Auto merge of #445 - kvark:image_mask, r=glennw

Image mask support

Closes #405

I'm not completely sure if this is the right approach, hoping to get some review/feedback to proceed. The API and logic works for me with `wr_sample`, although the implementation lacks a lot of features to support, like image repeating and layout transformations.

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Author: bors-servo

webrender/res/clip_shared.glsl

@@ -5,14 +5,19 @@
 
 flat varying vec4 vClipRect;
 flat varying vec4 vClipRadius;
+flat varying vec4 vClipMaskUvRect;
+flat varying vec4 vClipMaskLocalRect;
 
 #ifdef WR_VERTEX_SHADER
-void write_clip(Clip clip) {
+void write_clip(ClipInfo clip) {
     vClipRect = vec4(clip.rect.rect.xy, clip.rect.rect.xy + clip.rect.rect.zw);
     vClipRadius = vec4(clip.top_left.outer_inner_radius.x,
                        clip.top_right.outer_inner_radius.x,
                        clip.bottom_right.outer_inner_radius.x,
                        clip.bottom_left.outer_inner_radius.x);
+    //TODO: interpolate the final mask UV
+    vClipMaskUvRect = clip.mask_info.uv_rect;
+    vClipMaskLocalRect = clip.mask_info.local_rect; //TODO: transform
 }
 #endif
 
@@ -29,23 +34,31 @@ float do_clip(vec2 pos) {
     float d_bl = distance(pos, ref_bl);
 
     float pixels_per_fragment = length(fwidth(pos.xy));
-    // TODO: compute the `nudge` separately for X and Y
     float nudge = 0.5 * pixels_per_fragment;
+    vec4 distances = vec4(d_tl, d_tr, d_br, d_bl) - vClipRadius + nudge;
 
-    bool out0 = pos.x < ref_tl.x && pos.y < ref_tl.y && d_tl > vClipRadius.x - nudge;
-    bool out1 = pos.x > ref_tr.x && pos.y < ref_tr.y && d_tr > vClipRadius.y - nudge;
-    bool out2 = pos.x > ref_br.x && pos.y > ref_br.y && d_br > vClipRadius.z - nudge;
-    bool out3 = pos.x < ref_bl.x && pos.y > ref_bl.y && d_bl > vClipRadius.w - nudge;
+    bvec4 is_out = bvec4(pos.x < ref_tl.x && pos.y < ref_tl.y,
+                         pos.x > ref_tr.x && pos.y < ref_tr.y,
+                         pos.x > ref_br.x && pos.y > ref_br.y,
+                         pos.x < ref_bl.x && pos.y > ref_bl.y);
 
-    vec4 distances = vec4(d_tl, d_tr, d_br, d_bl) - vClipRadius + nudge;
-    float distance_from_border = dot(vec4(out0, out1, out2, out3), distances);
+    float distance_from_border = dot(vec4(is_out),
+                                     max(vec4(0.0, 0.0, 0.0, 0.0), distances));
 
     // Move the distance back into pixels.
     distance_from_border /= pixels_per_fragment;
-
     // Apply a more gradual fade out to transparent.
     //distance_from_border -= 0.5;
 
-    return 1.0 - smoothstep(0.0, 1.0, distance_from_border);
+    float border_alpha = 1.0 - smoothstep(0.0, 1.0, distance_from_border);
+
+    bool repeat_mask = false; //TODO
+    vec2 vMaskUv = (pos - vClipMaskLocalRect.xy) / vClipMaskLocalRect.zw;
+    vec2 clamped_mask_uv = repeat_mask ? fract(vMaskUv) :
+        clamp(vMaskUv, vec2(0.0, 0.0), vec2(1.0, 1.0));
+    vec2 source_uv = clamped_mask_uv * vClipMaskUvRect.zw + vClipMaskUvRect.xy;
+    float mask_alpha = texture(sMask, source_uv).r; //careful: texture has type A8
+
+    return border_alpha * mask_alpha;
 }
 #endif

