moving from https://github.com/perberos/mate-desktop-environment

1 files changed, 1277 insertions, 0 deletions

diff --git a/src/core/edge-resistance.c b/src/core/edge-resistance.c
new file mode 100644
index 00000000..fd3f2d44
--- /dev/null
+++ b/src/core/edge-resistance.c
@@ -0,0 +1,1277 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/* Edge resistance for move/resize operations */
+
+/* 
+ * Copyright (C) 2005, 2006 Elijah Newren
+ * 
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include <config.h>
+#include "edge-resistance.h"
+#include "boxes.h"
+#include "display-private.h"
+#include "workspace.h"
+
+/* A simple macro for whether a given window's edges are potentially
+ * relevant for resistance/snapping during a move/resize operation
+ */
+#define WINDOW_EDGES_RELEVANT(window, display) \
+  meta_window_should_be_showing (window) &&    \
+  window->screen == display->grab_screen &&    \
+  window         != display->grab_window &&    \
+  window->type   != META_WINDOW_DESKTOP &&     \
+  window->type   != META_WINDOW_MENU    &&     \
+  window->type   != META_WINDOW_SPLASHSCREEN
+
+struct ResistanceDataForAnEdge
+{
+  gboolean     timeout_setup;
+  guint        timeout_id;
+  int          timeout_edge_pos;
+  gboolean     timeout_over;
+  GSourceFunc  timeout_func;
+  MetaWindow  *window;
+  int          keyboard_buildup;
+};
+typedef struct ResistanceDataForAnEdge ResistanceDataForAnEdge;
+
+struct MetaEdgeResistanceData
+{
+  GArray *left_edges;
+  GArray *right_edges;
+  GArray *top_edges;
+  GArray *bottom_edges;
+
+  ResistanceDataForAnEdge left_data;
+  ResistanceDataForAnEdge right_data;
+  ResistanceDataForAnEdge top_data;
+  ResistanceDataForAnEdge bottom_data;
+};
+
+/* !WARNING!: this function can return invalid indices (namely, either -1 or
+ * edges->len); this is by design, but you need to remember this.
+ */
+static int
+find_index_of_edge_near_position (const GArray *edges,
+                                  int           position,
+                                  gboolean      want_interval_min,
+                                  gboolean      horizontal)
+{
+  /* This is basically like a binary search, except that we're trying to
+   * find a range instead of an exact value.  So, if we have in our array
+   *   Value: 3  27 316 316 316 505 522 800 1213
+   *   Index: 0   1   2   3   4   5   6   7    8
+   * and we call this function with position=500 & want_interval_min=TRUE
+   * then we should get 5 (because 505 is the first value bigger than 500).
+   * If we call this function with position=805 and want_interval_min=FALSE
+   * then we should get 7 (because 800 is the last value smaller than 800).
+   * A couple more, to make things clear:
+   *    position  want_interval_min  correct_answer
+   *         316               TRUE               2
+   *         316              FALSE               4
+   *           2              FALSE              -1
+   *        2000               TRUE               9
+   */
+  int low, high, mid;
+  int compare;
+  MetaEdge *edge;
+
+  /* Initialize mid, edge, & compare in the off change that the array only
+   * has one element.
+   */
+  mid  = 0;
+  edge = g_array_index (edges, MetaEdge*, mid);
+  compare = horizontal ? edge->rect.x : edge->rect.y;
+
+  /* Begin the search... */
+  low  = 0;
+  high = edges->len - 1;
+  while (low < high)
+    {
+      mid = low + (high - low)/2;
+      edge = g_array_index (edges, MetaEdge*, mid);
+      compare = horizontal ? edge->rect.x : edge->rect.y;
+
+      if (compare == position)
+        break;
+
+      if (compare > position)
+        high = mid - 1;
+      else
+        low = mid + 1;
+    }
+
+  /* mid should now be _really_ close to the index we want, so we start
+   * linearly searching.  However, note that we don't know if mid is less
+   * than or greater than what we need and it's possible that there are
+   * several equal values equal to what we were searching for and we ended
+   * up in the middle of them instead of at the end.  So we may need to
+   * move mid multiple locations over.
+   */
+  if (want_interval_min)
+    {
+      while (compare >= position && mid > 0)
+        {
+          mid--;
+          edge = g_array_index (edges, MetaEdge*, mid);
+          compare = horizontal ? edge->rect.x : edge->rect.y;
+        }
+      while (compare < position && mid < (int)edges->len - 1)
+        {
+          mid++;
+          edge = g_array_index (edges, MetaEdge*, mid);
+          compare = horizontal ? edge->rect.x : edge->rect.y;
+        }
+
+      /* Special case for no values in array big enough */
+      if (compare < position)
+        return edges->len;
+
+      /* Return the found value */
+      return mid;
+    }
+  else
+    {
+      while (compare <= position && mid < (int)edges->len - 1)
+        {
+          mid++;
+          edge = g_array_index (edges, MetaEdge*, mid);
+          compare = horizontal ? edge->rect.x : edge->rect.y;
+        }
+      while (compare > position && mid > 0)
+        {
+          mid--;
+          edge = g_array_index (edges, MetaEdge*, mid);
+          compare = horizontal ? edge->rect.x : edge->rect.y;
+        }
+
+      /* Special case for no values in array small enough */
+      if (compare > position)
+        return -1;
+
+      /* Return the found value */
+      return mid;
+    }
+}
+
+static gboolean
+points_on_same_side (int ref, int pt1, int pt2)
+{
+  return (pt1 - ref) * (pt2 - ref) > 0;
+}
+
+static int
+find_nearest_position (const GArray        *edges,
+                       int                  position,
+                       int                  old_position,
+                       const MetaRectangle *new_rect,
+                       gboolean             horizontal,
+                       gboolean             only_forward)
+{
+  /* This is basically just a binary search except that we're looking
+   * for the value closest to position, rather than finding that
+   * actual value.  Also, we ignore any edges that aren't relevant
+   * given the horizontal/vertical position of new_rect.
