Canvas display bug in Firefox

[Dromin]

Affected browser: Firefox
How to reproduce: In the Semantic Web presentation, start at outline mode and open any slide before the slides that have canvas graphics (these start from slide 13 onwards) and navigate to the slide with canvas graphics using the ↓ key. The canvas graphics are distorted and displayed in the top left corner of the slide, with only a small part being visible. Note: canvas is displayed correctly if I navigate directly to these slides by clicking them in outline mode.

[RubenVerborgh]

Hmm, that looks wrong indeed. Unfortunately, I couldn't reproduce it on my Firefox (tried on versions 43, 44, and 45 on OS X). I clicked on a slide in the overview to open it full screen, and then navigated to the next slide. What version/OS do you have?

These figures are actually canvas elements inside of an iframe. I suspect either the iframe or the canvas are not receiving (or mishandling) resize events.

[Dromin]

I'm using Firefox 45.0, on Windows 10.

There are other problems that are probably related to JS events as well that are difficult to reproduce consistently. For instance, I sometimes get a black screen when using the back button. And sometimes it's impossible to navigate to outline mode, because I get automatically redirected to the first slide (this happens in Firefox as well as in Chrome). But when I tried to file a bug report for these, it suddenly started working again. Only to stop working when I went back to testing the print stylesheet....

[RubenVerborgh]

Thanks for letting me know; will use Firefox to work on my slides the coming time, hoping to see some of the bugs first-hand.

[RubenVerborgh]

I've been using Firefox now recently, and I have encountered this behavior a couple of times myself. I think it has to do with the iframes being loaded before the CSS kicks in, and not triggering a resize event. A hack would be to trigger the resize event after 2 seconds or so; trying to think of an actually appropriate solution here.

[RubenVerborgh]

Will likely need to be fixed in Shower. Perhaps an iframe plugin could help, also for other issues like OpenWebslides/ICT-Lerarenopleiding#8 and OpenWebslides/ICT-Lerarenopleiding#11.