              gimp_transform_grid_tool_push_internal_undo (tg_tool);
+            }
+          else
+            {
+              /*  restore the old transformation info  */
+              memcpy (tg_tool->trans_infos, old_trans_infos,
+                      sizeof (old_trans_infos));
+
+              /*  recalculate the tool's transformation matrix  */
+              direction_linked             = tg_options->direction_linked;
+              tg_options->direction_linked = FALSE;
+              gimp_transform_tool_recalc_matrix (tr_tool, display);
+              tg_options->direction_linked = direction_linked;
+
+              gimp_tool_message_literal (tool, tool->display,
+                                         _("Cannot readjust the transformation"));
+            }
         }
       break;
 
@@ -1315,12 +1387,14 @@ gimp_transform_grid_tool_update_sensitivity (GimpTransformGridTool *tg_tool)
 
   gimp_tool_gui_set_response_sensitive (
     tg_tool->gui, RESPONSE_RESET,
-    memcmp (tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD],
-            tg_tool->init_trans_info,
-            sizeof (TransInfo)) ||
-    memcmp (tg_tool->trans_infos[GIMP_TRANSFORM_BACKWARD],
-            tg_tool->init_trans_info,
-            sizeof (TransInfo)));
+    ! (trans_info_equal (tg_tool->trans_infos[GIMP_TRANSFORM_FORWARD],
+                         tg_tool->init_trans_info) &&
+       trans_info_equal (tg_tool->trans_infos[GIMP_TRANSFORM_BACKWARD],
+                         tg_tool->init_trans_info)));
+
+  gimp_tool_gui_set_response_sensitive (
+    tg_tool->gui, RESPONSE_READJUST,
+    tr_tool->transform_valid);
 }
 
 static void
@@ -1429,6 +1503,31 @@ undo_info_free (UndoInfo *info)
   g_slice_free (UndoInfo, info);
 }
 
+static gboolean
+trans_info_equal (const TransInfo trans_info1,
+                  const TransInfo trans_info2)
+{
+  gint i;
+
+  for (i = 0; i < TRANS_INFO_SIZE; i++)
+    {
+      if (fabs (trans_info1[i] - trans_info2[i]) > EPSILON)
+        return FALSE;
+    }
+
+  return TRUE;
+}
+
+static gboolean
+trans_infos_equal (const TransInfo *trans_infos1,
+                   const TransInfo *trans_infos2)
+{
+  return trans_info_equal (trans_infos1[GIMP_TRANSFORM_FORWARD],
+                           trans_infos2[GIMP_TRANSFORM_FORWARD]) &&
+         trans_info_equal (trans_infos1[GIMP_TRANSFORM_BACKWARD],
+                           trans_infos2[GIMP_TRANSFORM_BACKWARD]);
+}
+
 gboolean
 gimp_transform_grid_tool_info_to_matrix (GimpTransformGridTool *tg_tool,
                                          GimpMatrix3           *transform)
@@ -1472,8 +1571,7 @@ gimp_transform_grid_tool_push_internal_undo (GimpTransformGridTool *tg_tool)
   /* push current state on the undo list and set this state as the
    * current state, but avoid doing this if there were no changes
    */
-  if (memcmp (undo_info->trans_infos, tg_tool->trans_infos,
-              sizeof (tg_tool->trans_infos)) != 0)
+  if (! trans_infos_equal (undo_info->trans_infos, tg_tool->trans_infos))
     {
       GimpTransformOptions *tr_options = GIMP_TRANSFORM_TOOL_GET_OPTIONS (tg_tool);