[gnome-flashback] monitor-manager: add gf_monitor_manager_get_monitor_matrix

[Alberts Muktupāvels <muktupavels src gnome org>]

commit d0ae823ef2322ed66a008c85a4abc9c89f0dc624
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Sep 29 13:48:22 2017 +0300

    monitor-manager: add gf_monitor_manager_get_monitor_matrix

 backends/gf-monitor-manager-private.h |    4 ++
 backends/gf-monitor-manager.c         |   65 +++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 0 deletions(-)
---
diff --git a/backends/gf-monitor-manager-private.h b/backends/gf-monitor-manager-private.h
index 51db111..0c43e77 100644
--- a/backends/gf-monitor-manager-private.h
+++ b/backends/gf-monitor-manager-private.h
@@ -180,6 +180,10 @@ gboolean                    gf_monitor_manager_has_hotplug_mode_update      (GfM
 void                        gf_monitor_manager_read_current_state           (GfMonitorManager            
*manager);
 void                        gf_monitor_manager_on_hotplug                   (GfMonitorManager            
*manager);
 
+gboolean                    gf_monitor_manager_get_monitor_matrix           (GfMonitorManager            
*manager,
+                                                                             GfLogicalMonitor            
*logical_monitor,
+                                                                             gfloat                       
matrix[6]);
+
 void                        gf_monitor_manager_tiled_monitor_added          (GfMonitorManager            
*manager,
                                                                              GfMonitor                   
*monitor);
 
diff --git a/backends/gf-monitor-manager.c b/backends/gf-monitor-manager.c
index a796650..533f852 100644
--- a/backends/gf-monitor-manager.c
+++ b/backends/gf-monitor-manager.c
@@ -83,6 +83,54 @@ G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GfMonitorManager, gf_monitor_manager, GF_DBUS_
                                   G_ADD_PRIVATE (GfMonitorManager)
                                   G_IMPLEMENT_INTERFACE (GF_DBUS_TYPE_DISPLAY_CONFIG, 
gf_monitor_manager_display_config_init))
 
+/* Array index matches GfMonitorTransform */
+static gfloat transform_matrices[][6] =
+  {
+    {  1,  0,  0,  0,  1,  0 }, /* normal */
+    {  0, -1,  1,  1,  0,  0 }, /* 90° */
+    { -1,  0,  1,  0, -1,  1 }, /* 180° */
+    {  0,  1,  0, -1,  0,  1 }, /* 270° */
+    { -1,  0,  1,  0,  1,  0 }, /* normal flipped */
+    {  0,  1,  0,  1,  0,  0 }, /* 90° flipped */
+    {  1,  0,  0,  0, -1,  1 }, /* 180° flipped */
+    {  0, -1,  1, -1,  0,  1 }, /* 270° flipped */
+  };
+
+static inline void
+multiply_matrix (gfloat a[6],
+                 gfloat b[6],
+                 gfloat res[6])
+{
+  res[0] = a[0] * b[0] + a[1] * b[3];
+  res[1] = a[0] * b[1] + a[1] * b[4];
+  res[2] = a[0] * b[2] + a[1] * b[5] + a[2];
+  res[3] = a[3] * b[0] + a[4] * b[3];
+  res[4] = a[3] * b[1] + a[4] * b[4];
+  res[5] = a[3] * b[2] + a[4] * b[5] + a[5];
+}
+
+static gboolean
+calculate_viewport_matrix (GfMonitorManager *manager,
+                           GfLogicalMonitor *logical_monitor,
+                           gfloat            viewport[6])
+{
+  gfloat x, y, width, height;
+
+  x = (gfloat) logical_monitor->rect.x / manager->screen_width;
+  y = (gfloat) logical_monitor->rect.y / manager->screen_height;
+  width  = (gfloat) logical_monitor->rect.width / manager->screen_width;
+  height = (gfloat) logical_monitor->rect.height / manager->screen_height;
+
+  viewport[0] = width;
+  viewport[1] = 0.0f;
+  viewport[2] = x;
+  viewport[3] = 0.0f;
+  viewport[4] = height;
+  viewport[5] = y;
+
+  return TRUE;
+}
+
 static void
 power_save_mode_changed (GfMonitorManager *manager,
                          GParamSpec       *pspec,
@@ -2220,6 +2268,23 @@ gf_monitor_manager_on_hotplug (GfMonitorManager *manager)
   gf_monitor_manager_ensure_configured (manager);
 }
 
+gboolean
+gf_monitor_manager_get_monitor_matrix (GfMonitorManager *manager,
+                                       GfLogicalMonitor *logical_monitor,
+                                       gfloat            matrix[6])
+{
+  GfMonitorTransform transform;
+  gfloat viewport[9];
+
+  if (!calculate_viewport_matrix (manager, logical_monitor, viewport))
+    return FALSE;
+
+  transform = logical_monitor->transform;
+  multiply_matrix (viewport, transform_matrices[transform], matrix);
+
+  return TRUE;
+}
+
 void
 gf_monitor_manager_tiled_monitor_added (GfMonitorManager *manager,
                                         GfMonitor        *monitor)