webrender/res/prim_shared.glsl

@@ -257,7 +257,6 @@ PrimitiveInstance fetch_instance(int index) {
 
     return pi;
 }
-
 struct Primitive {
     Layer layer;
     Tile tile;
@@ -298,11 +297,28 @@ ClipRect fetch_clip_rect(int index) {
     ivec2 uv = get_fetch_uv_2(index);
 
     rect.rect = texelFetchOffset(sData32, uv, 0, ivec2(0, 0));
-    rect.dummy = texelFetchOffset(sData32, uv, 0, ivec2(1, 0));
+    //rect.dummy = texelFetchOffset(sData32, uv, 0, ivec2(1, 0));
+    rect.dummy = vec4(0.0, 0.0, 0.0, 0.0);
 
     return rect;
 }
 
+struct ImageMaskInfo {
+    vec4 uv_rect;
+    vec4 local_rect;
+};
+
+ImageMaskInfo fetch_mask_info(int index) {
+    ImageMaskInfo info;
+
+    ivec2 uv = get_fetch_uv_2(index);
+
+    info.uv_rect = texelFetchOffset(sData32, uv, 0, ivec2(0, 0));
+    info.local_rect = texelFetchOffset(sData32, uv, 0, ivec2(1, 0));
+
+    return info;
+}
+
 struct ClipCorner {
     vec4 rect;
     vec4 outer_inner_radius;
@@ -319,22 +335,24 @@ ClipCorner fetch_clip_corner(int index) {
     return corner;
 }
 
-struct Clip {
+struct ClipInfo {
     ClipRect rect;
     ClipCorner top_left;
     ClipCorner top_right;
     ClipCorner bottom_left;
     ClipCorner bottom_right;
+    ImageMaskInfo mask_info;
 };
 
-Clip fetch_clip(int index) {
-    Clip clip;
+ClipInfo fetch_clip(int index) {
+    ClipInfo clip;
 
     clip.rect = fetch_clip_rect(index + 0);
     clip.top_left = fetch_clip_corner(index + 1);
     clip.top_right = fetch_clip_corner(index + 2);
     clip.bottom_left = fetch_clip_corner(index + 3);
     clip.bottom_right = fetch_clip_corner(index + 4);
+    clip.mask_info = fetch_mask_info(index+5);
 
     return clip;
 }

webrender/res/ps_gradient.fs.glsl

@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+void main(void) {
+#ifdef WR_FEATURE_TRANSFORM
+    float alpha = 0.0;
+    vec2 local_pos = init_transform_fs(vLocalPos, vLocalRect, alpha);
+#else
+    float alpha = 1.0;
+    vec2 local_pos = vPos;
+#endif
+
+    oFragColor = vColor * vec4(1, 1, 1, alpha);
+}

webrender/res/ps_gradient.glsl

@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+varying vec4 vColor;
+
+#ifdef WR_FEATURE_TRANSFORM
+varying vec3 vLocalPos;
+flat varying vec4 vLocalRect;
+#else
+varying vec2 vPos;
+#endif

