Ichthyostega
a7c57e98ce
I observed same strange behaviour already last year on my »Video Output« talk. The return value indicates an unkown error, but the subsequent usage seemingly works... On my Laptop, I don not see this error; it might be due to the very old graphics card on my PC...
377 lines
16 KiB
C++
377 lines
16 KiB
C++
/*
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egl-display.hpp - output video from a GTK application, using EGL - OpenGL binding
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Copyright (C)
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2025, Benny Lyons <benny.lyons@gmx.net>
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2025, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or modify it
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under the terms of the GNU GPL version 2+ See the LICENSE file for details.
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* ************************************************************************/
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#include "commons.hpp"
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#include "gtk-uring-app.hpp"
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#include <functional>
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#include <algorithm>
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#include <cassert>
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#include <string>
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#include <array>
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#include <set>
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// for low-level access -> X-Window
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#include <gdk/gdkx.h>
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// X11, EGL and GLEW for OpenGL
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#include <X11/Xlib.h>
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#include <EGL/egl.h>
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#include <EGL/eglext.h> // defines plattform-specific config and extensions
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#include <GL/glew.h> // provides system-specific bindings for OpenGL extensions
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using std::string;
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/**
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* Connection and drawing context used for EGL based video display.
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*/
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template<typename PIX, uint WIDTH, uint HEIGHT>
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class EglDisplay
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: NonCopyable
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{
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public:
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using Buffer = std::array<PIX, WIDTH*HEIGHT * 3 >;
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/**
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* Interface: retrieve pixel data for video frames to display.
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* - this is a Glib::Dispatcher, and the attached slot shall be
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* triggered whenever data for a new frame is available
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* - pixel data is accessed (threadsafe) by invoking #retrieveFrame()
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* - when processing is complete and the data will no longer be needed,
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* access to the pixel buffer is yielded by invoking #completedFrame()
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*/
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class PixelFeed
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: public Glib::Dispatcher
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{
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public:
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virtual ~PixelFeed() { }; ///< this is an interface
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virtual Buffer* retrieveFrame() =0;
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virtual void completedFrame() =0;
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};
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EglDisplay (Gtk::Window& appWindow, PixelFeed& pixelFeed)
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: pixelFeed_{pixelFeed}
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{
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openDisplay (appWindow);
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pixelFeed_.connect([this]{ displayFrame(); });
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}
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void cleanUp();
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private:
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/** EGL / X11 connection. */
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EGLDisplay display_{nullptr};
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EGLSurface surface_{nullptr};
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EGLContext egl_{nullptr};
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uint texID_{0};
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uint vboID_{0};
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uint vaoID_{0};
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float scaleX_{1};
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float scaleY_{1};
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/** Callback to retrieve pixel data */
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PixelFeed& pixelFeed_{};
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void openDisplay (Gtk::Window&);
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void displayFrame();
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};
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template<typename PIX, uint WIDTH, uint HEIGHT>
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void
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EglDisplay<PIX,WIDTH,HEIGHT>::openDisplay (Gtk::Window& appWindow)
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{
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std::cout << "Open display-connection through EGL..." << std::endl;
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// use the X-Window as anchor to build an OpenGL context via EGL
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Glib::RefPtr<Gdk::Window> gdkWindow = appWindow.get_window();
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Window xWindow = GDK_WINDOW_XID (gdkWindow->gobj());
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Display* xDisplay = GDK_WINDOW_XDISPLAY (gdkWindow->gobj());
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long xScreen;
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XWindowAttributes xWinAttrs;
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if (XGetWindowAttributes (xDisplay, xWindow, &xWinAttrs))
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xScreen = XScreenNumberOfScreen (xWinAttrs.screen);
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else
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__FAIL ("unable to retrieve screen number from the X11 window attributes.");
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long SCREEN_SPEC[]
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{EGL_PLATFORM_X11_SCREEN_EXT, xScreen
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,EGL_NONE};
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display_ = eglGetPlatformDisplay (EGL_PLATFORM_X11_EXT, xDisplay, SCREEN_SPEC);
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if (EGL_NO_DISPLAY == display_
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or not eglInitialize(display_, NULL,NULL))
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__FAIL ("could not establish EGL Display connection.");
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EGLint DESIRED_ATTRIBS[]
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{EGL_COLOR_BUFFER_TYPE, EGL_RGB_BUFFER
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,EGL_RED_SIZE, 4
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,EGL_GREEN_SIZE, 4
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,EGL_BLUE_SIZE, 4
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,EGL_RENDERABLE_TYPE, EGL_OPENGL_BIT // config must support creating an OpenGL context
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,EGL_SURFACE_TYPE, EGL_WINDOW_BIT // want to create a window surface
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,EGL_DEPTH_SIZE, 0 // prefer config without depth buffer (occlusion testing not needed)
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,EGL_STENCIL_SIZE, 0 // prefer config without stencil buffer (no advanced visual effects)
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,EGL_NONE};
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EGLint _cnt;
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EGLConfig config;
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if (not eglChooseConfig (display_
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,DESIRED_ATTRIBS
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,& config
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,1,&_cnt)
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or not config)
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__FAIL ("unable to select a EGL display config with the required attributes");
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surface_ = eglCreateWindowSurface (display_,config,xWindow,nullptr);
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if (not surface_)
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switch (eglGetError())
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{
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case EGL_BAD_CONFIG:
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__FAIL ("selected display configuration is not valid");
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break;
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case EGL_BAD_ALLOC:
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__FAIL ("unable to allocate resources or collision with existing resources");
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break;
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case EGL_BAD_MATCH:
