1 files changed, 123 insertions, 0 deletions
diff --git a/image/ImgDrawResult.h b/image/ImgDrawResult.h
new file mode 100644
index 0000000000..ff466d823a
--- /dev/null
+++ b/image/ImgDrawResult.h
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_ImgDrawResult_h
+#define mozilla_image_ImgDrawResult_h
+
+#include <cstdint>  // for uint8_t
+#include "mozilla/Attributes.h"
+#include "mozilla/Likely.h"
+
+namespace mozilla {
+namespace image {
+
+/**
+ * An enumeration representing the result of a drawing operation.
+ *
+ * Most users of ImgDrawResult will only be interested in whether the value is
+ * SUCCESS or not. The other values are primarily useful for debugging and error
+ * handling.
+ *
+ * SUCCESS: We successfully drew a completely decoded frame of the requested
+ * size. Drawing again with FLAG_SYNC_DECODE would not change the result.
+ *
+ * SUCCESS_NOT_COMPLETE: The image was drawn successfully and completely, but
+ * it hasn't notified about the sync-decode yet. This can only happen when
+ * layout pokes at the internal image state beforehand via the result of
+ * StartDecodingWithResult. This should probably go away eventually, somehow,
+ * see bug 1471583.
+ *
+ * INCOMPLETE: We successfully drew a frame that was partially decoded. (Note
+ * that successfully drawing a partially decoded frame may not actually draw any
+ * pixels!) Drawing again with FLAG_SYNC_DECODE would improve the result.
+ *
+ * WRONG_SIZE: We successfully drew a wrongly-sized frame that had to be scaled.
+ * This is only returned if drawing again with FLAG_SYNC_DECODE would improve
+ * the result; if the size requested was larger than the intrinsic size of the
+ * image, for example, we would generally have to scale whether FLAG_SYNC_DECODE
+ * was specified or not, and therefore we would not return WRONG_SIZE.
+ *
+ * NOT_READY: We failed to draw because no decoded version of the image was
+ * available. Drawing again with FLAG_SYNC_DECODE would improve the result.
+ * (Though FLAG_SYNC_DECODE will not necessarily work until after the image's
+ * load event!)
+ *
+ * TEMPORARY_ERROR: We failed to draw due to a temporary error. Drawing may
+ * succeed at a later time.
+ *
+ * BAD_IMAGE: We failed to draw because the image has an error. This is a
+ * permanent condition.
+ *
+ * BAD_ARGS: We failed to draw because bad arguments were passed to draw().
+ *
+ * NOT_SUPPORTED: The requested operation is not supported, but the image is
+ *                otherwise valid.
+ */
+enum class MOZ_MUST_USE_TYPE ImgDrawResult : uint8_t {
+  SUCCESS,
+  SUCCESS_NOT_COMPLETE,
+  INCOMPLETE,
+  WRONG_SIZE,
+  NOT_READY,
+  TEMPORARY_ERROR,
+  BAD_IMAGE,
+  BAD_ARGS,
+  NOT_SUPPORTED
+};
+
+/**
+ * You can combine ImgDrawResults with &. By analogy to bitwise-&, the result is
+ * ImgDrawResult::SUCCESS only if both operands are ImgDrawResult::SUCCESS.
+ * Otherwise, a failing ImgDrawResult is returned; we favor the left operand's
+ * failure when deciding which failure to return, with the exception that we
+ * always prefer any other kind of failure over ImgDrawResult::BAD_IMAGE, since
+ * other failures are recoverable and we want to know if any recoverable
+ * failures occurred.
+ */
+inline ImgDrawResult operator&(const ImgDrawResult aLeft,
+                               const ImgDrawResult aRight) {
+  if (MOZ_LIKELY(aLeft == ImgDrawResult::SUCCESS)) {
+    return aRight;
+  }
+
+  if (aLeft == ImgDrawResult::NOT_SUPPORTED ||
+      aRight == ImgDrawResult::NOT_SUPPORTED) {
+    return ImgDrawResult::NOT_SUPPORTED;
+  }
+
+  if ((aLeft == ImgDrawResult::BAD_IMAGE ||
+       aLeft == ImgDrawResult::SUCCESS_NOT_COMPLETE) &&
+      aRight != ImgDrawResult::SUCCESS &&
+      aRight != ImgDrawResult::SUCCESS_NOT_COMPLETE) {
+    return aRight;
+  }
+  return aLeft;
+}
+
+inline ImgDrawResult& operator&=(ImgDrawResult& aLeft,
+                                 const ImgDrawResult aRight) {
+  aLeft = aLeft & aRight;
+  return aLeft;
+}
+
+/**
+ * A struct used during painting to provide input flags to determine how
+ * imagelib draw calls should behave and an output ImgDrawResult to return
+ * information about the result of any imagelib draw calls that may have
+ * occurred.
+ */
+struct imgDrawingParams {
+  explicit imgDrawingParams(uint32_t aImageFlags = 0)
+      : imageFlags(aImageFlags), result(ImgDrawResult::SUCCESS) {}
+
+  const uint32_t imageFlags;  // imgIContainer::FLAG_* image flags to pass to
+                              // image lib draw calls.
+  ImgDrawResult result;       // To return results from image lib painting.
+};
+
+}  // namespace image
+}  // namespace mozilla
+
+#endif  // mozilla_image_ImgDrawResult_h