ui/gl/gl_gl_api_implementation.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ui/gl/gl_gl_api_implementation.h"
   6
   7 #include <algorithm>
   8 #include <vector>
   9
  10 #include "base/command_line.h"
  11 #include "base/strings/string_split.h"
  12 #include "base/strings/string_util.h"
  13 #include "ui/gl/gl_context.h"
  14 #include "ui/gl/gl_implementation.h"
  15 #include "ui/gl/gl_state_restorer.h"
  16 #include "ui/gl/gl_surface.h"
  17 #include "ui/gl/gl_switches.h"
  18 #include "ui/gl/gl_version_info.h"
  19
  20 namespace gfx {
  21
  22 // The GL Api being used. This could be g_real_gl or gl_trace_gl
  23 static GLApi* g_gl = NULL;
  24 // A GL Api that calls directly into the driver.
  25 static RealGLApi* g_real_gl = NULL;
  26 // A GL Api that does nothing but warn about illegal GL calls without a context
  27 // current.
  28 static NoContextGLApi* g_no_context_gl = NULL;
  29 // A GL Api that calls TRACE and then calls another GL api.
  30 static TraceGLApi* g_trace_gl = NULL;
  31 // GL version used when initializing dynamic bindings.
  32 static GLVersionInfo* g_version_info = NULL;
  33
  34 namespace {
  35
  36 static inline GLenum GetInternalFormat(GLenum internal_format) {
  37   if (gfx::GetGLImplementation() != gfx::kGLImplementationEGLGLES2) {
  38     if (internal_format == GL_BGRA_EXT || internal_format == GL_BGRA8_EXT)
  39       return GL_RGBA8;
  40   }
  41   return internal_format;
  42 }
  43
  44 // TODO(epenner): Could the above function be merged into this and removed?
  45 static inline GLenum GetTexInternalFormat(GLenum internal_format,
  46                                           GLenum format,
  47                                           GLenum type) {
  48   GLenum gl_internal_format = GetInternalFormat(internal_format);
  49
  50   // g_version_info must be initialized when this function is bound.
  51   DCHECK(gfx::g_version_info);
  52   if (gfx::g_version_info->is_es3) {
  53     if (internal_format == GL_RED_EXT) {
  54       // GL_EXT_texture_rg case in ES2.
  55       switch (type) {
  56         case GL_UNSIGNED_BYTE:
  57           gl_internal_format = GL_R8_EXT;
  58           break;
  59         case GL_HALF_FLOAT_OES:
  60           gl_internal_format = GL_R16F_EXT;
  61           break;
  62         case GL_FLOAT:
  63           gl_internal_format = GL_R32F_EXT;
  64           break;
  65         default:
  66           NOTREACHED();
  67           break;
  68       }
  69       return gl_internal_format;
  70     } else if (internal_format == GL_RG_EXT) {
  71       // GL_EXT_texture_rg case in ES2.
  72       switch (type) {
  73         case GL_UNSIGNED_BYTE:
  74           gl_internal_format = GL_RG8_EXT;
  75           break;
  76         case GL_HALF_FLOAT_OES:
  77           gl_internal_format = GL_RG16F_EXT;
  78           break;
  79         case GL_FLOAT:
  80           gl_internal_format = GL_RG32F_EXT;
  81           break;
  82         default:
  83           NOTREACHED();
  84           break;
  85       }
  86       return gl_internal_format;
  87     }
  88   }
  89
  90   if (type == GL_FLOAT && gfx::g_version_info->is_angle &&
  91       gfx::g_version_info->is_es && gfx::g_version_info->major_version == 2) {
  92     // It's possible that the texture is using a sized internal format, and
  93     // ANGLE exposing GLES2 API doesn't support those.
  94     // TODO(oetuaho@nvidia.com): Remove these conversions once ANGLE has the
  95     // support.
  96     // http://code.google.com/p/angleproject/issues/detail?id=556
  97     switch (format) {
  98       case GL_RGBA:
  99         gl_internal_format = GL_RGBA;
 100         break;
 101       case GL_RGB:
 102         gl_internal_format = GL_RGB;
 103         break;
 104       default:
 105         break;
 106     }
 107   }
 108
 109   if (gfx::g_version_info->is_es)
 110     return gl_internal_format;
 111
 112   if (type == GL_FLOAT) {
 113     switch (internal_format) {
 114       // We need to map all the unsized internal formats from ES2 clients.
