Use the window system's color transform matrix, when available

When the window system supports color transform matrices, use libcolord to
compute an adaptation matrix to convert from an sRGB reference profile to the
measured profile for each display. Use gnome_rr_output_set_color_transform from
libgnome-desktop to apply that matrix to the window system.

Modify the code that sets the _ICC_PROFILE root window property to hard-code a
standard sRGB reference profile when a color transform is in use; color-aware
applications should not try to apply their own correction if the window system
is already doing it.

2 files changed, 138 insertions, 5 deletions

diff --git a/meson.build b/meson.build
index 7dbee64b..41378a5d 100644
--- a/meson.build
+++ b/meson.build
@@ -93,7 +93,7 @@ glib_dep = dependency('glib-2.0', version: '>=' + glib_min_version)
 geocode_glib_dep = dependency('geocode-glib-1.0', version: '>= 3.10.0')
 gio_dep = dependency('gio-2.0', version: '>= 2.53.0')
 gio_unix_dep = dependency('gio-unix-2.0')
-gnome_desktop_dep = dependency('gnome-desktop-3.0', version: '>= 3.34.2')
+gnome_desktop_dep = dependency('gnome-desktop-3.0', version: '>= 3.37.1')
 gsettings_desktop_dep = dependency('gsettings-desktop-schemas', version: '>= 3.35.91')
 gtk_dep = dependency('gtk+-3.0', version: '>= 3.15.3')
 gtk_x11_dep = dependency('gtk+-x11-3.0')
@@ -227,7 +227,7 @@ config_h.set10('HAVE_NETWORK_MANAGER', enable_network_manager)
 # colord
 enable_colord = get_option('colord')
 if enable_colord
-  colord_dep = dependency('colord', version: '>= 1.3.5')
+  colord_dep = dependency('colord', version: '>= 1.4.5')
 endif
 
 gnome = import('gnome')
diff --git a/plugins/color/gsd-color-state.c b/plugins/color/gsd-color-state.c
index 746cf230..1088a2db 100644
--- a/plugins/color/gsd-color-state.c
+++ b/plugins/color/gsd-color-state.c
@@ -2,6 +2,7 @@
  *
  * Copyright (C) 2007 William Jon McCann <mccann@jhu.edu>
  * Copyright (C) 2011-2013 Richard Hughes <richard@hughsie.com>
+ * Copyright (C) 2020 NVIDIA CORPORATION
  *
  * 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
@@ -26,6 +27,7 @@
 #include <stdlib.h>
 #include <lcms2.h>
 #include <canberra-gtk.h>
+#include <math.h>
 
 #define GNOME_DESKTOP_USE_UNSTABLE_API
 #include <libgnome-desktop/gnome-rr.h>
@@ -126,8 +128,47 @@ gcm_session_get_output_edid (GsdColorState *state, GnomeRROutput *output, GError
         return edid;
 }
 
+static CdIcc *
+gcm_get_srgb_icc (GError **error)
+{
+        /* load the reference sRGB profile */
+        CdIcc *srgb_icc = cd_icc_new ();
+        if (!srgb_icc)
+                return NULL;
+
+        if (!cd_icc_create_default_full (srgb_icc,
+                                         CD_ICC_LOAD_FLAGS_PRIMARIES,
+                                         error)) {
+                g_object_unref (srgb_icc);
+                return NULL;
+        }
+
+        return srgb_icc;
+}
+
+static char *
+gcm_get_srgb_bytes (gsize *length,
+                    GError **error)
+{
+        g_autoptr(CdIcc) srgb_icc = NULL;
+        GBytes *bytes;
+
+        srgb_icc = gcm_get_srgb_icc (error);
+        if (srgb_icc == NULL)
+                return NULL;
+
+        bytes = cd_icc_save_data (srgb_icc,
+                                  CD_ICC_SAVE_FLAGS_NONE,
+                                  error);
+        if (bytes == NULL)
+                return NULL;
+
+        return g_bytes_unref_to_data (bytes, length);
+}
+
 static gboolean
 gcm_session_screen_set_icc_profile (GsdColorState *state,
+                                    GnomeRROutput *output,
                                     const gchar *filename,
                                     GError **error)
 {
@@ -145,9 +186,21 @@ gcm_session_screen_set_icc_profile (GsdColorState *state,
 
         g_debug ("setting root window ICC profile atom from %s", filename);
 
