stencil_operations

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Author : hendrikw
Date : 2015-10-20 15:30:53
Hash : bb7740cc
Message : angle: prevent huge allocations when GL_MAX_VERTEX_ATTRIBS fails I'm not sure why yet, but when using angle in skia, getIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxVertexAttribs) sometimes fails, and when that happens we attempt to allocate and array with the size of maxVertexAttribs, which is uninitialized, which could be huge. Prevent this by initializing the variable. Also sweep through other similar calls and ensure that these use initialized values (test code has not been updated) BUG=skia:4380 Change-Id: If1f3cf72f2b2829ad3933637af8778d574a20f61 Reviewed-on: https://chromium-review.googlesource.com/307239 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tryjob-Request: Jamie Madill <jmadill@chromium.org> Tryjob-Request: Dian Xiang <dianx@google.com> Tested-by: Hendrik Wagenaar <hendrikw@chromium.org>

StencilOperations.cpp

//
// Copyright (c) 2014 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

//            Based on Stencil_Test.c from
// Book:      OpenGL(R) ES 2.0 Programming Guide
// Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
// ISBN-10:   0321502795
// ISBN-13:   9780321502797
// Publisher: Addison-Wesley Professional
// URLs:      http://safari.informit.com/9780321563835
//            http://www.opengles-book.com

#include "SampleApplication.h"
#include "shader_utils.h"

class StencilOperationsSample : public SampleApplication
{
  public:
    StencilOperationsSample()
        : SampleApplication("StencilOperations", 1280, 720)
    {
    }

    virtual bool initialize()
    {
        const std::string vs = SHADER_SOURCE
        (
            attribute vec4 a_position;
            void main()
            {
                gl_Position = a_position;
            }
        );

        const std::string fs = SHADER_SOURCE
        (
            precision mediump float;
            uniform vec4 u_color;
            void main()
            {
                gl_FragColor = u_color;
            }
        );

        mProgram = CompileProgram(vs, fs);
        if (!mProgram)
        {
            return false;
        }

        // Get the attribute locations
        mPositionLoc = glGetAttribLocation(mProgram, "a_position");

        // Get the sampler location
        mColorLoc = glGetUniformLocation(mProgram, "u_color");

        // Set the clear color
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

        // Set the stencil clear value
        glClearStencil(0x01);

        // Set the depth clear value
        glClearDepthf(0.75f);

        // Enable the depth and stencil tests
        glEnable(GL_DEPTH_TEST);
        glEnable(GL_STENCIL_TEST);

        return true;
    }

    virtual void destroy()
    {
        glDeleteProgram(mProgram);
    }

    virtual void draw()
    {
        GLfloat vertices[] =
        {
            -0.75f,  0.25f, 0.50f, // Quad #0
            -0.25f,  0.25f, 0.50f,
            -0.25f,  0.75f, 0.50f,
            -0.75f,  0.75f, 0.50f,
             0.25f,  0.25f, 0.90f, // Quad #1
             0.75f,  0.25f, 0.90f,
             0.75f,  0.75f, 0.90f,
             0.25f,  0.75f, 0.90f,
            -0.75f, -0.75f, 0.50f, // Quad #2
            -0.25f, -0.75f, 0.50f,
            -0.25f, -0.25f, 0.50f,
            -0.75f, -0.25f, 0.50f,
             0.25f, -0.75f, 0.50f, // Quad #3
             0.75f, -0.75f, 0.50f,
             0.75f, -0.25f, 0.50f,
             0.25f, -0.25f, 0.50f,
            -1.00f, -1.00f, 0.00f, // Big Quad
             1.00f, -1.00f, 0.00f,
             1.00f,  1.00f, 0.00f,
            -1.00f,  1.00f, 0.00f,
        };

        GLubyte indices[][6] =
        {
            {  0,  1,  2,  0,  2,  3 }, // Quad #0
            {  4,  5,  6,  4,  6,  7 }, // Quad #1
            {  8,  9, 10,  8, 10, 11 }, // Quad #2
            { 12, 13, 14, 12, 14, 15 }, // Quad #3
            { 16, 17, 18, 16, 18, 19 }, // Big Quad
        };

        static const size_t testCount = 4;
        GLfloat colors[testCount][4] =
        {
            { 1.0f, 0.0f, 0.0f, 1.0f },
            { 0.0f, 1.0f, 0.0f, 1.0f },
            { 0.0f, 0.0f, 1.0f, 1.0f },
            { 1.0f, 1.0f, 0.0f, 0.0f },
        };