 115       case GL_RGBA:
 116         gl_internal_format = GL_RGBA32F_ARB;
 117         break;
 118       case GL_RGB:
 119         gl_internal_format = GL_RGB32F_ARB;
 120         break;
 121       case GL_LUMINANCE_ALPHA:
 122         gl_internal_format = GL_LUMINANCE_ALPHA32F_ARB;
 123         break;
 124       case GL_LUMINANCE:
 125         gl_internal_format = GL_LUMINANCE32F_ARB;
 126         break;
 127       case GL_ALPHA:
 128         gl_internal_format = GL_ALPHA32F_ARB;
 129         break;
 130       default:
 131         // We can't assert here because if the client context is ES3,
 132         // all sized internal_format will reach here.
 133         break;
 134     }
 135   } else if (type == GL_HALF_FLOAT_OES) {
 136     switch (internal_format) {
 137       case GL_RGBA:
 138         gl_internal_format = GL_RGBA16F_ARB;
 139         break;
 140       case GL_RGB:
 141         gl_internal_format = GL_RGB16F_ARB;
 142         break;
 143       case GL_LUMINANCE_ALPHA:
 144         gl_internal_format = GL_LUMINANCE_ALPHA16F_ARB;
 145         break;
 146       case GL_LUMINANCE:
 147         gl_internal_format = GL_LUMINANCE16F_ARB;
 148         break;
 149       case GL_ALPHA:
 150         gl_internal_format = GL_ALPHA16F_ARB;
 151         break;
 152       default:
 153         NOTREACHED();
 154         break;
 155     }
 156   }
 157   return gl_internal_format;
 158 }
 159
 160 static inline GLenum GetTexType(GLenum type) {
 161    if (gfx::GetGLImplementation() != gfx::kGLImplementationEGLGLES2) {
 162      if (type == GL_HALF_FLOAT_OES)
 163        return GL_HALF_FLOAT_ARB;
 164    }
 165    return type;
 166 }
 167
 168 static void GL_BINDING_CALL CustomTexImage2D(
 169     GLenum target, GLint level, GLint internalformat,
 170     GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type,
 171     const void* pixels) {
 172   GLenum gl_internal_format = GetTexInternalFormat(
 173       internalformat, format, type);
 174   GLenum gl_type = GetTexType(type);
 175   g_driver_gl.orig_fn.glTexImage2DFn(
 176       target, level, gl_internal_format, width, height, border, format, gl_type,
 177       pixels);
 178 }
 179
 180 static void GL_BINDING_CALL CustomTexSubImage2D(
 181       GLenum target, GLint level, GLint xoffset, GLint yoffset, GLsizei width,
 182       GLsizei height, GLenum format, GLenum type, const void* pixels) {
 183   GLenum gl_type = GetTexType(type);
 184   g_driver_gl.orig_fn.glTexSubImage2DFn(
 185       target, level, xoffset, yoffset, width, height, format, gl_type, pixels);
 186 }
 187
 188 static void GL_BINDING_CALL CustomTexStorage2DEXT(
 189     GLenum target, GLsizei levels, GLenum internalformat, GLsizei width,
 190     GLsizei height) {
 191   GLenum gl_internal_format = GetInternalFormat(internalformat);
 192   g_driver_gl.orig_fn.glTexStorage2DEXTFn(
 193       target, levels, gl_internal_format, width, height);
 194 }
 195
 196 static void GL_BINDING_CALL CustomRenderbufferStorageEXT(
 197     GLenum target, GLenum internalformat, GLsizei width, GLsizei height) {
 198   GLenum gl_internal_format = GetInternalFormat(internalformat);
 199   g_driver_gl.orig_fn.glRenderbufferStorageEXTFn(
 200       target, gl_internal_format, width, height);
 201 }
 202
 203 // The ANGLE and IMG variants of glRenderbufferStorageMultisample currently do
 204 // not support BGRA render buffers so only the EXT one is customized. If
 205 // GL_CHROMIUM_renderbuffer_format_BGRA8888 support is added to ANGLE then the
 206 // ANGLE version should also be customized.