webrender/res/ps_gradient.vs.glsl

@@ -0,0 +1,69 @@
+#line 1
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+void main(void) {
+    Primitive prim = load_primitive(gl_InstanceID);
+    Gradient gradient = fetch_gradient(prim.prim_index);
+
+    int stop_index = prim.user_data.x + prim.user_data.y;
+    GradientStop g0 = fetch_gradient_stop(stop_index + 0);
+    GradientStop g1 = fetch_gradient_stop(stop_index + 1);
+
+    vec4 segment_rect;
+    switch (int(gradient.kind.x)) {
+        case GRADIENT_HORIZONTAL:
+            float x0 = mix(gradient.start_end_point.x,
+                           gradient.start_end_point.z,
+                           g0.offset.x);
+            float x1 = mix(gradient.start_end_point.x,
+                           gradient.start_end_point.z,
+                           g1.offset.x);
+            segment_rect.yw = prim.local_rect.yw;
+            segment_rect.x = x0;
+            segment_rect.z = x1 - x0;
+            break;
+        case GRADIENT_VERTICAL:
+            float y0 = mix(gradient.start_end_point.y,
+                           gradient.start_end_point.w,
+                           g0.offset.x);
+            float y1 = mix(gradient.start_end_point.y,
+                           gradient.start_end_point.w,
+                           g1.offset.x);
+            segment_rect.xz = prim.local_rect.xz;
+            segment_rect.y = y0;
+            segment_rect.w = y1 - y0;
+            break;
+    }
+
+#ifdef WR_FEATURE_TRANSFORM
+    TransformVertexInfo vi = write_transform_vertex(segment_rect,
+                                                    prim.local_clip_rect,
+                                                    prim.layer,
+                                                    prim.tile);
+    vLocalRect = vi.clipped_local_rect;
+    vLocalPos = vi.local_pos;
+    vec2 f = (vi.local_pos.xy - prim.local_rect.xy) / prim.local_rect.zw;
+#else
+    VertexInfo vi = write_vertex(segment_rect,
+                                 prim.local_clip_rect,
+                                 prim.layer,
+                                 prim.tile);
+
+    vec2 f = (vi.local_clamped_pos - segment_rect.xy) / segment_rect.zw;
+    vPos = vi.local_clamped_pos;
+#endif
+
+    switch (int(gradient.kind.x)) {
+        case GRADIENT_HORIZONTAL:
+            vColor = mix(g0.color, g1.color, f.x);
+            break;
+        case GRADIENT_VERTICAL:
+            vColor = mix(g0.color, g1.color, f.y);
+            break;
+        case GRADIENT_ROTATED:
+            vColor = vec4(1.0, 0.0, 1.0, 1.0);
+            break;
+    }
+}

webrender/res/ps_gradient_clip.fs.glsl

@@ -13,8 +13,4 @@ void main(void) {
 
     alpha = min(alpha, do_clip(local_pos));
     oFragColor = vColor * vec4(1, 1, 1, alpha);
-
-#ifdef WR_FEATURE_TRANSFORM
-    oFragColor.a *= alpha;
-#endif
 }

webrender/res/ps_gradient_clip.vs.glsl

@@ -67,6 +67,6 @@ void main(void) {
             break;
     }
 
-    Clip clip = fetch_clip(prim.clip_index);
+    ClipInfo clip = fetch_clip(prim.clip_index);
     write_clip(clip);
 }

webrender/res/ps_image_clip.vs.glsl

@@ -23,7 +23,7 @@ void main(void) {
     vLocalPos = vi.local_clamped_pos;
 #endif
 
-    Clip clip = fetch_clip(prim.clip_index);
+    ClipInfo clip = fetch_clip(prim.clip_index);
     write_clip(clip);
 
     // vUv will contain how many times this image has wrapped around the image size.

webrender/res/ps_rectangle_clip.vs.glsl

@@ -22,6 +22,6 @@ void main(void) {
     vPos = vi.local_clamped_pos;
 #endif
 
-    Clip clip = fetch_clip(prim.clip_index);
+    ClipInfo clip = fetch_clip(prim.clip_index);
     write_clip(clip);
 }

webrender/src/frame.rs

@@ -11,12 +11,13 @@ use internal_types::{CompositionOp};
 use internal_types::{LowLevelFilterOp};
 use internal_types::{RendererFrame};
 use layer::{Layer, ScrollingState};
-use prim_store::Clip;
-use resource_cache::ResourceCache;
+use prim_store::ClipInfo;
+use resource_cache::{DummyResources, ResourceCache};
 use scene::{SceneStackingContext, ScenePipeline, Scene, SceneItem, SpecificSceneItem};
 use std::collections::{HashMap, HashSet};
 use std::hash::BuildHasherDefault;
-use tiling::{FrameBuilder, FrameBuilderConfig, InsideTest, PrimitiveFlags};
+use tiling::{FrameBuilder, FrameBuilderConfig, InsideTest, Clip, MaskImageSource};
+use tiling::PrimitiveFlags;
 use util::MatrixHelpers;
 use webrender_traits::{AuxiliaryLists, PipelineId, Epoch, ScrollPolicy, ScrollLayerId};
 use webrender_traits::{ColorF, StackingContext, FilterOp, MixBlendMode};
@@ -35,6 +36,7 @@ static DEFAULT_SCROLLBAR_COLOR: ColorF = ColorF { r: 0.3, g: 0.3, b: 0.3, a: 0.6
 