        GLuint stencilValues[testCount] =
        {
            0x7, // Result of test 0
            0x0, // Result of test 1
            0x2, // Result of test 2
            0xff // Result of test 3.  We need to fill this value in at run-time
        };

        // Set the viewport
        glViewport(0, 0, getWindow()->getWidth(), getWindow()->getHeight());

        // Clear the color, depth, and stencil buffers.  At this point, the stencil
        // buffer will be 0x1 for all pixels
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

        // Use the program object
        glUseProgram(mProgram);

        // Load the vertex data
        glVertexAttribPointer(mPositionLoc, 3, GL_FLOAT, GL_FALSE, 0, vertices);
        glEnableVertexAttribArray(mPositionLoc);

        // Test 0:
        //
        // Initialize upper-left region.  In this case, the stencil-buffer values will
        // be replaced because the stencil test for the rendered pixels will fail the
        // stencil test, which is
        //
        //      ref   mask   stencil  mask
        //    ( 0x7 & 0x3 ) < ( 0x1 & 0x7 )
        //
        // The value in the stencil buffer for these pixels will be 0x7.
        glStencilFunc(GL_LESS, 0x7, 0x3);
        glStencilOp(GL_REPLACE, GL_DECR, GL_DECR);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[0]);

        // Test 1:
        //
        // Initialize the upper-right region. Here, we'll decrement the stencil-buffer
        // values where the stencil test passes but the depth test fails. The stencil test is
        //
        //      ref  mask    stencil  mask
        //    ( 0x3 & 0x3 ) > ( 0x1 & 0x3 )
        //
        // but where the geometry fails the depth test. The stencil values for these pixels
        // will be 0x0.
        glStencilFunc(GL_GREATER, 0x3, 0x3);
        glStencilOp(GL_KEEP, GL_DECR, GL_KEEP);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[1]);

        // Test 2:
        //
        // Initialize the lower-left region.  Here we'll increment (with saturation) the
        // stencil value where both the stencil and depth tests pass.  The stencil test for
        // these pixels will be
        //
        //      ref  mask     stencil  mask
        //    ( 0x1 & 0x3 ) == ( 0x1 & 0x3 )
        //
        // The stencil values for these pixels will be 0x2.
        glStencilFunc(GL_EQUAL, 0x1, 0x3);
        glStencilOp(GL_KEEP, GL_INCR, GL_INCR);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[2]);

        // Test 3:
        //
        // Finally, initialize the lower-right region.  We'll invert the stencil value
        // where the stencil tests fails. The stencil test for these pixels will be
        //
        //      ref   mask    stencil  mask
        //    ( 0x2 & 0x1 ) == ( 0x1 & 0x1 )
        //
        // The stencil value here will be set to ~((2^s-1) & 0x1), (with the 0x1 being
        // from the stencil clear value), where 's' is the number of bits in the stencil
        // buffer
        glStencilFunc(GL_EQUAL, 0x2, 0x1);
        glStencilOp(GL_INVERT, GL_KEEP, GL_KEEP);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[3]);

        // Since we don't know at compile time how many stencil bits are present, we'll
        // query, and update the value correct value in the  stencilValues arrays for the
        // fourth tests. We'll use this value later in rendering.
        GLint stencilBitCount = 0;
        glGetIntegerv(GL_STENCIL_BITS, &stencilBitCount);
        stencilValues[3] = ~(((1 << stencilBitCount) - 1) & 0x1) & 0xff;

        // Use the stencil buffer for controlling where rendering will occur.  We disable
        // writing to the stencil buffer so we can test against them without modifying
        // the values we generated.
        glStencilMask(0x0);

        for (size_t i = 0; i < testCount; ++i)
        {
            glStencilFunc(GL_EQUAL, stencilValues[i], 0xff);
            glUniform4fv(mColorLoc, 1, colors[i]);
            glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[4]);
        }

        // Reset the stencil mask
        glStencilMask(0xFF);
    }

  private:
    // Handle to a program object
    GLuint mProgram;

    // Attribute locations
    GLint mPositionLoc;

    // Uniform locations
    GLint mColorLoc;
};

int main(int argc, char **argv)
{
    StencilOperationsSample app;
    return app.run();
}

kc3-lang/angle/samples/stencil_operations

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kc3-lang/angle /samples/stencil_operations