cmds/flatland/GLHelper.cpp - android_frameworks_native - Gitiles

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>

 #include <ui/DisplayInfo.h>
 #include <gui/SurfaceComposerClient.h>

 #include "GLHelper.h"

  namespace android {

 GLHelper::GLHelper() :
     mDisplay(EGL_NO_DISPLAY),
     mContext(EGL_NO_CONTEXT),
     mDummySurface(EGL_NO_SURFACE),
     mConfig(0),
     mShaderPrograms(NULL),
     mDitherTexture(0) {
 }

 GLHelper::~GLHelper() {
 }

 bool GLHelper::setUp(const ShaderDesc* shaderDescs, size_t numShaders) {
     bool result;

     mDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
     if (mDisplay == EGL_NO_DISPLAY) {
         fprintf(stderr, "eglGetDisplay error: %#x\n", eglGetError());
         return false;
     }

     EGLint majorVersion;
     EGLint minorVersion;
     result = eglInitialize(mDisplay, &majorVersion, &minorVersion);
     if (result != EGL_TRUE) {
         fprintf(stderr, "eglInitialize error: %#x\n", eglGetError());
         return false;
     }

     EGLint numConfigs = 0;
     EGLint configAttribs[] = {
         EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
         EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
         EGL_RED_SIZE, 8,
         EGL_GREEN_SIZE, 8,
         EGL_BLUE_SIZE, 8,
         EGL_ALPHA_SIZE, 8,
         EGL_NONE
     };
     result = eglChooseConfig(mDisplay, configAttribs, &mConfig, 1,
             &numConfigs);
     if (result != EGL_TRUE) {
         fprintf(stderr, "eglChooseConfig error: %#x\n", eglGetError());
         return false;
     }

     EGLint contextAttribs[] = {
         EGL_CONTEXT_CLIENT_VERSION, 2,
         EGL_NONE
     };
     mContext = eglCreateContext(mDisplay, mConfig, EGL_NO_CONTEXT,
             contextAttribs);
     if (mContext == EGL_NO_CONTEXT) {
         fprintf(stderr, "eglCreateContext error: %#x\n", eglGetError());
         return false;
     }

     bool resultb = createNamedSurfaceTexture(0, 1, 1, &mDummyGLConsumer,
             &mDummySurface);
     if (!resultb) {
         return false;
     }

     resultb = makeCurrent(mDummySurface);
     if (!resultb) {
         return false;
     }

     resultb = setUpShaders(shaderDescs, numShaders);
     if (!resultb) {
         return false;
     }

     return true;
 }

 void GLHelper::tearDown() {
     if (mShaderPrograms != NULL) {
         delete[] mShaderPrograms;
         mShaderPrograms = NULL;
     }

     if (mSurfaceComposerClient != NULL) {
         mSurfaceComposerClient->dispose();
         mSurfaceComposerClient.clear();
     }

     if (mDisplay != EGL_NO_DISPLAY) {
         eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
                 EGL_NO_CONTEXT);
     }

     if (mContext != EGL_NO_CONTEXT) {
         eglDestroyContext(mDisplay, mContext);
     }

     if (mDummySurface != EGL_NO_SURFACE) {
         eglDestroySurface(mDisplay, mDummySurface);
     }

     mDisplay = EGL_NO_DISPLAY;
     mContext = EGL_NO_CONTEXT;
     mDummySurface = EGL_NO_SURFACE;
     mDummyGLConsumer.clear();
     mConfig = 0;
 }

 bool GLHelper::makeCurrent(EGLSurface surface) {
     EGLint result;

     result = eglMakeCurrent(mDisplay, surface, surface, mContext);
     if (result != EGL_TRUE) {
         fprintf(stderr, "eglMakeCurrent error: %#x\n", eglGetError());
         return false;
     }

     EGLint w, h;
     eglQuerySurface(mDisplay, surface, EGL_WIDTH, &w);
     eglQuerySurface(mDisplay, surface, EGL_HEIGHT, &h);
     glViewport(0, 0, w, h);

     return true;
 }

 bool GLHelper::createSurfaceTexture(uint32_t w, uint32_t h,
         sp<GLConsumer>* glConsumer, EGLSurface* surface,
         GLuint* name) {
     if (!makeCurrent(mDummySurface)) {
         return false;
     }