 207 static void GL_BINDING_CALL CustomRenderbufferStorageMultisampleEXT(
 208     GLenum target, GLsizei samples, GLenum internalformat, GLsizei width,
 209     GLsizei height) {
 210   GLenum gl_internal_format = GetInternalFormat(internalformat);
 211   g_driver_gl.orig_fn.glRenderbufferStorageMultisampleEXTFn(
 212       target, samples, gl_internal_format, width, height);
 213 }
 214
 215 }  // anonymous namespace
 216
 217 void DriverGL::InitializeCustomDynamicBindings(GLContext* context) {
 218   InitializeDynamicBindings(context);
 219
 220   DCHECK(orig_fn.glTexImage2DFn == NULL);
 221   orig_fn.glTexImage2DFn = fn.glTexImage2DFn;
 222   fn.glTexImage2DFn =
 223       reinterpret_cast<glTexImage2DProc>(CustomTexImage2D);
 224
 225   DCHECK(orig_fn.glTexSubImage2DFn == NULL);
 226   orig_fn.glTexSubImage2DFn = fn.glTexSubImage2DFn;
 227   fn.glTexSubImage2DFn =
 228       reinterpret_cast<glTexSubImage2DProc>(CustomTexSubImage2D);
 229
 230   DCHECK(orig_fn.glTexStorage2DEXTFn == NULL);
 231   orig_fn.glTexStorage2DEXTFn = fn.glTexStorage2DEXTFn;
 232   fn.glTexStorage2DEXTFn =
 233       reinterpret_cast<glTexStorage2DEXTProc>(CustomTexStorage2DEXT);
 234
 235   DCHECK(orig_fn.glRenderbufferStorageEXTFn == NULL);
 236   orig_fn.glRenderbufferStorageEXTFn = fn.glRenderbufferStorageEXTFn;
 237   fn.glRenderbufferStorageEXTFn =
 238       reinterpret_cast<glRenderbufferStorageEXTProc>(
 239       CustomRenderbufferStorageEXT);
 240
 241   DCHECK(orig_fn.glRenderbufferStorageMultisampleEXTFn == NULL);
 242   orig_fn.glRenderbufferStorageMultisampleEXTFn =
 243       fn.glRenderbufferStorageMultisampleEXTFn;
 244   fn.glRenderbufferStorageMultisampleEXTFn =
 245       reinterpret_cast<glRenderbufferStorageMultisampleEXTProc>(
 246       CustomRenderbufferStorageMultisampleEXT);
 247 }
 248
 249 static void GL_BINDING_CALL NullDrawClearFn(GLbitfield mask) {
 250   if (!g_driver_gl.null_draw_bindings_enabled)
 251     g_driver_gl.orig_fn.glClearFn(mask);
 252 }
 253
 254 static void GL_BINDING_CALL
 255 NullDrawDrawArraysFn(GLenum mode, GLint first, GLsizei count) {
 256   if (!g_driver_gl.null_draw_bindings_enabled)
 257     g_driver_gl.orig_fn.glDrawArraysFn(mode, first, count);
 258 }
 259
 260 static void GL_BINDING_CALL NullDrawDrawElementsFn(GLenum mode,
 261                                                    GLsizei count,
 262                                                    GLenum type,
 263                                                    const void* indices) {
 264   if (!g_driver_gl.null_draw_bindings_enabled)
 265     g_driver_gl.orig_fn.glDrawElementsFn(mode, count, type, indices);
 266 }
 267
 268 void DriverGL::InitializeNullDrawBindings() {
 269   DCHECK(orig_fn.glClearFn == NULL);
 270   orig_fn.glClearFn = fn.glClearFn;
 271   fn.glClearFn = NullDrawClearFn;
 272
 273   DCHECK(orig_fn.glDrawArraysFn == NULL);
 274   orig_fn.glDrawArraysFn = fn.glDrawArraysFn;
 275   fn.glDrawArraysFn = NullDrawDrawArraysFn;
 276
 277   DCHECK(orig_fn.glDrawElementsFn == NULL);
 278   orig_fn.glDrawElementsFn = fn.glDrawElementsFn;
 279   fn.glDrawElementsFn = NullDrawDrawElementsFn;
 280
 281   null_draw_bindings_enabled = true;
 282 }
 283
 284 bool DriverGL::HasInitializedNullDrawBindings() {
 285   return orig_fn.glClearFn != NULL && orig_fn.glDrawArraysFn != NULL &&
 286          orig_fn.glDrawElementsFn != NULL;
 287 }
 288
 289 bool DriverGL::SetNullDrawBindingsEnabled(bool enabled) {
 290   DCHECK(orig_fn.glClearFn != NULL);
 291   DCHECK(orig_fn.glDrawArraysFn != NULL);
 292   DCHECK(orig_fn.glDrawElementsFn != NULL);
 293
 294   bool before = null_draw_bindings_enabled;
 295   null_draw_bindings_enabled = enabled;
 296   return before;
 297 }
