The double-negative DisabledOp is harder to understand than a
straightforward EnabledOp. Note that the absence of an EnabledOp
implies still means that the widget is enabled.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
When storing a string in an interface value that escapes, Go has to heap
allocate space for the string header, as interface values can only store
pointers. In text-heavy applications, this can lead to hundreds of
allocations per frame due to semantic.LabelOp, the primary user of
string-typed references in ops.
Instead of allocating each string header individually, provide a slice
of strings to store string-typed references in, and store pointers into
this slice as the actual references. This only allocates when resizing
the slice's backing array, and averages out to no allocations, as the
backing array gets reused between calls to Ops.Reset.
We introduce two new functions, Write1String and Write2String, which
make use of this new slice for their last argument. We could've
automated this in the existing Write1 and Write2 methods, but that would
require type assertions on each call, and the vast majority of ops do
not make use of strings.
Signed-off-by: Dominik Honnef <dominik@honnef.co>
Putting a string in an interface value has to (normally) heap allocate
the string header and string. However, putting the address of a local
string variable in an interface value has the same effect, as this
causes the local variable to escape to the heap.
Signed-off-by: Dominik Honnef <dominik@honnef.co>
Software such as screen readers require semantic descriptions of user
interfaces to effectively present and interact with them. Package
semantic, combined with the existing package clip provide the operations
for Gio programs to describe themselves.
This change implements the semantic package and the routing changes for
accessing semantic trees; follow-ups add semantic information to widgets
and implement mapping semantic tree to platform representations.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Elias Naur