[gtk/image-loading: 11/28] Load pngs without gdk-pixbuf

[Matthias Clasen <matthiasc src gnome org>]

commit e4656f45f2854206ee30d4bc8da86dbb3f2d187c
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Sep 11 16:23:53 2021 -0400

    Load pngs without gdk-pixbuf
    
    Use our own loader for pngs, which will allow
    us to get e.g. 16-bit data in the future.

 gdk/gdktexture.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)
---
diff --git a/gdk/gdktexture.c b/gdk/gdktexture.c
index ed5b7816b3..42776a06a6 100644
--- a/gdk/gdktexture.c
+++ b/gdk/gdktexture.c
@@ -46,6 +46,7 @@
 #include "gdksnapshot.h"
 
 #include <graphene.h>
+#include "loaders/gdkpngprivate.h"
 
 G_DEFINE_QUARK (gdk-texture-error-quark, gdk_texture_error)
 
@@ -423,24 +424,40 @@ GdkTexture *
 gdk_texture_new_from_bytes (GBytes  *bytes,
                             GError **error)
 {
-  GInputStream *stream;
-  GdkPixbuf *pixbuf;
-  GdkTexture *texture;
+  const char *data;
+  gsize size;
 
   g_return_val_if_fail (bytes != NULL, NULL);
   g_return_val_if_fail (error == NULL || *error == NULL, NULL);
 
-  stream = g_memory_input_stream_new_from_bytes (bytes);
-  pixbuf = gdk_pixbuf_new_from_stream (stream, NULL, error);
-  g_object_unref (stream);
+  data = g_bytes_get_data (bytes, &size);
 
-  if (pixbuf == NULL)
-    return NULL;
+  if (size > strlen (PNG_SIGNATURE) &&
+      memcmp (data, PNG_SIGNATURE, strlen (PNG_SIGNATURE)) == 0)
+    {
+      return gdk_load_png (bytes, error);
+    }
+  else
+    {
+      GInputStream *stream;
+      GdkPixbuf *pixbuf;
 
-  texture = gdk_texture_new_for_pixbuf (pixbuf);
-  g_object_unref (pixbuf);
+      stream = g_memory_input_stream_new_from_bytes (bytes);
+      pixbuf = gdk_pixbuf_new_from_stream (stream, NULL, error);
+      g_object_unref (stream);
 
-  return texture;
+      if (pixbuf)
+        {
+          GdkTexture *texture;
+
+          texture = gdk_texture_new_for_pixbuf (pixbuf);
+          g_object_unref (pixbuf);
+
+          return texture;
+        }
+    }
+
+  return NULL;
 }
 
 /**