+   */
+  int low, high, mid;
+  int compare;
+  MetaEdge *edge;
+  int best, best_dist, i;
+  gboolean edges_align;
+
+  /* Initialize mid, edge, & compare in the off change that the array only
+   * has one element.
+   */
+  mid  = 0;
+  edge = g_array_index (edges, MetaEdge*, mid);
+  compare = horizontal ? edge->rect.x : edge->rect.y;
+
+  /* Begin the search... */
+  low  = 0;
+  high = edges->len - 1;
+  while (low < high)
+    {
+      mid = low + (high - low)/2;
+      edge = g_array_index (edges, MetaEdge*, mid);
+      compare = horizontal ? edge->rect.x : edge->rect.y;
+
+      if (compare == position)
+        break;
+
+      if (compare > position)
+        high = mid - 1;
+      else
+        low = mid + 1;
+    }
+
+  /* mid should now be _really_ close to the index we want, so we
+   * start searching nearby for something that overlaps and is closer
+   * than the original position.
+   */
+  best = old_position;
+  best_dist = INT_MAX;
+
+  /* Start the search at mid */
+  edge = g_array_index (edges, MetaEdge*, mid);
+  compare = horizontal ? edge->rect.x : edge->rect.y;
+  edges_align = meta_rectangle_edge_aligns (new_rect, edge);
+  if (edges_align &&
+      (!only_forward || !points_on_same_side (position, compare, old_position)))
+    {
+      int dist = ABS (compare - position);
+      if (dist < best_dist)
+        {
+          best = compare;
+          best_dist = dist;
+        }
+    }
+
+  /* Now start searching higher than mid */
+  for (i = mid + 1; i < (int)edges->len; i++)
+    {
+      edge = g_array_index (edges, MetaEdge*, i);
+      compare = horizontal ? edge->rect.x : edge->rect.y;
+  
+      edges_align = horizontal ? 
+        meta_rectangle_vert_overlap (&edge->rect, new_rect) :
+        meta_rectangle_horiz_overlap (&edge->rect, new_rect);
+
+      if (edges_align &&
+          (!only_forward ||
+           !points_on_same_side (position, compare, old_position)))
+        {
+          int dist = ABS (compare - position);
+          if (dist < best_dist)
+            {
+              best = compare;
+              best_dist = dist;
+            }
+          break;
+        }
+    }
+
+  /* Now start searching lower than mid */
+  for (i = mid-1; i >= 0; i--)
+    {
+      edge = g_array_index (edges, MetaEdge*, i);
+      compare = horizontal ? edge->rect.x : edge->rect.y;
+  
+      edges_align = horizontal ? 
+        meta_rectangle_vert_overlap (&edge->rect, new_rect) :
+        meta_rectangle_horiz_overlap (&edge->rect, new_rect);
+
+      if (edges_align &&
+          (!only_forward ||
+           !points_on_same_side (position, compare, old_position)))
+        {
+          int dist = ABS (compare - position);
+          if (dist < best_dist)
+            {
+              best = compare;
+              best_dist = dist;
+            }
+          break;
+        }
+    }
+
+  /* Return the best one found */
+  return best;
+}
+
+static gboolean
+movement_towards_edge (MetaSide side, int increment)
+{
+  switch (side)
+    {
+    case META_SIDE_LEFT:
+    case META_SIDE_TOP:
+      return increment < 0;
+    case META_SIDE_RIGHT:
+    case META_SIDE_BOTTOM:
+      return increment > 0;
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static gboolean
+edge_resistance_timeout (gpointer data)
+{
+  ResistanceDataForAnEdge *resistance_data = data;
+
+  resistance_data->timeout_over = TRUE;
+  resistance_data->timeout_id = 0;
+  (*resistance_data->timeout_func)(resistance_data->window);
+
+  return FALSE;
+}
+
+static int
+apply_edge_resistance (MetaWindow                *window,
+                       int                        old_pos,
+                       int                        new_pos,
+                       const MetaRectangle       *old_rect,
+                       const MetaRectangle       *new_rect,
+                       GArray                    *edges,
+                       ResistanceDataForAnEdge   *resistance_data,
+                       GSourceFunc                timeout_func,
+                       gboolean                   xdir,
+                       gboolean                   keyboard_op)
+{
+  int i, begin, end;
+  int last_edge;
+  gboolean increasing = new_pos > old_pos;
+  int      increment = increasing ? 1 : -1;
+
+  const int PIXEL_DISTANCE_THRESHOLD_TOWARDS_WINDOW    = 16;
+  const int PIXEL_DISTANCE_THRESHOLD_AWAYFROM_WINDOW   =  0;
+  const int PIXEL_DISTANCE_THRESHOLD_TOWARDS_XINERAMA  = 32;
+  const int PIXEL_DISTANCE_THRESHOLD_AWAYFROM_XINERAMA =  0;
+  const int PIXEL_DISTANCE_THRESHOLD_TOWARDS_SCREEN    = 32;
+  const int PIXEL_DISTANCE_THRESHOLD_AWAYFROM_SCREEN   =  0;
+  const int TIMEOUT_RESISTANCE_LENGTH_MS_WINDOW   =   0;
+  const int TIMEOUT_RESISTANCE_LENGTH_MS_XINERAMA =   0;
+  const int TIMEOUT_RESISTANCE_LENGTH_MS_SCREEN   =   0;
+
+  /* Quit if no movement was specified */
+  if (old_pos == new_pos)
+    return new_pos;
+
+  /* Remove the old timeout if it's no longer relevant */
+  if (resistance_data->timeout_setup &&
+      ((resistance_data->timeout_edge_pos > old_pos &&
+        resistance_data->timeout_edge_pos > new_pos)  ||
+       (resistance_data->timeout_edge_pos < old_pos &&
+        resistance_data->timeout_edge_pos < new_pos)))
+    {
+      resistance_data->timeout_setup = FALSE;
+      if (resistance_data->timeout_id != 0)
+        {
+          g_source_remove (resistance_data->timeout_id);
+          resistance_data->timeout_id = 0;
+        }
+    }
+
+  /* Get the range of indices in the edge array that we move past/to. */
+  begin = find_index_of_edge_near_position (edges, old_pos,  increasing, xdir);
