[mutter] monitor-manager: Add method to find an output matrix

[Jasper St. Pierre <jstpierre src gnome org>]

commit 71c4138933af72302f256c7dc7552ba86c36b23b
Author: Carlos Garnacho <carlosg gnome org>
Date:   Thu Dec 11 18:14:00 2014 +0100

    monitor-manager: Add method to find an output matrix
    
    This will be useful to determine input device matrices for touchscreens
    and tablets.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=739397

 src/backends/meta-monitor-manager.c |   65 +++++++++++++++++++++++++++++++++++
 src/backends/meta-monitor-manager.h |    4 ++
 2 files changed, 69 insertions(+), 0 deletions(-)
---
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 3e6207f..3f11716 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -45,6 +45,18 @@ enum {
   SIGNALS_LAST
 };
 
+/* Array index matches MetaMonitorTransform */
+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 int signals[SIGNALS_LAST];
 
 static void meta_monitor_manager_display_config_init (MetaDBusDisplayConfigIface *iface);
@@ -1262,3 +1274,56 @@ meta_monitor_manager_on_hotplug (MetaMonitorManager *manager)
   if (!applied_config)
     meta_monitor_config_make_default (manager->config, manager);
 }
+
+static gboolean
+calculate_viewport_matrix (MetaMonitorManager *manager,
+                           MetaOutput         *output,
+                           gfloat              viewport[6])
+{
+  gfloat x, y, width, height;
+
+  if (!output->crtc)
+    return FALSE;
+
+  x = (float) output->crtc->rect.x / manager->screen_width;
+  y = (float) output->crtc->rect.y / manager->screen_height;
+  width  = (float) output->crtc->rect.width / manager->screen_width;
+  height = (float) output->crtc->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 inline void
+multiply_matrix (float a[6],
+                float b[6],
+                float 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];
+}
+
+gboolean
+meta_monitor_manager_get_monitor_matrix (MetaMonitorManager *manager,
+                                         MetaOutput         *output,
+                                         gfloat              matrix[6])
+{
+  gfloat viewport[9];
+
+  if (!calculate_viewport_matrix (manager, output, viewport))
+    return FALSE;
+
+  multiply_matrix (viewport, transform_matrices[output->crtc->transform],
+                   matrix);
+  return TRUE;
+}
diff --git a/src/backends/meta-monitor-manager.h b/src/backends/meta-monitor-manager.h
index b4a0eeb..d1f1530 100644
--- a/src/backends/meta-monitor-manager.h
+++ b/src/backends/meta-monitor-manager.h
@@ -371,6 +371,10 @@ gboolean           meta_monitor_manager_has_hotplug_mode_update (MetaMonitorMana
 void               meta_monitor_manager_read_current_config (MetaMonitorManager *manager);
 void               meta_monitor_manager_on_hotplug (MetaMonitorManager *manager);
 
+gboolean           meta_monitor_manager_get_monitor_matrix (MetaMonitorManager *manager,
+                                                            MetaOutput         *output,
+                                                            gfloat              matrix[6]);
+
 /* Returns true if transform causes width and height to be inverted
    This is true for the odd transforms in the enum */
 static inline gboolean