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use std::rc::Rc; use crate::error::Result; use crate::graphics::{DrawParams, FilterMode, Texture}; use crate::platform::{GraphicsDevice, RawFramebuffer, RawRenderbuffer}; use crate::Context; /// A texture that can be used for off-screen rendering. /// /// This is sometimes referred to as a 'render texture' or 'render target' in other /// frameworks. /// /// Canvases can be useful if you want to do some rendering upfront and then cache the result /// (e.g. a static background), or if you want to apply transformations/shaders to multiple /// things simultaneously. /// /// # Performance /// /// Creating a `Canvas` is a relatively expensive operation. If you can, store them in your /// [`State`](crate::State) struct rather than recreating them each frame. /// /// Cloning a `Canvas` is a very cheap operation, as the underlying data is shared between the /// original instance and the clone via [reference-counting](https://doc.rust-lang.org/std/rc/struct.Rc.html). /// This does mean, however, that updating a `Canvas` (for example, changing its filter mode) will also /// update any other clones of that `Canvas`. /// /// # Examples /// /// The [`canvas`](https://github.com/17cupsofcoffee/tetra/blob/main/examples/canvas.rs) /// example demonstrates how to draw to a canvas, and then draw that canvas to /// the screen. #[derive(Debug, Clone, PartialEq)] pub struct Canvas { pub(crate) framebuffer: Rc<RawFramebuffer>, pub(crate) texture: Texture, pub(crate) multisample: Option<Rc<RawRenderbuffer>>, } impl Canvas { /// Creates a new canvas. /// /// # Errors /// /// * [`TetraError::PlatformError`](crate::TetraError::PlatformError) will be returned if the underlying /// graphics API encounters an error. pub fn new(ctx: &mut Context, width: i32, height: i32) -> Result<Canvas> { Canvas::with_device( &mut ctx.device, width, height, ctx.graphics.default_filter_mode, 0, ) } /// Creates a new canvas, with the specified level of multisample anti-aliasing. /// /// The number of samples that can be used varies between graphics cards - `2`, `4` and `8` are reasonably /// well supported. /// /// # Errors /// /// * [`TetraError::PlatformError`](crate::TetraError::PlatformError) will be returned if the underlying /// graphics API encounters an error. pub fn multisampled(ctx: &mut Context, width: i32, height: i32, samples: u8) -> Result<Canvas> { Canvas::with_device( &mut ctx.device, width, height, ctx.graphics.default_filter_mode, samples, ) } pub(crate) fn with_device( device: &mut GraphicsDevice, width: i32, height: i32, filter_mode: FilterMode, samples: u8, ) -> Result<Canvas> { let texture = Texture::with_device_empty(device, width, height, filter_mode)?; let framebuffer = device.new_framebuffer()?; let multisample = if samples > 0 { let multisample = device.new_renderbuffer(width, height, samples)?; device.attach_renderbuffer_to_framebuffer(&framebuffer, &multisample, true); Some(Rc::new(multisample)) } else { device.attach_texture_to_framebuffer(&framebuffer, &texture.data.handle, true); None }; Ok(Canvas { framebuffer: Rc::new(framebuffer), texture, multisample, }) } /// Draws the canvas to the screen (or to another canvas, if one is enabled). pub fn draw<P>(&self, ctx: &mut Context, params: P) where P: Into<DrawParams>, { self.texture.draw(ctx, params) } /// Returns the width of the canvas. pub fn width(&self) -> i32 { self.texture.width() } /// Returns the height of the canvas. pub fn height(&self) -> i32 { self.texture.height() } /// Returns the size of the canvas. pub fn size(&self) -> (i32, i32) { self.texture.size() } /// Returns the filter mode being used by the canvas. pub fn filter_mode(&self) -> FilterMode { self.texture.filter_mode() } /// Sets the filter mode that should be used by the canvas. pub fn set_filter_mode(&mut self, ctx: &mut Context, filter_mode: FilterMode) { self.texture.set_filter_mode(ctx, filter_mode); } /// Writes RGBA pixel data to a specified region of the canvas. /// /// This method requires you to provide enough data to fill the target rectangle. /// If you provide too little data, an error will be returned. /// If you provide too much data, it will be truncated. /// /// If you want to overwrite the entire canvas, the `replace_data` method offers a /// more concise way of doing this. /// /// # Errors /// /// * [`TetraError::NotEnoughData`](crate::TetraError::NotEnoughData) will be returned /// if not enough data is provided to fill the target rectangle. This is to prevent /// the graphics API from trying to read uninitialized memory. /// /// # Panics /// /// Panics if any part of the target rectangle is outside the bounds of the canvas. pub fn set_data( &self, ctx: &mut Context, x: i32, y: i32, width: i32, height: i32, data: &[u8], ) -> Result { self.texture.set_data(ctx, x, y, width, height, data) } /// Overwrites the entire canvas with new RGBA pixel data. /// /// This method requires you to provide enough data to fill the canvas. /// If you provide too little data, an error will be returned. /// If you provide too much data, it will be truncated. /// /// If you only want to write to a subsection of the canvas, use the `set_data` /// method instead. /// /// # Errors /// /// * [`TetraError::NotEnoughData`](crate::TetraError::NotEnoughData) will be returned /// if not enough data is provided to fill the target rectangle. This is to prevent /// the graphics API from trying to read uninitialized memory. pub fn replace_data(&self, ctx: &mut Context, data: &[u8]) -> Result { self.texture.replace_data(ctx, data) } /// Returns a reference to the canvas' underlying texture. pub fn texture(&self) -> &Texture { &self.texture } }