This requires the image size query to be window independent and go
through the backend instead.
This implies minor changes for the Qt backend and bigger ones for the GL
backend:
* There exists now a thread-local IMAGE_CACHE, which is used by the
backend's image_size() function as well as by the renderer for
loading CPU side images.
* The image remain as decoded images in there (including SVG tree)
and the window now has a texture_cache, which holds CachedImage
with ImageData::Texture.
* Rendering an image item therefore fetches the CPU side image,
calls upload_to_gpu() on it, which creates a new Rc<CachedImage>
and that's stored in the texture_cache.
* The texture cache continues to be pruned when hiding the window.
By moving the image cache to the GraphicsWindow we can now decode images
first without a window and later upload to the GPU.
This also allows removing the window_map_pending property hack.
Decouple the Texture from the HTML image loading logic and introduce an
ImageData state that represents just the DOM element.
This will make it possible later to also load the images without a canvas.
Instead a "manual" refresh is needed (like mouse mover). This regressed
in commit 8d2554ff3b, which removed the
event loop proxy clone. For some reason that's not sending the event
from the DOM callback, but winit requires a clone of the proxy.
With wasm there is no current context (can alwasy render) but we own the
winit::Window. With glutin own the ContextWrapper and have to make it
current (and resize). This patch hides all that behind the OpenGLContext
type.
This replaces the box gradient with a new implementation that
behaves like the HTML Canvas element, by applying a gaussian
blur to the alpha of the rectangle to shadow.
The drop-shadow-blur property is changed to be now just a "level", like
the HTML Canvas shadowBlur property, which is defined to be half of the
standard deviation of the gaussian blur to be applied.
When rendering into a layer, we applied the y coordinate system flip
using a transform. That transform is incompatible with
Canvas::fill/stroke_text, which uses transform_point to transform the
glyph quads. That appears to not work, as opposed to the
y-flip in the main vertex shader.
Fortunately we can work around it by doing the flip when rendering the
layer image (as part of the fill).
Closes#199
