backends: Add simple object to delegate logical monitor layout queries

This object can be passed to random places, and be trusted to remain unchanged
till replaced. Makes it an ideal replacement for MetaMonitorManager across
threads.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1403>

src/backends/meta-monitor-manager-private.h

@@ -31,6 +31,7 @@
 #include "backends/meta-cursor.h"
 #include "backends/meta-display-config-shared.h"
 #include "backends/meta-monitor-transform.h"
+#include "backends/meta-viewport-info.h"
 #include "core/util-private.h"
 #include "meta/display.h"
 #include "meta/meta-monitor-manager.h"
@@ -404,4 +405,6 @@ meta_find_output_assignment (MetaOutputAssignment **outputs,
 
 void meta_monitor_manager_post_init (MetaMonitorManager *manager);
 
+MetaViewportInfo * meta_monitor_manager_get_viewports (MetaMonitorManager *manager);
+
 #endif /* META_MONITOR_MANAGER_PRIVATE_H */

src/backends/meta-monitor-manager.c

@@ -3250,3 +3250,37 @@ meta_monitor_manager_post_init (MetaMonitorManager *manager)
                            G_CALLBACK (update_panel_orientation_managed), manager,
                            G_CONNECT_SWAPPED);
 }
+
+MetaViewportInfo *
+meta_monitor_manager_get_viewports (MetaMonitorManager *manager)
+{
+  MetaViewportInfo *info;
+  GArray *views, *scales;
+  GList *logical_monitors, *l;
+
+  views = g_array_new (FALSE, FALSE, sizeof (cairo_rectangle_int_t));
+  scales = g_array_new (FALSE, FALSE, sizeof (float));
+
+  logical_monitors = meta_monitor_manager_get_logical_monitors (manager);
+
+  for (l = logical_monitors; l; l = l->next)
+    {
+      MetaLogicalMonitor *logical_monitor = l->data;
+      cairo_rectangle_int_t rect;
+      float scale;
+
+      rect = logical_monitor->rect;
+      g_array_append_val (views, rect);
+
+      scale = logical_monitor->scale;
+      g_array_append_val (scales, scale);
+    }
+
+  info = meta_viewport_info_new ((cairo_rectangle_int_t *) views->data,
+                                 (float *) scales->data,
+                                 views->len);
+  g_array_unref (views);
+  g_array_unref (scales);
+
+  return info;
+}

