Remove the scroll bar APIs.

It's much better if applications draw scrollbars by adding normal
primitives to the display list. This means:

* Better control of how they look visually.
* Can make them clickable / draggable.
* Less code complexity in WR.
* Better control of scrollbar behavior (where enabled etc).

webrender/src/display_list_flattener.rs

@@ -33,16 +33,9 @@ use resource_cache::{FontInstanceMap, ImageRequest};
 use scene::{Scene, ScenePipeline, StackingContextHelpers};
 use spatial_node::{SpatialNodeType, StickyFrameInfo};
 use std::{f32, mem};
-use tiling::{CompositeOps, ScrollbarPrimitive};
+use tiling::{CompositeOps};
 use util::{MaxRect, RectHelpers};
 
-static DEFAULT_SCROLLBAR_COLOR: ColorF = ColorF {
-    r: 0.3,
-    g: 0.3,
-    b: 0.3,
-    a: 0.6,
-};
-
 #[derive(Debug, Copy, Clone)]
 struct ClipNode {
     id: ClipChainId,
@@ -144,9 +137,6 @@ pub struct DisplayListFlattener<'a> {
     /// The stack keeping track of the root clip chains associated with pipelines.
     pipeline_clip_chain_stack: Vec<ClipChainId>,
 
-    /// A list of scrollbar primitives.
-    pub scrollbar_prims: Vec<ScrollbarPrimitive>,
-
     /// The store of primitives.
     pub prim_store: PrimitiveStore,
 
@@ -196,7 +186,6 @@ impl<'a> DisplayListFlattener<'a> {
             output_pipelines,
             id_to_index_mapper: ClipIdToIndexMapper::default(),
             hit_testing_runs: Vec::new(),
-            scrollbar_prims: Vec::new(),
             shadow_stack: Vec::new(),
             sc_stack: Vec::new(),
             pipeline_clip_chain_stack: vec![ClipChainId::NONE],
@@ -259,7 +248,6 @@ impl<'a> DisplayListFlattener<'a> {
         );
 
         let root_scroll_node = ClipId::root_scroll_node(pipeline_id);
-        let scroll_frame_info = self.simple_scroll_and_clip_chain(&root_scroll_node);
 
         self.push_stacking_context(
             pipeline_id,
@@ -295,17 +283,6 @@ impl<'a> DisplayListFlattener<'a> {
 
         self.flatten_items(&mut pipeline.display_list.iter(), pipeline_id, LayoutVector2D::zero());
 
-        if self.config.enable_scrollbars {
-            let scrollbar_rect = LayoutRect::new(LayoutPoint::zero(), LayoutSize::new(10.0, 70.0));
-            let container_rect = LayoutRect::new(LayoutPoint::zero(), *frame_size);
-            self.add_scroll_bar(
-                reference_frame_info.spatial_node_index,
-                &LayoutPrimitiveInfo::new(scrollbar_rect),
-                DEFAULT_SCROLLBAR_COLOR,
-                ScrollbarInfo(scroll_frame_info.spatial_node_index, container_rect),
-            );
-        }
-
         self.pop_stacking_context();
     }
 
@@ -1528,40 +1505,6 @@ impl<'a> DisplayListFlattener<'a> {
         );
     }
 
-    pub fn add_scroll_bar(
-        &mut self,
-        spatial_node_index: SpatialNodeIndex,
-        info: &LayoutPrimitiveInfo,
-        color: ColorF,
-        scrollbar_info: ScrollbarInfo,
-    ) {
-        if color.a == 0.0 {
-            return;
-        }
-
-        let prim = BrushPrimitive::new(
-            BrushKind::new_solid(color),
-            None,
-        );
-
-        let prim_index = self.create_primitive(
-            info,
-            ClipChainId::NONE,
-            spatial_node_index,
-            PrimitiveContainer::Brush(prim),
-        );
-
-        self.add_primitive_to_draw_list(
-            prim_index,
-        );
-
-        self.scrollbar_prims.push(ScrollbarPrimitive {
-            prim_index,
-            scroll_frame_index: scrollbar_info.0,
-            frame_rect: scrollbar_info.1,
-        });
-    }
-
     pub fn add_line(
         &mut self,
         clip_and_scroll: ScrollNodeAndClipChain,
@@ -2117,6 +2060,3 @@ struct FlattenedStackingContext {
     participating_in_3d_context: bool,
     has_mix_blend_mode: bool,
 }
-
-#[derive(Debug)]
-pub struct ScrollbarInfo(pub SpatialNodeIndex, pub LayoutRect);

