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lib.rs
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// Copyright © SixtyFPS GmbH <info@slint-ui.com>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
#![doc = include_str!("README.md")]
#![doc(html_logo_url = "https://slint-ui.com/logo/slint-logo-square-light.svg")]
use std::cell::RefCell;
use std::pin::Pin;
use std::rc::Rc;
use i_slint_common::sharedfontdb;
use i_slint_core::api::{
PhysicalSize as PhysicalWindowSize, RenderingNotifier, RenderingState,
SetRenderingNotifierError,
};
use i_slint_core::graphics::FontRequest;
use i_slint_core::graphics::{euclid, rendering_metrics_collector::RenderingMetricsCollector};
use i_slint_core::lengths::{
LogicalLength, LogicalPoint, LogicalRect, LogicalSize, PhysicalPx, ScaleFactor,
};
use i_slint_core::platform::PlatformError;
use i_slint_core::renderer::Renderer;
use i_slint_core::window::WindowInner;
use i_slint_core::Brush;
type PhysicalLength = euclid::Length<f32, PhysicalPx>;
type PhysicalRect = euclid::Rect<f32, PhysicalPx>;
type PhysicalSize = euclid::Size2D<f32, PhysicalPx>;
type PhysicalPoint = euclid::Point2D<f32, PhysicalPx>;
use self::itemrenderer::CanvasRc;
mod fonts;
mod images;
mod itemrenderer;
/// Trait that the FemtoVGRenderer uses to ensure that the OpenGL context is current, before running
/// OpenGL commands. The trait also provides access to the symbols of the OpenGL implementation.
///
/// Safety: This trait is unsafe because an implementation of get_proc_address could return dangling
/// pointers. In practice an implementation of this trait should just forward to the EGL/WGL/CGL
/// C library that implements EGL/CGL/WGL.
pub unsafe trait OpenGLContextWrapper {
/// Ensures that the GL context is current.
fn ensure_current(&self) -> Result<(), PlatformError>;
fn swap_buffers(&self) -> Result<(), PlatformError>;
fn resize(&self, size: PhysicalWindowSize) -> Result<(), PlatformError>;
#[cfg(not(target_arch = "wasm32"))]
fn get_proc_address(&self, name: &std::ffi::CStr) -> *const std::ffi::c_void;
}
#[cfg(target_arch = "wasm32")]
struct WebGLNeedsNoCurrentContext;
#[cfg(target_arch = "wasm32")]
unsafe impl OpenGLContextWrapper for WebGLNeedsNoCurrentContext {
fn ensure_current(&self) -> Result<(), PlatformError> {
Ok(())
}
fn swap_buffers(&self) -> Result<(), PlatformError> {
Ok(())
}
fn resize(&self, _size: PhysicalWindowSize) -> Result<(), PlatformError> {
Ok(())
}
}
/// Use the FemtoVG renderer when implementing a custom Slint platform where you deliver events to
/// Slint and want the scene to be rendered using OpenGL and the FemtoVG renderer.
pub struct FemtoVGRenderer {
rendering_notifier: RefCell<Option<Box<dyn RenderingNotifier>>>,
canvas: CanvasRc,
graphics_cache: itemrenderer::ItemGraphicsCache,
texture_cache: RefCell<images::TextureCache>,
rendering_metrics_collector: RefCell<Option<Rc<RenderingMetricsCollector>>>,
// Last field, so that it's dropped last and context exists and is current when destroying the FemtoVG canvas
opengl_context: Box<dyn OpenGLContextWrapper>,
#[cfg(target_arch = "wasm32")]
canvas_id: String,
}
impl FemtoVGRenderer {
/// Creates a new renderer is associated with an implementation
/// of the OpenGLContextWrapper trait. The trait serves the purpose of giving the renderer control
/// over when the make the context current, how to retrieve the address of GL functions, and when
/// to swap back and front buffers.
pub fn new(
#[cfg(not(target_arch = "wasm32"))] opengl_context: impl OpenGLContextWrapper + 'static,
#[cfg(target_arch = "wasm32")] html_canvas: web_sys::HtmlCanvasElement,
) -> Result<Self, 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));
Ok(Self {
rendering_notifier: Default::default(),
canvas,
graphics_cache: Default::default(),
texture_cache: Default::default(),
rendering_metrics_collector: Default::default(),
opengl_context,
#[cfg(target_arch = "wasm32")]
canvas_id: html_canvas.id(),
})
}
/// Notifiers the renderer that the underlying window is becoming visible.
pub fn show(&self) -> Result<(), PlatformError> {
self.opengl_context.ensure_current()?;
*self.rendering_metrics_collector.borrow_mut() =
RenderingMetricsCollector::new(&format!("FemtoVG renderer"));
if let Some(callback) = self.rendering_notifier.borrow_mut().as_mut() {
self.with_graphics_api(|api| callback.notify(RenderingState::RenderingSetup, &api))?;
}
Ok(())
}
/// Notifiers the renderer that the underlying window will be hidden soon.
