Struct Transaction

pub struct Transaction {
    pub resource_updates: Vec<ResourceUpdate>,
    pub invalidate_rendered_frame: bool,
    /* private fields */
}

A Transaction is a group of commands to apply atomically to a document.

This mechanism ensures that:

• no other message can be interleaved between two commands that need to be applied together.
• no redundant work is performed if two commands in the same transaction cause the scene or the frame to be rebuilt.

Fields

resource_updates: Vec<ResourceUpdate>

Persistent resource updates to apply as part of this transaction.

invalidate_rendered_frame: bool

Set to true in order to force re-rendering even if WebRender can’t internally detect that something has changed.

Implementations

impl Transaction

pub fn new() -> Self

Constructor.

pub fn skip_scene_builder(&mut self)

Marks this transaction to allow it to skip going through the scene builder thread.

This is useful to avoid jank in transaction associated with animated property updates, panning and zooming.

Note that transactions that skip the scene builder thread can race ahead of transactions that don’t skip it.

pub fn use_scene_builder_thread(&mut self)

Marks this transaction to enforce going through the scene builder thread.

pub fn is_empty(&self) -> bool

Returns true if the transaction has no effect.

pub fn update_epoch(&mut self, pipeline_id: PipelineId, epoch: Epoch)

Update a pipeline’s epoch.

pub fn set_root_pipeline(&mut self, pipeline_id: PipelineId)

Sets the root pipeline.

Examples

let pipeline_id = PipelineId(0, 0);
let mut txn = Transaction::new();
txn.set_root_pipeline(pipeline_id);

pub fn remove_pipeline(&mut self, pipeline_id: PipelineId)

Removes data associated with a pipeline from the internal data structures. If the specified pipeline_id is for the root pipeline, the root pipeline is reset back to None.

pub fn set_display_list( &mut self, epoch: Epoch, background: Option<ColorF>, viewport_size: LayoutSize, (pipeline_id, display_list): (PipelineId, BuiltDisplayList), preserve_frame_state: bool, )

Supplies a new frame to WebRender.

Non-blocking, it notifies a worker process which processes the display list.

Note: Scrolling doesn’t require an own Frame.

Arguments:

• epoch: The unique Frame ID, monotonically increasing.
• background: The background color of this pipeline.
• viewport_size: The size of the viewport for this frame.
• pipeline_id: The ID of the pipeline that is supplying this display list.
• display_list: The root Display list used in this frame.
• preserve_frame_state: If a previous frame exists which matches this pipeline id, this setting determines if frame state (such as scrolling position) should be preserved for this new display list.

pub fn update_resources(&mut self, resources: Vec<ResourceUpdate>)

Add a set of persistent resource updates to apply as part of this transaction.

pub fn notify(&mut self, event: NotificationRequest)

Trigger a notification at a certain stage of the rendering pipeline.

Not that notification requests are skipped during serialization, so is is best to use them for synchronization purposes and not for things that could affect the WebRender’s state.

pub fn set_document_view(&mut self, device_rect: DeviceIntRect)

Setup the output region in the framebuffer for a given document.

pub fn scroll_node_with_id( &mut self, origin: LayoutPoint, id: ExternalScrollId, clamp: ScrollClamping, )

Scrolls the node identified by the given external scroll id to the given scroll position, relative to the pre-scrolled offset for the scrolling layer. That is, providing an origin of (0,0) will reset any WR-side scrolling and just render the display items at the pre-scrolled offsets as provided in the display list. Larger origin values will cause the layer to be scrolled further towards the end of the scroll range. If the ScrollClamping argument is set to clamp, the scroll position is clamped to what WebRender understands to be the bounds of the scroll range, based on the sizes of the scrollable content and the scroll port.

pub fn set_quality_settings(&mut self, settings: QualitySettings)

Set the current quality / performance settings for this document.

pub fn set_is_transform_async_zooming( &mut self, is_zooming: bool, animation_id: PropertyBindingId, )

pub fn generate_frame(&mut self, id: u64)

Generate a new frame. When it’s done and a RenderNotifier has been set in webrender::Renderer, new_frame_ready() gets called. Note that the notifier is called even if the frame generation was a no-op; the arguments passed to new_frame_ready will provide information as to when happened.

pub fn invalidate_rendered_frame(&mut self)

Invalidate rendered frame. It ensure that frame will be rendered during next frame generation. WebRender could skip frame rendering if there is no update. But there are cases that needs to force rendering.

• Content of image is updated by reusing same ExternalImageId.
• Platform requests it if pixels become stale (like wakeup from standby).

pub fn update_dynamic_properties(&mut self, properties: DynamicProperties)

Supply a list of animated property bindings that should be used to resolve bindings in the current display list.

pub fn append_dynamic_transform_properties( &mut self, transforms: Vec<PropertyValue<LayoutTransform>>, )

Add to the list of animated property bindings that should be used to resolve bindings in the current display list. This is a convenience method so the caller doesn’t have to figure out all the dynamic properties before setting them on the transaction but can do them incrementally.

pub fn get_frame_ops(self) -> Vec<FrameMsg>

Consumes this object and just returns the frame ops.

pub fn add_image( &mut self, key: ImageKey, descriptor: ImageDescriptor, data: ImageData, tiling: Option<TileSize>, )

See ResourceUpdate::AddImage.

pub fn update_image( &mut self, key: ImageKey, descriptor: ImageDescriptor, data: ImageData, dirty_rect: &ImageDirtyRect, )

See ResourceUpdate::UpdateImage.

pub fn delete_image(&mut self, key: ImageKey)

See ResourceUpdate::DeleteImage.

pub fn add_blob_image( &mut self, key: BlobImageKey, descriptor: ImageDescriptor, data: Arc<BlobImageData>, visible_rect: DeviceIntRect, tile_size: Option<TileSize>, )

See ResourceUpdate::AddBlobImage.

pub fn update_blob_image( &mut self, key: BlobImageKey, descriptor: ImageDescriptor, data: Arc<BlobImageData>, visible_rect: DeviceIntRect, dirty_rect: &BlobDirtyRect, )

See ResourceUpdate::UpdateBlobImage.

pub fn delete_blob_image(&mut self, key: BlobImageKey)

See ResourceUpdate::DeleteBlobImage.

pub fn set_blob_image_visible_area( &mut self, key: BlobImageKey, area: DeviceIntRect, )

See ResourceUpdate::SetBlobImageVisibleArea.

pub fn add_raw_font(&mut self, key: FontKey, bytes: Vec<u8>, index: u32)

See ResourceUpdate::AddFont.

pub fn add_native_font(&mut self, key: FontKey, native_handle: NativeFontHandle)

See ResourceUpdate::AddFont.

pub fn delete_font(&mut self, key: FontKey)

See ResourceUpdate::DeleteFont.

pub fn add_font_instance( &mut self, key: FontInstanceKey, font_key: FontKey, glyph_size: f32, options: Option<FontInstanceOptions>, platform_options: Option<FontInstancePlatformOptions>, variations: Vec<FontVariation>, )

See ResourceUpdate::AddFontInstance.

pub fn delete_font_instance(&mut self, key: FontInstanceKey)

See ResourceUpdate::DeleteFontInstance.

pub fn set_low_priority(&mut self, low_priority: bool)

A hint that this transaction can be processed at a lower priority. High- priority transactions can jump ahead of regular-priority transactions, but both high- and regular-priority transactions are processed in order relative to other transactions of the same priority.

pub fn is_low_priority(&self) -> bool

Returns whether this transaction is marked as low priority.