This intends to provide a configurable rectangular "drop shadow". The
API is modeled after CSS/HTML5 Canvas where the element can be "bound"
to an existing rectangular shape (geometry and radius), the offset can
be used to place the shadow and color and blur configure the shadow.
The shadow's color fades into transparent.
TODO (in subsequent changes):
* Documentation
* Qt implementation
Use a save/restore state pattern for the entire renderer instead of passing around clip rectangles as data structure.
That's less data copying and maps naturally to existing mechanisms,
which in turn can use their own dirty handling to make
save_state/restore_state as cheap as possible.
This means going back to an immutable renderer reference and interior
mutability for the canvas and the gpu cache. This is because while
traversing the item tree for rendering we may end up destroying
other items due to the lazyness of the models.
... to a more general gpu_cache and store an enum. That way we can
encapsulate the resource releasing - in the future - entirely in the
backend through run-time polymorphism in the backend (gpu cache data
enum) instead of a vtable method in the item to destruct the correct
type of data.
Instead of determining the focus item through item tree traversal and
pointer comparison and storing the intermediate indices in the
components in the tree, remember the focus item by a pair of
VWeak<ComponentVTable, Dyn> and item_index: usize.
This speeds up determining the focus item as well as delivering events,
which can now be done directly after retrieving an ItemRef with
get_item_ref.
This also fixes the duplicate line edit focus in the 7gui cells
test case.
This is in preparation for allowing the run-time / items to clone VRc's
of the component.
ComponentVTable functions like visit_children_item contine to take a
ComponentRefPin as "self" parameter type, as a VRc would not be
supported by rust right now. That means the implementation then uses
self_weak to obtain a strong self-reference.
Destroying a component releases the item's graphics resources, which requires
a mutable reference to the rendering cache. That reference is acquired fine grained,
but when rendering items itself we also acquired a mutable reference
at the start of the rendering phase. That is too early and too long, and not necessary.
Borrow the rendering and cache individually with different mutability.
We might later, for destruction handling, need to borrow the rendering
cache mutably. That in turn *may* happen even during rendering itself,
as the models are updated lazily during visitor traversal and that may
result in item destruction.
Move fields out of the HighLevelRenderingPrimitive that are suitable to
represent as uniform variables. That reduces fields like Image or
Rectangle to their image or dimension, and only if *they* change, then
we re-do the work of building geometry and uploading it to the GPU.
Instead, the typically animated properties such as the position or the
color are passed separately with each draw call. This avoids re-decoding
PNG files and uploading them again when moving an image element around
on the screen.
Removed the drop and create from the ComponentVTable:
since we are not using VBox<ComponentVTable>, this simplifies a bit
the code of the interpreter and everything else.
But there is still a lot of changes everywhere to support that the Component
is pinned.
This is just for the component. Which would be required if later we want
to access the properties as Pin<Property<_>>. But we have not yet ability
to do projections
Remove the Optional from the evaluation context passing for property
evaluation. Unfortunately there are nullptr uses left on the C++ side,
that need to be replaced with passing through.