webrender/src/frame_builder.rs

@@ -24,8 +24,7 @@ use spatial_node::SpatialNode;
 use std::f32;
 use std::sync::Arc;
 use tiling::{Frame, RenderPass, RenderPassKind, RenderTargetContext};
-use tiling::{ScrollbarPrimitive, SpecialRenderPasses};
-use util;
+use tiling::{SpecialRenderPasses};
 
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -47,7 +46,6 @@ impl Default for ChasePrimitive {
 #[cfg_attr(feature = "capture", derive(Serialize))]
 #[cfg_attr(feature = "replay", derive(Deserialize))]
 pub struct FrameBuilderConfig {
-    pub enable_scrollbars: bool,
     pub default_font_render_mode: FontRenderMode,
     pub dual_source_blending_is_supported: bool,
     pub dual_source_blending_is_enabled: bool,
@@ -64,7 +62,6 @@ pub struct FrameBuilder {
     pub clip_store: ClipStore,
     pub hit_testing_runs: Vec<HitTestingRun>,
     pub config: FrameBuilderConfig,
-    pub scrollbar_prims: Vec<ScrollbarPrimitive>,
 }
 
 pub struct FrameBuildingContext<'a> {
@@ -135,15 +132,13 @@ impl FrameBuilder {
     pub fn empty() -> Self {
         FrameBuilder {
             hit_testing_runs: Vec::new(),
-            scrollbar_prims: Vec::new(),
             prim_store: PrimitiveStore::new(),
             clip_store: ClipStore::new(),
             screen_rect: DeviceUintRect::zero(),
             window_size: DeviceUintSize::zero(),
             background_color: None,
             scene_id: 0,
             config: FrameBuilderConfig {
-                enable_scrollbars: false,
                 default_font_render_mode: FontRenderMode::Mono,
                 dual_source_blending_is_enabled: true,
                 dual_source_blending_is_supported: false,
@@ -161,7 +156,6 @@ impl FrameBuilder {
     ) -> Self {
         FrameBuilder {
             hit_testing_runs: flattener.hit_testing_runs,
-            scrollbar_prims: flattener.scrollbar_prims,
             prim_store: flattener.prim_store,
             clip_store: flattener.clip_store,
             screen_rect,
@@ -290,35 +284,6 @@ impl FrameBuilder {
         Some(render_task_id)
     }
 
-    fn update_scroll_bars(&mut self, clip_scroll_tree: &ClipScrollTree, gpu_cache: &mut GpuCache) {
-        static SCROLLBAR_PADDING: f32 = 8.0;
-
-        for scrollbar_prim in &self.scrollbar_prims {
-            let metadata = &mut self.prim_store.primitives[scrollbar_prim.prim_index.0].metadata;
-            let scroll_frame = &clip_scroll_tree.spatial_nodes[scrollbar_prim.scroll_frame_index.0];
-
-            // Invalidate what's in the cache so it will get rebuilt.
-            gpu_cache.invalidate(&metadata.gpu_location);
-
-            let scrollable_distance = scroll_frame.scrollable_size().height;
-            if scrollable_distance <= 0.0 {
-                metadata.local_clip_rect.size = LayoutSize::zero();
-                continue;
-            }
-            let amount_scrolled = -scroll_frame.scroll_offset().y / scrollable_distance;
-
-            let frame_rect = scrollbar_prim.frame_rect;
-            let min_y = frame_rect.origin.y + SCROLLBAR_PADDING;
-            let max_y = frame_rect.origin.y + frame_rect.size.height -
-                (SCROLLBAR_PADDING + metadata.local_rect.size.height);
-
-            metadata.local_rect.origin.x = frame_rect.origin.x + frame_rect.size.width -
-                (metadata.local_rect.size.width + SCROLLBAR_PADDING);
-            metadata.local_rect.origin.y = util::lerp(min_y, max_y, amount_scrolled);
-            metadata.local_clip_rect = metadata.local_rect;
-        }
-    }
-
     pub fn build(
         &mut self,
         resource_cache: &mut ResourceCache,
@@ -355,8 +320,6 @@ impl FrameBuilder {
             Some(&mut transform_palette),
         );
 