 298
 299 void InitializeStaticGLBindingsGL() {
 300   g_current_gl_context_tls = new base::ThreadLocalPointer<GLApi>;
 301   g_driver_gl.InitializeStaticBindings();
 302   if (!g_real_gl) {
 303     g_real_gl = new RealGLApi();
 304     g_trace_gl = new TraceGLApi(g_real_gl);
 305     g_no_context_gl = new NoContextGLApi();
 306   }
 307   g_real_gl->Initialize(&g_driver_gl);
 308   g_gl = g_real_gl;
 309   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
 310           switches::kEnableGPUServiceTracing)) {
 311     g_gl = g_trace_gl;
 312   }
 313   SetGLToRealGLApi();
 314 }
 315
 316 GLApi* GetCurrentGLApi() {
 317   return g_current_gl_context_tls ? g_current_gl_context_tls->Get() : nullptr;
 318 }
 319
 320 void SetGLApi(GLApi* api) {
 321   g_current_gl_context_tls->Set(api);
 322 }
 323
 324 void SetGLToRealGLApi() {
 325   SetGLApi(g_gl);
 326 }
 327
 328 void SetGLApiToNoContext() {
 329   SetGLApi(g_no_context_gl);
 330 }
 331
 332 const GLVersionInfo* GetGLVersionInfo() {
 333   return g_version_info;
 334 }
 335
 336 void InitializeDynamicGLBindingsGL(GLContext* context) {
 337   g_real_gl->InitializeFilteredExtensions();
 338   g_driver_gl.InitializeCustomDynamicBindings(context);
 339   DCHECK(context && context->IsCurrent(NULL) && !g_version_info);
 340   g_version_info = new GLVersionInfo(
 341       context->GetGLVersion().c_str(),
 342       context->GetGLRenderer().c_str(),
 343       context->GetExtensions().c_str());
 344 }
 345
 346 void InitializeDebugGLBindingsGL() {
 347   g_driver_gl.InitializeDebugBindings();
 348 }
 349
 350 void InitializeNullDrawGLBindingsGL() {
 351   g_driver_gl.InitializeNullDrawBindings();
 352 }
 353
 354 bool HasInitializedNullDrawGLBindingsGL() {
 355   return g_driver_gl.HasInitializedNullDrawBindings();
 356 }
 357
 358 bool SetNullDrawGLBindingsEnabledGL(bool enabled) {
 359   return g_driver_gl.SetNullDrawBindingsEnabled(enabled);
 360 }
 361
 362 void ClearGLBindingsGL() {
 363   if (g_real_gl) {
 364     delete g_real_gl;
 365     g_real_gl = NULL;
 366   }
 367   if (g_trace_gl) {
 368     delete g_trace_gl;
 369     g_trace_gl = NULL;
 370   }
 371   if (g_no_context_gl) {
 372     delete g_no_context_gl;
 373     g_no_context_gl = NULL;
 374   }
 375   g_gl = NULL;
 376   g_driver_gl.ClearBindings();
 377   if (g_current_gl_context_tls) {
 378     delete g_current_gl_context_tls;
 379     g_current_gl_context_tls = NULL;
 380   }
 381   if (g_version_info) {
 382     delete g_version_info;
 383     g_version_info = NULL;
 384   }
 385 }
 386
 387 GLApi::GLApi() {
 388 }
 389
 390 GLApi::~GLApi() {
 391   if (GetCurrentGLApi() == this)
 392     SetGLApi(NULL);
 393 }
 394
 395 GLApiBase::GLApiBase()
 396     : driver_(NULL) {
 397 }
 398
 399 GLApiBase::~GLApiBase() {
 400 }
 401
 402 void GLApiBase::InitializeBase(DriverGL* driver) {
 403   driver_ = driver;
 404 }
 405
 406 RealGLApi::RealGLApi() {
 407 #if DCHECK_IS_ON()
 408   filtered_exts_initialized_ = false;
 409 #endif
 410 }
 411
 412 RealGLApi::~RealGLApi() {
 413 }
 414
 415 void RealGLApi::Initialize(DriverGL* driver) {
 416   InitializeWithCommandLine(driver, base::CommandLine::ForCurrentProcess());
 417 }
 418
 419 void RealGLApi::InitializeWithCommandLine(DriverGL* driver,
 420                                           base::CommandLine* command_line) {
 421   DCHECK(command_line);
 422   InitializeBase(driver);
 423
 424   const std::string disabled_extensions = command_line->GetSwitchValueASCII(
 425       switches::kDisableGLExtensions);
 426   if (!disabled_extensions.empty()) {
 427     disabled_exts_ = base::SplitString(
 428         disabled_extensions, ", ;",
 429         base::KEEP_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