+  end   = find_index_of_edge_near_position (edges, new_pos, !increasing, xdir);
+
+  /* begin and end can be outside the array index, if the window is partially
+   * off the screen
+   */
+  last_edge = edges->len - 1;
+  begin = CLAMP (begin, 0, last_edge);
+  end   = CLAMP (end,   0, last_edge);
+
+  /* Loop over all these edges we're moving past/to. */
+  i = begin;
+  while ((increasing  && i <= end) ||
+         (!increasing && i >= end))
+    {
+      gboolean  edges_align;
+      MetaEdge *edge = g_array_index (edges, MetaEdge*, i);
+      int       compare = xdir ? edge->rect.x : edge->rect.y;
+
+      /* Find out if this edge is relevant */
+      edges_align = meta_rectangle_edge_aligns (new_rect, edge)  ||
+                    meta_rectangle_edge_aligns (old_rect, edge);
+
+      /* Nothing to do unless the edges align */
+      if (!edges_align)
+        {
+          /* Go to the next edge in the range */
+          i += increment;
+          continue;
+        }
+
+      /* Rest is easier to read if we split on keyboard vs. mouse op */
+      if (keyboard_op)
+        {
+          if ((old_pos < compare && compare < new_pos) ||
+              (old_pos > compare && compare > new_pos))
+            return compare;
+        }
+      else /* mouse op */
+        {
+          int threshold;
+
+          /* TIMEOUT RESISTANCE: If the edge is relevant and we're moving
+           * towards it, then we may want to have some kind of time delay
+           * before the user can move past this edge.
+           */
+          if (movement_towards_edge (edge->side_type, increment))
+            {
+              /* First, determine the length of time for the resistance */
+              int timeout_length_ms = 0;
+              switch (edge->edge_type)
+                {
+                case META_EDGE_WINDOW:
+                  timeout_length_ms = TIMEOUT_RESISTANCE_LENGTH_MS_WINDOW;
+                  break;
+                case META_EDGE_XINERAMA:
+                  timeout_length_ms = TIMEOUT_RESISTANCE_LENGTH_MS_XINERAMA;
+                  break;
+                case META_EDGE_SCREEN:
+                  timeout_length_ms = TIMEOUT_RESISTANCE_LENGTH_MS_SCREEN;
+                  break;
+                }
+
+              if (!resistance_data->timeout_setup &&
+                  timeout_length_ms != 0)
+                {
+                  resistance_data->timeout_id = 
+                    g_timeout_add (timeout_length_ms,
+                                   edge_resistance_timeout,
+                                   resistance_data);
+                  resistance_data->timeout_setup = TRUE;
+                  resistance_data->timeout_edge_pos = compare;
+                  resistance_data->timeout_over = FALSE;
+                  resistance_data->timeout_func = timeout_func;
+                  resistance_data->window = window;
+                }
+              if (!resistance_data->timeout_over &&
+                  timeout_length_ms != 0)
+                return compare;
+            }
+
+          /* PIXEL DISTANCE MOUSE RESISTANCE: If the edge matters and the
+           * user hasn't moved at least threshold pixels past this edge,
+           * stop movement at this edge.  (Note that this is different from
+           * keyboard resistance precisely because keyboard move ops are
+           * relative to previous positions, whereas mouse move ops are
+           * relative to differences in mouse position and mouse position
+           * is an absolute quantity rather than a relative quantity)
+           */
+
+          /* First, determine the threshold */
+          threshold = 0;
+          switch (edge->edge_type)
+            {
+            case META_EDGE_WINDOW:
+              if (movement_towards_edge (edge->side_type, increment))
+                threshold = PIXEL_DISTANCE_THRESHOLD_TOWARDS_WINDOW;
+              else
+                threshold = PIXEL_DISTANCE_THRESHOLD_AWAYFROM_WINDOW;
+              break;
+            case META_EDGE_XINERAMA:
+              if (movement_towards_edge (edge->side_type, increment))
+                threshold = PIXEL_DISTANCE_THRESHOLD_TOWARDS_XINERAMA;
+              else
+                threshold = PIXEL_DISTANCE_THRESHOLD_AWAYFROM_XINERAMA;
+              break;
+            case META_EDGE_SCREEN:
+              if (movement_towards_edge (edge->side_type, increment))
+                threshold = PIXEL_DISTANCE_THRESHOLD_TOWARDS_SCREEN;
+              else
+                threshold = PIXEL_DISTANCE_THRESHOLD_AWAYFROM_SCREEN;
+              break;
+            }
+
+          if (ABS (compare - new_pos) < threshold)
+            return compare;
+        }
+
+      /* Go to the next edge in the range */
+      i += increment;
+    }
+
+  return new_pos;
+}
+
+static int
+apply_edge_snapping (int                  old_pos,
+                     int                  new_pos,
+                     const MetaRectangle *new_rect,
+                     GArray              *edges,
+                     gboolean             xdir,
+                     gboolean             keyboard_op)
+{
+  int snap_to;
+
+  if (old_pos == new_pos)
+    return new_pos;
+
+  snap_to = find_nearest_position (edges,
+                                   new_pos,
+                                   old_pos,
+                                   new_rect,
+                                   xdir,
+                                   keyboard_op);
+
+  /* If mouse snap-moving, the user could easily accidentally move just a
+   * couple pixels in a direction they didn't mean to move; so ignore snap
+   * movement in those cases unless it's only a small number of pixels
+   * anyway.
