# Demo using eglCreatePbufferSurface() **URL:** \ **Category:** PowerVR Insider\ **Created:** [August 17, 2009, 8:55am UTC](https://forums.imgtec.com/t/demo-using-eglcreatepbuffersurface/447 "2009-08-17T08:55:11Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![bujji00](https://avatars.discourse-cdn.com/v4/letter/b/d78d45/32.png) [@bujji00](https://forums.imgtec.com/u/bujji00)\ **Post date:** [August 17, 2009, 8:55am UTC](https://forums.imgtec.com/t/demo-using-eglcreatepbuffersurface/447/1 "2009-08-17T08:55:11Z")
Hi I am a newbie trying to modify the trainign course demo "02\_HelloTriangle" to use the eglCreatePbufferSurface() instead of eglCreateWindowSurface() The modifications done are as follows  EGLint s\_surfaceAttribs[] =  { EGL\_WIDTH, 240,  EGL\_HEIGHT, 320,  EGL\_NONE  };  //eglSurface = eglCreateWindowSurface(eglDisplay, eglConfig,(void\*) m\_glutWindow, NULL);  eglSurface = eglCreatePbufferSurface(eglDisplay,eglConfig,s\_surfaceAttribs); After teh above changes i am not able to see the traingle. The output is scattered. What changes are to be done for displaying the frame to the screen? will the eglSwapBuffers() work with pBuffer? i am using the Imagination Technologies PowerVR SDK OVG-1.0\_WINDOWS\_PCEMULATION\_2.04.24.0811. thnks RK ---
**Author:** ![bujji00](https://avatars.discourse-cdn.com/v4/letter/b/d78d45/32.png) [@bujji00](https://forums.imgtec.com/u/bujji00)\ **Post date:** [August 17, 2009, 9:04am UTC](https://forums.imgtec.com/t/demo-using-eglcreatepbuffersurface/447/2 "2009-08-17T09:04:40Z")
missed out in earlier post i hve modified the following also to be compatible for Pbuffer (added EGL\_PBUFFER\_BIT)  static const int ai32ConfigAttribs[] =  {  EGL\_RED\_SIZE, 5,  EGL\_GREEN\_SIZE, 6,  EGL\_BLUE\_SIZE, 5,  EGL\_ALPHA\_SIZE, 0,  EGL\_SURFACE\_TYPE, EGL\_WINDOW\_BIT|EGL\_PBUFFER\_BIT,  EGL\_RENDERABLE\_TYPE, EGL\_OPENVG\_BIT,  EGL\_NONE  }; ---
**Author:** ![bujji00](https://avatars.discourse-cdn.com/v4/letter/b/d78d45/32.png) [@bujji00](https://forums.imgtec.com/u/bujji00)\ **Post date:** [August 17, 2009, 12:16pm UTC](https://forums.imgtec.com/t/demo-using-eglcreatepbuffersurface/447/3 "2009-08-17T12:16:47Z")
I am attaching the file after my changes Thic works good if the macro  DRAWABLES\_SIM\_USING\_2PBUFFER is disabled. If i enable this macro , Pbuffer is used. If i change teh values of afClearColor,fillColor it is not refledcted in the app. Please help me with this Thnks RK /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*  @File OVGHelloTriangle\_Glut.cpp  @Title OpenVG Intitalization Tutorial  @Copyright Copyright (C) Imagination Technologies Limited.  @Platform .  @Description Basic Tutorial that shows step-by-step how to initialize OpenVG,  use it for drawing a line, and terminate it. \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/ #include "vg/openvg.h" #include "EGL/egl.h" #include \ // No C++ Standard Library or exception handling on Symbian platform #include \ #define DRAWABLES\_SIM\_USING\_2PBUFFER /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* \*\* Constants \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/ const char pszAppName[] = "OpenVG Intialization Tutorial"; int i32Frame = 0; EGLDisplay eglDisplay = 0; EGLSurface eglSurface = 0; #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER EGLSurface eglSurface1 = 0; EGLContext eglContext = 0; #endif int i32WindowWidth = 240; int i32WindowHeight= 320; VGfloat afClearColor[4]={1.0f,0.0f,0.0f,1.0f}; VGuint fillColor= 0x00FF00FF; VGPath vgTriangle; VGPaint