 struct FlattenContext<'a> {
     resource_cache: &'a mut ResourceCache,
+    dummy_resources: &'a DummyResources,
     scene: &'a Scene,
     pipeline_sizes: &'a mut HashMap<PipelineId, Size2D<f32>>,
     builder: &'a mut FrameBuilder,
@@ -368,6 +370,7 @@ impl Frame {
     pub fn create(&mut self,
                   scene: &Scene,
                   resource_cache: &mut ResourceCache,
+                  dummy_resources: &DummyResources,
                   pipeline_sizes: &mut HashMap<PipelineId, Size2D<f32>>,
                   device_pixel_ratio: f32) {
         if let Some(root_pipeline_id) = scene.root_pipeline_id {
@@ -415,6 +418,7 @@ impl Frame {
                     {
                         let mut context = FlattenContext {
                             resource_cache: resource_cache,
+                            dummy_resources: dummy_resources,
                             scene: scene,
                             pipeline_sizes: pipeline_sizes,
                             builder: &mut frame_builder,
@@ -530,33 +534,50 @@ impl Frame {
                                                 PrimitiveFlags::None);
         }
 
+        let dummy_mask_source = {
+            let cache_id = context.dummy_resources.opaque_mask_image_id;
+            let cache_item = context.resource_cache.get_image_by_cache_id(cache_id);
+            MaskImageSource::Renderer(cache_item.texture_id)
+        };
+
         for item in scene_items {
             match item.specific {
                 SpecificSceneItem::DrawList(draw_list_id) => {
                     let draw_list = context.resource_cache.get_draw_list(draw_list_id);
                     let builder = &mut context.builder;
-
-                    let auxiliary_lists = {
-                        self.pipeline_auxiliary_lists
+                    let auxiliary_lists = self.pipeline_auxiliary_lists
                                               .get(&parent_info.pipeline_id)
-                                              .expect("No auxiliary lists?!")
-                    };
+                                              .expect("No auxiliary lists?!");
 
                     for item in &draw_list.items {
                         let clips = auxiliary_lists.complex_clip_regions(&item.clip.complex);
-                        let clip = match clips.len() {
-                            0 => None,
-                            1 => Some(Box::new(Clip::from_clip_region(&clips[0]))),
+                        let mut clip = match clips.len() {
+                            0 if item.clip.image_mask.is_none() => None,
+                            0 => Some(Clip::new(ClipInfo::uniform(item.clip.main, 0.0), dummy_mask_source)),
+                            1 => Some(Clip::new(ClipInfo::from_clip_region(&clips[0]), dummy_mask_source)),
                             _ => {
                                 let internal_clip = clips.last().unwrap();
-                                if clips.iter().all(|current_clip| current_clip.might_contain(internal_clip)) {
-                                    Some(Box::new(Clip::from_clip_region(internal_clip)))
+                                let region = if clips.iter().all(|current_clip| current_clip.might_contain(internal_clip)) {
+                                    internal_clip
                                 } else {
-                                    Some(Box::new(Clip::from_clip_region(&clips[0])))
-                                }
+                                    &clips[0]
+                                };
+                                Some(Clip::new(ClipInfo::from_clip_region(region), dummy_mask_source))
                             },
                         };
 
+                        if let Some(ref mask) = item.clip.image_mask {
+                            let old = match clip {
+                                Some(masked) => *masked.clip,
+                                None => ClipInfo::uniform(item.clip.main, 0.0),
+                            };
+                            //Note: can't call `tex_cache.aligned_uv_rect()` here since the image
+                            // is not yet marked as needed this frame.
+                            clip = Some(Clip::new(old.with_mask(Rect::zero(), mask.rect),
+                                                         MaskImageSource::User(mask.image)));
+                        }
+
+
                         match item.item {
                             SpecificDisplayItem::WebGL(ref info) => {
                                 builder.add_webgl_rectangle(item.rect,