     *name = 0;
     glGenTextures(1, name);
     if (*name == 0) {
         fprintf(stderr, "glGenTextures error: %#x\n", glGetError());
         return false;
     }

     return createNamedSurfaceTexture(*name, w, h, glConsumer, surface);
 }

 void GLHelper::destroySurface(EGLSurface* surface) {
     if (eglGetCurrentSurface(EGL_READ) == *surface ||
             eglGetCurrentSurface(EGL_DRAW) == *surface) {
         eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
                 EGL_NO_CONTEXT);
     }
     eglDestroySurface(mDisplay, *surface);
     *surface = EGL_NO_SURFACE;
 }

 bool GLHelper::swapBuffers(EGLSurface surface) {
     EGLint result;
     result = eglSwapBuffers(mDisplay, surface);
     if (result != EGL_TRUE) {
         fprintf(stderr, "eglSwapBuffers error: %#x\n", eglGetError());
         return false;
     }
     return true;
 }

 bool GLHelper::getShaderProgram(const char* name, GLuint* outPgm) {
     for (size_t i = 0; i < mNumShaders; i++) {
         if (strcmp(mShaderDescs[i].name, name) == 0) {
             *outPgm = mShaderPrograms[i];
             return true;
         }
     }

     fprintf(stderr, "unknown shader name: \"%s\"\n", name);

     return false;
 }

 bool GLHelper::createNamedSurfaceTexture(GLuint name, uint32_t w, uint32_t h,
         sp<GLConsumer>* glConsumer, EGLSurface* surface) {
     sp<IGraphicBufferProducer> producer;
     sp<IGraphicBufferConsumer> consumer;
     BufferQueue::createBufferQueue(&producer, &consumer);
     sp<GLConsumer> glc = new GLConsumer(consumer, name,
             GL_TEXTURE_EXTERNAL_OES, false, true);
     glc->setDefaultBufferSize(w, h);
     producer->setMaxDequeuedBufferCount(2);
     glc->setConsumerUsageBits(GRALLOC_USAGE_HW_COMPOSER);

     sp<ANativeWindow> anw = new Surface(producer);
     EGLSurface s = eglCreateWindowSurface(mDisplay, mConfig, anw.get(), NULL);
     if (s == EGL_NO_SURFACE) {
         fprintf(stderr, "eglCreateWindowSurface error: %#x\n", eglGetError());
         return false;
     }

     *glConsumer = glc;
     *surface = s;
     return true;
 }

 bool GLHelper::computeWindowScale(uint32_t w, uint32_t h, float* scale) {
     sp<IBinder> dpy = mSurfaceComposerClient->getBuiltInDisplay(0);
     if (dpy == NULL) {
         fprintf(stderr, "SurfaceComposer::getBuiltInDisplay failed.\n");
         return false;
     }

     DisplayInfo info;
     status_t err = mSurfaceComposerClient->getDisplayInfo(dpy, &info);
     if (err != NO_ERROR) {
         fprintf(stderr, "SurfaceComposer::getDisplayInfo failed: %#x\n", err);
         return false;
     }

     float scaleX = float(info.w) / float(w);
     float scaleY = float(info.h) / float(h);
     *scale = scaleX < scaleY ? scaleX : scaleY;

     return true;
 }

 bool GLHelper::createWindowSurface(uint32_t w, uint32_t h,
         sp<SurfaceControl>* surfaceControl, EGLSurface* surface) {
     bool result;
     status_t err;

     if (mSurfaceComposerClient == NULL) {
         mSurfaceComposerClient = new SurfaceComposerClient;
     }
     err = mSurfaceComposerClient->initCheck();
     if (err != NO_ERROR) {
         fprintf(stderr, "SurfaceComposerClient::initCheck error: %#x\n", err);
         return false;
     }

     sp<SurfaceControl> sc = mSurfaceComposerClient->createSurface(
             String8("Benchmark"), w, h, PIXEL_FORMAT_RGBA_8888, 0);
     if (sc == NULL || !sc->isValid()) {
         fprintf(stderr, "Failed to create SurfaceControl.\n");
         return false;
     }

     float scale;
     result = computeWindowScale(w, h, &scale);
     if (!result) {
         return false;
     }

     SurfaceComposerClient::Transaction{}.setLayer(sc, 0x7FFFFFFF)
             .setMatrix(sc, scale, 0.0f, 0.0f, scale)
             .show(sc)
             .apply();

     sp<ANativeWindow> anw = sc->getSurface();
     EGLSurface s = eglCreateWindowSurface(mDisplay, mConfig, anw.get(), NULL);
     if (s == EGL_NO_SURFACE) {
         fprintf(stderr, "eglCreateWindowSurface error: %#x\n", eglGetError());
         return false;
     }