pub fn hide(&self) -> Result<(), PlatformError> {
self.opengl_context.ensure_current()?;
self.rendering_metrics_collector.borrow_mut().take();
if let Some(callback) = self.rendering_notifier.borrow_mut().as_mut() {
self.with_graphics_api(|api| callback.notify(RenderingState::RenderingTeardown, &api))?;
}
Ok(())
}
/// Render the scene using OpenGL. This function assumes that the context is current.
pub fn render(
&self,
window: &i_slint_core::api::Window,
) -> Result<(), i_slint_core::platform::PlatformError> {
self.opengl_context.ensure_current()?;
let size = window.size();
let width = size.width;
let height = size.height;
let window_inner = WindowInner::from_pub(window);
let scale = window_inner.scale_factor().ceil();
window_inner
.draw_contents(|components| -> Result<(), PlatformError> {
let window_background_brush =
window_inner.window_item().map(|w| w.as_pin_ref().background());
{
let mut femtovg_canvas = self.canvas.borrow_mut();
// We pass an integer that is greater than or equal to the scale factor as
// dpi / device pixel ratio as the anti-alias of femtovg needs that to draw text clearly.
// We need to care about that `ceil()` when calculating metrics.
femtovg_canvas.set_size(width, height, scale);
// Clear with window background if it is a solid color otherwise it will drawn as gradient
if let Some(Brush::SolidColor(clear_color)) = window_background_brush {
femtovg_canvas.clear_rect(
0,
0,
width,
height,
self::itemrenderer::to_femtovg_color(&clear_color),
);
}
}
if let Some(notifier_fn) = self.rendering_notifier.borrow_mut().as_mut() {
let mut femtovg_canvas = self.canvas.borrow_mut();
// For the BeforeRendering rendering notifier callback it's important that this happens *after* clearing
// the back buffer, in order to allow the callback to provide its own rendering of the background.
// femtovg's clear_rect() will merely schedule a clear call, so flush right away to make it immediate.
femtovg_canvas.flush();
femtovg_canvas.set_size(width, height, scale);
drop(femtovg_canvas);
self.with_graphics_api(|api| {
notifier_fn.notify(RenderingState::BeforeRendering, &api)
})?;
}
let mut item_renderer = self::itemrenderer::GLItemRenderer::new(
&self.canvas,
&self.graphics_cache,
&self.texture_cache,
window,
width,
height,
);
// Draws the window background as gradient
match window_background_brush {
Some(Brush::SolidColor(..)) | None => {}
Some(brush @ _) => {
item_renderer.draw_rect(
i_slint_core::lengths::logical_size_from_api(
size.to_logical(window_inner.scale_factor()),
),
brush,
);
}
}
for (component, origin) in components {
i_slint_core::item_rendering::render_component_items(
component,
&mut item_renderer,
*origin,
);
}
if let Some(collector) = &self.rendering_metrics_collector.borrow().as_ref() {
collector.measure_frame_rendered(&mut item_renderer);
}
self.canvas.borrow_mut().flush();
// Delete any images and layer images (and their FBOs) before making the context not current anymore, to
// avoid GPU memory leaks.
self.texture_cache.borrow_mut().drain();
drop(item_renderer);
Ok(())
})
.unwrap_or(Ok(()))?;
if let Some(callback) = self.rendering_notifier.borrow_mut().as_mut() {
self.with_graphics_api(|api| callback.notify(RenderingState::AfterRendering, &api))?;
}
self.opengl_context.swap_buffers()
}
/// Inform the renderer about the new size of the underlying window.
pub fn resize(&self, size: PhysicalWindowSize) -> Result<(), PlatformError> {
self.opengl_context.resize(size)
}
#[cfg(not(target_arch = "wasm32"))]
fn with_graphics_api(
&self,
callback: impl FnOnce(i_slint_core::api::GraphicsAPI<'_>),
) -> Result<(), PlatformError> {
use i_slint_core::api::GraphicsAPI;
self.opengl_context.ensure_current()?;
let api = GraphicsAPI::NativeOpenGL {
get_proc_address: &|name| self.opengl_context.get_proc_address(name),
};
callback(api);
Ok(())
}
#[cfg(target_arch = "wasm32")]
fn with_graphics_api(
&self,
callback: impl FnOnce(i_slint_core::api::GraphicsAPI<'_>),
) -> Result<(), PlatformError> {
use i_slint_core::api::GraphicsAPI;
let api = GraphicsAPI::WebGL {
canvas_element_id: self.canvas_id.as_str(),
context_type: "webgl",
};
callback(api);
Ok(())
}
}
impl Renderer for FemtoVGRenderer {
fn text_size(
&self,
font_request: i_slint_core::graphics::FontRequest,
text: &str,
max_width: Option<LogicalLength>,
scale_factor: ScaleFactor,
) -> LogicalSize {
crate::fonts::text_size(&font_request, scale_factor, text, max_width)
}
fn text_input_byte_offset_for_position(
&self,
text_input: Pin<&i_slint_core::items::TextInput>,
pos: LogicalPoint,
font_request: FontRequest,
scale_factor: ScaleFactor,
