nx-X11/programs/Xserver/hw/nxagent/Screen.c: add low-level screen box…

…es merging algorithm/functions.

nx-X11/programs/Xserver/hw/nxagent/Screen.c

@@ -4354,6 +4354,379 @@ static nxagentScreenBoxes* nxagentGenerateScreenCrtcs(nxagentScreenSplits *split
   return(ret);
 }
 
+/*
+ * Helper returning true of a given box intersects with a given screen,
+ * otherwise and on error false.
+ */
+static Bool nxagentScreenBoxIntersectsScreen(const nxagentScreenBoxesElem *box, const XineramaScreenInfo *screen_info) {
+  Bool ret = FALSE;
+
+  if ((!(box)) || (!(box->box)) || (!(screen_info))) {
+    return(ret);
+  }
+
+  /* Find out if this box has intersections with display. */
+  INT32 box_width  = (box->box->x2 - box->box->x1),
+        box_height = (box->box->y2 - box->box->y1);
+  ret = intersect(box->box->x1, box->box->y1,
+                  box_width, box_height,
+                  screen_info->x_org, screen_info->y_org,
+                  screen_info->width, screen_info->height,
+                  NULL, NULL, NULL, NULL);
+
+  return(ret);
+}
+
+/* Helper printing out a single screen box. */
+static char* nxagentPrintScreenBoxElem(const nxagentScreenBoxesElem *box) {
+  char *ret = NULL;
+
+  BoxPtr box_data = box->box;
+  if ((!(box)) || (!(box_data))) {
+    return(ret);
+  }
+
+  char *construct = NULL;
+  if (-1 == asprintf(&construct, "[(%d, %d), (%d, %d)]", box_data->x1, box_data->y1, box_data->x2, box_data->y2)) {
+    return(ret);
+  }
+
+  ret = construct;
+
+  return(ret);
+}
+
+/*
+ * Helper comparing two box elements.
+ * Returns true if both data sections match, false otherwise or on error.
+ */
+static Bool nxagentCompareScreenBoxData(const BoxPtr lhs, const BoxPtr rhs) {
+  Bool ret = FALSE;
+
+  if ((!(lhs)) || (!(rhs))) {
+    return(ret);
+  }
+
+  if ((lhs->x1 == rhs->x1) && (lhs->x2 == rhs->x2) && (lhs->y1 == rhs->y1) && (lhs->y2 == rhs->y2)) {
+    ret = TRUE;
+  }
+
+  return(ret);
+}
+
+/*
+ * Helper merging boxes on a low level.
+ * Returns true if merging succeeded, otherwise or on error false.
+ *
+ * If merging succeded, the merge_boxes list shall contain only one element:
+ * the extended box representing a screen.
+ *
+ * In case of errors, the original list may or may not be modified.
+ * Assume that the data is invalid.
+ */
+static Bool nxagentMergeBoxes(nxagentScreenBoxes *all_boxes, nxagentScreenBoxes *merge_boxes) {
+  Bool ret = FALSE;
+
+  if (!(all_boxes)) || (!(merge_boxes)) {
+    return(ret);
+  }
+
+  /* Naïve approach: merge of all boxes is the bounding box. */
+  BoxRec bounding_box = { 0 };
+  nxagentScreenBoxesElem *cur = NULL;
+  Bool init = FALSE;
+  size_t merge_boxes_count = 0;
+  xorg_list_for_each_entry(cur, merge_boxes, entry) {
+    if (!(cur->box)) {
+      return(ret);
+    }
+
+    if (!(init)) {
+      bounding_box.x1 = cur->box->x1;
+      bounding_box.x2 = cur->box->x2;
+      bounding_box.y1 = cur->box->y1;
+      bounding_box.y2 = cur->box->y2;
+
+      init = TRUE;
+
+      ++merge_boxes_count;
+
+      continue;
+    }
+
+    bounding_box.x1 = MIN(cur->box->x1, bounding_box.x1);
+    bounding_box.x2 = MAX(cur->box->x2, bounding_box.x2);
+    bounding_box.y1 = MIN(cur->box->y1, bounding_box.y1);
+    bounding_box.y2 = MAX(cur->box->y2, bounding_box.y2);
+
+    ++merge_boxes_count;
+  }
+
+  if (1 >= merge_boxes_count) {
+    /* Special case: empty or one-element merge list. */
+    ret = TRUE;
+    return(ret);
+  }
+
+  /* Try to find a suitable merge pair. */
+  cur = NULL;
+  nxagentScreenBoxesElem *merge_rhs = NULL;
+  Bool restart = TRUE;
+  while (restart) {
+    restart = FALSE;
+
+    xorg_list_for_each_entry(cur, merge_boxes, entry) {
+      if (!(cur->box)) {
+        return(ret);
+      }
+
+      xorg_list_for_each_entry(merge_rhs, &(cur->entry), entry) {