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__FAIL ("mismatch between X11 window visuals and the capabilities of the selected config");
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break;
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default:
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__FAIL ("unable to create EGL window surface, for unknown reasons");
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break;
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}
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if (not eglBindAPI( EGL_OPENGL_API))
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__FAIL ("unable to configure EGL for usage with the OpenGL API.");
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EGLint CTX_ATTRIBS[] // Note: require modern OpenGL
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{EGL_CONTEXT_OPENGL_PROFILE_MASK, EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT
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// ,EGL_CONTEXT_MAJOR_VERSION, 3
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// ,EGL_CONTEXT_MINOR_VERSION, 3
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,EGL_NONE};
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egl_ = eglCreateContext (display_, config
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,EGL_NO_CONTEXT // do not share definitions and data with another context
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,CTX_ATTRIBS);
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if (not egl_)
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__FAIL ("failed to create OpenGL context for this display with desired visuals");
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// create a binding for the current thread to use this context on this window
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if (not eglMakeCurrent (display_, surface_,surface_, egl_))
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__FAIL ("failed to attach an OpenGL context to the application X-Window");
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// use lib-GLEW to manage OpenGL extensions (notably GL Shader Language)
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GLenum glewErr = glewInit();
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////////////////////////////////////////////////////////////////////////////////////TODO for some reason I get glewErr == 4 ("unknown error"), but it works non the less
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//if (GLEW_OK != glewErr)
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// __FAIL ("could not bind OpenGL extensions through lib-GLEW:\n"
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// +string{reinterpret_cast<const char*> (glewGetErrorString(glewErr))});
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auto compileShader = [](GLenum kind, string code)
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{
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uint shaderID = glCreateShader (kind);
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const GLchar* codeSegment = code.c_str();
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glShaderSource (shaderID, 1, &codeSegment, NULL);
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glCompileShader(shaderID);
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// diagnostics...
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int success;
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glGetShaderiv (shaderID, GL_COMPILE_STATUS, &success);
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if (not success)
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{
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int logSiz{0};
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glGetShaderiv (shaderID, GL_INFO_LOG_LENGTH, &logSiz);
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string report(logSiz,'.');
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glGetShaderInfoLog (shaderID, logSiz, NULL, & report[0]);
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std::cout << "\n■□■□■□■□■----Shader-Code-------------------------\n"
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<< code
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<< "\n■□■□■□■□■----Failure-Report----------------------\n"
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<< report.c_str()
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<< std::endl;
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__FAIL ("shader compilation failure");
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}
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return shaderID;
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};
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auto checkLinkError = [](uint programID)
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{
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int success;
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glGetProgramiv (programID, GL_LINK_STATUS, &success);
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if (not success)
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{
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int logSiz{0};
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glGetProgramiv (programID, GL_INFO_LOG_LENGTH, &logSiz);
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string report(logSiz,'.');
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glGetProgramInfoLog (programID, logSiz, NULL, & report[0]);
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std::cout << "\n■□■□■□■□■----Failure-Report----------------------\n"
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<< report.c_str()
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<< std::endl;
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__FAIL ("unable to link shader code");
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}
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};
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uint vertexShader
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= compileShader (GL_VERTEX_SHADER,
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R"-(#version 330 core
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layout(location = 0) in vec2 position;
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layout(location = 1) in vec2 texCoord;
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out vec2 fragTexCoord;
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void main() {
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gl_Position = vec4 (position, 0.0, 1.0);
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fragTexCoord = texCoord;
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}
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)-");
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uint fragmentShader
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= compileShader (GL_FRAGMENT_SHADER,
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R"-(#version 330 core
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in vec2 fragTexCoord;
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out vec4 colour;
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uniform sampler2D textureSampler;
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void main() {
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colour = texture (textureSampler, fragTexCoord);
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}
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)-");
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uint gpuProgram = glCreateProgram();
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glAttachShader (gpuProgram, vertexShader);
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glAttachShader (gpuProgram, fragmentShader);
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glLinkProgram (gpuProgram);
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checkLinkError (gpuProgram);
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glUseProgram (gpuProgram);
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glDeleteShader(vertexShader);
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glDeleteShader(fragmentShader);
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/* === setup a 2D texture, to be mapped into the viewport === */
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glActiveTexture(GL_TEXTURE0); // activate texture-unit #0 on the GPU
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glGenTextures (1, &texID_); // allocate 1 new texture ID
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glBindTexture (GL_TEXTURE_2D, texID_); // use this textureID as "the" TEXTURE_2D
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // configure image scaling filter
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); // clamp, don't wrap at the texture edges
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
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// configure the `textureSampler` parameter (»uniform« is a global parameter visible in all shaders)
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GLint samplerParam = glGetUniformLocation(gpuProgram, "textureSampler");
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glUniform1i(samplerParam, 0); // configure the shader to use texture-unit #0 of the GPU
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/* === setup a fixed geometry to hold that texture === */
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glDisable (GL_DEPTH_TEST); // we do not need 3D layering / positioning
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glViewport (0, 0, WIDTH, HEIGHT); // Origin in the middle of the window (note Y points upwards)
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// Note: this demo uses a fixed-size window and hard-coded video size;
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// a real-world implementation would have to place the video frame
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// dynamically into the available screen space, possibly scaling up/down
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GLfloat sX{scaleX_};
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GLfloat sY{scaleY_}; // Note: positions use »normalised device coordinates« (NDC)
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GLfloat w{1}; // TEXTURE_2D points cover the range (0,0) ... (1,1)
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GLfloat h{1};
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GLfloat vertexData[] // Geometry and mapping data to be sent to the GPU...
