649618 - If the canvas has a horizontal dimension of zero, then toDataURL() must return the string "data:,".

Status: VERIFIED FIXED

(Core :: Graphics: Canvas2D, defect)

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

At least one problem here: when canvas.width=0 is called we don't actually set the width to 0 ... see http://mxr.mozilla.org/mozilla-central/source/content/html/content/src/nsHTMLCanvasElement.cpp#121

Comment 2

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

If I change the clamp from <= to < we crash in Cairo while trying to get an inputstream from the context.

Comment 3

[Masatoshi Kimura [:emk]]

The check was added by bug 291216.

Comment 4

[:Benjamin Peterson]

Attachment: patch to fix the issue

Here is a patch and test.

Comment 5

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Comment on attachment 527714 [details] [diff] [review]
patch to fix the issue

Thanks for the patch Benjamin.

Joe, can you review this?  Not sure who reviews canvas stuff these days ...

Comment 6

[Joe Drew (not getting mail)]

Comment on attachment 527714 [details] [diff] [review]
patch to fix the issue

Review of attachment 527714 [details] [diff] [review]:

::: content/html/content/src/nsHTMLCanvasElement.cpp
@@ +124,3 @@
     size.width = DEFAULT_CANVAS_WIDTH;
+  if (size.height < 0)
+    size.height = DEFAULT_CANVAS_HEIGHT;

I think I would rather GetWidthHeightInternal didn't do any frobbing of the returned data; if users want to get the raw data, they should be ready to handle silly results.

(This would also imply changing GetWidthHeight to contain <= rather than ==.)

@@ +360,5 @@
+    nsIntSize size = GetWidthHeightInternal();
+    if (size.height == 0 || size.width == 0) {
+      aDataURL = NS_LITERAL_STRING("data:,");
+      return NS_OK;
+    }

Similarly, here we'd change this to <= 0.

Comment 7

[:Benjamin Peterson]

Attachment: fix the issue

This addresses review comments. However, it does not change "width == 0" to "width <= 0" because I don't think a negative value can get past ParseNonNegativeIntValue in ParseAttribute(). Correct me if I'm wrong.

Comment 8

[Joe Drew (not getting mail)]

Comment on attachment 530456 [details] [diff] [review]
fix the issue

's fine with me! :)

Comment 9

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

I don't think we should do this until we fix bug 421865.

Comment 10

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

http://www.w3c-test.org/html/tests/approved/canvas/toDataURL.zerosize.html

Comment 11

[:Benjamin Peterson]

Attachment: fix based on 421865

This simple patch (requiring the the patch to 421865) fixes the issue.

Comment 12

[Joe Drew (not getting mail)]

Comment on attachment 531507 [details] [diff] [review]
fix based on 421865

Review of attachment 531507 [details] [diff] [review]:
-----------------------------------------------------------------

Love it.

Comment 13

[Mounir Lamouri (:mounir)]

Pushed:
http://hg.mozilla.org/mozilla-central/rev/951de6cc1fdb

Comment 14

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Thanks for fixing this Benjamin.

Comment 15

[AndreiD[QA]]

Verified fixed on:

-> Linux: Mozilla/5.0 (X11; Linux i686; rv:6.0) Gecko/20100101 Firefox/6.0
-> Mac: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:6.0) Gecko/20100101 Firefox/6.0
-> Windows: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:6.0) Gecko/20100101 Firefox/6.0

The test toDataURL on w3c-test.org (Comment 10) is PASS, as well as the test at the link:
http://samples.msdn.microsoft.com/ietestcenter/html5/canvas_harness.htm?url=canvas-canvasElement-001
Also the depending bug 421865 has been fixed

Comment 16

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

Thanks for the verification, Andrei.