lvgl
Automatically delete `Obj` and related on drop
Yet more work towards #140, currently very broken and will require removing some quality-of-life functions i.e. new().
Considering changing removal of functions to be behind a feature gate i.e. static-obj-memory so that platforms where the overhead is "tolerated" don't need to worry about all of this and can still make everything 'static. Alternatively, we can just have this done anyways with e.g. Box<T>::leak(mut self) -> &'static mut T which is still in the code but commented out and expose .leak() on T: NativeObject types. Would like to hear some opinions
One other nice feature would be a solution (macro?) to support styles in Flash not ram ....
On Wed, Jun 21, 2023, 11:13 AM Nia @.***> wrote:
Considering removal of functions to be behind a feature gate i.e. static-obj-memory so that platforms where the overhead is "tolerated" don't need to worry about all of this and can still make everything 'static. Alternatively, we can just have this done anyways with e.g. Box<T>::leak(mut self) -> &'static mut T which is still in the code but commented out and expose .leak() on T: NativeObject types. Would like to hear some opinions
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With a variable declaration attribute
On Wed, Jun 21, 2023, 11:17 AM Nia @.***> wrote:
How is this handled in C?
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See an example here: static LV_STYLE_CONST_INIT(focus_style, focus_style_props);
Working from this branch, I get
(cd ~/workspace/rust/lvgl-mm/ && RUST_LOG=debug RUST_BACKTRACE=1 DEP_LV_CONFIG_PATH=$(pwd) cargo build)
5 Compiling lvgl-mm v0.1.0 (/home/jcrisp/workspace/rust/lvgl-mm)
6 error[E0597]: `screen_style` does not live long enough
7 --> src/main.rs:144:34
8 |
9 144 | screen.add_style(Part::Main, &mut screen_style);
10 | -----------------------------^^^^^^^^^^^^^^^^^-
11 | | |
12 | | borrowed value does not live long enough
13 | argument requires that `screen_style` is borrowed for `'static`
14 ...
15 187 | }
16 | - `screen_style` dropped here while still borrowed
17
18 error[E0597]: `screen` does not live long enough
19 --> src/main.rs:151:45
20 |
21 151 | let root_id = build_tree(None, Box::new(&mut screen), cfg, &mut widget_tree);
22 | --------------------------^^^^^^^^^^^------------------------- 23 | | | 24 | | borrowed value does not live long enough
25 | argument requires that `screen` is borrowed for `'static` 26 ...
27 187 | }
28 | - `screen` dropped here while still borrowed
115 async fn display() -> Result<(), LvError> {
116 const HOR_RES: u32 = 480;
117 const VER_RES: u32 = 320;
118
119 let sim_display: SimulatorDisplay<Rgb565> =
120 SimulatorDisplay::new(Size::new(HOR_RES, VER_RES));
121 let output_settings = OutputSettingsBuilder::new().scale(1).build();
122 let mut window = Window::new("LVGL-MM", &output_settings);
123
124 // LVGL will render the graphics here first, and seed the rendered image to the
125 // display. The buffer size can be set freely.
126 let buffer = DrawBuffer::<{ (HOR_RES * VER_RES) as usize }>::default();
127
128 // Register your display update callback with LVGL. The closure you pass here will be called
129 // whenever LVGL has updates to be painted to the display.
130 // let display = Display::register(buffer, HOR_RES, VER_RES, |refresh| {
131 // sim_display.draw_iter(refresh.as_pixels()).unwrap();
132 // })?;
133
134 println!("Before all widgets: {:?}", mem_info());
135
136 let mut screen_style = Style::default();
137 screen_style.set_bg_color(Color::from_rgb((0, 0, 0)));
138 screen_style.set_text_color(Color::from_rgb((255, 255, 255)));
139 screen_style.set_bg_opa(Opacity::OPA_COVER);
140 screen_style.set_radius(0);
141
142 // Create screen and widgets
143 let (_display, mut screen) = lv_drv_disp_sdl!(buffer, HOR_RES, VER_RES)?;
144 screen.add_style(Part::Main, &mut screen_style);
.....
Not sure how this is supposed to work with code which isn't in the main() function or 'static scope
This is "intended" and fixable but needs documentation. The issue is that theoretically Box::new(x: T) requires that T lives arbitrarily long, which is fine to say for structs etc. but not for most references. I think what you could do is make the Boxing happen sooner and access the screen through it, so
let boxed_screen = Box::new(screen); // not &mut screen
boxed_screen.add_style(&mut style);
Not sure how this is supposed to work with code which isn't in the main() function or 'static scope
Assigning the style in a function that doesn't move that style into the same scope or greater than the object/screen it's assigned to is technically a use-after-free. You can get around this by leaking the style object (with mem::leak(), or by wrapping it in a ManuallyDrop) or by returning the style(s) from the called function.
Also note that this branch is WIP and will segfault if you do anything with it - tests pass, examples don't work though. I'm currently in the middle of a move so can't really work more until wednesday, sorry.