 430   }
 431 }
 432
 433 void RealGLApi::glGetIntegervFn(GLenum pname, GLint* params) {
 434   if (pname == GL_NUM_EXTENSIONS && disabled_exts_.size()) {
 435 #if DCHECK_IS_ON()
 436     DCHECK(filtered_exts_initialized_);
 437 #endif
 438     *params = static_cast<GLint>(filtered_exts_.size());
 439   } else {
 440     GLApiBase::glGetIntegervFn(pname, params);
 441   }
 442 }
 443
 444 const GLubyte* RealGLApi::glGetStringFn(GLenum name) {
 445   if (name == GL_EXTENSIONS && disabled_exts_.size()) {
 446 #if DCHECK_IS_ON()
 447     DCHECK(filtered_exts_initialized_);
 448 #endif
 449     return reinterpret_cast<const GLubyte*>(filtered_exts_str_.c_str());
 450   }
 451   return GLApiBase::glGetStringFn(name);
 452 }
 453
 454 const GLubyte* RealGLApi::glGetStringiFn(GLenum name, GLuint index) {
 455   if (name == GL_EXTENSIONS && disabled_exts_.size()) {
 456 #if DCHECK_IS_ON()
 457     DCHECK(filtered_exts_initialized_);
 458 #endif
 459     if (index >= filtered_exts_.size()) {
 460       return NULL;
 461     }
 462     return reinterpret_cast<const GLubyte*>(filtered_exts_[index].c_str());
 463   }
 464   return GLApiBase::glGetStringiFn(name, index);
 465 }
 466
 467 void RealGLApi::glFlushFn() {
 468   GLApiBase::glFlushFn();
 469 }
 470
 471 void RealGLApi::glFinishFn() {
 472   GLApiBase::glFinishFn();
 473 }
 474
 475 void RealGLApi::InitializeFilteredExtensions() {
 476   if (disabled_exts_.size()) {
 477     filtered_exts_.clear();
 478     if (gfx::WillUseGLGetStringForExtensions()) {
 479       filtered_exts_str_ =
 480           FilterGLExtensionList(reinterpret_cast<const char*>(
 481                                     GLApiBase::glGetStringFn(GL_EXTENSIONS)),
 482                                 disabled_exts_);
 483       filtered_exts_ = base::SplitString(
 484           filtered_exts_str_, " ", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
 485     } else {
 486       GLint num_extensions = 0;
 487       GLApiBase::glGetIntegervFn(GL_NUM_EXTENSIONS, &num_extensions);
 488       for (GLint i = 0; i < num_extensions; ++i) {
 489         const char* gl_extension = reinterpret_cast<const char*>(
 490             GLApiBase::glGetStringiFn(GL_EXTENSIONS, i));
 491         DCHECK(gl_extension != NULL);
 492         if (std::find(disabled_exts_.begin(), disabled_exts_.end(),
 493                       gl_extension) == disabled_exts_.end()) {
 494           filtered_exts_.push_back(gl_extension);
 495         }
 496       }
 497       filtered_exts_str_ = base::JoinString(filtered_exts_, " ");
 498     }
 499 #if DCHECK_IS_ON()
 500     filtered_exts_initialized_ = true;
 501 #endif
 502   }
 503 }
 504
 505 TraceGLApi::~TraceGLApi() {
 506 }
 507
 508 NoContextGLApi::NoContextGLApi() {
 509 }
 510
 511 NoContextGLApi::~NoContextGLApi() {
 512 }
 513
 514 VirtualGLApi::VirtualGLApi()
 515     : real_context_(NULL),
 516       current_context_(NULL) {
 517 }
 518
 519 VirtualGLApi::~VirtualGLApi() {
 520 }
 521
 522 void VirtualGLApi::Initialize(DriverGL* driver, GLContext* real_context) {
 523   InitializeBase(driver);
 524   real_context_ = real_context;
 525
 526   DCHECK(real_context->IsCurrent(NULL));
 527   extensions_ = real_context->GetExtensions();
 528 }
 529
 530 bool VirtualGLApi::MakeCurrent(GLContext* virtual_context, GLSurface* surface) {
 531   bool switched_contexts = g_current_gl_context_tls->Get() != this;
 532   GLSurface* current_surface = GLSurface::GetCurrent();
 533   if (switched_contexts || surface != current_surface) {
 534     // MakeCurrent 'lite' path that avoids potentially expensive MakeCurrent()
 535     // calls if the GLSurface uses the same underlying surface or renders to
 536     // an FBO.
