[gtk/wip/otte/color-profiles: 7/18] gdk: Add srgb_linear color profile

[Benjamin Otte <otte src gnome org>]

commit 2f958e5b89331acae53620af7d1bcc30fa08103e
Author: Benjamin Otte <otte redhat com>
Date:   Sun Sep 26 02:42:40 2021 +0200

    gdk: Add srgb_linear color profile
    
    ... and gdk_color_profile_is_linear()

 gdk/gdkcolorprofile.c        | 69 ++++++++++++++++++++++++++++++++++++++++++++
 gdk/gdkcolorprofile.h        |  2 ++
 gdk/gdkcolorprofileprivate.h |  2 ++
 3 files changed, 73 insertions(+)
---
diff --git a/gdk/gdkcolorprofile.c b/gdk/gdkcolorprofile.c
index d0b06d4071..6722b44b6f 100644
--- a/gdk/gdkcolorprofile.c
+++ b/gdk/gdkcolorprofile.c
@@ -214,6 +214,49 @@ gdk_color_profile_get_srgb (void)
   return srgb_profile;
 }
 
+/*<private>
+ * gdk_color_profile_get_srgb_linear:
+ *
+ * Returns the linear color profile corresponding to the sRGB
+ * color space.
+ *
+ * It can display the same colors, but it does not have a gamma curve.
+ *
+ * Returns: (transfer none): the color profile for the linear sRGB
+ *   color space.
+ */
+GdkColorProfile *
+gdk_color_profile_get_srgb_linear (void)
+{
+  static GdkColorProfile *srgb_linear_profile;
+
+  if (g_once_init_enter (&srgb_linear_profile))
+    {
+      cmsToneCurve *curve;
+      cmsHPROFILE lcms_profile;
+      GdkColorProfile *new_profile;
+
+      curve = cmsBuildGamma (NULL, 1.0);
+      lcms_profile = cmsCreateRGBProfile (&(cmsCIExyY) {
+                                            0.3127, 0.3290, 1.0
+                                          },
+                                          &(cmsCIExyYTRIPLE) {
+                                            { 0.6400, 0.3300, 1.0 },
+                                            { 0.3000, 0.6000, 1.0 },
+                                            { 0.1500, 0.0600, 1.0 }
+                                          },
+                                          (cmsToneCurve*[3]) { curve, curve, curve });
+      cmsFreeToneCurve (curve);
+
+      new_profile = gdk_color_profile_new_from_lcms_profile (lcms_profile, NULL);
+      g_assert (new_profile);
+
+      g_once_init_leave (&srgb_linear_profile, new_profile);
+    }
+
+  return srgb_linear_profile;
+}
+
 /**
  * gdk_color_profile_new_from_icc_bytes:
  * @icc_profile: The ICC profiles given as a `GBytes`
@@ -298,6 +341,32 @@ gdk_color_profile_get_lcms_profile (GdkColorProfile *self)
   return self->lcms_profile;
 }
 
+/**
+ * gdk_color_profile_is_linear:
+ * @profile: a `GdkColorProfile`
+ *
+ * Checks if the given profile is linear.
+ * GTK tries to do compositing in a linear profile.
+ *
+ * Some profiles may be linear, but it is not possible to
+ * determine this easily. In those cases %FALSE will be returned.
+ *
+ * Returns: %TRUE if the profile can be proven linear
+ *
+ * Since: 4.6
+ */
+gboolean
+gdk_color_profile_is_linear (GdkColorProfile *self)
+{
+  g_return_val_if_fail (GDK_IS_COLOR_PROFILE (self), FALSE);
+
+  /* FIXME: Make this useful */
+  if (self == gdk_color_profile_get_srgb_linear ())
+    return TRUE;
+
+  return FALSE;
+}
+
 /**
  * gdk_color_profile_equal:
  * @profile1: (type GdkColorProfile): a `GdkColorProfile`
diff --git a/gdk/gdkcolorprofile.h b/gdk/gdkcolorprofile.h
index 66cb59dab1..189363f7f2 100644
--- a/gdk/gdkcolorprofile.h
+++ b/gdk/gdkcolorprofile.h
@@ -54,6 +54,8 @@ GdkColorProfile *            gdk_color_profile_new_from_icc_bytes         (GByte
 GDK_AVAILABLE_IN_4_6
 GBytes *                     gdk_color_profile_get_icc_profile            (GdkColorProfile      *self);
 
+GDK_AVAILABLE_IN_4_6
+gboolean                     gdk_color_profile_is_linear                  (GdkColorProfile      *self) 
G_GNUC_PURE;
 GDK_AVAILABLE_IN_4_6
 gboolean                     gdk_color_profile_equal                      (gconstpointer         profile1,
                                                                            gconstpointer         profile2);
diff --git a/gdk/gdkcolorprofileprivate.h b/gdk/gdkcolorprofileprivate.h
index 48bf6fd3e1..16a02196ed 100644
--- a/gdk/gdkcolorprofileprivate.h
+++ b/gdk/gdkcolorprofileprivate.h
@@ -7,6 +7,8 @@
 
 G_BEGIN_DECLS
 
+GdkColorProfile *            gdk_color_profile_get_srgb_linear            (void) G_GNUC_CONST;
+
 GdkColorProfile *            gdk_color_profile_new_from_lcms_profile      (cmsHPROFILE           
lcms_profile,
                                                                            GError              **error);