+        if (!(merge_rhs->box)) {
+          return(ret);
+        }
+
+        if (&(merge_rhs->entry) == merge_boxes) {
+          /* Reached end of list. */
+          merge_rhs = NULL;
+          break;
+        }
+
+        /* Check adjacency. */
+        /*            left side                               right side */
+        if ((cur->box->x1 == merge_rhs->box->x2) || (cur->box->x2 == merge_rhs->box->x1)) {
+          /* Check starting y position and height. */
+          if ((cur->box->y1 == merge_rhs->box->y1) && (cur->box->y2 == merge_rhs->box->y2)) {
+            break;
+          }
+        }
+
+        /*             top side                              bottom side */
+        if ((cur->box->y1 == merge_rhs->box->y2) || (cur->box->y2 == merge_rhs->box->y1)) {
+          /* Check starting x position and width. */
+          if ((cur->box->x1 == merge_rhs->box->x1) && (cur->box->x2 == merge_rhs->box->x2)) {
+            break;
+          }
+        }
+      }
+
+      /* cur and merge_rhs are mergeable. */
+      if (merge_rhs) {
+#ifdef DEBUG
+        {
+          char *box_left_str = nxagentPrintScreenBoxElem(cur);
+          char *box_right_str = nxagentPrintScreenBoxElem(merge_rhs);
+
+          fprintf(stderr, "%s: mergeable boxes found: ", __func__);
+          if (!(box_left_str)) {
+            fprintf(stderr, "box with invalid data [%p]\n", cur);
+          }
+          else {
+            fprintf(stderr, "%s\n", box_left_str);
+          }
+
+          if (!(box_right_str)) {
+            fprintf(stderr, ", box with invalid data [%p]\n", merge_rhs);
+          }
+          else {
+            fprintf(stderr, ", %s\n", box_right_str);
+          }
+
+          SAFE_FREE(box_left_str);
+          SAFE_FREE(box_right_str);
+        }
+#endif
+        cur->box->x1 = MIN(cur->box->x1, merge_rhs->box->x1);
+        cur->box->x2 = MAX(cur->box->x2, merge_rhs->box->x2);
+        cur->box->y1 = MIN(cur->box->y1, merge_rhs->box->y1);
+        cur->box->y2 = MAX(cur->box->y2, merge_rhs->box->y2);
+
+        /* Delete merge_rhs box out of merge list ... */
+        xorg_list_del(&(merge_rhs->entry));
+
+        /*
+         * ... and mark an equivalent box in the all boxes list as obsolete.
+         *
+         * Note that it is not an error condition if no such box exists in the
+         * all boxes list. More likely we tried to mark a box obsolete that
+         * has already been merged with a different one (and now covers more
+         * than one entry in the all boxes list).
+         */
+        if (merge_rhs->obsolete) {
+          nxagentScreenBoxesElem *cur_obsolete = NULL;
+          xorg_list_for_each_entry(cur_obsolete, all_boxes, entry) {
+            if (nxagentCompareScreenBoxData(cur_obsolete->box, merge_rhs->box)) {
+              cur_obsolete->obsolete = TRUE;
+
+              /*
+               * Set iterator to NULL and break out, this condition marks that
+               * a box has been deleted out of the bigger array.
+               */
+              cur_obsolete = NULL;
+
+              break;
+            }
+          }
+
+          if (cur_obsolete) {
+            /* Non-NULL means that we haven't found a box to mark obsolete. */
+#ifdef WARNING
+            fprintf(stderr, "%s: merged boxes from merge list, but couldn't find right-hand box in original list - box has likely already been merged into a different one.\n", __func__);
+#endif
+          }
+        }
+
+        /*
+         * Remove merge_rhs's internal box data.
+         * Since it's a deep copy, only this element will be affected.
+         */
+        SAFE_FREE(merge_rhs->box);
+
+        /*
+         * At this point, merge_rhs's data has been free()d and the box
+         * element is not part of the merge_boxes lists.
+         * Delete the box element.
