WebGL 2: add readPixels API to read pixels into pixel pack buffer

Source/modules/webgl/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 949 matching lines @@
     ASSERT(drawingBuffer());
 
     m_markedCanvasDirty = false;
     m_activeTextureUnit = 0;
     m_packAlignment = 4;
     m_unpackAlignment = 4;
     m_unpackFlipY = false;
     m_unpackPremultiplyAlpha = false;
     m_unpackColorspaceConversion = GC3D_BROWSER_DEFAULT_WEBGL;
     m_boundArrayBuffer = nullptr;
+    m_boundPixelPackBuffer = nullptr;
     m_currentProgram = nullptr;
     m_framebufferBinding = nullptr;
     m_renderbufferBinding = nullptr;
     m_valuebufferBinding = nullptr;
     m_depthMask = true;
     m_stencilEnabled = false;
     m_stencilMask = 0xFFFFFFFF;
     m_stencilMaskBack = 0xFFFFFFFF;
     m_stencilFuncRef = 0;
     m_stencilFuncRefBack = 0;
@@ skipping 111 matching lines @@
     if (!context->is3d())
         return 0;
     return static_cast<const WebGLRenderingContextBase*>(context)->version();
 }
 
 WebGLRenderingContextBase::~WebGLRenderingContextBase()
 {
     // Remove all references to WebGLObjects so if they are the last reference
     // they will be freed before the last context is removed from the context group.
     m_boundArrayBuffer = nullptr;
+    m_boundPixelPackBuffer = nullptr;
     m_defaultVertexArrayObject = nullptr;
     m_boundVertexArrayObject = nullptr;
     m_vertexAttrib0Buffer = nullptr;
     m_currentProgram = nullptr;
     m_framebufferBinding = nullptr;
     m_renderbufferBinding = nullptr;
     m_valuebufferBinding = nullptr;
 
     for (size_t i = 0; i < m_textureUnits.size(); ++i) {
         m_textureUnits[i].m_texture2DBinding = nullptr;
@@ skipping 2611 matching lines @@
     case GL_FLOAT:
         return DOMArrayBufferView::TypeFloat32;
     case GL_HALF_FLOAT_OES:
         return DOMArrayBufferView::TypeUint16;
     default:
         ASSERT_NOT_REACHED();
         return DOMArrayBufferView::TypeUint8;
     }
 }
 
+bool WebGLRenderingContextBase::validateReadPixelsFuncParameters(GLsizei width, GLsizei height, GLenum format, GLenum type, unsigned domArrayBufferLength, WebGLFramebuffer*& readFramebufferBinding)
+{
+    if (!validateReadPixelsFormatAndType(format, type))
+        return false;
+    GLenum readBufferInternalFormat = 0, readBufferType = 0;
+    if (!validateReadBufferAndGetInfo("readPixels", readFramebufferBinding, &readBufferInternalFormat, &readBufferType))
+        return false;
+    if (!validateReadPixelsFormatTypeCombination(format, type, readBufferInternalFormat, readBufferType))
+        return false;
+
+    // Calculate array size, taking into consideration of PACK_ALIGNMENT.
+    unsigned totalBytesRequired = 0;
+    unsigned padding = 0;
+    GLenum error = WebGLImageConversion::computeImageSizeInBytes(format, type, width, height, m_packAlignment, &totalBytesRequired, &padding);
+    if (error != GL_NO_ERROR) {
+        synthesizeGLError(error, "readPixels", "invalid dimensions");
+        return false;
+    }
+    if (domArrayBufferLength && domArrayBufferLength < totalBytesRequired) {
+        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "ArrayBufferView not large enough for dimensions");
+        return false;
+    }
+    return true;
+}
+
 void WebGLRenderingContextBase::readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, DOMArrayBufferView* pixels)
 {
     if (isContextLost())
         return;
     // Due to WebGL's same-origin restrictions, it is not possible to
     // taint the origin using the WebGL API.
     ASSERT(canvas()->originClean());
+    if (isWebGL2OrHigher() && m_boundPixelPackBuffer.get()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "PIXEL_PACK buffer should not bound");
+        return;
+    }
     // Validate input parameters.
     if (!pixels) {
         synthesizeGLError(GL_INVALID_VALUE, "readPixels", "no destination ArrayBufferView");
         return;
     }
-    if (!validateReadPixelsFormatAndType(format, type))
-        return;
-    GLenum readBufferInternalFormat = 0, readBufferType = 0;
-    WebGLFramebuffer* readFramebufferBinding = nullptr;
-    if (!validateReadBufferAndGetInfo("readPixels", readFramebufferBinding, &readBufferInternalFormat, &readBufferType))
-        return;
-    if (!validateReadPixelsFormatTypeCombination(format, type, readBufferInternalFormat, readBufferType))
-        return;
 
