Add WebRender integration to Servo.

WebRender is an experimental GPU accelerated rendering backend for Servo.

The WebRender backend can be specified by running Servo with the -w option (otherwise the default rendering backend will be used).

WebRender has many bugs, and missing features - but it is usable to browse most websites - please report any WebRender specific rendering bugs you encounter!

resources/shaders/blend.fs.glsl

@@ -0,0 +1,193 @@
+/* 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/. */
+
+vec3 Multiply(vec3 Cb, vec3 Cs) {
+    return Cb * Cs;
+}
+
+vec3 Screen(vec3 Cb, vec3 Cs) {
+    return Cb + Cs - (Cb * Cs);
+}
+
+vec3 HardLight(vec3 Cb, vec3 Cs) {
+    vec3 m = Multiply(Cb, 2.0 * Cs);
+    vec3 s = Screen(Cb, 2.0 * Cs - 1.0);
+    vec3 edge = vec3(0.5, 0.5, 0.5);
+    return mix(m, s, step(edge, Cs));
+}
+
+// TODO: Worth doing with mix/step? Check GLSL output.
+float ColorDodge(float Cb, float Cs) {
+    if (Cb == 0.0)
+        return 0.0;
+    else if (Cs == 1.0)
+        return 1.0;
+    else
+        return min(1.0, Cb / (1.0 - Cs));
+}
+
+// TODO: Worth doing with mix/step? Check GLSL output.
+float ColorBurn(float Cb, float Cs) {
+    if (Cb == 1.0)
+        return 1.0;
+    else if (Cs == 0.0)
+        return 0.0;
+    else
+        return 1.0 - min(1.0, (1.0 - Cb) / Cs);
+}
+
+float SoftLight(float Cb, float Cs) {
+    if (Cs <= 0.5) {
+        return Cb - (1.0 - 2.0 * Cs) * Cb * (1.0 - Cb);
+    } else {
+        float D;
+
+        if (Cb <= 0.25)
+            D = ((16.0 * Cb - 12.0) * Cb + 4.0) * Cb;
+        else
+            D = sqrt(Cb);
+
+        return Cb + (2.0 * Cs - 1.0) * (D - Cb);
+    }
+}
+
+vec3 Difference(vec3 Cb, vec3 Cs) {
+    return abs(Cb - Cs);
+}
+
+vec3 Exclusion(vec3 Cb, vec3 Cs) {
+    return Cb + Cs - 2.0 * Cb * Cs;
+}
+
+// These functions below are taken from the spec.
+// There's probably a much quicker way to implement
+// them in GLSL...
+float Sat(vec3 c) {
+    return max(c.r, max(c.g, c.b)) - min(c.r, min(c.g, c.b));
+}
+
+float Lum(vec3 c) {
+    vec3 f = vec3(0.3, 0.59, 0.11);
+    return dot(c, f);
+}
+
+vec3 ClipColor(vec3 C) {
+    float L = Lum(C);
+    float n = min(C.r, min(C.g, C.b));
+    float x = max(C.r, max(C.g, C.b));
+
+    if (n < 0.0)
+        C = L + (((C - L) * L) / (L - n));
+
+    if (x > 1.0)
+        C = L + (((C - L) * (1.0 - L)) / (x - L));
+
+    return C;
+}
+
+vec3 SetLum(vec3 C, float l) {
+    float d = l - Lum(C);
+    return ClipColor(C + d);
+}
+
+void SetSatInner(inout float Cmin, inout float Cmid, inout float Cmax, float s) {
+    if (Cmax > Cmin) {
+        Cmid = (((Cmid - Cmin) * s) / (Cmax - Cmin));
+        Cmax = s;
+    } else {
+        Cmid = 0.0;
+        Cmax = 0.0;
+    }
+    Cmin = 0.0;
+}
+
+vec3 SetSat(vec3 C, float s) {
+    if (C.r <= C.g) {
+        if (C.g <= C.b) {
+            SetSatInner(C.r, C.g, C.b, s);
+        } else {
+            if (C.r <= C.b) {
+                SetSatInner(C.r, C.b, C.g, s);
+            } else {
+                SetSatInner(C.b, C.r, C.g, s);
+            }
+        }
+    } else {
+        if (C.r <= C.b) {
+            SetSatInner(C.g, C.r, C.b, s);
+        } else {
+            if (C.g <= C.b) {
+                SetSatInner(C.g, C.b, C.r, s);
+            } else {
+                SetSatInner(C.b, C.g, C.r, s);
+            }
+        }
+    }
+    return C;
+}
+
+vec3 Hue(vec3 Cb, vec3 Cs) {
+    return SetLum(SetSat(Cs, Sat(Cb)), Lum(Cb));
+}
+
+vec3 Saturation(vec3 Cb, vec3 Cs) {
+    return SetLum(SetSat(Cb, Sat(Cs)), Lum(Cb));
+}
+
+vec3 Color(vec3 Cb, vec3 Cs) {
+    return SetLum(Cs, Lum(Cb));
+}
+
+vec3 Luminosity(vec3 Cb, vec3 Cs) {
+    return SetLum(Cb, Lum(Cs));
+}
+
+void main(void)
+{
+    vec3 Cs = Texture(sDiffuse, vColorTexCoord).xyz;
+    vec3 Cb = Texture(sMask, vMaskTexCoord).xyz;
+
+    // TODO: Relies on the ordering of MixBlendMode enum!
+    // TODO: May be best to have separate shaders (esp. on Tegra)
+    int blend_mode = int(uBlendParams.x);
+
+    // Return yellow if none of the branches match (shouldn't happen).
+    vec3 result = vec3(1.0, 1.0, 0.0);
+
+    if (blend_mode == 2) {
+        result = Screen(Cb, Cs);
+    } else if (blend_mode == 3) {
+        result = HardLight(Cs, Cb);        // Overlay is inverse of Hardlight
+    } else if (blend_mode == 6) {
+        result.r = ColorDodge(Cb.r, Cs.r);
+        result.g = ColorDodge(Cb.g, Cs.g);
+        result.b = ColorDodge(Cb.b, Cs.b);
+    } else if (blend_mode == 7) {
+        result.r = ColorBurn(Cb.r, Cs.r);
+        result.g = ColorBurn(Cb.g, Cs.g);
+        result.b = ColorBurn(Cb.b, Cs.b);
+    } else if (blend_mode == 8) {
+        result = HardLight(Cb, Cs);
+    } else if (blend_mode == 9) {
+        result.r = SoftLight(Cb.r, Cs.r);
+        result.g = SoftLight(Cb.g, Cs.g);
+        result.b = SoftLight(Cb.b, Cs.b);
+    } else if (blend_mode == 10) {
+        result = Difference(Cb, Cs);
+    } else if (blend_mode == 11) {
+        result = Exclusion(Cb, Cs);
+    } else if (blend_mode == 12) {
+        result = Hue(Cb, Cs);
+    } else if (blend_mode == 13) {
+        result = Saturation(Cb, Cs);
+    } else if (blend_mode == 14) {
+        result = Color(Cb, Cs);
+    } else if (blend_mode == 15) {
+        result = Luminosity(Cb, Cs);
+    }
+
+    // TODO: Handle output alpha correctly.
+    SetFragColor(vec4(result, 1.0));
+}
+