     *surfaceControl = sc;
     *surface = s;
     return true;
 }

 static bool compileShader(GLenum shaderType, const char* src,
         GLuint* outShader) {
     GLuint shader = glCreateShader(shaderType);
     if (shader == 0) {
         fprintf(stderr, "glCreateShader error: %#x\n", glGetError());
         return false;
     }

     glShaderSource(shader, 1, &src, NULL);
     glCompileShader(shader);

     GLint compiled = 0;
     glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
     if (!compiled) {
         GLint infoLen = 0;
         glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
         if (infoLen) {
             char* buf = new char[infoLen];
             if (buf) {
                 glGetShaderInfoLog(shader, infoLen, NULL, buf);
                 fprintf(stderr, "Shader compile log:\n%s\n", buf);
                 delete[] buf;
             }
         }
         glDeleteShader(shader);
         return false;
     }
     *outShader = shader;
     return true;
 }

 static void printShaderSource(const char* const* src) {
     for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
         fprintf(stderr, "%3zu: %s\n", i+1, src[i]);
     }
 }

 static const char* makeShaderString(const char* const* src) {
     size_t len = 0;
     for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
         // The +1 is for the '\n' that will be added.
         len += strlen(src[i]) + 1;
     }

     char* result = new char[len+1];
     char* end = result;
     for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
         strcpy(end, src[i]);
         end += strlen(src[i]);
         *end = '\n';
         end++;
     }
     *end = '\0';

     return result;
 }

 static bool compileShaderLines(GLenum shaderType, const char* const* lines,
         GLuint* outShader) {
     const char* src = makeShaderString(lines);
     bool result = compileShader(shaderType, src, outShader);
     if (!result) {
         fprintf(stderr, "Shader source:\n");
         printShaderSource(lines);
         delete[] src;
         return false;
     }
     delete[] src;

     return true;
 }

 static bool linkShaderProgram(GLuint vs, GLuint fs, GLuint* outPgm) {
     GLuint program = glCreateProgram();
     if (program == 0) {
         fprintf(stderr, "glCreateProgram error: %#x\n", glGetError());
         return false;
     }

     glAttachShader(program, vs);
     glAttachShader(program, fs);
     glLinkProgram(program);
     GLint linkStatus = GL_FALSE;
     glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
     if (linkStatus != GL_TRUE) {
         GLint bufLength = 0;
         glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
         if (bufLength) {
             char* buf = new char[bufLength];
             if (buf) {
                 glGetProgramInfoLog(program, bufLength, NULL, buf);
                 fprintf(stderr, "Program link log:\n%s\n", buf);
                 delete[] buf;
             }
         }
         glDeleteProgram(program);
         program = 0;
     }

     *outPgm = program;
     return program != 0;
 }

 bool GLHelper::setUpShaders(const ShaderDesc* shaderDescs, size_t numShaders) {
     mShaderPrograms = new GLuint[numShaders];
     bool result = true;

     for (size_t i = 0; i < numShaders && result; i++) {
         GLuint vs, fs;

         result = compileShaderLines(GL_VERTEX_SHADER,
                 shaderDescs[i].vertexShader, &vs);
         if (!result) {
             return false;
         }

         result = compileShaderLines(GL_FRAGMENT_SHADER,
                 shaderDescs[i].fragmentShader, &fs);
         if (!result) {
             glDeleteShader(vs);
             return false;
         }

         result = linkShaderProgram(vs, fs, &mShaderPrograms[i]);
         glDeleteShader(vs);
         glDeleteShader(fs);
     }

     mNumShaders = numShaders;
     mShaderDescs = shaderDescs;

     return result;
 }

 bool GLHelper::getDitherTexture(GLuint* outTexName) {
     if (mDitherTexture == 0) {
         const uint8_t pattern[] = {
              0,  8,  2, 10,
             12,  4, 14,  6,
              3, 11,  1,  9,
             15,  7, 13,  5
         };

         glGenTextures(1, &mDitherTexture);
         glBindTexture(GL_TEXTURE_2D, mDitherTexture);

         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

         glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE,
                 DITHER_KERNEL_SIZE, 0, GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
     }

