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painter.rs
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painter.rs
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#![allow(deprecated)] // legacy implement_vertex macro
#![allow(semicolon_in_expressions_from_macros)] // glium::program! macro
use egui::epaint::Primitive;
use {
egui::{emath::Rect, epaint::Mesh},
glium::{
implement_vertex,
index::PrimitiveType,
program,
texture::{self, srgb_texture2d::SrgbTexture2d},
uniform,
uniforms::{MagnifySamplerFilter, SamplerWrapFunction},
},
std::rc::Rc,
};
pub struct Painter {
max_texture_side: usize,
program: glium::Program,
textures: ahash::HashMap<egui::TextureId, Rc<SrgbTexture2d>>,
/// [`egui::TextureId::User`] index
next_native_tex_id: u64,
}
impl Painter {
pub fn new(facade: &dyn glium::backend::Facade) -> Painter {
use glium::CapabilitiesSource as _;
let max_texture_side = facade.get_capabilities().max_texture_size as _;
let program = program! {
facade,
120 => {
vertex: include_str!("shader/vertex_120.glsl"),
fragment: include_str!("shader/fragment_120.glsl"),
},
140 => {
vertex: include_str!("shader/vertex_140.glsl"),
fragment: include_str!("shader/fragment_140.glsl"),
},
100 es => {
vertex: include_str!("shader/vertex_100es.glsl"),
fragment: include_str!("shader/fragment_100es.glsl"),
},
300 es => {
vertex: include_str!("shader/vertex_300es.glsl"),
fragment: include_str!("shader/fragment_300es.glsl"),
},
}
.expect("Failed to compile shader");
Painter {
max_texture_side,
program,
textures: Default::default(),
next_native_tex_id: 0,
}
}
pub fn max_texture_side(&self) -> usize {
self.max_texture_side
}
pub fn paint_and_update_textures<T: glium::Surface>(
&mut self,
display: &glium::Display,
target: &mut T,
pixels_per_point: f32,
clipped_primitives: &[egui::ClippedPrimitive],
textures_delta: &egui::TexturesDelta,
) {
for (id, image_delta) in &textures_delta.set {
self.set_texture(display, *id, image_delta);
}
self.paint_primitives(display, target, pixels_per_point, clipped_primitives);
for &id in &textures_delta.free {
self.free_texture(id);
}
}
/// Main entry-point for painting a frame.
/// You should call `target.clear_color(..)` before
/// and `target.finish()` after this.
pub fn paint_primitives<T: glium::Surface>(
&mut self,
display: &glium::Display,
target: &mut T,
pixels_per_point: f32,
clipped_primitives: &[egui::ClippedPrimitive],
) {
for egui::ClippedPrimitive {
clip_rect,
primitive,
} in clipped_primitives
{
match primitive {
Primitive::Mesh(mesh) => {
self.paint_mesh(target, display, pixels_per_point, clip_rect, mesh);
}
Primitive::Callback(_) => {
panic!("Custom rendering callbacks are not implemented in egui_glium");
}
}
}
}
#[inline(never)] // Easier profiling
fn paint_mesh<T: glium::Surface>(
&mut self,
target: &mut T,
display: &glium::Display,
pixels_per_point: f32,
clip_rect: &Rect,
mesh: &Mesh,
) {
debug_assert!(mesh.is_valid());
let vertex_buffer = {
#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Vertex {
a_pos: [f32; 2],
a_tc: [f32; 2],
a_srgba: [u8; 4],
}
implement_vertex!(Vertex, a_pos, a_tc, a_srgba);
let vertices: &[Vertex] = bytemuck::cast_slice(&mesh.vertices);
// TODO(emilk): we should probably reuse the [`VertexBuffer`] instead of allocating a new one each frame.
glium::VertexBuffer::new(display, vertices).unwrap()
};
// TODO(emilk): we should probably reuse the [`IndexBuffer`] instead of allocating a new one each frame.
let index_buffer =
glium::IndexBuffer::new(display, PrimitiveType::TrianglesList, &mesh.indices).unwrap();
let (width_in_pixels, height_in_pixels) = display.get_framebuffer_dimensions();
let width_in_points = width_in_pixels as f32 / pixels_per_point;
let height_in_points = height_in_pixels as f32 / pixels_per_point;
if let Some(texture) = self.texture(mesh.texture_id) {
// The texture coordinates for text are so that both nearest and linear should work with the egui font texture.
