text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "ui/gl/gl_context.h"
  
  #include "base/logging.h"
  #include "base/memory/ref_counted.h"
  #include "base/sys_info.h"
  #include "ui/gl/gl_bindings.h"
  #include "ui/gl/gl_context_egl.h"
  #include "ui/gl/gl_context_osmesa.h"
  #include "ui/gl/gl_context_stub.h"
  #include "ui/gl/gl_implementation.h"
  #include "ui/gl/gl_surface.h"
  
  namespace gfx {
  
  namespace {
  
  // Used to render into an already current context+surface,
  // that we do not have ownership of (draw callback).
  // TODO(boliu): Make this inherit from GLContextEGL.
  class GLNonOwnedContext : public GLContextReal {
   public:
    GLNonOwnedContext(GLShareGroup* share_group);
  
    // Implement GLContext.
    virtual bool Initialize(GLSurface* compatible_surface,
                            GpuPreference gpu_preference) override;
    virtual void Destroy() override {}
    virtual bool MakeCurrent(GLSurface* surface) override;
    virtual void ReleaseCurrent(GLSurface* surface) override {}
    virtual bool IsCurrent(GLSurface* surface) override { return true; }
    virtual void* GetHandle() override { return NULL; }
    virtual void SetSwapInterval(int interval) override {}
    virtual std::string GetExtensions() override;
  
   protected:
    virtual ~GLNonOwnedContext() {}
  
   private:
    DISALLOW_COPY_AND_ASSIGN(GLNonOwnedContext);
  
    EGLDisplay display_;
  };
  
  GLNonOwnedContext::GLNonOwnedContext(GLShareGroup* share_group)
    : GLContextReal(share_group), display_(NULL) {}
  
  bool GLNonOwnedContext::Initialize(GLSurface* compatible_surface,
                          GpuPreference gpu_preference) {
    display_ = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    return true;
  }
  
  bool GLNonOwnedContext::MakeCurrent(GLSurface* surface) {
    SetCurrent(surface);
    SetRealGLApi();
    return true;
  }
  
  std::string GLNonOwnedContext::GetExtensions() {
    const char* extensions = eglQueryString(display_, EGL_EXTENSIONS);
    if (!extensions)
      return GLContext::GetExtensions();
  
    return GLContext::GetExtensions() + " " + extensions;
  }
  
  }  // anonymous namespace
  
  // static
  scoped_refptr<GLContext> GLContext::CreateGLContext(
      GLShareGroup* share_group,
      GLSurface* compatible_surface,
      GpuPreference gpu_preference) {
    scoped_refptr<GLContext> context;
    switch (GetGLImplementation()) {
      case kGLImplementationMockGL:
        return scoped_refptr<GLContext>(new GLContextStub());
      case kGLImplementationOSMesaGL:
        context = new GLContextOSMesa(share_group);
        break;
      default:
        if (compatible_surface->GetHandle())
          context = new GLContextEGL(share_group);
        else
          context = new GLNonOwnedContext(share_group);
        break;
    }
  
    if (!context->Initialize(compatible_surface, gpu_preference))
      return NULL;
  
    return context;
  }
  
  bool GLContextEGL::GetTotalGpuMemory(size_t* bytes) {
    DCHECK(bytes);
    *bytes = 0;
  
    // We can't query available GPU memory from the system on Android.
    // Physical memory is also mis-reported sometimes (eg. Nexus 10 reports
    // 1262MB when it actually has 2GB, while Razr M has 1GB but only reports
    // 128MB java heap size). First we estimate physical memory using both.
    size_t dalvik_mb = base::SysInfo::DalvikHeapSizeMB();
    size_t physical_mb = base::SysInfo::AmountOfPhysicalMemoryMB();
    size_t physical_memory_mb = 0;
    if (dalvik_mb >= 256)
      physical_memory_mb = dalvik_mb * 4;
    else
      physical_memory_mb = std::max(dalvik_mb * 4,
                                    (physical_mb * 4) / 3);
  
    // Now we take a default of 1/8th of memory on high-memory devices,
    // and gradually scale that back for low-memory devices (to be nicer
    // to other apps so they don't get killed). Examples:
    // Nexus 4/10(2GB)    256MB (normally 128MB)
    // Droid Razr M(1GB)  114MB (normally 57MB)
    // Galaxy Nexus(1GB)  100MB (normally 50MB)
    // Xoom(1GB)          100MB (normally 50MB)
    // Nexus S(low-end)   12MB (normally 8MB)
    // Note that the compositor now uses only some of this memory for
    // pre-painting and uses the rest only for 'emergencies'.
    static size_t limit_bytes = 0;
    if (limit_bytes == 0) {
      // NOTE: Non-low-end devices use only 50% of these limits,
      // except during 'emergencies' where 100% can be used.
      if (!base::SysInfo::IsLowEndDevice()) {
        if (physical_memory_mb >= 1536)
          limit_bytes = physical_memory_mb / 8; // >192MB
        else if (physical_memory_mb >= 1152)
          limit_bytes = physical_memory_mb / 8; // >144MB
        else if (physical_memory_mb >= 768)
          limit_bytes = physical_memory_mb / 10; // >76MB
        else
          limit_bytes = physical_memory_mb / 12; // <64MB
      } else {
        // Low-end devices have 512MB or less memory by definition
        // so we hard code the limit rather than relying on the heuristics
        // above. Low-end devices use 4444 textures so we can use a lower limit.
        // NOTE: Low-end uses 2/3 (67%) of this memory in practice, so we have
        // increased the limit to 12 (8MB, or 12MB in emergencies).
        limit_bytes = 12;
      }
      limit_bytes = limit_bytes * 1024 * 1024;
    }
    *bytes = limit_bytes;
    return true;
  }
  
  }
  