+         */
+        SAFE_FREE(merge_rhs);
+
+        restart = TRUE;
+
+        break;
+      }
+      else {
+#ifdef DEBUG
+        char *box_str = nxagentPrintScreenBoxElem(cur);
+
+        fprintf(stderr, "%s: no mergeable box found for ", __func__);
+        if (box_str) {
+          fprintf(stderr, " current box %s\n", box_str);
+        }
+        else {
+          fprintf(stderr, " box with invalid data [%p]\n", cur);
+        }
+
+        SAFE_FREE(box_str);
+#endif
+      }
+    }
+  }
+
+  /* All boxes merged, we should only have one left. */
+  merge_boxes_count = 0;
+  xorg_list_for_each_entry(cur, merge_boxes, entry) {
+    if (!(cur->box)) {
+      return(ret);
+    }
+
+    ++merge_boxes_count;
+  }
+
+  if (1 < merge_boxes_count) {
+#ifdef WARNING
+    fprintf(stderr, "%s: WARNING: box merge operation produced more than one box - initial merge list was not a rectangle!\n", __func__);
+#endif
+  }
+  else if (0 == merge_boxes_count) {
+#ifdef WARNING
+    fprintf(stderr, "%s: WARNING: box merge operation produced a merged box count of 0!\n", __func__);
+#endif
+  }
+  else {
+    cur = NULL;
+    xorg_list_for_each_entry(cur, merge_boxes, entry) {
+      /* Just break out here directly, there should only be one box. */
+      break;
+    }
+
+    if (nxagentCompareScreenBoxData(&bounding_box, cur->box)) {
+#ifdef DEBUG
+      fprintf("%s: merging operations result is equal to bounding box, could have avoided complex calculations.\n", __func__);
+#endif
+      ret = TRUE;
+    }
+  }
+
+  return(ret);
+}
+
+/* Helper merging boxes that pertain to specific screen.
+ *
+ * In case of errors, the original list may or may not be modified.
+ * Assume that the data is invalid.
+ */
+static Bool nxagentMergeScreenBoxes(nxagentScreenBoxes *all_boxes, nxagentScreenBoxes *screen_boxes, const XineramaScreenInfo *screen_info, const size_t screen_count) {
+  Bool ret = FALSE;
+
+  if ((!(all_boxes)) || (!(screen_boxes)) || (!(screen_info)) || (!(screen_count))) {
+    return(ret);
+  }
+
+  for (size_t i = 0; i < screen_count; ++i) {
+    /*
+     * Structure holding the box elements intersecting with
+     * the current screen.
+     */
+    nxagentScreenBoxes *cur_screen_boxes = screen_boxes[i];
+    xorg_list_init(&cur_screen_boxes);
+
+    nxagentScreenBoxesElem *cur_box = NULL;
+    xorg_list_for_each_entry(cur_box, all_boxes, entry) {
+      Bool cur_intersect = nxagentScreenBoxIntersectsScreen(cur_box, &(screen_info[i]));
+
+      if (cur_intersect) {
+        /*
+         * If a screen intersects the current box, we must:
+         *  - create a deep copy of this box
+         *  - add the copy to the screen boxes list
+         *  - set the obsolete flag appropriately
+         *  - start the low-level merge operation on the screen boxes list
+         *
+         * After this, assuming no error happened, the screen boxes list will
+         * contain only one element: a box containing the screen area.
+         */
+        nxagentScreenBoxesElem *box_copy = calloc(sizeof(nxagentScreenBoxesElem), 1);
+
+        if (!(box_copy)) {
+          nxagentFreeScreenBoxes(all_boxes, TRUE);
+          return(ret);
+        }
+
+        /* Create new low-level BoxRec. */
+        box_copy->box = calloc(sizeof(BoxRec), 1);
+
+        if (!(box_copy->box)) {
+          nxagentFreeScreenBoxes(cur_box, TRUE);
+          nxagentFreeScreenBoxes(all_boxes, TRUE);
+          return(ret);
+        }
+
+        /* Copy BoxRec contents. */
+        memmove(box_copy->box, cur_box->box, sizeof(BoxRec));
+
+        box_copy->obsolete = TRUE;
+
+        for (size_t y = (i + 1); y < screen_count; ++y) {
+          if (nxagentScreenBoxIntersectsScreen(cur_box, &(screen_info[y]))) {
+            /* Protect box, if still needed later on after merging this set. */
+            box_copy->obsolete = FALSE;
+            break;
+          }
+        }
+
+        xorg_list_append(&(box_copy->entry), cur_screen_boxes);
+      }
+    }
+
+    /* Actually merge the boxes. */
+    if (!(nxagentMergeBoxes(all_boxes, cur_screen_boxes))) {
+      return(ret);
+    }
+  }
+
+  ret = TRUE;
+
+  return(ret);
+}
+
 /*
  Destroy an output after removing it from any crtc that might reference it
  */