[gtk/wip/otte/color-profiles: 3/4] FIXME: Add crude color management impl for cairo

[Benjamin Otte <otte src gnome org>]

commit ed0047352f3adf0aec7799175b958d7ba3af9f26
Author: Benjamin Otte <otte redhat com>
Date:   Sun Sep 26 02:44:54 2021 +0200

    FIXME: Add crude color management impl for cairo
    
    It runs at 2fps here, but it runs.

 gsk/gskcairorenderer.c | 43 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)
---
diff --git a/gsk/gskcairorenderer.c b/gsk/gskcairorenderer.c
index 074b54b97f..34625c66a8 100644
--- a/gsk/gskcairorenderer.c
+++ b/gsk/gskcairorenderer.c
@@ -25,6 +25,8 @@
 #include "gskdebugprivate.h"
 #include "gskrendererprivate.h"
 #include "gskrendernodeprivate.h"
+
+#include "gdk/gdkcolorprofileprivate.h"
 #include "gdk/gdktextureprivate.h"
 
 #ifdef G_ENABLE_DEBUG
@@ -40,6 +42,7 @@ struct _GskCairoRenderer
 
   GdkCairoContext *cairo_context;
 
+  gboolean color_managed;
 #ifdef G_ENABLE_DEBUG
   ProfileTimers profile_timers;
 #endif
@@ -77,8 +80,8 @@ gsk_cairo_renderer_do_render (GskRenderer   *renderer,
                               cairo_t       *cr,
                               GskRenderNode *root)
 {
-#ifdef G_ENABLE_DEBUG
   GskCairoRenderer *self = GSK_CAIRO_RENDERER (renderer);
+#ifdef G_ENABLE_DEBUG
   GskProfiler *profiler;
   gint64 cpu_time;
 #endif
@@ -88,7 +91,41 @@ gsk_cairo_renderer_do_render (GskRenderer   *renderer,
   gsk_profiler_timer_begin (profiler, self->profile_timers.cpu_time);
 #endif
 
-  gsk_render_node_draw (root, cr);
+  if (!self->color_managed ||
+      gdk_color_profile_is_linear (gdk_cairo_get_color_profile (cr)))
+    {
+      gsk_render_node_draw (root, cr);
+    }
+  else
+    {
+      GdkSurface *surface = gsk_renderer_get_surface (renderer);
+      cairo_surface_t *cairo_surface;
+      cairo_t *cr2;
+      GdkTexture *color_correct;
+
+      /* We can't use cairo_push_group() here, because we'd lose the
+       * color profile information. */
+      cairo_surface = gdk_surface_create_similar_surface (surface,
+                                                          CAIRO_CONTENT_COLOR_ALPHA,
+                                                          gdk_surface_get_width (surface),
+                                                          gdk_surface_get_height (surface));
+      gdk_cairo_surface_set_color_profile (cairo_surface,
+                                           gdk_color_profile_get_srgb_linear ());
+
+      cr2 = cairo_create (cairo_surface);
+      gsk_render_node_draw (root, cr2);
+      cairo_destroy (cr2);
+
+      color_correct = gdk_texture_new_for_surface (cairo_surface);
+      cairo_surface_destroy (cairo_surface);
+      cairo_surface = gdk_texture_download_surface (color_correct,
+                                                    gdk_cairo_get_color_profile (cr));
+      g_object_unref (color_correct);
+
+      cairo_set_source_surface (cr, cairo_surface, 0, 0);
+      cairo_paint (cr);
+      cairo_surface_destroy (cairo_surface);
+    }
 
 #ifdef G_ENABLE_DEBUG
   cpu_time = gsk_profiler_timer_end (profiler, self->profile_timers.cpu_time);
@@ -173,6 +210,8 @@ gsk_cairo_renderer_class_init (GskCairoRendererClass *klass)
 static void
 gsk_cairo_renderer_init (GskCairoRenderer *self)
 {
+  self->color_managed = TRUE;
+
 #ifdef G_ENABLE_DEBUG
   GskProfiler *profiler = gsk_renderer_get_profiler (GSK_RENDERER (self));