1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
use std::{borrow::Cow, path::Path, sync::PoisonError};

use bevy_app::Plugin;
use bevy_asset::{load_internal_asset, Handle};
use bevy_ecs::{entity::EntityHashMap, prelude::*};
use bevy_log::{error, info, info_span};
use bevy_tasks::AsyncComputeTaskPool;
use std::sync::Mutex;
use thiserror::Error;
use wgpu::{
    CommandEncoder, Extent3d, ImageDataLayout, TextureFormat, COPY_BYTES_PER_ROW_ALIGNMENT,
};

use crate::{
    prelude::{Image, Shader},
    render_asset::RenderAssetUsages,
    render_resource::{
        binding_types::texture_2d, BindGroup, BindGroupLayout, BindGroupLayoutEntries, Buffer,
        CachedRenderPipelineId, FragmentState, PipelineCache, RenderPipelineDescriptor,
        SpecializedRenderPipeline, SpecializedRenderPipelines, Texture, VertexState,
    },
    renderer::RenderDevice,
    texture::TextureFormatPixelInfo,
    RenderApp,
};

use super::ExtractedWindows;

pub type ScreenshotFn = Box<dyn FnOnce(Image) + Send + Sync>;

/// A resource which allows for taking screenshots of the window.
#[derive(Resource, Default)]
pub struct ScreenshotManager {
    // this is in a mutex to enable extraction with only an immutable reference
    pub(crate) callbacks: Mutex<EntityHashMap<ScreenshotFn>>,
}

#[derive(Error, Debug)]
#[error("A screenshot for this window has already been requested.")]
pub struct ScreenshotAlreadyRequestedError;

impl ScreenshotManager {
    /// Signals the renderer to take a screenshot of this frame.
    ///
    /// The given callback will eventually be called on one of the [`AsyncComputeTaskPool`]s threads.
    pub fn take_screenshot(
        &mut self,
        window: Entity,
        callback: impl FnOnce(Image) + Send + Sync + 'static,
    ) -> Result<(), ScreenshotAlreadyRequestedError> {
        self.callbacks
            .get_mut()
            .unwrap_or_else(PoisonError::into_inner)
            .try_insert(window, Box::new(callback))
            .map(|_| ())
            .map_err(|_| ScreenshotAlreadyRequestedError)
    }

    /// Signals the renderer to take a screenshot of this frame.
    ///
    /// The screenshot will eventually be saved to the given path, and the format will be derived from the extension.
    pub fn save_screenshot_to_disk(
        &mut self,
        window: Entity,
        path: impl AsRef<Path>,
    ) -> Result<(), ScreenshotAlreadyRequestedError> {
        let path = path.as_ref().to_owned();
        self.take_screenshot(window, move |img| match img.try_into_dynamic() {
            Ok(dyn_img) => match image::ImageFormat::from_path(&path) {
                Ok(format) => {
                    // discard the alpha channel which stores brightness values when HDR is enabled to make sure
                    // the screenshot looks right
                    let img = dyn_img.to_rgb8();
                    #[cfg(not(target_arch = "wasm32"))]
                    match img.save_with_format(&path, format) {
                        Ok(_) => info!("Screenshot saved to {}", path.display()),
                        Err(e) => error!("Cannot save screenshot, IO error: {e}"),
                    }

                    #[cfg(target_arch = "wasm32")]
                    {
                        match (|| {
                            use image::EncodableLayout;
                            use wasm_bindgen::{JsCast, JsValue};

                            let mut image_buffer = std::io::Cursor::new(Vec::new());
                            img.write_to(&mut image_buffer, format)
                                .map_err(|e| JsValue::from_str(&format!("{e}")))?;
                            // SAFETY: `image_buffer` only exist in this closure, and is not used after this line
                            let parts = js_sys::Array::of1(&unsafe {
                                js_sys::Uint8Array::view(image_buffer.into_inner().as_bytes())
                                    .into()
                            });
                            let blob = web_sys::Blob::new_with_u8_array_sequence(&parts)?;
                            let url = web_sys::Url::create_object_url_with_blob(&blob)?;
                            let window = web_sys::window().unwrap();
                            let document = window.document().unwrap();
                            let link = document.create_element("a")?;
                            link.set_attribute("href", &url)?;
                            link.set_attribute(
                                "download",
                                path.file_name()
                                    .and_then(|filename| filename.to_str())
                                    .ok_or_else(|| JsValue::from_str("Invalid filename"))?,
                            )?;
                            let html_element = link.dyn_into::<web_sys::HtmlElement>()?;
                            html_element.click();
                            web_sys::Url::revoke_object_url(&url)?;
                            Ok::<(), JsValue>(())
                        })() {
                            Ok(_) => info!("Screenshot saved to {}", path.display()),
                            Err(e) => error!("Cannot save screenshot, error: {e:?}"),
                        };
                    }
                }
                Err(e) => error!("Cannot save screenshot, requested format not recognized: {e}"),
            },
            Err(e) => error!("Cannot save screenshot, screen format cannot be understood: {e}"),
        })
    }
}

