Add color space get/set for cairo

Add a centralized place to attach color space to.

Nothing uses that information yet, but all the
backends do set it.

gdk/broadway/gdkcairocontext-broadway.c

@@ -46,9 +46,10 @@ gdk_broadway_cairo_context_begin_frame (GdkDrawContext *draw_context,
   width = gdk_surface_get_width (surface);
   height = gdk_surface_get_height (surface);
   scale = gdk_surface_get_scale_factor (surface);
-  self->paint_surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
-                                                    width * scale, height * scale);
-  cairo_surface_set_device_scale (self->paint_surface, scale, scale);
+
+  self->paint_surface = gdk_surface_create_similar_surface (surface,
+                                                            CAIRO_CONTENT_COLOR_ALPHA,
+                                                            width * scale, height *scale);
 
   repaint_region = cairo_region_create_rectangle (&(cairo_rectangle_int_t) { 0, 0, width, height });
   cairo_region_union (region, repaint_region);

gdk/gdkcairo.c

@@ -21,6 +21,7 @@
 
 #include "gdkrgba.h"
 #include "gdktexture.h"
+#include "gdkcolorstate.h"
 
 #include <math.h>
 
@@ -303,3 +304,98 @@ gdk_cairo_region_create_from_surface (cairo_surface_t *surface)
 
   return region;
 }
+
+static cairo_user_data_key_t color_state_key;
+
+/**
+ * gdk_cairo_surface_set_color_state:
+ * @surface: a surface
+ * @color_state: the color state to attach to the surface
+ *
+ * Attaches a `GdkColorState` to the Cairo surface.
+ *
+ * This is just auxiliary data for use by GTK, no Cairo functions
+ * do interact with this information.
+ *
+ * Note that all Cairo compositing operations are assumed to happen
+ * in a linear RGB color state, so if you want to use the surface
+ * as a target for rendering in a color managed way, you should use
+ * such a color state.
+ *
+ * The default color state is assumed to be sRGB, which is not
+ * linear.
+ *
+ * Since: 4.16
+ */
+void
+gdk_cairo_surface_set_color_state (cairo_surface_t *surface,
+                                   GdkColorState   *color_state)
+{
+  g_return_if_fail (surface != NULL);
+  g_return_if_fail (color_state != NULL);
+
+  cairo_surface_set_user_data (surface,
+                               &color_state_key,
+                               gdk_color_state_ref (color_state),
+                               (cairo_destroy_func_t) gdk_color_state_unref);
+}
+
+/**
+ * gdk_cairo_surface_get_color_state:
+ * @surface: a surface
+ *
+ * Gets the color state GTK assumes for the surface.
+ *
+ * See [method@Gdk.CairoSurface.set_color_state] for details.
+ *
+ * Returns: (transfer none): the color state
+ *
+ * Since: 4.16
+ */
+GdkColorState *
+gdk_cairo_surface_get_color_state (cairo_surface_t *surface)
+{
+  GdkColorState *color_state;
+
+  g_return_val_if_fail (surface != NULL, gdk_color_state_get_srgb ());
+
+  color_state = cairo_surface_get_user_data (surface, &color_state_key);
+  if (color_state == NULL)
+    color_state = gdk_color_state_get_srgb ();
+
+  return color_state;
+}
+
+/**
+ * gdk_cairo_get_color_state:
+ * @cr: a cairo context
+ *
+ * Gets the color state GTK assumes for the cairo context.
+ *
+ * Returns: (transfer none): the color state
+ *
+ * Since: 4.16
+ */
+GdkColorState *
+gdk_cairo_get_color_state (cairo_t *cr)
+{
+  GdkColorState *color_state;
+  cairo_surface_t *surface;
+
+  g_return_val_if_fail (cr != NULL, gdk_color_state_get_srgb ());
+
+  surface = cairo_get_group_target (cr);
+  color_state = cairo_surface_get_user_data (surface, &color_state_key);
+  if (color_state != NULL)
+    return color_state;
+
+  /* theoretically, we should walk the whole group stack, but I don't
+   * think Cairo lets us do that
+   */
+  surface = cairo_get_target (cr);
+  color_state = cairo_surface_get_user_data (surface, &color_state_key);
+  if (color_state != NULL)
+    return color_state;
+
+  return gdk_color_state_get_srgb ();
+}

gdk/gdkcairo.h

@@ -44,9 +44,15 @@ void       gdk_cairo_region             (cairo_t              *cr,
                                          const cairo_region_t *region);
 
