gdk_pixbuf_get_from_surface.h: new file copy/pasted from GDK

This contains the implementation of the (deprecated) function
gdk_pixbuf_get_from_surface(). The main reason we want it inline is to
avoid the need to link with GTK/GDK itself in our pixbuf loader, on
which GDK and GTK should depend. Specifically we don't want to have to
worry about mismatched major versions of GTK.

diff --git a/gdk_pixbuf_get_from_surface.h b/gdk_pixbuf_get_from_surface.h
new file mode 100644 (file)
index 0000000..c3a5f96
--- /dev/null
+++ b/gdk_pixbuf_get_from_surface.h
@@ -0,0 +1,194 @@
+/* This file contains gdk_pixbuf_get_from_surface() and its
+ * dependencies, copy & pasted from gdk/deprecated/gdkpixbuf.c.
+ * Having it inline means that we don't have to link against a
+ * specific version of GTK, risking that (say) a gtk4-linked
+ * pixbuf loader gets used on a gtk3 desktop environment.
+ */
+static cairo_format_t
+gdk_cairo_format_for_content (cairo_content_t content)
+{
+  switch (content)
+    {
+    case CAIRO_CONTENT_COLOR:
+      return CAIRO_FORMAT_RGB24;
+    case CAIRO_CONTENT_ALPHA:
+      return CAIRO_FORMAT_A8;
+    case CAIRO_CONTENT_COLOR_ALPHA:
+    default:
+      return CAIRO_FORMAT_ARGB32;
+    }
+}
+
+
+static cairo_surface_t *
+gdk_cairo_surface_coerce_to_image (cairo_surface_t *surface,
+                                   cairo_content_t  content,
+                                   int              src_x,
+                                   int              src_y,
+                                   int              width,
+                                   int              height)
+{
+  cairo_surface_t *copy;
+  cairo_t *cr;
+
+  copy = cairo_image_surface_create (gdk_cairo_format_for_content (content),
+                                     width,
+                                     height);
+
+  cr = cairo_create (copy);
+  cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
+  cairo_set_source_surface (cr, surface, -src_x, -src_y);
+  cairo_paint (cr);
+  cairo_destroy (cr);
+
+  return copy;
+}
+
+
+static void
+convert_alpha (guchar *dest_data,
+               int     dest_stride,
+               guchar *src_data,
+               int     src_stride,
+               int     src_x,
+               int     src_y,
+               int     width,
+               int     height)
+{
+  int x, y;
+
+  src_data += src_stride * src_y + src_x * 4;
+
+  for (y = 0; y < height; y++) {
+    guint32 *src = (guint32 *) src_data;
+
+    for (x = 0; x < width; x++) {
+      guint alpha = src[x] >> 24;
+
+      if (alpha == 0)
+        {
+          dest_data[x * 4 + 0] = 0;
+          dest_data[x * 4 + 1] = 0;
+          dest_data[x * 4 + 2] = 0;
+        }
+      else
+        {
+          dest_data[x * 4 + 0] = (((src[x] & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
+          dest_data[x * 4 + 1] = (((src[x] & 0x00ff00) >>  8) * 255 + alpha / 2) / alpha;
+          dest_data[x * 4 + 2] = (((src[x] & 0x0000ff) >>  0) * 255 + alpha / 2) / alpha;
+        }
+      dest_data[x * 4 + 3] = alpha;
+    }
+
+    src_data += src_stride;
+    dest_data += dest_stride;
+  }
+}
+
+static void
+convert_no_alpha (guchar *dest_data,
+                  int     dest_stride,
+                  guchar *src_data,
+                  int     src_stride,
+                  int     src_x,
+                  int     src_y,
+                  int     width,
+                  int     height)
+{
+  int x, y;
+
+  src_data += src_stride * src_y + src_x * 4;
+
+  for (y = 0; y < height; y++) {
+    guint32 *src = (guint32 *) src_data;
+
+    for (x = 0; x < width; x++) {
+      dest_data[x * 3 + 0] = src[x] >> 16;
+      dest_data[x * 3 + 1] = src[x] >>  8;
+      dest_data[x * 3 + 2] = src[x];
+    }
+
+    src_data += src_stride;
+    dest_data += dest_stride;
+  }
+}
+
+/**
+ * gdk_pixbuf_get_from_surface:
+ * @surface: surface to copy from
+ * @src_x: Source X coordinate within @surface
+ * @src_y: Source Y coordinate within @surface
+ * @width: Width in pixels of region to get
+ * @height: Height in pixels of region to get
+ *
+ * Transfers image data from a `cairo_surface_t` and converts it
+ * to a `GdkPixbuf`.
+ *
+ * This allows you to efficiently read individual pixels from cairo surfaces.
+ *
+ * This function will create an RGB pixbuf with 8 bits per channel.
+ * The pixbuf will contain an alpha channel if the @surface contains one.
+ *
+ * Returns: (nullable) (transfer full): A newly-created pixbuf with a
+ *   reference count of 1
+ *
+ * Deprecated: 4.12: Use [class@Gdk.Texture] and subclasses instead
+ *   cairo surfaces and pixbufs
+ */
+GdkPixbuf *
+gdk_pixbuf_get_from_surface (cairo_surface_t *surface,
+                             int              src_x,
+                             int              src_y,
+                             int              width,
+                             int              height)
+{
+  cairo_content_t content;
+  GdkPixbuf *dest;
+
+  /* General sanity checks */
+  g_return_val_if_fail (surface != NULL, NULL);
+  g_return_val_if_fail (width > 0 && height > 0, NULL);
+
+  content = cairo_surface_get_content (surface) | CAIRO_CONTENT_COLOR;
+  dest = gdk_pixbuf_new (GDK_COLORSPACE_RGB,
+                         !!(content & CAIRO_CONTENT_ALPHA),
+                         8,
+                         width, height);
+
+  if (cairo_surface_get_type (surface) == CAIRO_SURFACE_TYPE_IMAGE &&
+      cairo_image_surface_get_format (surface) == gdk_cairo_format_for_content (content))
+    surface = cairo_surface_reference (surface);
+  else
+    {
+      surface = gdk_cairo_surface_coerce_to_image (surface, content,
+                                                  src_x, src_y,
+                                                  width, height);
+      src_x = 0;
+      src_y = 0;
+    }
+  cairo_surface_flush (surface);
+  if (cairo_surface_status (surface) || dest == NULL)
+    {
+      cairo_surface_destroy (surface);
+      g_clear_object (&dest);
+      return NULL;
+    }
+
+  if (gdk_pixbuf_get_has_alpha (dest))
+    convert_alpha (gdk_pixbuf_get_pixels (dest),
+                   gdk_pixbuf_get_rowstride (dest),
+                   cairo_image_surface_get_data (surface),
+                   cairo_image_surface_get_stride (surface),
+                   src_x, src_y,
+                   width, height);
+  else
+    convert_no_alpha (gdk_pixbuf_get_pixels (dest),
+                      gdk_pixbuf_get_rowstride (dest),
+                      cairo_image_surface_get_data (surface),
+                      cairo_image_surface_get_stride (surface),
+                      src_x, src_y,
+                      width, height);
+
+  cairo_surface_destroy (surface);
+  return dest;
+}