src/backends/meta-viewport-info.c

@@ -0,0 +1,189 @@
+/*
+ * Copyright (C) 2020 Red Hat
+ *
+ * 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.
+ *
+ * Written by:
+ *     Carlos Garnacho <carlosg@gnome.org>
+ */
+
+#include "config.h"
+
+#include "backends/meta-viewport-info.h"
+#include "core/main-private.h"
+#include "core/boxes-private.h"
+
+typedef struct _ViewInfo ViewInfo;
+
+struct _ViewInfo
+{
+  MetaRectangle rect;
+  float scale;
+};
+
+struct _MetaViewportInfo
+{
+  GObject parent;
+  GArray *views;
+};
+
+G_DEFINE_TYPE (MetaViewportInfo, meta_viewport_info, G_TYPE_OBJECT)
+
+static void
+meta_viewport_info_finalize (GObject *object)
+{
+  MetaViewportInfo *info = META_VIEWPORT_INFO (object);
+
+  g_array_unref (info->views);
+
+  G_OBJECT_CLASS (meta_viewport_info_parent_class)->finalize (object);
+}
+
+static void
+meta_viewport_info_class_init (MetaViewportInfoClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->finalize = meta_viewport_info_finalize;
+}
+
+static void
+meta_viewport_info_init (MetaViewportInfo *info)
+{
+  info->views = g_array_new (FALSE, FALSE, sizeof (ViewInfo));
+}
+
+MetaViewportInfo *
+meta_viewport_info_new (cairo_rectangle_int_t *views,
+                        float                 *scales,
+                        int                    n_views)
+{
+  MetaViewportInfo *viewport_info;
+  int i;
+
+  viewport_info = g_object_new (META_TYPE_VIEWPORT_INFO, NULL);
+
+  for (i = 0; i < n_views; i++)
+    {
+      ViewInfo info;
+
+      info.rect = views[i];
+      info.scale = scales[i];
+      g_array_append_val (viewport_info->views, info);
+    }
+
+  return viewport_info;
+}
+
+int
+meta_viewport_info_get_view_at (MetaViewportInfo *viewport_info,
+                                float             x,
+                                float             y)
+{
+  int i;
+
+  for (i = 0; i < viewport_info->views->len; i++)
+    {
+      ViewInfo *info = &g_array_index (viewport_info->views, ViewInfo, i);
+
+      if (META_POINT_IN_RECT (x, y, info->rect))
+        return i;
+    }
+
+  return -1;
+}
+
+gboolean
+meta_viewport_info_get_view_info (MetaViewportInfo      *viewport_info,
+                                  int                    idx,
+                                  cairo_rectangle_int_t *rect,
+                                  float                 *scale)
+{
+  ViewInfo *info;
+
+  if (idx < 0 || idx >= viewport_info->views->len)
+    return FALSE;
+
+  info = &g_array_index (viewport_info->views, ViewInfo, idx);
+  if (rect)
+    *rect = info->rect;
+  if (scale)
+    *scale = info->scale;
+
+  return TRUE;
+}
+
+static gboolean
+view_has_neighbor (cairo_rectangle_int_t *view,
+                   cairo_rectangle_int_t *neighbor,
+                   MetaDisplayDirection   neighbor_direction)
+{
+  switch (neighbor_direction)
+    {
+    case META_DISPLAY_RIGHT:
+      if (neighbor->x == (view->x + view->width) &&
+          meta_rectangle_vert_overlap (neighbor, view))
+        return TRUE;
+      break;
+    case META_DISPLAY_LEFT:
+      if (view->x == (neighbor->x + neighbor->width) &&
+          meta_rectangle_vert_overlap (neighbor, view))
+        return TRUE;
+      break;
+    case META_DISPLAY_UP:
+      if (view->y == (neighbor->y + neighbor->height) &&
+          meta_rectangle_horiz_overlap (neighbor, view))
+        return TRUE;
+      break;
+    case META_DISPLAY_DOWN:
+      if (neighbor->y == (view->y + view->height) &&
+          meta_rectangle_horiz_overlap (neighbor, view))
+        return TRUE;
+      break;
+    }
+
+  return FALSE;
+}
+
+int
+meta_viewport_info_get_neighbor (MetaViewportInfo     *viewport_info,
+                                 int                   idx,
+                                 MetaDisplayDirection  direction)
+{
+  cairo_rectangle_int_t rect;
+  int i;
+
+  if (!meta_viewport_info_get_view_info (viewport_info, idx, &rect, NULL))
+    return -1;
+
+  for (i = 0; i < viewport_info->views->len; i++)
+    {
+      ViewInfo *info = &g_array_index (viewport_info->views, ViewInfo, i);
+
+      if (idx == i)
+        continue;
+      if (view_has_neighbor (&rect, &info->rect, direction))
+        return i;
+    }
+
+  return -1;
+}
+
+int
+meta_viewport_info_get_num_views (MetaViewportInfo *info)
+{
+  return info->views->len;
+}

src/backends/meta-viewport-info.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2020 Red Hat
+ *
+ * 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.
+ *
+ * Written by:
+ *     Carlos Garnacho <carlosg@gnome.org>
+ */
+
+#ifndef META_VIEWPORT_INFO_H
+#define META_VIEWPORT_INFO_H
+
+#include <cairo.h>
+#include <glib-object.h>
+
+#include "meta/display.h"
+
+#define META_TYPE_VIEWPORT_INFO (meta_viewport_info_get_type ())
+G_DECLARE_FINAL_TYPE (MetaViewportInfo, meta_viewport_info,
+                      META, VIEWPORT_INFO, GObject)
+
+MetaViewportInfo * meta_viewport_info_new (cairo_rectangle_int_t *views,
+                                           float                 *scales,
+                                           int                    n_views);
+
+int meta_viewport_info_get_view_at (MetaViewportInfo *info,
+                                    float             x,
+                                    float             y);
+
+gboolean meta_viewport_info_get_view_info (MetaViewportInfo      *viewport_info,
+                                           int                    idx,
+                                           cairo_rectangle_int_t *rect,
+                                           float                 *scale);
+
+int meta_viewport_info_get_neighbor (MetaViewportInfo     *info,
+                                     int                   idx,
+                                     MetaDisplayDirection  direction);
+
+int meta_viewport_info_get_num_views (MetaViewportInfo *info);
+
+#endif /* META_VIEWPORT_INFO_H */

src/meson.build

@@ -233,6 +233,8 @@ mutter_sources = [
   'backends/meta-settings-private.h',
   'backends/meta-stage.c',
   'backends/meta-stage-private.h',
+  'backends/meta-viewport-info.c',
+  'backends/meta-viewport-info.h',
   'backends/x11/cm/meta-backend-x11-cm.c',
   'backends/x11/cm/meta-backend-x11-cm.h',
   'backends/x11/cm/meta-cursor-sprite-xfixes.c',