-        self.update_scroll_bars(clip_scroll_tree, gpu_cache);
-
         let mut render_tasks = RenderTaskTree::new(frame_id);
 
         let screen_size = self.screen_rect.size.to_i32();

webrender/src/renderer.rs

@@ -1721,7 +1721,6 @@ impl Renderer {
         };
 
         let config = FrameBuilderConfig {
-            enable_scrollbars: options.enable_scrollbars,
             default_font_render_mode,
             dual_source_blending_is_enabled: true,
             dual_source_blending_is_supported: ext_dual_source_blending,
@@ -4400,7 +4399,6 @@ pub struct RendererOptions {
     pub enable_aa: bool,
     pub enable_dithering: bool,
     pub max_recorded_profiles: usize,
-    pub enable_scrollbars: bool,
     pub precache_shaders: bool,
     pub renderer_kind: RendererKind,
     pub enable_subpixel_aa: bool,
@@ -4433,7 +4431,6 @@ impl Default for RendererOptions {
             enable_dithering: true,
             debug_flags: DebugFlags::empty(),
             max_recorded_profiles: 0,
-            enable_scrollbars: false,
             precache_shaders: false,
             renderer_kind: RendererKind::Native,
             enable_subpixel_aa: false,

webrender/src/tiling.rs

@@ -4,10 +4,10 @@
 
 use api::{ColorF, BorderStyle, DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePixelScale};
 use api::{DeviceUintPoint, DeviceUintRect, DeviceUintSize, DocumentLayer, FilterOp, ImageFormat};
-use api::{LayoutRect, MixBlendMode, PipelineId};
+use api::{MixBlendMode, PipelineId};
 use batch::{AlphaBatchBuilder, AlphaBatchContainer, ClipBatcher, resolve_image};
 use clip::{ClipDataStore, ClipStore};
-use clip_scroll_tree::{ClipScrollTree, SpatialNodeIndex};
+use clip_scroll_tree::{ClipScrollTree};
 use device::{FrameId, Texture};
 #[cfg(feature = "pathfinder")]
 use euclid::{TypedPoint2D, TypedVector2D};
@@ -17,7 +17,7 @@ use gpu_types::{TransformData, TransformPalette};
 use internal_types::{FastHashMap, SavedTargetIndex, SourceTexture};
 #[cfg(feature = "pathfinder")]
 use pathfinder_partitioner::mesh::Mesh;
-use prim_store::{PrimitiveIndex, PrimitiveStore, DeferredResolve};
+use prim_store::{PrimitiveStore, DeferredResolve};
 use profiler::FrameProfileCounters;
 use render_task::{BlitSource, RenderTaskAddress, RenderTaskId, RenderTaskKind};
 use render_task::{BlurTask, ClearMode, GlyphTask, RenderTaskLocation, RenderTaskTree, ScalingTask};
@@ -31,13 +31,6 @@ const MIN_TARGET_SIZE: u32 = 2048;
 const STYLE_SOLID: i32 = ((BorderStyle::Solid as i32) << 8) | ((BorderStyle::Solid as i32) << 16);
 const STYLE_MASK: i32 = 0x00FF_FF00;
 
-#[derive(Debug)]
-pub struct ScrollbarPrimitive {
-    pub scroll_frame_index: SpatialNodeIndex,
-    pub prim_index: PrimitiveIndex,
-    pub frame_rect: LayoutRect,
-}
-
 #[derive(Debug, Copy, Clone)]
 #[cfg_attr(feature = "capture", derive(Serialize))]
 #[cfg_attr(feature = "replay", derive(Deserialize))]