pub struct ScreenshotPlugin;

const SCREENSHOT_SHADER_HANDLE: Handle<Shader> = Handle::weak_from_u128(11918575842344596158);

impl Plugin for ScreenshotPlugin {
    fn build(&self, app: &mut bevy_app::App) {
        app.init_resource::<ScreenshotManager>();

        load_internal_asset!(
            app,
            SCREENSHOT_SHADER_HANDLE,
            "screenshot.wgsl",
            Shader::from_wgsl
        );
    }

    fn finish(&self, app: &mut bevy_app::App) {
        if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
            render_app.init_resource::<SpecializedRenderPipelines<ScreenshotToScreenPipeline>>();
        }

        #[cfg(feature = "bevy_ci_testing")]
        if app
            .world
            .contains_resource::<bevy_app::ci_testing::CiTestingConfig>()
        {
            app.add_systems(bevy_app::Update, ci_testing_screenshot_at);
        }
    }
}

#[cfg(feature = "bevy_ci_testing")]
fn ci_testing_screenshot_at(
    mut current_frame: Local<u32>,
    ci_testing_config: Res<bevy_app::ci_testing::CiTestingConfig>,
    mut screenshot_manager: ResMut<ScreenshotManager>,
    main_window: Query<Entity, With<bevy_window::PrimaryWindow>>,
) {
    if ci_testing_config
        .screenshot_frames
        .contains(&*current_frame)
    {
        info!("Taking a screenshot at frame {}.", *current_frame);
        let path = format!("./screenshot-{}.png", *current_frame);
        screenshot_manager
            .save_screenshot_to_disk(main_window.single(), path)
            .unwrap();
    }
    *current_frame += 1;
}

pub(crate) fn align_byte_size(value: u32) -> u32 {
    value + (COPY_BYTES_PER_ROW_ALIGNMENT - (value % COPY_BYTES_PER_ROW_ALIGNMENT))
}

pub(crate) fn get_aligned_size(width: u32, height: u32, pixel_size: u32) -> u32 {
    height * align_byte_size(width * pixel_size)
}

pub(crate) fn layout_data(width: u32, height: u32, format: TextureFormat) -> ImageDataLayout {
    ImageDataLayout {
        bytes_per_row: if height > 1 {
            // 1 = 1 row
            Some(get_aligned_size(width, 1, format.pixel_size() as u32))
        } else {
            None
        },
        rows_per_image: None,
        ..Default::default()
    }
}

#[derive(Resource)]
pub struct ScreenshotToScreenPipeline {
    pub bind_group_layout: BindGroupLayout,
}

impl FromWorld for ScreenshotToScreenPipeline {
    fn from_world(render_world: &mut World) -> Self {
        let device = render_world.resource::<RenderDevice>();

        let bind_group_layout = device.create_bind_group_layout(
            "screenshot-to-screen-bgl",
            &BindGroupLayoutEntries::single(
                wgpu::ShaderStages::FRAGMENT,
                texture_2d(wgpu::TextureSampleType::Float { filterable: false }),
            ),
        );

        Self { bind_group_layout }
    }
}

impl SpecializedRenderPipeline for ScreenshotToScreenPipeline {
    type Key = TextureFormat;

    fn specialize(&self, key: Self::Key) -> RenderPipelineDescriptor {
        RenderPipelineDescriptor {
            label: Some(Cow::Borrowed("screenshot-to-screen")),
            layout: vec![self.bind_group_layout.clone()],
            vertex: VertexState {
                buffers: vec![],
                shader_defs: vec![],
                entry_point: Cow::Borrowed("vs_main"),
                shader: SCREENSHOT_SHADER_HANDLE,
            },
            primitive: wgpu::PrimitiveState {
                cull_mode: Some(wgpu::Face::Back),
                ..Default::default()
            },
            depth_stencil: None,
            multisample: Default::default(),
            fragment: Some(FragmentState {
                shader: SCREENSHOT_SHADER_HANDLE,
                entry_point: Cow::Borrowed("fs_main"),
                shader_defs: vec![],
                targets: vec![Some(wgpu::ColorTargetState {
                    format: key,
                    blend: None,
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            push_constant_ranges: Vec::new(),
        }
    }
}

