Support GL_SHADER_SOURCE_LENGTH parameter for glGetShaderiv. (#5373)

* Support GL_SHADER_SOURCE_LENGTH parameter for glGetShaderiv.

* Fix behavior of glGetShaderiv after review; Added test code.

AUTHORS

@@ -297,4 +297,5 @@ a license to everyone to use it as detailed in LICENSE.)
 * Matjaž Drolc <mdrolc@gmail.com>
 * James Swift <james@3dengineer.com> (copyright owned by PSPDFKit GmbH)
 * Ryan Lester <ryan@cyph.com> (copyright owned by Cyph, Inc.)
+* Nikolay Zapolnov <zapolnov@gmail.com>
 * Nazar Mokrynskyi <nazar@mokrynskyi.com>

src/library_gl.js

@@ -3598,6 +3598,10 @@ var LibraryGL = {
       var log = GLctx.getShaderInfoLog(GL.shaders[shader]);
       if (log === null) log = '(unknown error)';
       {{{ makeSetValue('p', '0', 'log.length + 1', 'i32') }}};
+    } else if (pname == 0x8B88) { // GL_SHADER_SOURCE_LENGTH
+      var source = GLctx.getShaderSource(GL.shaders[shader]);
+      var sourceLength = (source === null || source.length == 0) ? 0 : source.length + 1;
+      {{{ makeSetValue('p', '0', 'sourceLength', 'i32') }}};
     } else {
       {{{ makeSetValue('p', '0', 'GLctx.getShaderParameter(GL.shaders[shader], pname)', 'i32') }}};
     }

tests/test_browser.py

@@ -2278,6 +2278,12 @@ Module["preRun"].push(function () {
     if WINDOWS: return self.skip('SKIPPED due to bug https://bugzilla.mozilla.org/show_bug.cgi?id=1310005 - WebGL implementation advertises implementation defined GL_IMPLEMENTATION_COLOR_READ_TYPE/FORMAT pair that it cannot read with')
     self.btest(path_from_root('tests', 'webgl_color_buffer_readpixels.cpp'), args=['-lGL'], expected='0', timeout=20)
 
+  # Test for PR#5373 (https://github.com/kripken/emscripten/pull/5373)
+  def test_webgl_shader_source_length(self):
+    for opts in [[], ['-s', 'FULL_ES2=1']]:
+      print opts
+      self.btest(path_from_root('tests', 'webgl_shader_source_length.cpp'), args=opts + ['-lGL'], expected='0', timeout=20)
+
   def test_webgl2(self):
     for opts in [[], ['-O2', '-g1', '--closure', '1'], ['-s', 'FULL_ES2=1']]:
       print opts

tests/webgl_shader_source_length.cpp

@@ -0,0 +1,70 @@
+#define GL_GLEXT_PROTOTYPES
+#include <GLES/gl.h>
+#include <GLES/glext.h>
+#include <GLES2/gl2.h>
+#include <stdio.h>
+#include <emscripten.h>
+#include <emscripten/html5.h>
+#include <assert.h>
+#include <string.h>
+
+int result = 0;
+
+#define GL_CALL( x ) \
+    { \
+        x; \
+        GLenum error = glGetError(); \
+        if( error != GL_NO_ERROR ) { \
+            printf( "GL ERROR: %d,  %s\n", (int)error, #x ); \
+            result = 1; \
+        } \
+    } \
+
+
+int main()
+{
+  emscripten_set_canvas_size( 100, 100 );
+
+  EmscriptenWebGLContextAttributes attrs;
+  emscripten_webgl_init_context_attributes(&attrs);
+
+  EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context( 0, &attrs );
+  if (!context)
+  {
+    printf("Skipped: WebGL is not supported.\n");
+#ifdef REPORT_RESULT
+    REPORT_RESULT();
+#endif
+    return 0;
+  }
+  emscripten_webgl_make_context_current(context);
+
+  GLuint shader;
+  GL_CALL( shader = glCreateShader(GL_VERTEX_SHADER) );
+
+  GLint value = -97631;
+  GL_CALL( glGetShaderiv(shader, GL_SHADER_SOURCE_LENGTH, &value) );
+  assert(value == 0);
+
+  const GLchar* tempSource = (const GLchar*)"";
+  GL_CALL( glShaderSource(shader, 1, &tempSource, NULL) );
+
+  value = -97631;
+  GL_CALL( glGetShaderiv(shader, GL_SHADER_SOURCE_LENGTH, &value) );
+  assert(value == 0);
+
+  tempSource = (const GLchar*)"void main() { gl_Position = vec4(0); }";
+  GL_CALL( glShaderSource(shader, 1, &tempSource, NULL) );
+
+  value = -97631;
+  GL_CALL( glGetShaderiv(shader, GL_SHADER_SOURCE_LENGTH, &value) );
+  assert(value == strlen(tempSource) + 1);
+
+  EMSCRIPTEN_RESULT res = emscripten_webgl_destroy_context(context);
+  assert(res == EMSCRIPTEN_RESULT_SUCCESS);
+
+#ifdef REPORT_RESULT
+  REPORT_RESULT();
+#endif
+  return 0;
+}