+   */
+  if (!keyboard_op &&
+      ABS (snap_to - old_pos) >= 8 &&
+      ABS (new_pos - old_pos) < 8)
+    return old_pos;
+  else
+    /* Otherwise, return the snapping position found */
+    return snap_to;
+}
+
+/* This function takes the position (including any frame) of the window and
+ * a proposed new position (ignoring edge resistance/snapping), and then
+ * applies edge resistance to EACH edge (separately) updating new_outer.
+ * It returns true if new_outer is modified, false otherwise.
+ *
+ * display->grab_edge_resistance_data MUST already be setup or calling this
+ * function will cause a crash.
+ */
+static gboolean 
+apply_edge_resistance_to_each_side (MetaDisplay         *display,
+                                    MetaWindow          *window,
+                                    const MetaRectangle *old_outer,
+                                    MetaRectangle       *new_outer,
+                                    GSourceFunc          timeout_func,
+                                    gboolean             auto_snap,
+                                    gboolean             keyboard_op,
+                                    gboolean             is_resize)
+{
+  MetaEdgeResistanceData *edge_data;
+  MetaRectangle           modified_rect;
+  gboolean                modified;
+  int new_left, new_right, new_top, new_bottom;
+
+  g_assert (display->grab_edge_resistance_data != NULL);
+  edge_data = display->grab_edge_resistance_data;
+
+  if (auto_snap)
+    {
+      /* Do the auto snapping instead of normal edge resistance; in all
+       * cases, we allow snapping to opposite kinds of edges (e.g. left
+       * sides of windows to both left and right edges.
+       */
+
+      new_left   = apply_edge_snapping (BOX_LEFT (*old_outer),
+                                        BOX_LEFT (*new_outer),
+                                        new_outer,
+                                        edge_data->left_edges,
+                                        TRUE,
+                                        keyboard_op);
+
+      new_right  = apply_edge_snapping (BOX_RIGHT (*old_outer),
+                                        BOX_RIGHT (*new_outer),
+                                        new_outer,
+                                        edge_data->right_edges,
+                                        TRUE,
+                                        keyboard_op);
+
+      new_top    = apply_edge_snapping (BOX_TOP (*old_outer),
+                                        BOX_TOP (*new_outer),
+                                        new_outer,
+                                        edge_data->top_edges,
+                                        FALSE,
+                                        keyboard_op);
+
+      new_bottom = apply_edge_snapping (BOX_BOTTOM (*old_outer),
+                                        BOX_BOTTOM (*new_outer),
+                                        new_outer,
+                                        edge_data->bottom_edges,
+                                        FALSE,
+                                        keyboard_op);
+    }
+  else
+    {
+      /* Disable edge resistance for resizes when windows have size
+       * increment hints; see #346782.  For all other cases, apply
+       * them.
+       */
+      if (!is_resize || window->size_hints.width_inc == 1)
+        {
+          /* Now, apply the normal horizontal edge resistance */
+          new_left   = apply_edge_resistance (window,
+                                              BOX_LEFT (*old_outer),
+                                              BOX_LEFT (*new_outer),
+                                              old_outer,
+                                              new_outer,
+                                              edge_data->left_edges,
+                                              &edge_data->left_data,
+                                              timeout_func,
+                                              TRUE,
+                                              keyboard_op);
+          new_right  = apply_edge_resistance (window,
+                                              BOX_RIGHT (*old_outer),
+                                              BOX_RIGHT (*new_outer),
+                                              old_outer,
+                                              new_outer,
+                                              edge_data->right_edges,
+                                              &edge_data->right_data,
+                                              timeout_func,
+                                              TRUE,
+                                              keyboard_op);
+        }
+      else
+        {
+          new_left  = new_outer->x;
+          new_right = new_outer->x + new_outer->width;
+        }
+      /* Same for vertical resizes... */
+      if (!is_resize || window->size_hints.height_inc == 1)
+        {
+          new_top    = apply_edge_resistance (window,
+                                              BOX_TOP (*old_outer),
+                                              BOX_TOP (*new_outer),
+                                              old_outer,
+                                              new_outer,
+                                              edge_data->top_edges,
+                                              &edge_data->top_data,
+                                              timeout_func,
+                                              FALSE,
+                                              keyboard_op);
+          new_bottom = apply_edge_resistance (window,
