wasm: store and pass canvases as emscripten::val

Store and pass canvases as emscripten::val instead of
a QString containing the element id.

This simplifies code which interacts with the canvas
using the emscripten::val API, by removing the need to
look up with getElementById.

The Emscripten C event API does not accept emscripten::val,
and using the element id is still needed here.

emscripten::val does not provide a hash key suitable
for use with QHash, but does provide an equality-compare
in the form of val::equals(). Change the canvas->screen
mapping code to use a QVector instead of a QHash.

Change-Id: I1dbdbbc8fb06bb869031f1500e83ae2d64780a7f
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

0 files changed, 0 insertions, 0 deletions