vgFillPaint; /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* \*\* Declarations \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/ void GlutDisplayHandler() { #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER  VGint imageWidth=0;  VGint imageHeight=0;  VGImage image;  int i32NumConfigs1=0;  EGLConfig eglConfig1 = 0; #endif  if(i32Frame \> 1000)  exit(0);  // Set the clear color  vgSetfv(VG\_CLEAR\_COLOR, 4, afClearColor);  // Clear the whole surface with the clear color  vgClear(0, 0, i32WindowWidth, i32WindowHeight); #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER  vgFinish();  // create a VGImage  imageWidth = 120;  imageHeight= 160;  image = vgCreateImage(VG\_sARGB\_8888\_PRE, imageWidth, imageHeight, VG\_IMAGE\_QUALITY\_BETTER );  static const int ai32ConfigAttribs1[] =  {  EGL\_RED\_SIZE, 5,  EGL\_GREEN\_SIZE, 6,  EGL\_BLUE\_SIZE, 5,  EGL\_ALPHA\_SIZE, 0,  EGL\_SURFACE\_TYPE, EGL\_WINDOW\_BIT|EGL\_PBUFFER\_BIT,  EGL\_RENDERABLE\_TYPE, EGL\_OPENVG\_BIT,  EGL\_NONE  };  EGLint s\_surfaceAttribs1[] =  { EGL\_WIDTH, 120,  EGL\_HEIGHT, 160,  EGL\_NONE  };  if(!eglChooseConfig(eglDisplay, ai32ConfigAttribs1, &eglConfig1, 1, &i32NumConfigs1) || (i32NumConfigs1 != 1))  {  printf("Error: eglChooseConfig() failed.n");  exit(0);  }  eglSurface1 = eglCreatePbufferSurface(eglDisplay,eglConfig1,s\_surfaceAttribs1);  if((eglGetError() != EGL\_SUCCESS) || (eglSurface1 == EGL\_NO\_SURFACE))  {  printf("Error: eglCreateWindowSurface() failed.n");  exit(0);  }  eglMakeCurrent(eglDisplay, eglSurface1, eglSurface1, eglContext);  if(eglGetError() != EGL\_SUCCESS)  {  printf("Error: eglMakeCurrent() failed.n");  exit(0);  }  vgSeti(VG\_MATRIX\_MODE, VG\_MATRIX\_PATH\_USER\_TO\_SURFACE);  vgLoadIdentity();  vgScale((float)imageWidth, (float)imageHeight);  vgTriangle = vgCreatePath(  VG\_PATH\_FORMAT\_STANDARD,  VG\_PATH\_DATATYPE\_F,  1.0f, 0.0f, 4, 3,  (unsigned int)VG\_PATH\_CAPABILITY\_APPEND\_TO);  VGubyte aui8PathSegments[4];  aui8PathSegments[0] = VG\_MOVE\_TO\_ABS;  aui8PathSegments[1] = VG\_LINE\_TO\_ABS;  aui8PathSegments[2] = VG\_LINE\_TO\_ABS;  aui8PathSegments[3] = VG\_CLOSE\_PATH;  VGfloat afPoints[6];  afPoints[0] = 0.3f;  afPoints[1] = 0.3f;  afPoints[2] = 0.7f;  afPoints[3] = 0.3f;  afPoints[4] = 0.5f;  afPoints[5] = 0.7f;  vgAppendPathData(vgTriangle, 4, aui8PathSegments, afPoints);  vgRemovePathCapabilities(vgTriangle, VG\_PATH\_CAPABILITY\_APPEND\_TO);  vgFillPaint = vgCreatePaint();  vgSetParameteri(vgFillPaint, VG\_PAINT\_TYPE, VG\_PAINT\_TYPE\_COLOR);  vgSetColor(vgFillPaint, fillColor);  vgSetfv(VG\_CLEAR\_COLOR, 4, afClearColor);  // Clear the whole surface with the clear color  vgClear(0, 0, imageWidth, imageHeight); #endif  // Set the current fill paint...  vgSetPaint(vgFillPaint, VG\_FILL\_PATH);  // Draw the triangle!  vgDrawPath(vgTriangle, VG\_FILL\_PATH); #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER  vgFinish();  vgGetPixels(image,0,0,0,0,imageWidth,imageHeight);  vgFinish();  vgDestroyPath(vgTriangle);  eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext);  if(eglGetError() != EGL\_SUCCESS)  {  printf("Error: eglMakeCurrent() failed.n");  exit(0);  }  eglDestroySurface(eglDisplay,eglSurface1);  if(eglGetError() != EGL\_SUCCESS)  {  printf("Error: eglMakeCurrent() failed.n");  exit(0);  }  vgDrawImage(image);  vgFinish(); #endif  /\*  Drawing is double buffered, so you never see any intermediate  results of the drawing. When you have finished drawing  you have to call eglSwapBuffers to make the results appear on  screen.  \*/ #ifndef DRAWABLES\_SIM\_USING\_2PBUFFER  eglSwapBuffers(eglDisplay, eglSurface); #endif  glutSwapBuffers();  ++i32Frame;  glutPostRedisplay(); } void CleanupOnExit() {  /\*  Step 6 - Destroy resources  * * *  OpenVG resources like paths and paints need to be destroyed  when they are no longer needed.  \*/  vgDestroyPath(vgTriangle);  vgDestroyPaint(vgFillPaint);  // Terminate OpenVG  eglMakeCurrent(eglDisplay, EGL\_NO\_SURFACE, EGL\_NO\_SURFACE, EGL\_NO\_CONTEXT);  eglTerminate(eglDisplay); } /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* \*\* Application entry point \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/ int main(int argc, char \*argv[]) {  EGLConfig eglConfig = 0; #ifndef DRAWABLES\_SIM\_USING\_2PBUFFER  EGLContext eglContext = 0; #endif  int i32NumConfigs, i32MajorVersion, i32MinorVersion;  /\*  Step 0 - Create a window that we can use for OpenVG output  Window creation is platform specific so it should be done by  a separate function.  \*/  glutInit(&argc, argv);  glutInitDisplayMode(GLUT\_DOUBLE | GLUT\_RGB);  glutInitWindowSize(240, 320);  glutInitWindowPosition(100, 100);  int m\_glutWindow = glutCreateWindow("");  if(!m\_glutWindow)  {  return 1;  }  glutDisplayFunc(GlutDisplayHandler);  atexit(CleanupOnExit);  /\*  Step 1 - Get the default display  EGL uses the concept of a "display" which in most environments  corresponds to a single physical screen. Since we usually want  to draw to the main screen or only have a single screen to begin  with, we let EGL pick the default display.  Querying other displays is platform specific.  \*/  eglDisplay = (NativeDisplayType)eglGetDisplay(EGL\_DEFAULT\_DISPLAY);  /\*  Step 2 - Initialize EGL  EGL has to be initialized with the display obtained in the  previous step. We cannot use other EGL functions except  eglGetDisplay and eglGetError before eglInitialize has been  called.  If we're not interested in the EGL version number we can just  pass NULL for the second and third parameters.  \*/  if(!eglInitialize(eglDisplay, &i32MajorVersion, &i32MinorVersion))  {  printf("Error: eglInitialize() failed.n");  return 1;  }  /\*  Step 3 - Make OpenVG the current API  EGL provides ways to set up OpenGL ES and OpenVG contexts  (and possibly other graphics APIs in the future), so we need  to specify the "current API".  \*/  eglBindAPI(EGL\_OPENVG\_API);  /\*  Step 4 - Specify the required configuration attributes  An EGL "configuration" describes the pixel format and type of  surfaces that can be used for drawing.  For now we just want to use a 16 bit RGB surface that is a  window surface, i.e. it will be visible on screen. The list  has to contain key/value pairs, terminated with EGL\_NONE.  \*/  static const int ai32ConfigAttribs[] =  {  EGL\_RED\_SIZE, 5,  EGL\_GREEN\_SIZE, 6,  EGL\_BLUE\_SIZE, 5,  EGL\_ALPHA\_SIZE, 0, #ifndef DRAWABLES\_SIM\_USING\_2PBUFFER  EGL\_SURFACE\_TYPE, EGL\_WINDOW\_BIT, #else  EGL\_SURFACE\_TYPE, EGL\_WINDOW\_BIT|EGL\_PBUFFER\_BIT, #endif  EGL\_RENDERABLE\_TYPE, EGL\_OPENVG\_BIT,  EGL\_NONE  }; #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER  EGLint s\_surfaceAttribs[] =  { EGL\_WIDTH, 240,  EGL\_HEIGHT, 320,  EGL\_NONE  }; #endif  /\*  Step 5 - Find a config that matches all requirements  eglChooseConfig provides a list of all available configurations  that meet or exceed the requirements given as the second  argument. In most cases we just want the first config that meets  all criteria, so we can limit the number of configs returned to 1.  \*/  if(!eglChooseConfig(eglDisplay, ai32ConfigAttribs, &eglConfig, 1, &i32NumConfigs) || (i32NumConfigs != 1))  {  printf("Error: eglChooseConfig() failed.n");  exit(0);  }  /\*  Step 6 - Create a window surface to draw to  Use the config picked in the previous step and the native window  handle to create a window surface. A window surface is one that  will be visible on screen inside the native window (or  fullscreen if there is no window system).  Pixmaps and pbuffers are surfaces which only exist in off-screen  memory.  \*/ #ifdef DRAWABLES\_SIM\_USING\_2PBUFFER  eglSurface = eglCreatePbufferSurface(eglDisplay,eglConfig,s\_surfaceAttribs); #else  eglSurface = eglCreateWindowSurface(eglDisplay, eglConfig,(void\*) m\_glutWindow, NULL); #endif  if((eglGetError() != EGL\_SUCCESS) || (eglSurface == EGL\_NO\_SURFACE))  {  printf("Error: eglCreateWindowSurface() failed.n");  exit(0);  }  /\*  Step 7 - Create a context  EGL has to create a context for OpenVG. Our OpenVG resources  like paths and images will only be valid inside this context  (or shared contexts)  \*/  eglContext = eglCreateContext(eglDisplay, eglConfig, NULL, NULL);  if((eglGetError() != EGL\_SUCCESS) || (eglContext == EGL\_NO\_CONTEXT))  {  printf("Error: eglCreateContext() failed.n");  exit(0);  }  /\*  Step 8 - Bind the context to the current thread and use our  window surface for drawing and reading  Contexts are bound to a thread. This means you don't have to  worry about other threads and processes interfering with your  OpenVG application.  We need to specify a surface that will be the target of all  subsequent drawing operations, and one that will be the source  of read operations. They can be the same surface.  \*/  eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext);  if(eglGetError() != EGL\_SUCCESS)  {  printf("Error: eglMakeCurrent() failed.n");  exit(0);  } /\*  Steps 1 to 4 - Prepare OpenVG to draw a triangle  * * *  At this point we could theoretically start drawing with OpenVG. But  we have to specify what to draw and how to draw it first.  \*/  /\*  Step 1 - Set up a device independent coordinate system  * * *  Initially, the OpenVG coordinate system is based on the output resolution.  To get a device independent coordinate system, we need to apply a  transformation: Scaling by the output resolution means that coordinates  between (0, 0) and (1, 1) will be visible on screen, with the origin  in the lower left corner.  Transformations are described more in-depth in the Transforms tutorial.  It should be noted that different aspect ratios often require  special attention regarding the layout of elements on screen.  \*/  eglQuerySurface(eglDisplay, eglSurface, EGL\_WIDTH, &i32WindowWidth);  eglQuerySurface(eglDisplay, eglSurface, EGL\_HEIGHT, &i32WindowHeight); #ifndef DRAWABLES\_SIM\_USING\_2PBUFFER  vgSeti(VG\_MATRIX\_MODE, VG\_MATRIX\_PATH\_USER\_TO\_SURFACE);  vgLoadIdentity();  vgScale((float)i32WindowWidth, (float)i32WindowHeight);  /\*  Step 2 - Create a path  * * *  Drawing shapes with OpenVG requires a path which represents a series of  line and curve segments describing the outline of the shape. The shape  does not need to be closed, but for now we will start with a simple  triangle.  First we create a path handle, then we append segment and point data.  Creating a path involves choosing a datatype used for point data (we use  float here, indicated by VG\_PATH\_DATATYPE\_F) and capabilities that we want  to use. Picking the right capabilities is important as the OpenVG driver  can use a more efficient and compact internal representation for paths  with limited capabilities. We only need two capabilities for this tutorial:  adding data to the path and drawing it, with the latter being implicitly  enabled for all paths.  \*/  vgTriangle = vgCreatePath(  VG\_PATH\_FORMAT\_STANDARD,  VG\_PATH\_DATATYPE\_F,  1.0f, 0.0f, 4, 3,  (unsigned int)VG\_PATH\_CAPABILITY\_APPEND\_TO);  /\*  The segments of a path are described as a series of commands, represented as  an array of bytes. You can imagine the commands being performed by a pen:  First the pen moves to a starting location without drawing, from there it  draws a line to a second point. Then another line to a third point. After  that, it closes the shape by drawing a line from the last point to the  starting location: triangle finished!  The suffixes \_ABS and \_REL attached to the commands indicate whether the  coordinates are to be interpreted as absolute locations (seen from the  origin)or as being relative to the location of the current point.  \*/  VGubyte aui8PathSegments[4];  aui8PathSegments[0] = VG\_MOVE\_TO\_ABS;  aui8PathSegments[1] = VG\_LINE\_TO\_ABS;  aui8PathSegments[2] = VG\_LINE\_TO\_ABS;  aui8PathSegments[3] = VG\_CLOSE\_PATH;  /\*  In addition to the array of commands, the path needs a list of points. A  command can "consume" from 0 to 6 values, depending on its type. MOVE\_TO  and LINE\_TO each take two values, CLOSE\_PATH takes none.  A triangle requires 3 2D vertices.  \*/  VGfloat afPoints[6];  afPoints[0] = 0.3f;  afPoints[1] = 0.3f;  afPoints[2] = 0.7f;  afPoints[3] = 0.3f;  afPoints[4] = 0.5f;  afPoints[5] = 0.7f;  /\*  When appending data to the path, only the number of segments needs to be  specified since the number of points used depends on the actual commands.  \*/  vgAppendPathData(vgTriangle, 4, aui8PathSegments, afPoints);  /\*  Path capabilities should be removed as soon as they are no longer needed.  The OpenVG implementation might work more efficiently if it knows that  path data will not change since it can use an optimized internal  representation.  \*/  vgRemovePathCapabilities(vgTriangle, VG\_PATH\_CAPABILITY\_APPEND\_TO);  /\*  Step 3 - Create a paint  * * *  To fill a shape, we need a paint that describes how to fill it: a gradient,  pattern, or single color. Here we choose a paint with type COLOR that  is a simple opaque red. vgSetColor is a shortcut function that takes a  non-premultiplied sRGBA color encoded as a 32bit integer in RGBA\_8888 form.  \*/  vgFillPaint = vgCreatePaint();  vgSetParameteri(vgFillPaint, VG\_PAINT\_TYPE, VG\_PAINT\_TYPE\_COLOR);  vgSetColor(vgFillPaint, fillColor);  /\*  Step 4 - Prepare the render loop  * * *  The clear color will be used whenever calling vgClear(). The color is given  as non-premultiplied sRGBA, represented by four float values.  \*/ #endif  // Set the clear color  vgSetfv(VG\_CLEAR\_COLOR, 4, afClearColor);  /\* Enter the main glut loop to render it.\*/  glutMainLoop();  // Say goodbye  printf("%s finished.", pszAppName);  return 0; } /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*  End of file (Initialization.cpp) \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/ ---
**Author:** ![hieuletrung](https://avatars.discourse-cdn.com/v4/letter/h/f05b48/32.png) [@hieuletrung](https://forums.imgtec.com/u/hieuletrung)\ **Post date:** [September 6, 2009, 2:55pm UTC](https://forums.imgtec.com/t/demo-using-eglcreatepbuffersurface/447/4 "2009-09-06T14:55:20Z")
You can’t use pbuffer to display on-screen since it is off-screen buffer. If you need to use pbuffer, you must bind it into a texture so that it can be displayed on-screen. Please see the EGL manual for more details -Hieu