 537     if (switched_contexts || !current_surface ||
 538         !virtual_context->IsCurrent(surface)) {
 539       if (!real_context_->MakeCurrent(surface)) {
 540         return false;
 541       }
 542     }
 543   }
 544
 545   bool state_dirtied_externally = real_context_->GetStateWasDirtiedExternally();
 546   real_context_->SetStateWasDirtiedExternally(false);
 547
 548   DCHECK_EQ(real_context_, GLContext::GetRealCurrent());
 549   DCHECK(real_context_->IsCurrent(NULL));
 550   DCHECK(virtual_context->IsCurrent(surface));
 551
 552   if (state_dirtied_externally || switched_contexts ||
 553       virtual_context != current_context_) {
 554 #if DCHECK_IS_ON()
 555     GLenum error = glGetErrorFn();
 556     // Accepting a context loss error here enables using debug mode to work on
 557     // context loss handling in virtual context mode.
 558     // There should be no other errors from the previous context leaking into
 559     // the new context.
 560     DCHECK(error == GL_NO_ERROR || error == GL_CONTEXT_LOST_KHR) <<
 561         "GL error was: " << error;
 562 #endif
 563
 564     // Set all state that is different from the real state
 565     GLApi* temp = GetCurrentGLApi();
 566     SetGLToRealGLApi();
 567     if (virtual_context->GetGLStateRestorer()->IsInitialized()) {
 568       GLStateRestorer* virtual_state = virtual_context->GetGLStateRestorer();
 569       GLStateRestorer* current_state = current_context_ ?
 570                                        current_context_->GetGLStateRestorer() :
 571                                        nullptr;
 572       if (switched_contexts || virtual_context != current_context_) {
 573         if (current_state)
 574           current_state->PauseQueries();
 575         virtual_state->ResumeQueries();
 576       }
 577
 578       virtual_state->RestoreState(
 579           (current_state && !state_dirtied_externally && !switched_contexts)
 580               ? current_state
 581               : NULL);
 582     }
 583     SetGLApi(temp);
 584     current_context_ = virtual_context;
 585   }
 586   SetGLApi(this);
 587
 588   virtual_context->SetCurrent(surface);
 589   if (!surface->OnMakeCurrent(virtual_context)) {
 590     LOG(ERROR) << "Could not make GLSurface current.";
 591     return false;
 592   }
 593   return true;
 594 }
 595
 596 void VirtualGLApi::OnReleaseVirtuallyCurrent(GLContext* virtual_context) {
 597   if (current_context_ == virtual_context)
 598     current_context_ = NULL;
 599 }
 600
 601 const GLubyte* VirtualGLApi::glGetStringFn(GLenum name) {
 602   switch (name) {
 603     case GL_EXTENSIONS:
 604       return reinterpret_cast<const GLubyte*>(extensions_.c_str());
 605     default:
 606       return driver_->fn.glGetStringFn(name);
 607   }
 608 }
 609
 610 void VirtualGLApi::glFlushFn() {
 611   GLApiBase::glFlushFn();
 612 }
 613
 614 void VirtualGLApi::glFinishFn() {
 615   GLApiBase::glFinishFn();
 616 }
 617
 618 }  // namespace gfx