     *outTexName = mDitherTexture;

     return true;
 }

 }
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <GLES2/gl2.h>
	#include <GLES2/gl2ext.h>

	#include <ui/DisplayInfo.h>
	#include <gui/SurfaceComposerClient.h>

	#include "GLHelper.h"

	namespace android {

	GLHelper::GLHelper() :
	mDisplay(EGL_NO_DISPLAY),
	mContext(EGL_NO_CONTEXT),
	mDummySurface(EGL_NO_SURFACE),
	mConfig(0),
	mShaderPrograms(NULL),
	mDitherTexture(0) {
	}

	GLHelper::~GLHelper() {
	}

	bool GLHelper::setUp(const ShaderDesc* shaderDescs, size_t numShaders) {
	bool result;

	mDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
	if (mDisplay == EGL_NO_DISPLAY) {
	fprintf(stderr, "eglGetDisplay error: %#x\n", eglGetError());
	return false;
	}

	EGLint majorVersion;
	EGLint minorVersion;
	result = eglInitialize(mDisplay, &majorVersion, &minorVersion);
	if (result != EGL_TRUE) {
	fprintf(stderr, "eglInitialize error: %#x\n", eglGetError());
	return false;
	}

	EGLint numConfigs = 0;
	EGLint configAttribs[] = {
	EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
	EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
	EGL_RED_SIZE, 8,
	EGL_GREEN_SIZE, 8,
	EGL_BLUE_SIZE, 8,
	EGL_ALPHA_SIZE, 8,
	EGL_NONE
	};
	result = eglChooseConfig(mDisplay, configAttribs, &mConfig, 1,
	&numConfigs);
	if (result != EGL_TRUE) {
	fprintf(stderr, "eglChooseConfig error: %#x\n", eglGetError());
	return false;
	}

	EGLint contextAttribs[] = {
	EGL_CONTEXT_CLIENT_VERSION, 2,
	EGL_NONE
	};
	mContext = eglCreateContext(mDisplay, mConfig, EGL_NO_CONTEXT,
	contextAttribs);
	if (mContext == EGL_NO_CONTEXT) {
	fprintf(stderr, "eglCreateContext error: %#x\n", eglGetError());
	return false;
	}

	bool resultb = createNamedSurfaceTexture(0, 1, 1, &mDummyGLConsumer,
	&mDummySurface);
	if (!resultb) {
	return false;
	}

	resultb = makeCurrent(mDummySurface);
	if (!resultb) {
	return false;
	}

	resultb = setUpShaders(shaderDescs, numShaders);
	if (!resultb) {
	return false;
	}

	return true;
	}

	void GLHelper::tearDown() {
	if (mShaderPrograms != NULL) {
	delete[] mShaderPrograms;
	mShaderPrograms = NULL;
	}

	if (mSurfaceComposerClient != NULL) {
	mSurfaceComposerClient->dispose();
	mSurfaceComposerClient.clear();
	}

	if (mDisplay != EGL_NO_DISPLAY) {
	eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
	EGL_NO_CONTEXT);
	}

	if (mContext != EGL_NO_CONTEXT) {
	eglDestroyContext(mDisplay, mContext);
	}

	if (mDummySurface != EGL_NO_SURFACE) {
	eglDestroySurface(mDisplay, mDummySurface);
	}

	mDisplay = EGL_NO_DISPLAY;
	mContext = EGL_NO_CONTEXT;
	mDummySurface = EGL_NO_SURFACE;
	mDummyGLConsumer.clear();
	mConfig = 0;
	}

	bool GLHelper::makeCurrent(EGLSurface surface) {
	EGLint result;

	result = eglMakeCurrent(mDisplay, surface, surface, mContext);
	if (result != EGL_TRUE) {
	fprintf(stderr, "eglMakeCurrent error: %#x\n", eglGetError());
	return false;
	}

	EGLint w, h;
	eglQuerySurface(mDisplay, surface, EGL_WIDTH, &w);
	eglQuerySurface(mDisplay, surface, EGL_HEIGHT, &h);
	glViewport(0, 0, w, h);

	return true;
	}

	bool GLHelper::createSurfaceTexture(uint32_t w, uint32_t h,
	sp<GLConsumer>* glConsumer, EGLSurface* surface,
	GLuint* name) {
	if (!makeCurrent(mDummySurface)) {
	return false;
	}