+                                              BOX_BOTTOM (*old_outer),
+                                              BOX_BOTTOM (*new_outer),
+                                              old_outer,
+                                              new_outer,
+                                              edge_data->bottom_edges,
+                                              &edge_data->bottom_data,
+                                              timeout_func,
+                                              FALSE,
+                                              keyboard_op);
+        }
+      else
+        {
+          new_top    = new_outer->y;
+          new_bottom = new_outer->y + new_outer->height;
+        }
+    }
+
+  /* Determine whether anything changed, and save the changes */
+  modified_rect = meta_rect (new_left, 
+                             new_top,
+                             new_right - new_left,
+                             new_bottom - new_top);
+  modified = !meta_rectangle_equal (new_outer, &modified_rect);
+  *new_outer = modified_rect;
+  return modified;
+}
+
+void
+meta_display_cleanup_edges (MetaDisplay *display)
+{
+  guint i,j;
+  MetaEdgeResistanceData *edge_data = display->grab_edge_resistance_data;
+  GHashTable *edges_to_be_freed;
+
+  g_assert (edge_data != NULL);
+
+  /* We first need to clean out any window edges */
+  edges_to_be_freed = g_hash_table_new_full (g_direct_hash, g_direct_equal,
+                                             g_free, NULL);
+  for (i = 0; i < 4; i++)
+    {
+      GArray *tmp = NULL;
+      MetaSide side;
+      switch (i)
+        {
+        case 0:
+          tmp = edge_data->left_edges;
+          side = META_SIDE_LEFT;
+          break;
+        case 1:
+          tmp = edge_data->right_edges;
+          side = META_SIDE_RIGHT;
+          break;
+        case 2:
+          tmp = edge_data->top_edges;
+          side = META_SIDE_TOP;
+          break;
+        case 3:
+          tmp = edge_data->bottom_edges;
+          side = META_SIDE_BOTTOM;
+          break;
+        default:
+          g_assert_not_reached ();
+        }
+
+      for (j = 0; j < tmp->len; j++)
+        {
+          MetaEdge *edge = g_array_index (tmp, MetaEdge*, j);
+          if (edge->edge_type == META_EDGE_WINDOW &&
+              edge->side_type == side)
+            {
+              /* The same edge will appear in two arrays, and we can't free
+               * it yet we still need to compare edge->side_type for the other
+               * array that it is in.  So store it in a hash table for later
+               * freeing.  Could also do this in a simple linked list.
+               */
+              g_hash_table_insert (edges_to_be_freed, edge, edge);
+            }
+        }
+    }
+
+  /* Now free all the window edges (the key destroy function is g_free) */
+  g_hash_table_destroy (edges_to_be_freed);
+
+  /* Now free the arrays and data */
+  g_array_free (edge_data->left_edges, TRUE);
+  g_array_free (edge_data->right_edges, TRUE);
+  g_array_free (edge_data->top_edges, TRUE);
+  g_array_free (edge_data->bottom_edges, TRUE);
+  edge_data->left_edges = NULL;
+  edge_data->right_edges = NULL;
+  edge_data->top_edges = NULL;
+  edge_data->bottom_edges = NULL;
+
+  /* Cleanup the timeouts */
+  if (edge_data->left_data.timeout_setup   &&
+      edge_data->left_data.timeout_id   != 0)
+    g_source_remove (edge_data->left_data.timeout_id);
+  if (edge_data->right_data.timeout_setup  &&
+      edge_data->right_data.timeout_id  != 0)
+    g_source_remove (edge_data->right_data.timeout_id);
+  if (edge_data->top_data.timeout_setup    &&
+      edge_data->top_data.timeout_id    != 0)
+    g_source_remove (edge_data->top_data.timeout_id);
+  if (edge_data->bottom_data.timeout_setup &&
+      edge_data->bottom_data.timeout_id != 0)
+    g_source_remove (edge_data->bottom_data.timeout_id);
+
+  g_free (display->grab_edge_resistance_data);
+  display->grab_edge_resistance_data = NULL;
+}
+
+static int
+stupid_sort_requiring_extra_pointer_dereference (gconstpointer a, 
+                                                 gconstpointer b)
+{
+  const MetaEdge * const *a_edge = a;
+  const MetaEdge * const *b_edge = b;
+  return meta_rectangle_edge_cmp_ignore_type (*a_edge, *b_edge);
+}
+
+static void
+cache_edges (MetaDisplay *display,
+             GList *window_edges,
+             GList *xinerama_edges,
+             GList *screen_edges)
+{
+  MetaEdgeResistanceData *edge_data;
+  GList *tmp;
+  int num_left, num_right, num_top, num_bottom;
+  int i;
+
+  /*
+   * 0th: Print debugging information to the log about the edges
+   */
+#ifdef WITH_VERBOSE_MODE
+  if (meta_is_verbose())
+    {
+      int max_edges = MAX (MAX( g_list_length (window_edges), 
+                                g_list_length (xinerama_edges)),
+                           g_list_length (screen_edges));
+      char big_buffer[(EDGE_LENGTH+2)*max_edges];
+
+      meta_rectangle_edge_list_to_string (window_edges, ", ", big_buffer);
+      meta_topic (META_DEBUG_EDGE_RESISTANCE,
+                  "Window edges for resistance  : %s\n", big_buffer);
+
+      meta_rectangle_edge_list_to_string (xinerama_edges, ", ", big_buffer);
+      meta_topic (META_DEBUG_EDGE_RESISTANCE,
+                  "Xinerama edges for resistance: %s\n", big_buffer);
+
+      meta_rectangle_edge_list_to_string (screen_edges, ", ", big_buffer);
+      meta_topic (META_DEBUG_EDGE_RESISTANCE,
+                  "Screen edges for resistance  : %s\n", big_buffer);
+    }
+#endif
+
+  /*
+   * 1st: Get the total number of each kind of edge
+   */