// For user textures linear sampling is more likely to be the right choice.
let filter = MagnifySamplerFilter::Linear;
let uniforms = uniform! {
u_screen_size: [width_in_points, height_in_points],
u_sampler: texture.sampled().magnify_filter(filter).wrap_function(SamplerWrapFunction::Clamp),
};
// egui outputs colors with premultiplied alpha:
let color_blend_func = glium::BlendingFunction::Addition {
source: glium::LinearBlendingFactor::One,
destination: glium::LinearBlendingFactor::OneMinusSourceAlpha,
};
// Less important, but this is technically the correct alpha blend function
// when you want to make use of the framebuffer alpha (for screenshots, compositing, etc).
let alpha_blend_func = glium::BlendingFunction::Addition {
source: glium::LinearBlendingFactor::OneMinusDestinationAlpha,
destination: glium::LinearBlendingFactor::One,
};
let blend = glium::Blend {
color: color_blend_func,
alpha: alpha_blend_func,
..Default::default()
};
// egui outputs mesh in both winding orders:
let backface_culling = glium::BackfaceCullingMode::CullingDisabled;
// Transform clip rect to physical pixels:
let clip_min_x = pixels_per_point * clip_rect.min.x;
let clip_min_y = pixels_per_point * clip_rect.min.y;
let clip_max_x = pixels_per_point * clip_rect.max.x;
let clip_max_y = pixels_per_point * clip_rect.max.y;
// Make sure clip rect can fit within a `u32`:
let clip_min_x = clip_min_x.clamp(0.0, width_in_pixels as f32);
let clip_min_y = clip_min_y.clamp(0.0, height_in_pixels as f32);
let clip_max_x = clip_max_x.clamp(clip_min_x, width_in_pixels as f32);
let clip_max_y = clip_max_y.clamp(clip_min_y, height_in_pixels as f32);
let clip_min_x = clip_min_x.round() as u32;
let clip_min_y = clip_min_y.round() as u32;
let clip_max_x = clip_max_x.round() as u32;
let clip_max_y = clip_max_y.round() as u32;
let params = glium::DrawParameters {
blend,
backface_culling,
scissor: Some(glium::Rect {
left: clip_min_x,
bottom: height_in_pixels - clip_max_y,
width: clip_max_x - clip_min_x,
height: clip_max_y - clip_min_y,
}),
..Default::default()
};
target
.draw(
&vertex_buffer,
&index_buffer,
&self.program,
&uniforms,
¶ms,
)
.unwrap();
}
}
// ------------------------------------------------------------------------
pub fn set_texture(
&mut self,
facade: &dyn glium::backend::Facade,
tex_id: egui::TextureId,
delta: &egui::epaint::ImageDelta,
) {
let pixels: Vec<(u8, u8, u8, u8)> = match &delta.image {
egui::ImageData::Color(image) => {
assert_eq!(
image.width() * image.height(),
image.pixels.len(),
"Mismatch between texture size and texel count"
);
image.pixels.iter().map(|color| color.to_tuple()).collect()
}
egui::ImageData::Font(image) => {
let gamma = 1.0;
image
.srgba_pixels(gamma)
.map(|color| color.to_tuple())
.collect()
}
};
let glium_image = glium::texture::RawImage2d {
data: std::borrow::Cow::Owned(pixels),
width: delta.image.width() as _,
height: delta.image.height() as _,
format: glium::texture::ClientFormat::U8U8U8U8,
};
let format = texture::SrgbFormat::U8U8U8U8;
let mipmaps = texture::MipmapsOption::NoMipmap;
if let Some(pos) = delta.pos {
// update a sub-region
if let Some(gl_texture) = self.textures.get(&tex_id) {
let rect = glium::Rect {
left: pos[0] as _,
bottom: pos[1] as _,
width: glium_image.width,
height: glium_image.height,
};
gl_texture.main_level().write(rect, glium_image);
}
} else {
let gl_texture =
SrgbTexture2d::with_format(facade, glium_image, format, mipmaps).unwrap();
self.textures.insert(tex_id, gl_texture.into());
}
}
pub fn free_texture(&mut self, tex_id: egui::TextureId) {
self.textures.remove(&tex_id);
}
fn texture(&self, texture_id: egui::TextureId) -> Option<&SrgbTexture2d> {
self.textures.get(&texture_id).map(|rc| rc.as_ref())
}
pub fn register_native_texture(&mut self, native: Rc<SrgbTexture2d>) -> egui::TextureId {
let id = egui::TextureId::User(self.next_native_tex_id);
self.next_native_tex_id += 1;
self.textures.insert(id, native);
id
}
pub fn replace_native_texture(&mut self, id: egui::TextureId, replacing: Rc<SrgbTexture2d>) {
self.textures.insert(id, replacing);
}
}