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API Review: Remove suspend/resume related functions from FemtoVG rend…
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…erer

This could've been `set_opengl_context` taking an `Option`, but it turns
out that makes for an awkward interface when wanting to pass None,
because that also then requires a dummy type for the OpenGL context even
though none is wanted.
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@tronical
tronical committed Jul 7, 2024
1 parent a16e86b commit 7cb05b2
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Showing 2 changed files with 117 additions and 112 deletions.
11 changes: 7 additions & 4 deletions internal/backends/winit/renderer/femtovg.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use std::rc::Rc;

use i_slint_core::platform::PlatformError;
use i_slint_core::renderer::Renderer;
use i_slint_renderer_femtovg::FemtoVGRenderer;
use i_slint_renderer_femtovg::{FemtoVGRenderer, FemtoVGRendererExt};

#[cfg(target_arch = "wasm32")]
use winit::platform::web::WindowExtWebSys;
Expand All @@ -23,7 +23,10 @@ pub struct GlutinFemtoVGRenderer {

impl GlutinFemtoVGRenderer {
pub fn new_suspended() -> Box<dyn WinitCompatibleRenderer> {
Box::new(Self { renderer: FemtoVGRenderer::new_suspended(), suspended: Cell::new(true) })
Box::new(Self {
renderer: FemtoVGRenderer::new_without_context(),
suspended: Cell::new(true),
})
}
}

Expand Down Expand Up @@ -56,7 +59,7 @@ impl super::WinitCompatibleRenderer for GlutinFemtoVGRenderer {
})
})?);

self.renderer.resume(
self.renderer.set_opengl_context(
#[cfg(not(target_arch = "wasm32"))]
opengl_context,
#[cfg(target_arch = "wasm32")]
Expand All @@ -71,7 +74,7 @@ impl super::WinitCompatibleRenderer for GlutinFemtoVGRenderer {
}

fn suspend(&self) -> Result<(), PlatformError> {
self.renderer.suspend()
self.renderer.clear_opengl_context()
}

fn is_suspended(&self) -> bool {
Expand Down
218 changes: 110 additions & 108 deletions internal/renderers/femtovg/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -140,8 +140,8 @@ impl FemtoVGRenderer {
#[cfg(not(target_arch = "wasm32"))] opengl_context: impl OpenGLInterface + 'static,
#[cfg(target_arch = "wasm32")] html_canvas: web_sys::HtmlCanvasElement,
) -> Result<Self, PlatformError> {
let this = Self::new_suspended();
this.resume(
let this = Self::new_without_context();
this.set_opengl_context(
#[cfg(not(target_arch = "wasm32"))]
opengl_context,
#[cfg(target_arch = "wasm32")]
Expand All @@ -150,111 +150,6 @@ impl FemtoVGRenderer {
Ok(this)
}

/// Creates a new renderer in suspended state. Any attempts at rendering, etc. will produce an error,
/// until [`Self::resume()`] was called successfully.
pub fn new_suspended() -> Self {
let opengl_context = Box::new(SuspendedRenderer {});

Self {
maybe_window_adapter: Default::default(),
rendering_notifier: Default::default(),
canvas: RefCell::new(None),
graphics_cache: Default::default(),
texture_cache: Default::default(),
rendering_metrics_collector: Default::default(),
rendering_first_time: Cell::new(true),
opengl_context: RefCell::new(opengl_context),
#[cfg(target_arch = "wasm32")]
canvas_id: Default::default(),
}
}