 GDK_AVAILABLE_IN_ALL
-cairo_region_t *
-           gdk_cairo_region_create_from_surface
-                                        (cairo_surface_t      *surface);
+cairo_region_t *        gdk_cairo_region_create_from_surface    (cairo_surface_t        *surface);
+
+GDK_AVAILABLE_IN_4_16
+void                    gdk_cairo_surface_set_color_state       (cairo_surface_t        *surface,
+                                                                 GdkColorState          *color_state);
+GDK_AVAILABLE_IN_4_16
+GdkColorState *         gdk_cairo_surface_get_color_state       (cairo_surface_t        *surface);
+GDK_AVAILABLE_IN_4_16
+GdkColorState *         gdk_cairo_get_color_state               (cairo_t                *cr);
 
 GDK_DEPRECATED_IN_4_6_FOR(gdk_gl_texture_new)
 void       gdk_cairo_draw_from_gl (cairo_t              *cr,

gdk/gdksurface.c

@@ -30,6 +30,8 @@
 #include "gdksurface.h"
 
 #include "gdkprivate.h"
+#include "gdkcolorstate.h"
+#include "gdkcairo.h"
 #include "gdkcontentprovider.h"
 #include "gdkdeviceprivate.h"
 #include "gdkdisplayprivate.h"
@@ -2361,6 +2363,7 @@ gdk_surface_create_similar_surface (GdkSurface      *surface,
                                                 content == CAIRO_CONTENT_ALPHA ? CAIRO_FORMAT_A8 : CAIRO_FORMAT_ARGB32,
                                                 width * scale, height * scale);
   cairo_surface_set_device_scale (similar_surface, scale, scale);
+  gdk_cairo_surface_set_color_state (similar_surface, gdk_surface_get_color_state (surface));
 
   return similar_surface;
 }

gdk/gdktexture.c

@@ -45,6 +45,7 @@
 #include "gdkpaintable.h"
 #include "gdksnapshot.h"
 #include "gdkcolorstate.h"
+#include "gdkcairo.h"
 
 #include <graphene.h>
 #include "loaders/gdkpngprivate.h"
@@ -455,11 +456,12 @@ gdk_texture_new_for_surface (cairo_surface_t *surface)
                                       (GDestroyNotify) cairo_surface_destroy,
                                       cairo_surface_reference (surface));
 
-  texture = gdk_memory_texture_new (cairo_image_surface_get_width (surface),
-                                    cairo_image_surface_get_height (surface),
-                                    GDK_MEMORY_DEFAULT,
-                                    bytes,
-                                    cairo_image_surface_get_stride (surface));
+  texture = gdk_memory_texture_new_with_color_state (cairo_image_surface_get_width (surface),
+                                                     cairo_image_surface_get_height (surface),
+                                                     GDK_MEMORY_DEFAULT,
+                                                     gdk_cairo_surface_get_color_state (surface),
+                                                     bytes,
+                                                     cairo_image_surface_get_stride (surface));
 
   g_bytes_unref (bytes);
 

gdk/wayland/gdkcairocontext-wayland.c

@@ -158,6 +158,9 @@ gdk_wayland_cairo_context_begin_frame (GdkDrawContext *draw_context,
   else
     self->paint_surface = gdk_wayland_cairo_context_create_surface (self);
 
+  gdk_cairo_surface_set_color_state (self->paint_surface,
+                                     gdk_surface_get_color_state (gdk_draw_context_get_surface (draw_context)));
+
   surface_region = gdk_wayland_cairo_context_surface_get_region (self->paint_surface);
   if (surface_region)
     cairo_region_union (region, surface_region);

gdk/win32/gdkcairocontext-win32.c

@@ -47,6 +47,7 @@ create_cairo_surface_for_surface (GdkSurface *surface,
 
   cairo_surface = cairo_win32_surface_create_with_format (hdc, CAIRO_FORMAT_ARGB32);
   cairo_surface_set_device_scale (cairo_surface, scale, scale);
+  gdk_cairo_surface_set_color_state (cairo_surface, gdk_surface_get_color_state (surface));
 
   return cairo_surface;
 }

gdk/x11/gdkcairocontext-x11.c

@@ -49,6 +49,7 @@ create_cairo_surface_for_surface (GdkSurface *surface)
                                              gdk_surface_get_width (surface) * scale,
                                              gdk_surface_get_height (surface) * scale);
   cairo_surface_set_device_scale (cairo_surface, scale, scale);
+  gdk_cairo_surface_set_color_state (cairo_surface, gdk_surface_get_color_state (surface));
 
   return cairo_surface;
 }