Improved texture loading (#3315)

* rework loading around `Arc<Loaders>`

* use `Bytes` instead of splitting api

* remove unwraps in `texture_handle`

* make `FileLoader` optional under `file` feature

* hide http load error stack trace from UI

* implement image fit

* support more image sources

* center spinner if we know size ahead of time

* allocate final size for spinner

* improve image format guessing

* remove `ui.image`, `Image`, add `RawImage`

* deprecate `RetainedImage`

* `image2` -> `image`

* add viewer example

* update `examples/image` + remove `svg` and `download_image` exapmles

* fix lints and tests

* fix doc link

* add image controls to `images` example

* add more `From` str-like types

* add api to forget all images

* fix max size

* do not scale original size unless necessary

* fix doc link

* add more docs for `Image` and `RawImage`

* make paint_at `pub`

* update `ImageButton` to use new `Image` API

* fix double rendering

* `SizeHint::Original` -> `Scale` + remove `Option` wrapper

* Update crates/egui/src/load.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* remove special `None` value for `forget`

* Update crates/egui/src/load.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* add more examples to `ui.image` + add `include_image` macro

* Update crates/egui/src/ui.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* update `menu_image_button` to use `ImageSource`

* `OrderedFloat::get` -> `into_inner`

* derive `Eq` on `SizedTexture`

* add `id` to loaders + `is_installed` check

* move `images` to demo + simplify `images` example

* log trace when installing loaders

* fix lint

* fix doc link

* add more documentation

* more `egui_extras::loaders` docs

* Update examples/images/src/main.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* update `images` example screenshots + readme

* remove unused `rfd` from `images` example

* Update crates/egui_extras/src/loaders/ehttp_loader.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* add `must_use` on `Image` and `RawImage`

* document `loaders::install` multiple call safety

* Update crates/egui_extras/Cargo.toml

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* reshuffle `is_loader_installed`

* make `include_image` produce `ImageSource` + update docs

* update `include_image` docs

* remove `None` mentions from loader `forget`

* inline `From` texture id + size for `SizedTexture`

* add warning about statically known path

* change image load error + use in image button

* add `.size()` to `Image`

* Update crates/egui_demo_app/Cargo.toml

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* add explanations to image viewer ui

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/egui_extras/src/lib.rs

@@ -23,6 +23,7 @@ mod table;
 #[cfg(feature = "chrono")]
 pub use crate::datepicker::DatePickerButton;
 
+#[allow(deprecated)]
 pub use crate::image::RetainedImage;
 pub(crate) use crate::layout::StripLayout;
 pub use crate::sizing::Size;
@@ -63,6 +64,7 @@ pub(crate) use profiling_scopes::*;
 
 /// Log an error with either `log` or `eprintln`
 macro_rules! log_err {
+    ($fmt: literal) => {$crate::log_err!($fmt,)};
     ($fmt: literal, $($arg: tt)*) => {{
         #[cfg(feature = "log")]
         log::error!($fmt, $($arg)*);
@@ -77,6 +79,7 @@ pub(crate) use log_err;
 
 /// Panic in debug builds, log otherwise.
 macro_rules! log_or_panic {
+    ($fmt: literal) => {$crate::log_or_panic!($fmt,)};
     ($fmt: literal, $($arg: tt)*) => {{
         if cfg!(debug_assertions) {
             panic!($fmt, $($arg)*);