/// Suspends the renderer by deleting all OpenGL sources moving into a suspended state.
/// All subsequence attempt at rendering will produce an error, until [`Self::resume()`]
/// is called successfully.
///
/// Use this to transfer a renderer between different window surfaces.
pub fn suspend(&self) -> Result<(), i_slint_core::platform::PlatformError> {
// Ensure the context is current before the renderer is destroyed
if self.opengl_context.borrow().ensure_current().is_ok() {
// If we've rendered a frame before, then we need to invoke the RenderingTearDown notifier.
if !self.rendering_first_time.get() {
if let Some(callback) = self.rendering_notifier.borrow_mut().as_mut() {
self.with_graphics_api(|api| {
callback.notify(RenderingState::RenderingTeardown, &api)
})
.ok();
}
}

self.graphics_cache.clear_all();
self.texture_cache.borrow_mut().clear();
}

if let Some(canvas) = self.canvas.borrow_mut().take() {
if Rc::strong_count(&canvas) != 1 {
i_slint_core::debug_log!("internal warning: there are canvas references left when destroying the window. OpenGL resources will be leaked.")
}
}

*self.opengl_context.borrow_mut() = Box::new(SuspendedRenderer {});
Ok(())
}

/// Resumes a previously suspended renderer.
pub fn resume(
&self,
#[cfg(not(target_arch = "wasm32"))] opengl_context: impl OpenGLInterface + 'static,
#[cfg(target_arch = "wasm32")] html_canvas: web_sys::HtmlCanvasElement,
) -> Result<(), i_slint_core::platform::PlatformError> {
#[cfg(target_arch = "wasm32")]
let opengl_context = WebGLNeedsNoCurrentContext {};

let opengl_context = Box::new(opengl_context);
#[cfg(not(target_arch = "wasm32"))]
let gl_renderer = unsafe {
femtovg::renderer::OpenGl::new_from_function_cstr(|name| {
opengl_context.get_proc_address(name)
})
.unwrap()
};

#[cfg(target_arch = "wasm32")]
let gl_renderer = match femtovg::renderer::OpenGl::new_from_html_canvas(&html_canvas) {
Ok(gl_renderer) => gl_renderer,
Err(_) => {
use wasm_bindgen::JsCast;

// I don't believe that there's a way of disabling the 2D canvas.
let context_2d = html_canvas
.get_context("2d")
.unwrap()
.unwrap()
.dyn_into::<web_sys::CanvasRenderingContext2d>()
.unwrap();
context_2d.set_font("20px serif");
// We don't know if we're rendering on dark or white background, so choose a "color" in the middle for the text.
context_2d.set_fill_style(&wasm_bindgen::JsValue::from_str("red"));
context_2d
.fill_text("Slint requires WebGL to be enabled in your browser", 0., 30.)
.unwrap();
panic!("Cannot proceed without WebGL - aborting")
}
};

let femtovg_canvas = femtovg::Canvas::new_with_text_context(
gl_renderer,
self::fonts::FONT_CACHE.with(|cache| cache.borrow().text_context.clone()),
)
.unwrap();
let canvas = Rc::new(RefCell::new(femtovg_canvas));

*self.canvas.borrow_mut() = canvas.into();
*self.opengl_context.borrow_mut() = opengl_context;
self.rendering_first_time.set(true);
Ok(())
}

/// Render the scene using OpenGL.
pub fn render(&self) -> Result<(), i_slint_core::platform::PlatformError> {
self.internal_render_with_post_callback(
Expand Down Expand Up @@ -655,12 +550,19 @@ impl RendererSealed for FemtoVGRenderer {

impl Drop for FemtoVGRenderer {
fn drop(&mut self) {
self.suspend().ok();
self.clear_opengl_context().ok();
}
}

#[doc(hidden)]
pub trait FemtoVGRendererExt {
fn new_without_context() -> Self;
fn set_opengl_context(
&self,
#[cfg(not(target_arch = "wasm32"))] opengl_context: impl OpenGLInterface + 'static,
#[cfg(target_arch = "wasm32")] html_canvas: web_sys::HtmlCanvasElement,
) -> Result<(), i_slint_core::platform::PlatformError>;
fn clear_opengl_context(&self) -> Result<(), i_slint_core::platform::PlatformError>;
fn render_transformed_with_post_callback(
&self,
rotation_angle_degrees: f32,
Expand All @@ -672,6 +574,106 @@ pub trait FemtoVGRendererExt {