	*name = 0;
	glGenTextures(1, name);
	if (*name == 0) {
	fprintf(stderr, "glGenTextures error: %#x\n", glGetError());
	return false;
	}

	return createNamedSurfaceTexture(*name, w, h, glConsumer, surface);
	}

	void GLHelper::destroySurface(EGLSurface* surface) {
	if (eglGetCurrentSurface(EGL_READ) == *surface \|\|
	eglGetCurrentSurface(EGL_DRAW) == *surface) {
	eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
	EGL_NO_CONTEXT);
	}
	eglDestroySurface(mDisplay, *surface);
	*surface = EGL_NO_SURFACE;
	}

	bool GLHelper::swapBuffers(EGLSurface surface) {
	EGLint result;
	result = eglSwapBuffers(mDisplay, surface);
	if (result != EGL_TRUE) {
	fprintf(stderr, "eglSwapBuffers error: %#x\n", eglGetError());
	return false;
	}
	return true;
	}

	bool GLHelper::getShaderProgram(const char* name, GLuint* outPgm) {
	for (size_t i = 0; i < mNumShaders; i++) {
	if (strcmp(mShaderDescs[i].name, name) == 0) {
	*outPgm = mShaderPrograms[i];
	return true;
	}
	}

	fprintf(stderr, "unknown shader name: \"%s\"\n", name);

	return false;
	}

	bool GLHelper::createNamedSurfaceTexture(GLuint name, uint32_t w, uint32_t h,
	sp<GLConsumer>* glConsumer, EGLSurface* surface) {
	sp<IGraphicBufferProducer> producer;
	sp<IGraphicBufferConsumer> consumer;
	BufferQueue::createBufferQueue(&producer, &consumer);
	sp<GLConsumer> glc = new GLConsumer(consumer, name,
	GL_TEXTURE_EXTERNAL_OES, false, true);
	glc->setDefaultBufferSize(w, h);
	producer->setMaxDequeuedBufferCount(2);
	glc->setConsumerUsageBits(GRALLOC_USAGE_HW_COMPOSER);

	sp<ANativeWindow> anw = new Surface(producer);
	EGLSurface s = eglCreateWindowSurface(mDisplay, mConfig, anw.get(), NULL);
	if (s == EGL_NO_SURFACE) {
	fprintf(stderr, "eglCreateWindowSurface error: %#x\n", eglGetError());
	return false;
	}

	*glConsumer = glc;
	*surface = s;
	return true;
	}

	bool GLHelper::computeWindowScale(uint32_t w, uint32_t h, float* scale) {
	sp<IBinder> dpy = mSurfaceComposerClient->getBuiltInDisplay(0);
	if (dpy == NULL) {
	fprintf(stderr, "SurfaceComposer::getBuiltInDisplay failed.\n");
	return false;
	}

	DisplayInfo info;
	status_t err = mSurfaceComposerClient->getDisplayInfo(dpy, &info);
	if (err != NO_ERROR) {
	fprintf(stderr, "SurfaceComposer::getDisplayInfo failed: %#x\n", err);
	return false;
	}

	float scaleX = float(info.w) / float(w);
	float scaleY = float(info.h) / float(h);
	*scale = scaleX < scaleY ? scaleX : scaleY;

	return true;
	}

	bool GLHelper::createWindowSurface(uint32_t w, uint32_t h,
	sp<SurfaceControl>* surfaceControl, EGLSurface* surface) {
	bool result;
	status_t err;

	if (mSurfaceComposerClient == NULL) {
	mSurfaceComposerClient = new SurfaceComposerClient;
	}
	err = mSurfaceComposerClient->initCheck();
	if (err != NO_ERROR) {
	fprintf(stderr, "SurfaceComposerClient::initCheck error: %#x\n", err);
	return false;
	}

	sp<SurfaceControl> sc = mSurfaceComposerClient->createSurface(
	String8("Benchmark"), w, h, PIXEL_FORMAT_RGBA_8888, 0);
	if (sc == NULL \|\| !sc->isValid()) {
	fprintf(stderr, "Failed to create SurfaceControl.\n");
	return false;
	}

	float scale;
	result = computeWindowScale(w, h, &scale);
	if (!result) {
	return false;
	}

	SurfaceComposerClient::Transaction{}.setLayer(sc, 0x7FFFFFFF)
	.setMatrix(sc, scale, 0.0f, 0.0f, scale)
	.show(sc)
	.apply();

	sp<ANativeWindow> anw = sc->getSurface();
	EGLSurface s = eglCreateWindowSurface(mDisplay, mConfig, anw.get(), NULL);
	if (s == EGL_NO_SURFACE) {
	fprintf(stderr, "eglCreateWindowSurface error: %#x\n", eglGetError());
	return false;
	}