+  num_left = num_right = num_top = num_bottom = 0;
+  for (i = 0; i < 3; i++)
+    {
+      tmp = NULL;
+      switch (i)
+        {
+        case 0:
+          tmp = window_edges;
+          break;
+        case 1:
+          tmp = xinerama_edges;
+          break;
+        case 2:
+          tmp = screen_edges;
+          break;
+        default:
+          g_assert_not_reached ();
+        }
+
+      while (tmp)
+        {
+          MetaEdge *edge = tmp->data;
+          switch (edge->side_type)
+            {
+            case META_SIDE_LEFT:
+              num_left++;
+              break;
+            case META_SIDE_RIGHT:
+              num_right++;
+              break;
+            case META_SIDE_TOP:
+              num_top++;
+              break;
+            case META_SIDE_BOTTOM:
+              num_bottom++;
+              break;
+            default:
+              g_assert_not_reached ();
+            }
+          tmp = tmp->next;
+        }
+    }
+
+  /*
+   * 2nd: Allocate the edges
+   */
+  g_assert (display->grab_edge_resistance_data == NULL);
+  display->grab_edge_resistance_data = g_new (MetaEdgeResistanceData, 1);
+  edge_data = display->grab_edge_resistance_data;
+  edge_data->left_edges   = g_array_sized_new (FALSE,
+                                               FALSE,
+                                               sizeof(MetaEdge*),
+                                               num_left + num_right);
+  edge_data->right_edges  = g_array_sized_new (FALSE,
+                                               FALSE,
+                                               sizeof(MetaEdge*),
+                                               num_left + num_right);
+  edge_data->top_edges    = g_array_sized_new (FALSE,
+                                               FALSE,
+                                               sizeof(MetaEdge*),
+                                               num_top + num_bottom);
+  edge_data->bottom_edges = g_array_sized_new (FALSE,
+                                               FALSE,
+                                               sizeof(MetaEdge*),
+                                               num_top + num_bottom);
+
+  /*
+   * 3rd: Add the edges to the arrays
+   */
+  for (i = 0; i < 3; i++)
+    {
+      tmp = NULL;
+      switch (i)
+        {
+        case 0:
+          tmp = window_edges;
+          break;
+        case 1:
+          tmp = xinerama_edges;
+          break;
+        case 2:
+          tmp = screen_edges;
+          break;
+        default:
+          g_assert_not_reached ();
+        }
+
+      while (tmp)
+        {
+          MetaEdge *edge = tmp->data;
+          switch (edge->side_type)
+            {
+            case META_SIDE_LEFT:
+            case META_SIDE_RIGHT:
+              g_array_append_val (edge_data->left_edges, edge);
+              g_array_append_val (edge_data->right_edges, edge);
+              break;
+            case META_SIDE_TOP:
+            case META_SIDE_BOTTOM:
+              g_array_append_val (edge_data->top_edges, edge);
+              g_array_append_val (edge_data->bottom_edges, edge);
+              break;
+            default:
+              g_assert_not_reached ();
+            }
+          tmp = tmp->next;
+        }
+    }
+
+  /*
+   * 4th: Sort the arrays (FIXME: This is kinda dumb since the arrays were
+   * individually sorted earlier and we could have done this faster and
+   * avoided this sort by sticking them into the array with some simple
+   * merging of the lists).
+   */
+  g_array_sort (display->grab_edge_resistance_data->left_edges, 
+                stupid_sort_requiring_extra_pointer_dereference);
+  g_array_sort (display->grab_edge_resistance_data->right_edges, 
+                stupid_sort_requiring_extra_pointer_dereference);
+  g_array_sort (display->grab_edge_resistance_data->top_edges, 
+                stupid_sort_requiring_extra_pointer_dereference);
+  g_array_sort (display->grab_edge_resistance_data->bottom_edges, 
+                stupid_sort_requiring_extra_pointer_dereference);
+}
+
+static void
+initialize_grab_edge_resistance_data (MetaDisplay *display)
+{
+  MetaEdgeResistanceData *edge_data = display->grab_edge_resistance_data;
+
+  edge_data->left_data.timeout_setup   = FALSE;
+  edge_data->right_data.timeout_setup  = FALSE;
+  edge_data->top_data.timeout_setup    = FALSE;
+  edge_data->bottom_data.timeout_setup = FALSE;
+
+  edge_data->left_data.keyboard_buildup   = 0;
+  edge_data->right_data.keyboard_buildup  = 0;
+  edge_data->top_data.keyboard_buildup    = 0;
+  edge_data->bottom_data.keyboard_buildup = 0;
+}
+
+void
+meta_display_compute_resistance_and_snapping_edges (MetaDisplay *display)
+{
+  GList *stacked_windows;
+  GList *cur_window_iter;
+  GList *edges;
+  /* Lists of window positions (rects) and their relative stacking positions */
+  int stack_position;
+  GSList *obscuring_windows, *window_stacking;
+  /* The portions of the above lists that still remain at the stacking position
+   * in the layer that we are working on
+   */
+  GSList *rem_windows, *rem_win_stacking;
+
+  /*
+   * 1st: Get the list of relevant windows, from bottom to top
+   */
+  stacked_windows = 
+    meta_stack_list_windows (display->grab_screen->stack,
+                             display->grab_screen->active_workspace);
+
+  /*
+   * 2nd: we need to separate that stacked list into a list of windows that
+   * can obscure other edges.  To make sure we only have windows obscuring
+   * those below it instead of going both ways, we also need to keep a
+   * counter list.  Messy, I know.
