Auto merge of #2623 - kvark:shader-module, r=glennw

Separate primitive shaders from clip shaders

Includes #2622

Note: this is not done because I'm bored.
The problem Szeged team has bumped into is that `aDataX` attributes end up being used in the shaders they don't relate to (e.g. clip shaders). This isn't affecting GLSL but it does affect GLSL -> SPIRV -> XXX shader pipelines.

The solution I came up with involves moving parts of `prim_shared` into separate shared modules, and turning `clip_shared` into a catch-all header of clip shades.

Downsides: more shader modules (but not programs) to navigate between.
Any suggestions on alternative solutions are welcome ;)

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webrender/res/base.glsl

@@ -33,6 +33,5 @@
 
 #ifdef WR_FRAGMENT_SHADER
     precision highp float;
-
     #define varying in
 #endif

webrender/res/brush.glsl

@@ -103,14 +103,14 @@ void main(void) {
             brush_prim.local_rect
         );
 
-        // TODO(gw): vLocalBounds may be referenced by
+        // TODO(gw): transform bounds may be referenced by
         //           the fragment shader when running in
         //           the alpha pass, even on non-transformed
         //           items. For now, just ensure it has no
         //           effect. We can tidy this up as we move
         //           more items to be brush shaders.
 #ifdef WR_FEATURE_ALPHA_PASS
-        vLocalBounds = vec4(vec2(-1000000.0), vec2(1000000.0));
+        init_transform_vs(vec4(vec2(-1000000.0), vec2(1000000.0)));
 #endif
     } else {
         bvec4 edge_mask = notEqual(brush.edge_mask & ivec4(1, 2, 4, 8), ivec4(0));

webrender/res/clip_scroll.glsl

@@ -0,0 +1,88 @@
+/* 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/. */
+
+#ifdef WR_VERTEX_SHADER
+#define VECS_PER_CLIP_SCROLL_NODE   9
+
+uniform HIGHP_SAMPLER_FLOAT sampler2D sClipScrollNodes;
+
+struct ClipScrollNode {
+    mat4 transform;
+    mat4 inv_transform;
+    bool is_axis_aligned;
+};
+
+ClipScrollNode fetch_clip_scroll_node(int index) {
+    ClipScrollNode node;
+
+    // Create a UV base coord for each 8 texels.
+    // This is required because trying to use an offset
+    // of more than 8 texels doesn't work on some versions
+    // of OSX.
+    ivec2 uv = get_fetch_uv(index, VECS_PER_CLIP_SCROLL_NODE);
+    ivec2 uv0 = ivec2(uv.x + 0, uv.y);
+    ivec2 uv1 = ivec2(uv.x + 8, uv.y);
+
+    node.transform[0] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(0, 0));
+    node.transform[1] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(1, 0));
+    node.transform[2] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(2, 0));
+    node.transform[3] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(3, 0));
+
+    node.inv_transform[0] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(4, 0));
+    node.inv_transform[1] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(5, 0));
+    node.inv_transform[2] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(6, 0));
+    node.inv_transform[3] = TEXEL_FETCH(sClipScrollNodes, uv0, 0, ivec2(7, 0));
+
+    vec4 misc = TEXEL_FETCH(sClipScrollNodes, uv1, 0, ivec2(0, 0));
+    node.is_axis_aligned = misc.x == 0.0;
+
+    return node;
+}
+
+// Return the intersection of the plane (set up by "normal" and "point")
+// with the ray (set up by "ray_origin" and "ray_dir"),
+// writing the resulting scaler into "t".
+bool ray_plane(vec3 normal, vec3 pt, vec3 ray_origin, vec3 ray_dir, out float t)
+{
+    float denom = dot(normal, ray_dir);
+    if (abs(denom) > 1e-6) {
+        vec3 d = pt - ray_origin;
+        t = dot(d, normal) / denom;
+        return t >= 0.0;
+    }
+
+    return false;
+}
+
+// Apply the inverse transform "inv_transform"
+// to the reference point "ref" in CSS space,
+// producing a local point on a ClipScrollNode plane,
+// set by a base point "a" and a normal "n".
+vec4 untransform(vec2 ref, vec3 n, vec3 a, mat4 inv_transform) {
+    vec3 p = vec3(ref, -10000.0);
+    vec3 d = vec3(0, 0, 1.0);
+
+    float t = 0.0;
+    // get an intersection of the ClipScrollNode plane with Z axis vector,
+    // originated from the "ref" point
+    ray_plane(n, a, p, d, t);
+    float z = p.z + d.z * t; // Z of the visible point on the ClipScrollNode
+
+    vec4 r = inv_transform * vec4(ref, z, 1.0);
+    return r;
+}
+
+// Given a CSS space position, transform it back into the ClipScrollNode space.
+vec4 get_node_pos(vec2 pos, ClipScrollNode node) {
+    // get a point on the scroll node plane
+    vec4 ah = node.transform * vec4(0.0, 0.0, 0.0, 1.0);
+    vec3 a = ah.xyz / ah.w;
+
+    // get the normal to the scroll node plane
+    vec3 n = transpose(mat3(node.inv_transform)) * vec3(0.0, 0.0, 1.0);
+    return untransform(pos, n, a, node.inv_transform);
+}
+
+#endif //WR_VERTEX_SHADER
+

webrender/res/clip_shared.glsl

@@ -2,6 +2,8 @@
  * 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/. */
 
+#include rect,clip_scroll,render_task,resource_cache,snap,transform
+
 #ifdef WR_VERTEX_SHADER
 
 #define SEGMENT_ALL         0
@@ -88,10 +90,20 @@ ClipVertexInfo write_clip_tile_vertex(RectWithSize local_clip_rect,
 
     gl_Position = uTransform * vec4(vertex_pos, 0.0, 1);
 