	*surfaceControl = sc;
	*surface = s;
	return true;
	}

	static bool compileShader(GLenum shaderType, const char* src,
	GLuint* outShader) {
	GLuint shader = glCreateShader(shaderType);
	if (shader == 0) {
	fprintf(stderr, "glCreateShader error: %#x\n", glGetError());
	return false;
	}

	glShaderSource(shader, 1, &src, NULL);
	glCompileShader(shader);

	GLint compiled = 0;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
	if (!compiled) {
	GLint infoLen = 0;
	glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
	if (infoLen) {
	char* buf = new char[infoLen];
	if (buf) {
	glGetShaderInfoLog(shader, infoLen, NULL, buf);
	fprintf(stderr, "Shader compile log:\n%s\n", buf);
	delete[] buf;
	}
	}
	glDeleteShader(shader);
	return false;
	}
	*outShader = shader;
	return true;
	}

	static void printShaderSource(const char* const* src) {
	for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
	fprintf(stderr, "%3zu: %s\n", i+1, src[i]);
	}
	}

	static const char* makeShaderString(const char* const* src) {
	size_t len = 0;
	for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
	// The +1 is for the '\n' that will be added.
	len += strlen(src[i]) + 1;
	}

	char* result = new char[len+1];
	char* end = result;
	for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
	strcpy(end, src[i]);
	end += strlen(src[i]);
	*end = '\n';
	end++;
	}
	*end = '\0';

	return result;
	}

	static bool compileShaderLines(GLenum shaderType, const char* const* lines,
	GLuint* outShader) {
	const char* src = makeShaderString(lines);
	bool result = compileShader(shaderType, src, outShader);
	if (!result) {
	fprintf(stderr, "Shader source:\n");
	printShaderSource(lines);
	delete[] src;
	return false;
	}
	delete[] src;

	return true;
	}

	static bool linkShaderProgram(GLuint vs, GLuint fs, GLuint* outPgm) {
	GLuint program = glCreateProgram();
	if (program == 0) {
	fprintf(stderr, "glCreateProgram error: %#x\n", glGetError());
	return false;
	}

	glAttachShader(program, vs);
	glAttachShader(program, fs);
	glLinkProgram(program);
	GLint linkStatus = GL_FALSE;
	glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
	if (linkStatus != GL_TRUE) {
	GLint bufLength = 0;
	glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
	if (bufLength) {
	char* buf = new char[bufLength];
	if (buf) {
	glGetProgramInfoLog(program, bufLength, NULL, buf);
	fprintf(stderr, "Program link log:\n%s\n", buf);
	delete[] buf;
	}
	}
	glDeleteProgram(program);
	program = 0;
	}

	*outPgm = program;
	return program != 0;
	}

	bool GLHelper::setUpShaders(const ShaderDesc* shaderDescs, size_t numShaders) {
	mShaderPrograms = new GLuint[numShaders];
	bool result = true;

	for (size_t i = 0; i < numShaders && result; i++) {
	GLuint vs, fs;

	result = compileShaderLines(GL_VERTEX_SHADER,
	shaderDescs[i].vertexShader, &vs);
	if (!result) {
	return false;
	}

	result = compileShaderLines(GL_FRAGMENT_SHADER,
	shaderDescs[i].fragmentShader, &fs);
	if (!result) {
	glDeleteShader(vs);
	return false;
	}

	result = linkShaderProgram(vs, fs, &mShaderPrograms[i]);
	glDeleteShader(vs);
	glDeleteShader(fs);
	}

	mNumShaders = numShaders;
	mShaderDescs = shaderDescs;

	return result;
	}

	bool GLHelper::getDitherTexture(GLuint* outTexName) {
	if (mDitherTexture == 0) {
	const uint8_t pattern[] = {
	0, 8, 2, 10,
	12, 4, 14, 6,
	3, 11, 1, 9,
	15, 7, 13, 5
	};

	glGenTextures(1, &mDitherTexture);
	glBindTexture(GL_TEXTURE_2D, mDitherTexture);

	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

	glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE,
	DITHER_KERNEL_SIZE, 0, GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
	}

	*outTexName = mDitherTexture;

	return true;
	}

	}