Support line-continuation character in WebGL 2.0

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index 1c7cf0f6b1bd990e571bc530520c1ecd66fd4eb4..9f8d01d1b3b05d186ef42053be7af4dafa0dd8b1 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -448,6 +448,14 @@ void StripComments::process(UChar c)
         break;
 
     case InSingleLineComment:
+        // Handle line-continuation character in single line comment.
+        // Advance string to next nonspace character and eat it.

[Zhenyao Mo, 2016/06/29 18:16:07]

Can you also add a comment, saying that line-continuation characters are
processed before comment processing?

[Ken Russell (switch to Gerrit), 2016/06/30 00:04:31]

This change doesn't seem to implement the behavior of the line continuation
character in the GLSL ES 3.00.4 spec. No special handling should be needed
inside a single-line comment. Per Section 3.1 "Character Set", the line
continuation character only has that effect when immediately preceding a
newline.

[qiankun, 2016/06/30 15:12:47]

Done.

+        if (c == '\\') {
+            while (peek(temp) && WTF::isASCIISpace(temp))
+                advance();
+            advance();
+        }
+
         // The newline code at the top of this function takes care
         // of resetting our state when we get out of the
         // single-line comment. Swallow all other characters.
@@ -5461,6 +5469,9 @@ bool WebGLRenderingContextBase::validateSize(const char* functionName, GLint x,
 bool WebGLRenderingContextBase::validateString(const char* functionName, const String& string)
 {
     for (size_t i = 0; i < string.length(); ++i) {
+        // line-continuation character \ is supported in WebGL 2.0.
+        if (isWebGL2OrHigher() && string[i] == '\\')

[qiankun, 2016/06/29 05:31:21]

This isn't very accurate to say WebGL 2.0 here. WebGL 2.0 + GLSL ES 1.00 doesn't
support line-continuation, while WebGL 2.0 + GLSL ES 3.00 supports
line-continuation. So, it should check shader version. But no shader version
detecting in Blink side. Here we assume ANGLE or driver will do the final
validation.

Another problem is that ANGLE may change shader version according which GL
context is used, see GetShaderOutputLanguageForContext
(https://cs.chromium.org/chromium/src/gpu/command_buffer/service/shader_transl...).
Different visions of GLSL may have different supports on line-continuation. For
example, it's supported in GLSL ES 3.00.4, but it's not supported in GLSL
3.30.6.

[Zhenyao Mo, 2016/06/29 18:16:07]

This is not true.  See GLSL ES Spec 3.00.4 page 6, "Support of line continuation
and support of UTF-8 characters within comments is optional in GLSL ES 1.00 when
used with the OpenGL ES 2.0 API. However, support is mandated for both of these
when a GLSL ES 1.00 shader is used with the OpenGL ES 3.0 API."

Also, can you pass a WebGL version to validateCharacter() so we can handle the
behavior inside that function?
I am not sure we will support WebGL 2 on top of GLSL 3.30

[Ken Russell (switch to Gerrit), 2016/06/30 00:04:31]

This particular change (to validateString) seems wrong. This method takes in the
names of things like attribute and uniform locations. These should never contain
the line continuation character.

+            continue;
         if (!validateCharacter(string[i])) {
             synthesizeGLError(GL_INVALID_VALUE, functionName, "string not ASCII");
             return false;