mike-jumper commented on a change in pull request #446: GUACAMOLE-884: Leverage
createImageBitmap() for reading image data where supported.
URL: https://github.com/apache/guacamole-client/pull/446#discussion_r333141831
##########
File path: guacamole-common-js/src/main/webapp/modules/Display.js
##########
@@ -543,26 +549,97 @@ Guacamole.Display = function() {
*/
this.drawBlob = function(layer, x, y, blob) {
- // Create URL for blob
- var url = URL.createObjectURL(blob);
+ var task;
- // Draw and free blob URL when ready
- var task = scheduleTask(function __display_drawBlob() {
+ // Prefer createImageBitmap() over blob URLs if available
+ if (window.createImageBitmap) {
- // Draw the image only if it loaded without errors
- if (image.width && image.height)
- layer.drawImage(x, y, image);
+ var bitmap;
- // Blob URL no longer needed
- URL.revokeObjectURL(url);
+ // Draw image once loaded
+ task = scheduleTask(function drawImageBitmap() {
+ layer.drawImage(x, y, bitmap);
+ }, true);
- }, true);
+ // Load image from provided blob
+ window.createImageBitmap(blob).then(function bitmapLoaded(decoded)
{
+ bitmap = decoded;
+ task.unblock();
+ });
- // Load image from URL
- var image = new Image();
- image.onload = task.unblock;
- image.onerror = task.unblock;
- image.src = url;
+ }
+
+ // Use blob URLs and the Image object if createImageBitmap() is
+ // unavailable
+ else {
+
+ // Create URL for blob
+ var url = URL.createObjectURL(blob);
+
+ // Draw and free blob URL when ready
+ task = scheduleTask(function __display_drawBlob() {
+
+ // Draw the image only if it loaded without errors
+ if (image.width && image.height)
+ layer.drawImage(x, y, image);
+
+ // Blob URL no longer needed
+ URL.revokeObjectURL(url);
+
+ }, true);
+
+ // Load image from URL
+ var image = new Image();
+ image.onload = task.unblock;
+ image.onerror = task.unblock;
+ image.src = url;
+
+ }
+
+ };
+
+ /**
+ * Draws the image within the given stream at the given coordinates. The
+ * image will be loaded automatically, and this and any future operations
+ * will wait for the image to finish loading. This function will
+ * automatically choose an approriate method for reading and decoding the
+ * given image stream, and should be preferred for received streams except
+ * where manual decoding of the stream is unavoidable.
+ *
+ * @param {Guacamole.Layer} layer
+ * The layer to draw upon.
+ *
+ * @param {Number} x
+ * The destination X coordinate.
+ *
+ * @param {Number} y
+ * The destination Y coordinate.
+ *
+ * @param {Guacamole.InputStream} stream
+ * The stream along which image data will be received.
+ *
+ * @param {String} mimetype
+ * The mimetype of the image within the stream.
+ */
+ this.drawStream = function drawStream(layer, x, y, stream, mimetype) {
+
+ // If createImageBitmap() is available, load the image as a blob so
+ // that function can be used
+ if (window.createImageBitmap) {
+ var reader = new Guacamole.BlobReader(stream, mimetype);
+ reader.onend = function drawImageBlob() {
+ guac_display.drawBlob(layer, x, y, reader.getBlob());
+ };
+ }
+
+ // Lacking createImageBitmap(), fall back to data URIs and the Image
+ // object
+ else {
+ var reader = new Guacamole.DataURIReader(stream, mimetype);
+ reader.onend = function drawImageDataURI() {
+ guac_display.draw(layer, x, y, reader.getURI());
Review comment:
Yep, `draw()` is correct here as we are using a data URI.
`drawImage()` takes an `Image` (though the documentation is now updated to
acknowledge it can take anything considered a `CanvasImageSource`). The
`draw()` function is the one that accepts a URI.
See:
*
http://guacamole.apache.org/doc/guacamole-common-js/Guacamole.Display.html#draw
*
http://guacamole.apache.org/doc/guacamole-common-js/Guacamole.Display.html#drawImage
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