Expand description
The high-level module responsible for interfacing with the GPU.
Much of WebRender’s design is driven by separating work into different threads. To avoid the complexities of multi-threaded GPU access, we restrict all communication with the GPU to one thread, the render thread. But since issuing GPU commands is often a bottleneck, we move everything else (i.e. the computation of what commands to issue) to another thread, the RenderBackend thread. The RenderBackend, in turn, may delegate work to other thread (like the SceneBuilder threads or Rayon workers), but the Render-vs-RenderBackend distinction is the most important.
The consumer is responsible for initializing the render thread before
calling into WebRender, which means that this module also serves as the
initial entry point into WebRender, and is responsible for spawning the
various other threads discussed above. That said, WebRender initialization
returns both the Renderer instance as well as a channel for communicating
directly with the RenderBackend. Aside from a few high-level operations
like ‘render now’, most of interesting commands from the consumer go over
that channel and operate on the RenderBackend.
§Space conversion guidelines
At this stage, we shuld be operating with DevicePixel and FramebufferPixel only.
“Framebuffer” space represents the final destination of our rendeing,
and it happens to be Y-flipped on OpenGL. The conversion is done as follows:
- for rasterized primitives, the orthographics projection transforms the content rectangle to -1 to 1
- the viewport transformation is setup to map the whole range to
the framebuffer rectangle provided by the document view, stored in
DrawTarget - all the direct framebuffer operations, like blitting, reading pixels, and setting
up the scissor, are accepting already transformed coordinates, which we can get by
calling
DrawTarget::to_framebuffer_rect
Re-exports§
pub use debug::DebugRenderer;pub use shade::PendingShadersToPrecache;pub use shade::Shaders;pub use vertex::desc;pub use vertex::VertexArrayKind;pub use vertex::MAX_VERTEX_TEXTURE_WIDTH;pub use gpu_buffer::GpuBuffer;pub use gpu_buffer::GpuBufferF;pub use gpu_buffer::GpuBufferBuilderF;pub use gpu_buffer::GpuBufferI;pub use gpu_buffer::GpuBufferBuilderI;pub use gpu_buffer::GpuBufferAddress;pub use gpu_buffer::GpuBufferBuilder;
Modules§
- debug 🔒
- gpu_
buffer 🔒 - gpu_
cache 🔒 - init 🔒
- shade 🔒
- tests 🔒
- upload 🔒
- This module contains the convoluted logic that goes into uploading content into the texture cache’s textures.
- vertex 🔒
- Rendering logic related to the vertex shaders and their states, uncluding
Structs§
- Buffer
Damage 🔒Tracker - Tracks buffer damage rects over a series of frames.
- Cache
Texture 🔒 - CpuProfile
- Debug
Flags - Flags to enable/disable various builtin debugging tools.
- Debug
Overlay 🔒State - Information about the state of the debugging / profiler overlay in native compositing mode.
- Full
Frame Stats - The cumulative times spent in each painting phase to generate this frame.
- GpuProfile
- Graphics
ApiInfo - Occlusion
Item 🔒Key - Pipeline
Info - Plain
External 🔒Resources - Plain
Renderer 🔒 - Plain
Texture 🔒 - Render
Results - Return type from render(), which contains some repr(C) statistics as well as some non-repr(C) data.
- Renderer
- The renderer is responsible for submitting to the GPU the work prepared by the RenderBackend.
- Renderer
Stats - Some basic statistics about the rendered scene, used in Gecko, as well as in wrench reftests to ensure that tests are batching and/or allocating on render targets as we expect them to.
- Shader
Precache Flags - Flags that control how shaders are pre-cached, if at all.
- Swap
Chain 🔒Layer - Texture
Resolver 🔒 - Helper struct for resolving device Textures for use during rendering passes.
Enums§
- Blend
Mode - Framebuffer
Kind 🔒 - Graphics
Api - Partial
Present 🔒Mode - The selected partial present mode for a given frame.
- Renderer
Error - Shader
Color Mode - Texture
Sampler 🔒 - Enumeration of the texture samplers used across the various WebRender shaders.
Constants§
- BLOCKS_
PER_ UV_ RECT - Number of GPU blocks per UV rectangle provided for an image.
- GPU_
SAMPLER_ 🔒TAG_ ALPHA - GPU_
SAMPLER_ 🔒TAG_ OPAQUE - GPU_
SAMPLER_ 🔒TAG_ TRANSPARENT - GPU_
TAG_ 🔒BLIT - GPU_
TAG_ 🔒BLUR - GPU_
TAG_ 🔒BRUSH_ BLEND - GPU_
TAG_ 🔒BRUSH_ IMAGE - GPU_
TAG_ 🔒BRUSH_ LINEAR_ GRADIENT - GPU_
TAG_ 🔒BRUSH_ MIXBLEND - GPU_
TAG_ 🔒BRUSH_ OPACITY - GPU_
TAG_ 🔒BRUSH_ SOLID - GPU_
TAG_ 🔒BRUSH_ YUV_ IMAGE - GPU_
TAG_ 🔒CACHE_ BORDER - GPU_
TAG_ 🔒CACHE_ CLIP - GPU_
TAG_ 🔒CACHE_ FAST_ LINEAR_ GRADIENT - GPU_
TAG_ 🔒CACHE_ LINEAR_ GRADIENT - GPU_
TAG_ 🔒CACHE_ LINE_ DECORATION - GPU_
TAG_ 🔒COMPOSITE - GPU_
TAG_ 🔒CONIC_ GRADIENT - GPU_
TAG_ 🔒INDIRECT_ MASK - GPU_
TAG_ 🔒INDIRECT_ PRIM - GPU_
TAG_ 🔒PRIMITIVE - GPU_
TAG_ 🔒PRIM_ SPLIT_ COMPOSITE - GPU_
TAG_ 🔒PRIM_ TEXT_ RUN - GPU_
TAG_ 🔒RADIAL_ GRADIENT - GPU_
TAG_ 🔒SCALE - GPU_
TAG_ 🔒SETUP_ DATA - GPU_
TAG_ 🔒SETUP_ TARGET - GPU_
TAG_ 🔒SVG_ FILTER - GPU_
TAG_ 🔒SVG_ FILTER_ NODES - TEXTURE_
CACHE_ DBG_ CLEAR_ COLOR - The clear color used for the texture cache when the debug display is enabled. We use a shade of blue so that we can still identify completely blue items in the texture cache.
- VERTEX_
DATA_ TEXTURE_ COUNT - The size of the array of each type of vertex data texture that is round-robin-ed each frame during bind_frame_data. Doing this helps avoid driver stalls while updating the texture in some drivers. The size of these textures are typically very small (e.g. < 16 kB) so it’s not a huge waste of memory. Despite that, this is a short-term solution - we want to find a better way to provide this frame data, which will likely involve some combination of UBO/SSBO usage. Although this only affects some platforms, it’s enabled on all platforms to reduce testing differences between platforms.