) -> usize {
let pos = pos * scale_factor;
let text = text_input.text();
let mut result = text.len();
let width = text_input.width() * scale_factor;
let height = text_input.height() * scale_factor;
if width.get() <= 0. || height.get() <= 0. || pos.y < 0. {
return 0;
}
let font = crate::fonts::FONT_CACHE
.with(|cache| cache.borrow_mut().font(font_request, scale_factor, &text_input.text()));
let visual_representation = text_input.visual_representation(None);
let paint = font.init_paint(text_input.letter_spacing() * scale_factor, Default::default());
let text_context =
crate::fonts::FONT_CACHE.with(|cache| cache.borrow().text_context.clone());
let font_height = text_context.measure_font(&paint).unwrap().height();
crate::fonts::layout_text_lines(
&visual_representation.text,
&font,
PhysicalSize::from_lengths(width, height),
(text_input.horizontal_alignment(), text_input.vertical_alignment()),
text_input.wrap(),
i_slint_core::items::TextOverflow::Clip,
text_input.single_line(),
&paint,
|line_text, line_pos, start, metrics| {
if (line_pos.y..(line_pos.y + font_height)).contains(&pos.y) {
let mut current_x = 0.;
for glyph in &metrics.glyphs {
if line_pos.x + current_x + glyph.advance_x / 2. >= pos.x {
result = start + glyph.byte_index;
return;
}
current_x += glyph.advance_x;
}
result = start + line_text.trim_end().len();
}
},
);
visual_representation.map_byte_offset_from_byte_offset_in_visual_text(result)
}
fn text_input_cursor_rect_for_byte_offset(
&self,
text_input: Pin<&i_slint_core::items::TextInput>,
byte_offset: usize,
font_request: FontRequest,
scale_factor: ScaleFactor,
) -> LogicalRect {
let text = text_input.text();
let font_size = font_request.pixel_size.unwrap_or(fonts::DEFAULT_FONT_SIZE);
let mut result = PhysicalPoint::default();
let width = text_input.width() * scale_factor;
let height = text_input.height() * scale_factor;
if width.get() <= 0. || height.get() <= 0. {
return LogicalRect::new(
LogicalPoint::default(),
LogicalSize::from_lengths(LogicalLength::new(1.0), font_size),
);
}
let font = crate::fonts::FONT_CACHE
.with(|cache| cache.borrow_mut().font(font_request, scale_factor, &text_input.text()));
let paint = font.init_paint(text_input.letter_spacing() * scale_factor, Default::default());
fonts::layout_text_lines(
text.as_str(),
&font,
PhysicalSize::from_lengths(width, height),
(text_input.horizontal_alignment(), text_input.vertical_alignment()),
text_input.wrap(),
i_slint_core::items::TextOverflow::Clip,
text_input.single_line(),
&paint,
|line_text, line_pos, start, metrics| {
if (start..=(start + line_text.len())).contains(&byte_offset) {
for glyph in &metrics.glyphs {
if glyph.byte_index == (byte_offset - start) {
result = line_pos + PhysicalPoint::new(glyph.x, 0.0).to_vector();
return;
}
}
if let Some(last) = metrics.glyphs.last() {
if line_text.ends_with('\n') {
result = line_pos + euclid::vec2(0.0, last.y);
} else {
result = line_pos + euclid::vec2(last.x + last.advance_x, 0.0);
}
}
}
},
);
LogicalRect::new(
result / scale_factor,
LogicalSize::from_lengths(LogicalLength::new(1.0), font_size),
)
}
fn register_font_from_memory(
&self,
data: &'static [u8],
) -> Result<(), Box<dyn std::error::Error>> {
sharedfontdb::register_font_from_memory(data)
}
fn register_font_from_path(
&self,
path: &std::path::Path,
) -> Result<(), Box<dyn std::error::Error>> {
sharedfontdb::register_font_from_path(path)
}
fn default_font_size(&self) -> LogicalLength {
self::fonts::DEFAULT_FONT_SIZE
}
fn set_rendering_notifier(
&self,
callback: Box<dyn i_slint_core::api::RenderingNotifier>,
) -> Result<(), i_slint_core::api::SetRenderingNotifierError> {
let mut notifier = self.rendering_notifier.borrow_mut();
if notifier.replace(callback).is_some() {
Err(SetRenderingNotifierError::AlreadySet)
} else {
Ok(())
}
}
fn free_graphics_resources(
&self,
component: i_slint_core::component::ComponentRef,
_items: &mut dyn Iterator<Item = Pin<i_slint_core::items::ItemRef<'_>>>,
) -> Result<(), i_slint_core::platform::PlatformError> {
self.opengl_context.ensure_current()?;
self.graphics_cache.component_destroyed(component);
Ok(())
}
}
impl Drop for FemtoVGRenderer {
fn drop(&mut self) {
// Ensure the context is current before the renderer is destroyed
self.opengl_context.ensure_current().ok();
// Clear these manually to drop any Rc<Canvas>.
self.graphics_cache.clear_all();
self.texture_cache.borrow_mut().clear();
if Rc::strong_count(&self.canvas) != 1 {
i_slint_core::debug_log!("internal warning: there are canvas references left when destroying the window. OpenGL resources will be leaked.")
}
}
}