-    vLocalBounds = vec4(local_clip_rect.p0, local_clip_rect.p0 + local_clip_rect.size);
+    init_transform_vs(vec4(local_clip_rect.p0, local_clip_rect.p0 + local_clip_rect.size));
 
     ClipVertexInfo vi = ClipVertexInfo(node_pos.xyw, actual_pos, local_clip_rect);
     return vi;
 }
 
 #endif //WR_VERTEX_SHADER
+
+#ifdef WR_FRAGMENT_SHADER
+
+//Note: identical to prim_shared
+float distance_to_line(vec2 p0, vec2 perp_dir, vec2 p) {
+    vec2 dir_to_p0 = p0 - p;
+    return dot(normalize(perp_dir), dir_to_p0);
+}
+
+#endif //WR_FRAGMENT_SHADER

webrender/res/cs_clip_border.glsl

@@ -2,7 +2,7 @@
  * 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/. */
 
-#include shared,prim_shared,clip_shared
+#include shared,clip_shared
 
 varying vec3 vPos;
 

webrender/res/cs_clip_box_shadow.glsl

@@ -2,7 +2,7 @@
  * 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/. */
 
-#include shared,prim_shared,clip_shared
+#include shared,clip_shared
 
 varying vec3 vPos;
 varying vec2 vUv;
@@ -103,11 +103,7 @@ void main(void) {
     uv = mix(vUvBounds_NoClamp.xy, vUvBounds_NoClamp.zw, uv);
     uv = clamp(uv, vUvBounds.xy, vUvBounds.zw);
 
-    float in_shadow_rect = point_inside_rect(
-        local_pos,
-        vLocalBounds.xy,
-        vLocalBounds.zw
-    );
+    float in_shadow_rect = init_transform_rough_fs(local_pos);
 
     float texel = TEX_SAMPLE(sColor0, vec3(uv, vLayer)).r;
 

webrender/res/cs_clip_image.glsl

@@ -2,9 +2,11 @@
  * 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/. */
 
-#include shared,prim_shared,clip_shared
+#include shared,clip_shared
 
 varying vec3 vPos;
+varying vec3 vClipMaskImageUv;
+
 flat varying vec4 vClipMaskUvRect;
 flat varying vec4 vClipMaskUvInnerRect;
 flat varying float vLayer;
@@ -36,7 +38,7 @@ void main(void) {
     vPos = vi.local_pos;
     vLayer = res.layer;
 
-    vClipMaskUv = vec3((vPos.xy / vPos.z - local_rect.p0) / local_rect.size, 0.0);
+    vClipMaskImageUv = vec3((vPos.xy / vPos.z - local_rect.p0) / local_rect.size, 0.0);
     vec2 texture_size = vec2(textureSize(sColor0, 0));
     vClipMaskUvRect = vec4(res.uv_rect.p0, res.uv_rect.p1 - res.uv_rect.p0) / texture_size.xyxy;
     // applying a half-texel offset to the UV boundaries to prevent linear samples from the outside
@@ -50,8 +52,8 @@ void main(void) {
     float alpha = init_transform_fs(vPos.xy / vPos.z);
 
     bool repeat_mask = false; //TODO
-    vec2 clamped_mask_uv = repeat_mask ? fract(vClipMaskUv.xy) :
-        clamp(vClipMaskUv.xy, vec2(0.0, 0.0), vec2(1.0, 1.0));
+    vec2 clamped_mask_uv = repeat_mask ? fract(vClipMaskImageUv.xy) :
+        clamp(vClipMaskImageUv.xy, vec2(0.0, 0.0), vec2(1.0, 1.0));
     vec2 source_uv = clamp(clamped_mask_uv * vClipMaskUvRect.zw + vClipMaskUvRect.xy,
         vClipMaskUvInnerRect.xy, vClipMaskUvInnerRect.zw);
     float clip_alpha = texture(sColor0, vec3(source_uv, vLayer)).r; //careful: texture has type A8

webrender/res/cs_clip_line.glsl

@@ -2,7 +2,12 @@
  * 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/. */
 
-#include shared,prim_shared,clip_shared
+#include shared,clip_shared
+
+#define LINE_STYLE_SOLID        0
+#define LINE_STYLE_DOTTED       1
+#define LINE_STYLE_DASHED       2
+#define LINE_STYLE_WAVY         3
 
 varying vec3 vLocalPos;
 

webrender/res/cs_clip_rectangle.glsl

@@ -2,7 +2,7 @@
  * 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/. */
 
-#include shared,prim_shared,clip_shared,ellipse
+#include shared,clip_shared,ellipse
 
 varying vec3 vPos;
 flat varying float vClipMode;
@@ -19,7 +19,8 @@ struct ClipRect {
 
 ClipRect fetch_clip_rect(ivec2 address) {
     vec4 data[2] = fetch_from_resource_cache_2_direct(address);
-    return ClipRect(RectWithSize(data[0].xy, data[0].zw), data[1]);
+    ClipRect rect = ClipRect(RectWithSize(data[0].xy, data[0].zw), data[1]);
+    return rect;
 }
 
 struct ClipCorner {
@@ -32,7 +33,8 @@ struct ClipCorner {
 ClipCorner fetch_clip_corner(ivec2 address, float index) {
     address += ivec2(2 + 2 * int(index), 0);
     vec4 data[2] = fetch_from_resource_cache_2_direct(address);
-    return ClipCorner(RectWithSize(data[0].xy, data[0].zw), data[1]);
+    ClipCorner corner = ClipCorner(RectWithSize(data[0].xy, data[0].zw), data[1]);
+    return corner;
 }
 
 struct ClipData {