-        /* get contents of file */
-        if (!g_file_get_contents (filename, &data, &length, error))
-                return FALSE;
+        if (gnome_rr_output_supports_color_transform (output)) {
+                /*
+                 * If the window system supports color transforms, then
+                 * applications should use the standard sRGB color profile and
+                 * the window system will take care of converting colors to
+                 * match the output device's measured color profile.
+                 */
+                data = gcm_get_srgb_bytes (&length, error);
+                if (data == NULL)
+                        return FALSE;
+        } else {
+                /* get contents of file */
+                if (!g_file_get_contents (filename, &data, &length, error))
+                        return FALSE;
+        }
 
         /* set profile property */
         gdk_property_change (state->gdk_window,
@@ -432,6 +485,71 @@ out:
         return ret;
 }
 
+static uint64_t
+gcm_double_to_ctmval (double value)
+{
+        uint64_t sign = value < 0;
+        double integer, fractional;
+
+        if (sign)
+                value = -value;
+
+        fractional = modf (value, &integer);
+
+        return sign << 63 |
+               (uint64_t) integer << 32 |
+               (uint64_t) (fractional * 0xffffffffUL);
+}
+
+static GnomeRRCTM
+gcm_mat33_to_ctm (CdMat3x3 matrix)
+{
+        GnomeRRCTM ctm;
+
+        /*
+         * libcolord generates a matrix containing double values. RandR's CTM
+         * property expects values in S31.32 fixed-point sign-magnitude format
+         */
+        ctm.matrix[0] = gcm_double_to_ctmval (matrix.m00);
+        ctm.matrix[1] = gcm_double_to_ctmval (matrix.m01);
+        ctm.matrix[2] = gcm_double_to_ctmval (matrix.m02);
+        ctm.matrix[3] = gcm_double_to_ctmval (matrix.m10);
+        ctm.matrix[4] = gcm_double_to_ctmval (matrix.m11);
+        ctm.matrix[5] = gcm_double_to_ctmval (matrix.m12);
+        ctm.matrix[6] = gcm_double_to_ctmval (matrix.m20);
+        ctm.matrix[7] = gcm_double_to_ctmval (matrix.m21);
+        ctm.matrix[8] = gcm_double_to_ctmval (matrix.m22);
+
+        return ctm;
+}
+
+static gboolean
+gcm_set_csc_matrix (GnomeRROutput *output,
+                    CdProfile *profile,
+                    GError **error)
+{
+        g_autoptr(CdIcc) icc = NULL;
+        g_autoptr(CdIcc) srgb_icc = NULL;
+        CdMat3x3 csc;
+        GnomeRRCTM ctm;
+
+        /* open file */
+        icc = cd_profile_load_icc (profile, CD_ICC_LOAD_FLAGS_PRIMARIES, NULL,
+                                   error);
+        if (icc == NULL)
+                return FALSE;
+
+        srgb_icc = gcm_get_srgb_icc (error);
+        if (srgb_icc == NULL)
+                return FALSE;
+
+        if (!cd_icc_utils_get_adaptation_matrix (icc, srgb_icc, &csc, error))
+                return FALSE;
+
+        ctm = gcm_mat33_to_ctm (csc);
+        return gnome_rr_output_set_color_transform (output, ctm, error);
+}
+
 static GPtrArray *
 gcm_session_generate_vcgt (CdProfile *profile, guint color_temperature, guint size)
 {
@@ -805,6 +923,7 @@ gcm_session_device_assign_profile_connect_cb (GObject *object,
         ret = gcm_session_use_output_profile_for_screen (state, output);
         if (ret) {
                 ret = gcm_session_screen_set_icc_profile (state,
+                                                          output,
                                                           filename,
                                                           &error);
                 if (!ret) {
@@ -840,6 +959,20 @@ gcm_session_device_assign_profile_connect_cb (GObject *object,
                         goto out;
                 }
         }
+
+        if (gnome_rr_output_supports_color_transform (output)) {
+                ret = gcm_set_csc_matrix (output,
+                                          profile,
+                                          &error);
+                if (!ret) {
+                        g_warning ("failed to set %s color transform matrix: %s",
+                                   cd_device_get_id (helper->device),
+                                   error->message);
+                        g_error_free (error);
+                        goto out;
+                }
+        }
+
 out:
         gcm_session_async_helper_free (helper);
 }