pub struct ScreenshotPreparedState {
    pub texture: Texture,
    pub buffer: Buffer,
    pub bind_group: BindGroup,
    pub pipeline_id: CachedRenderPipelineId,
}

pub(crate) fn submit_screenshot_commands(world: &World, encoder: &mut CommandEncoder) {
    let windows = world.resource::<ExtractedWindows>();
    let pipelines = world.resource::<PipelineCache>();

    for window in windows.values() {
        if let Some(memory) = &window.screenshot_memory {
            let width = window.physical_width;
            let height = window.physical_height;
            let texture_format = window.swap_chain_texture_format.unwrap();

            encoder.copy_texture_to_buffer(
                memory.texture.as_image_copy(),
                wgpu::ImageCopyBuffer {
                    buffer: &memory.buffer,
                    layout: layout_data(width, height, texture_format),
                },
                Extent3d {
                    width,
                    height,
                    ..Default::default()
                },
            );
            if let Some(pipeline) = pipelines.get_render_pipeline(memory.pipeline_id) {
                let true_swapchain_texture_view = window
                    .swap_chain_texture
                    .as_ref()
                    .unwrap()
                    .texture
                    .create_view(&Default::default());
                let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some("screenshot_to_screen_pass"),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &true_swapchain_texture_view,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Load,
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    timestamp_writes: None,
                    occlusion_query_set: None,
                });
                pass.set_pipeline(pipeline);
                pass.set_bind_group(0, &memory.bind_group, &[]);
                pass.draw(0..3, 0..1);
            }
        }
    }
}

pub(crate) fn collect_screenshots(world: &mut World) {
    let _span = info_span!("collect_screenshots");

    let mut windows = world.resource_mut::<ExtractedWindows>();
    for window in windows.values_mut() {
        if let Some(screenshot_func) = window.screenshot_func.take() {
            let width = window.physical_width;
            let height = window.physical_height;
            let texture_format = window.swap_chain_texture_format.unwrap();
            let pixel_size = texture_format.pixel_size();
            let ScreenshotPreparedState { buffer, .. } = window.screenshot_memory.take().unwrap();

            let finish = async move {
                let (tx, rx) = async_channel::bounded(1);
                let buffer_slice = buffer.slice(..);
                // The polling for this map call is done every frame when the command queue is submitted.
                buffer_slice.map_async(wgpu::MapMode::Read, move |result| {
                    let err = result.err();
                    if err.is_some() {
                        panic!("{}", err.unwrap().to_string());
                    }
                    tx.try_send(()).unwrap();
                });
                rx.recv().await.unwrap();
                let data = buffer_slice.get_mapped_range();
                // we immediately move the data to CPU memory to avoid holding the mapped view for long
                let mut result = Vec::from(&*data);
                drop(data);
                drop(buffer);

                if result.len() != ((width * height) as usize * pixel_size) {
                    // Our buffer has been padded because we needed to align to a multiple of 256.
                    // We remove this padding here
                    let initial_row_bytes = width as usize * pixel_size;
                    let buffered_row_bytes = align_byte_size(width * pixel_size as u32) as usize;

                    let mut take_offset = buffered_row_bytes;
                    let mut place_offset = initial_row_bytes;
                    for _ in 1..height {
                        result.copy_within(
                            take_offset..take_offset + buffered_row_bytes,
                            place_offset,
                        );
                        take_offset += buffered_row_bytes;
                        place_offset += initial_row_bytes;
                    }
                    result.truncate(initial_row_bytes * height as usize);
                }

                screenshot_func(Image::new(
                    Extent3d {
                        width,
                        height,
                        depth_or_array_layers: 1,
                    },
                    wgpu::TextureDimension::D2,
                    result,
                    texture_format,
                    RenderAssetUsages::RENDER_WORLD,
                ));
            };

            AsyncComputeTaskPool::get().spawn(finish).detach();
        }
    }
}