+   */
+  obscuring_windows = window_stacking = NULL;
+  cur_window_iter = stacked_windows;
+  stack_position = 0;
+  while (cur_window_iter != NULL)
+    {
+      MetaWindow *cur_window = cur_window_iter->data;
+      if (WINDOW_EDGES_RELEVANT (cur_window, display))
+        {
+          MetaRectangle *new_rect;
+          new_rect = g_new (MetaRectangle, 1);
+          meta_window_get_outer_rect (cur_window, new_rect);
+          obscuring_windows = g_slist_prepend (obscuring_windows, new_rect);
+          window_stacking = 
+            g_slist_prepend (window_stacking, GINT_TO_POINTER (stack_position));
+        }
+
+      stack_position++;
+      cur_window_iter = cur_window_iter->next;
+    }
+  /* Put 'em in bottom to top order */
+  rem_windows = obscuring_windows = g_slist_reverse (obscuring_windows);
+  rem_win_stacking = window_stacking = g_slist_reverse (window_stacking);
+
+  /*
+   * 3rd: loop over the windows again, this time getting the edges from
+   * them and removing intersections with the relevant obscuring_windows &
+   * obscuring_docks.
+   */
+  edges = NULL;
+  stack_position = 0;
+  cur_window_iter = stacked_windows;
+  while (cur_window_iter != NULL)
+    {
+      MetaRectangle  cur_rect;
+      MetaWindow    *cur_window = cur_window_iter->data;
+      meta_window_get_outer_rect (cur_window, &cur_rect);
+
+      /* Check if we want to use this window's edges for edge
+       * resistance (note that dock edges are considered screen edges
+       * which are handled separately
+       */
+      if (WINDOW_EDGES_RELEVANT (cur_window, display) &&
+          cur_window->type != META_WINDOW_DOCK)
+        {
+          GList *new_edges;
+          MetaEdge *new_edge;
+          MetaRectangle reduced;
+
+          /* We don't care about snapping to any portion of the window that
+           * is offscreen (we also don't care about parts of edges covered
+           * by other windows or DOCKS, but that's handled below).
+           */
+          meta_rectangle_intersect (&cur_rect, 
+                                    &display->grab_screen->rect,
+                                    &reduced);
+
+          new_edges = NULL;
+
+          /* Left side of this window is resistance for the right edge of
+           * the window being moved.
+           */
+          new_edge = g_new (MetaEdge, 1);
+          new_edge->rect = reduced;
+          new_edge->rect.width = 0;
+          new_edge->side_type = META_SIDE_RIGHT;
+          new_edge->edge_type = META_EDGE_WINDOW;
+          new_edges = g_list_prepend (new_edges, new_edge);
+
+          /* Right side of this window is resistance for the left edge of
+           * the window being moved.
+           */
+          new_edge = g_new (MetaEdge, 1);
+          new_edge->rect = reduced;
+          new_edge->rect.x += new_edge->rect.width;
+          new_edge->rect.width = 0;
+          new_edge->side_type = META_SIDE_LEFT;
+          new_edge->edge_type = META_EDGE_WINDOW;
+          new_edges = g_list_prepend (new_edges, new_edge);
+          
+          /* Top side of this window is resistance for the bottom edge of
+           * the window being moved.
+           */
+          new_edge = g_new (MetaEdge, 1);
+          new_edge->rect = reduced;
+          new_edge->rect.height = 0;
+          new_edge->side_type = META_SIDE_BOTTOM;
+          new_edge->edge_type = META_EDGE_WINDOW;
+          new_edges = g_list_prepend (new_edges, new_edge);
+
+          /* Top side of this window is resistance for the bottom edge of
+           * the window being moved.
+           */
+          new_edge = g_new (MetaEdge, 1);
+          new_edge->rect = reduced;
+          new_edge->rect.y += new_edge->rect.height;
+          new_edge->rect.height = 0;
+          new_edge->side_type = META_SIDE_TOP;
+          new_edge->edge_type = META_EDGE_WINDOW;
+          new_edges = g_list_prepend (new_edges, new_edge);
+
+          /* Update the remaining windows to only those at a higher
+           * stacking position than this one.
+           */
+          while (rem_win_stacking && 
+                 stack_position >= GPOINTER_TO_INT (rem_win_stacking->data))
+            {
+              rem_windows      = rem_windows->next;
+              rem_win_stacking = rem_win_stacking->next;
+            }
+
+          /* Remove edge portions overlapped by rem_windows and rem_docks */
+          new_edges = 
+            meta_rectangle_remove_intersections_with_boxes_from_edges (
+              new_edges,
+              rem_windows);
+
+          /* Save the new edges */
+          edges = g_list_concat (new_edges, edges);
+        }
+
+      stack_position++;
+      cur_window_iter = cur_window_iter->next;
+    }
+
+  /*
+   * 4th: Free the extra memory not needed and sort the list
+   */
+  g_list_free (stacked_windows);
+  /* Free the memory used by the obscuring windows/docks lists */
+  g_slist_free (window_stacking);
+  /* FIXME: Shouldn't there be a helper function to make this one line of code
+   * to free a list instead of four ugly ones?
+   */
+  g_slist_foreach (obscuring_windows, 
+                   (void (*)(gpointer,gpointer))&g_free, /* ew, for ugly */
+                   NULL);
+  g_slist_free (obscuring_windows);
+
+  /* Sort the list.  FIXME: Should I bother with this sorting?  I just
+   * sort again later in cache_edges() anyway...
+   */
+  edges = g_list_sort (edges, meta_rectangle_edge_cmp);
+
+  /*
+   * 5th: Cache the combination of these edges with the onscreen and
+   * xinerama edges in an array for quick access.  Free the edges since
+   * they've been cached elsewhere.
+   */
+  cache_edges (display,
+               edges,
+               display->grab_screen->active_workspace->xinerama_edges,
+               display->grab_screen->active_workspace->screen_edges);
+  g_list_free (edges);
+
+  /*
+   * 6th: Initialize the resistance timeouts and buildups
+   */
+  initialize_grab_edge_resistance_data (display);
+}
+
+/* Note that old_[xy] and new_[xy] are with respect to inner positions of
+ * the window.