#[doc(hidden)]
impl FemtoVGRendererExt for FemtoVGRenderer {
/// Creates a new renderer in suspended state without OpenGL. Any attempts at rendering, etc. will produce an error,
/// until [`Self::set_opengl_context()`] was called successfully.
fn new_without_context() -> Self {
let opengl_context = Box::new(SuspendedRenderer {});

Self {
maybe_window_adapter: Default::default(),
rendering_notifier: Default::default(),
canvas: RefCell::new(None),
graphics_cache: Default::default(),
texture_cache: Default::default(),
rendering_metrics_collector: Default::default(),
rendering_first_time: Cell::new(true),
opengl_context: RefCell::new(opengl_context),
#[cfg(target_arch = "wasm32")]
canvas_id: Default::default(),
}
}

fn clear_opengl_context(&self) -> Result<(), i_slint_core::platform::PlatformError> {
// Ensure the context is current before the renderer is destroyed
if self.opengl_context.borrow().ensure_current().is_ok() {
// If we've rendered a frame before, then we need to invoke the RenderingTearDown notifier.
if !self.rendering_first_time.get() {
if let Some(callback) = self.rendering_notifier.borrow_mut().as_mut() {
self.with_graphics_api(|api| {
callback.notify(RenderingState::RenderingTeardown, &api)
})
.ok();
}
}

self.graphics_cache.clear_all();
self.texture_cache.borrow_mut().clear();
}

if let Some(canvas) = self.canvas.borrow_mut().take() {
if Rc::strong_count(&canvas) != 1 {
i_slint_core::debug_log!("internal warning: there are canvas references left when destroying the window. OpenGL resources will be leaked.")
}
}

*self.opengl_context.borrow_mut() = Box::new(SuspendedRenderer {});

Ok(())
}

fn set_opengl_context(
&self,
#[cfg(not(target_arch = "wasm32"))] opengl_context: impl OpenGLInterface + 'static,
#[cfg(target_arch = "wasm32")] html_canvas: web_sys::HtmlCanvasElement,
) -> Result<(), i_slint_core::platform::PlatformError> {
#[cfg(target_arch = "wasm32")]
let opengl_context = WebGLNeedsNoCurrentContext {};

let opengl_context = Box::new(opengl_context);
#[cfg(not(target_arch = "wasm32"))]
let gl_renderer = unsafe {
femtovg::renderer::OpenGl::new_from_function_cstr(|name| {
opengl_context.get_proc_address(name)
})
.unwrap()
};

#[cfg(target_arch = "wasm32")]
let gl_renderer = match femtovg::renderer::OpenGl::new_from_html_canvas(&html_canvas) {
Ok(gl_renderer) => gl_renderer,
Err(_) => {
use wasm_bindgen::JsCast;

// I don't believe that there's a way of disabling the 2D canvas.
let context_2d = html_canvas
.get_context("2d")
.unwrap()
.unwrap()
.dyn_into::<web_sys::CanvasRenderingContext2d>()
.unwrap();
context_2d.set_font("20px serif");
// We don't know if we're rendering on dark or white background, so choose a "color" in the middle for the text.
context_2d.set_fill_style(&wasm_bindgen::JsValue::from_str("red"));
context_2d
.fill_text("Slint requires WebGL to be enabled in your browser", 0., 30.)
.unwrap();
panic!("Cannot proceed without WebGL - aborting")
}
};

let femtovg_canvas = femtovg::Canvas::new_with_text_context(
gl_renderer,
self::fonts::FONT_CACHE.with(|cache| cache.borrow().text_context.clone()),
)
.unwrap();
let canvas = Rc::new(RefCell::new(femtovg_canvas));

*self.canvas.borrow_mut() = canvas.into();
*self.opengl_context.borrow_mut() = opengl_context;
self.rendering_first_time.set(true);
Ok(())
}

fn render_transformed_with_post_callback(
&self,
rotation_angle_degrees: f32,
Expand Down

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