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//-point-+--texture // We define the 4 edges of a rectangular »projection screen«
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{-sX,-sY , 0,h // For each edge, we define the position in NDC [-1 ... +1]
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, sX,-sY , w,h // and we specify which point in the texture to map there
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, sX, sY , w,0 // Note: the rows of the video image run top-down, and thus we
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,-sX, sY , 0,0 // have to map the texture flipped, since OpenGL orients Y upwards.
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};
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glGenBuffers (1, &vboID_); // allocate 1 new vertex-buffer-object
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glGenVertexArrays(1, &vaoID_); // allocate 1 new vertex-array-object (to attach all definitions)
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glBindVertexArray(vaoID_); // activate the VAO to pick up the following definitions...
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glBindBuffer (GL_ARRAY_BUFFER, vboID_);
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// copy the vertexData into the vertex-buffer-object currently bound to GL_ARRAY_BUFFER
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glBufferData (GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW);
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auto SIZ = sizeof(float); // parameters are transferred to the GPU as float data
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auto attrib = 2; // we use 2 input attributes for the shader pipeline
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auto coords = 2; // our data vectors have 2 coordinates (2D)
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auto stride = attrib * coords * SIZ; // stride is the offset in bytes between full data points
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auto offset = [&](uint elm){ return (void*) (elm * SIZ); }; // offset of one attribute relative to the start of a data point (packaged into a void*)
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auto normalise = GL_FALSE; // do not auto-normalise, positions are already [-1 ... +1]
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// define how two two attributes are packed into the data sequence we send to the GPU
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glVertexAttribPointer (0, coords, GL_FLOAT, normalise, stride, offset(0) );
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glVertexAttribPointer (1, coords, GL_FLOAT, normalise, stride, offset(2) );
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glEnableVertexAttribArray (0); // activate attribute #1 ≙ input argument `position` in vertexShader
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glEnableVertexAttribArray (1); // activate attribute #2 ≙ input argument `texCoord` in vertexShader
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std::cout << "Successfully established OpenGL display ("<<WIDTH<<"x"<<HEIGHT<<"px) within GTK-Window." << std::endl;
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}
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template<typename PIX, uint WIDTH, uint HEIGHT>
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void
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EglDisplay<PIX,WIDTH,HEIGHT>::displayFrame()
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{
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auto* currFrame = pixelFeed_.retrieveFrame();
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if (not currFrame) return;
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// pick up current buffer with RGB data
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// and send it to the GPU (into the prepared texture)...
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glTexImage2D (GL_TEXTURE_2D // the target texture store to work on, here "the" TEXTURE_2D
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,0 // detail level (when using mipmap reduction, which we don't)
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,GL_RGB // internal format or features to use for this texture
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,WIDTH,HEIGHT, /*border*/ 0
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,GL_RGB // data layout of the provided pixels
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,GL_UNSIGNED_BYTE // data format / size of the pixels
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,currFrame
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);
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// Draw the quadrilateral
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glDrawArrays(GL_QUADS, 0, 4);
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// double-buffer flip, automatically invokes glFlush()
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eglSwapBuffers (display_, surface_);
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// signal that processing of this frame is complete
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pixelFeed_.completedFrame();
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}
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template<typename PIX, uint WIDTH, uint HEIGHT>
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void
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EglDisplay<PIX,WIDTH,HEIGHT>::cleanUp()
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{
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// std::cout << "STOP " << imgGen_.getFrameNr() << " frames displayed." << std::endl;
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// detach binding with OpenGL context
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eglMakeCurrent (display_, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
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eglDestroySurface (display_, surface_);
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eglDestroyContext (display_, egl_);
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eglTerminate(display_); // detach EGL from display
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}
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