+ */
+void
+meta_window_edge_resistance_for_move (MetaWindow  *window,
+                                      int          old_x,
+                                      int          old_y,
+                                      int         *new_x,
+                                      int         *new_y,
+                                      GSourceFunc  timeout_func,
+                                      gboolean     snap,
+                                      gboolean     is_keyboard_op)
+{
+  MetaRectangle old_outer, proposed_outer, new_outer;
+  gboolean is_resize;
+
+  if (window == window->display->grab_window &&
+      window->display->grab_wireframe_active)
+    {
+      meta_window_get_xor_rect (window,
+                                &window->display->grab_wireframe_rect,
+                                &old_outer);
+    }
+  else
+    {
+      meta_window_get_outer_rect (window, &old_outer);
+    }
+  proposed_outer = old_outer;
+  proposed_outer.x += (*new_x - old_x);
+  proposed_outer.y += (*new_y - old_y);
+  new_outer = proposed_outer;
+
+  window->display->grab_last_user_action_was_snap = snap;
+  is_resize = FALSE;
+  if (apply_edge_resistance_to_each_side (window->display,
+                                          window,
+                                          &old_outer,
+                                          &new_outer,
+                                          timeout_func,
+                                          snap,
+                                          is_keyboard_op,
+                                          is_resize))
+    {
+      /* apply_edge_resistance_to_each_side independently applies
+       * resistance to both the right and left edges of new_outer as both
+       * could meet areas of resistance.  But we don't want a resize, so we
+       * just have both edges move according to the stricter of the
+       * resistances.  Same thing goes for top & bottom edges.
+       */
+      MetaRectangle *reference;
+      int left_change, right_change, smaller_x_change;
+      int top_change, bottom_change, smaller_y_change;
+
+      if (snap && !is_keyboard_op)
+        reference = &proposed_outer;
+      else
+        reference = &old_outer;
+
+      left_change  = BOX_LEFT (new_outer)  - BOX_LEFT (*reference);
+      right_change = BOX_RIGHT (new_outer) - BOX_RIGHT (*reference);
+      if (     snap && is_keyboard_op && left_change == 0)
+        smaller_x_change = right_change;
+      else if (snap && is_keyboard_op && right_change == 0)
+        smaller_x_change = left_change;
+      else if (ABS (left_change) < ABS (right_change))
+        smaller_x_change = left_change;
+      else
+        smaller_x_change = right_change;
+
+      top_change    = BOX_TOP (new_outer)    - BOX_TOP (*reference);
+      bottom_change = BOX_BOTTOM (new_outer) - BOX_BOTTOM (*reference);
+      if (     snap && is_keyboard_op && top_change == 0)
+        smaller_y_change = bottom_change;
+      else if (snap && is_keyboard_op && bottom_change == 0)
+        smaller_y_change = top_change;
+      else if (ABS (top_change) < ABS (bottom_change))
+        smaller_y_change = top_change;
+      else
+        smaller_y_change = bottom_change;
+
+      *new_x = old_x + smaller_x_change + 
+              (BOX_LEFT (*reference) - BOX_LEFT (old_outer));
+      *new_y = old_y + smaller_y_change +
+              (BOX_TOP (*reference) - BOX_TOP (old_outer));
+
+      meta_topic (META_DEBUG_EDGE_RESISTANCE,
+                  "outer x & y move-to coordinate changed from %d,%d to %d,%d\n",
+                  proposed_outer.x, proposed_outer.y,
+                  old_outer.x + (*new_x - old_x),
+                  old_outer.y + (*new_y - old_y));
+    }
+}
+
+/* Note that old_(width|height) and new_(width|height) are with respect to
+ * sizes of the inner window.
+ */
+void
+meta_window_edge_resistance_for_resize (MetaWindow  *window,
+                                        int          old_width,
+                                        int          old_height,
+                                        int         *new_width,
+                                        int         *new_height,
+                                        int          gravity,
+                                        GSourceFunc  timeout_func,
+                                        gboolean     snap,
+                                        gboolean     is_keyboard_op)
+{
+  MetaRectangle old_outer, new_outer;
+  int proposed_outer_width, proposed_outer_height;
+  gboolean is_resize;
+
+  if (window == window->display->grab_window &&
+      window->display->grab_wireframe_active)
+    {
+      meta_window_get_xor_rect (window,
+                                &window->display->grab_wireframe_rect,
+                                &old_outer);
+    }
+  else
+    {
+      meta_window_get_outer_rect (window, &old_outer);
+    }
+  proposed_outer_width  = old_outer.width  + (*new_width  - old_width);
+  proposed_outer_height = old_outer.height + (*new_height - old_height);
+  meta_rectangle_resize_with_gravity (&old_outer, 
+                                      &new_outer,
+                                      gravity,
+                                      proposed_outer_width,
+                                      proposed_outer_height);
+
+  window->display->grab_last_user_action_was_snap = snap;
+  is_resize = TRUE;
+  if (apply_edge_resistance_to_each_side (window->display,
+                                          window,
+                                          &old_outer,
+                                          &new_outer,
+                                          timeout_func,
+                                          snap,
+                                          is_keyboard_op,
+                                          is_resize))
+    {
+      *new_width  = old_width  + (new_outer.width  - old_outer.width);
+      *new_height = old_height + (new_outer.height - old_outer.height);
+
+      meta_topic (META_DEBUG_EDGE_RESISTANCE,
+                  "outer width & height got changed from %d,%d to %d,%d\n",
+                  proposed_outer_width, proposed_outer_height,
+                  new_outer.width, new_outer.height);
+    }
+}