     DOMArrayBufferView::ViewType expectedViewType = readPixelsExpectedArrayBufferViewType(type);
     // Validate array type against pixel type.
     if (pixels->type() != expectedViewType) {
         synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "ArrayBufferView was the wrong type for the pixel format");
         return;
     }
 
-    // Calculate array size, taking into consideration of PACK_ALIGNMENT.
-    unsigned totalBytesRequired = 0;
-    unsigned padding = 0;
-    GLenum error = WebGLImageConversion::computeImageSizeInBytes(format, type, width, height, m_packAlignment, &totalBytesRequired, &padding);
-    if (error != GL_NO_ERROR) {
-        synthesizeGLError(error, "readPixels", "invalid dimensions");
+    WebGLFramebuffer* readFramebufferBinding = nullptr;
+    if (!validateReadPixelsFuncParameters(format, type, width, height, pixels->byteLength(), readFramebufferBinding))
         return;
-    }
-    if (pixels->byteLength() < totalBytesRequired) {
-        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "ArrayBufferView not large enough for dimensions");
-        return;
-    }
 
     clearIfComposited();
     void* data = pixels->baseAddress();
 
     {
         ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
         webContext()->readPixels(x, y, width, height, format, type, data);
     }
 }
 
+void WebGLRenderingContextBase::readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, long long offset)
+{
+    if (isContextLost() || !isWebGL2OrHigher())
+        return;
+    // Due to WebGL's same-origin restrictions, it is not possible to
+    // taint the origin using the WebGL API.
+    ASSERT(canvas()->originClean());
+    if (!m_boundPixelPackBuffer.get()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "no PIXEL_PACK buffer bound");
+        return;
+    }
+
+    WebGLFramebuffer* readFramebufferBinding = nullptr;
+    if (!validateReadPixelsFuncParameters(format, type, width, height, 0, readFramebufferBinding))
+        return;
+
+    clearIfComposited();
+    {
+        ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
+        webContext()->readPixels(x, y, width, height, format, type, (void*)offset);
+    }
+}
+
 void WebGLRenderingContextBase::renderbufferStorageImpl(
     GLenum target, GLsizei samples, GLenum internalformat, GLsizei width, GLsizei height,
     const char* functionName)
 {
     ASSERT(!samples); // |samples| > 0 is only valid in WebGL2's renderbufferStorageMultisample().
     ASSERT(!isWebGL2OrHigher()); // Make sure this is overridden in WebGL 2.
     switch (internalformat) {
     case GL_DEPTH_COMPONENT16:
     case GL_RGBA4:
     case GL_RGB5_A1:
@@ skipping 2789 matching lines @@
     visitor->trace(m_texture3DBinding);
     visitor->trace(m_texture2DArrayBinding);
 }
 
 DEFINE_TRACE(WebGLRenderingContextBase)
 {
     visitor->trace(m_contextObjects);
     visitor->trace(m_contextLostCallbackAdapter);
     visitor->trace(m_errorMessageCallbackAdapter);
     visitor->trace(m_boundArrayBuffer);
+    visitor->trace(m_boundPixelPackBuffer);
     visitor->trace(m_defaultVertexArrayObject);
     visitor->trace(m_boundVertexArrayObject);
     visitor->trace(m_vertexAttrib0Buffer);
     visitor->trace(m_currentProgram);
     visitor->trace(m_framebufferBinding);
     visitor->trace(m_renderbufferBinding);
     visitor->trace(m_valuebufferBinding);
     visitor->trace(m_textureUnits);
     visitor->trace(m_blackTexture2D);
     visitor->trace(m_blackTextureCubeMap);
@@ skipping 26 matching lines @@
 
     return totalBytesPerPixel;
 }
 
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 
 } // namespace blink