# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1701012470 -3600
# Node ID bb715a82a8f11d9ac7e64f33bd04591b3735a526

project skeleton

diff -r 000000000000 -r bb715a82a8f1 .hgignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,7 @@
+build/
+nbproject/private/
+temp/
+
+.kdev4
+
+data/.*\.(aux|log|nav|out|snm|toc)
diff -r 000000000000 -r bb715a82a8f1 Buffer.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Buffer.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,45 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <unistd.h>
+
+class Buffer {
+protected:
+	char* data;
+	size_t size;
+
+public:
+
+	Buffer() {
+	}
+
+	virtual ~Buffer() {
+	}
+
+	Buffer(const Buffer&) = delete;
+	Buffer& operator=(const Buffer&) = delete;
+
+	const char* getData() const {
+		return data;
+	}
+
+	const size_t getSize() const {
+		return size;
+	}
+};
diff -r 000000000000 -r bb715a82a8f1 CLIParser.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CLIParser.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,86 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <vector>
+#include <string>
+
+#include "Configuration.h"
+
+class CLIParser {
+private:
+
+	static const std::string OPTION_TEXTURE;
+	static const std::string OPTION_BACKGROUND_COLOR;
+	static const std::string OPTION_ROOT_WINDOW;
+
+	const std::string
+	readNext(const std::vector<std::string>& arguments, int& i) {
+		if (i < arguments.size()) return arguments[i++];
+		else throw std::logic_error("Missing CLI argument"
+				+ (i > 0 ? (" after " + arguments[i - 1]) : ""));
+	}
+
+	bool parseBoolean(const std::string& value) {
+		if (value == "true") return true;
+		else if (value == "false") return false;
+		else throw std::logic_error("Unable to parse boolean value: "
+				+ value + " (expecting true or false)");
+	}
+
+	unsigned long
+	parseHexColor(const std::string& hex) {
+		int r, g, b;
+		int count = sscanf(hex.c_str(), "%02x%02x%02x", &r, &g, &b);
+		if (count == 3) {
+			unsigned long lr, lg, lb;
+			lr = r;
+			lg = g;
+			lb = b;
+			return (lr << 16 | lg << 8 | lb);
+		} else {
+			throw std::logic_error("Invalid hex color string");
+		}
+	}
+
+public:
+
+	const Configuration parse(const std::vector<std::string>& arguments) {
+		Configuration c;
+
+		for (int i = 0; i < arguments.size();) {
+			const std::string& option = readNext(arguments, i);
+
+			if (option == OPTION_TEXTURE) {
+				Configuration::Texture tex;
+				tex.fileName = readNext(arguments, i);
+				c.textures.push_back(tex);
+			} else if (option == OPTION_BACKGROUND_COLOR) {
+				c.backgroundColor = parseHexColor(readNext(arguments, i));
+			} else if (option == OPTION_ROOT_WINDOW) {
+				c.rootWindow = std::stoul(readNext(arguments, i));
+			} else throw std::logic_error("Unsupported CLI option: " + option);
+		}
+
+		return c;
+	}
+};
+
+const std::string CLIParser::OPTION_TEXTURE = "--texture";
+const std::string CLIParser::OPTION_BACKGROUND_COLOR = "--background-color";
+const std::string CLIParser::OPTION_ROOT_WINDOW = "--root-window";
diff -r 000000000000 -r bb715a82a8f1 Configuration.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Configuration.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,51 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <string>
+
+#include <X11/X.h>
+
+class Configuration {
+public:
+
+	class File {
+	public:
+		std::string fileName;
+	};
+
+	class Texture : public File {
+	};
+
+	class Shader : public File {
+	};
+
+	class VertexShader : public Shader {
+	};
+
+	class FragmentShader : public Shader {
+	};
+
+	// TODO: support loading whole directory and monitoring using inotify
+	std::vector<Texture> textures;
+	VertexShader vertexShader;
+	FragmentShader fragmentShader;
+
+	unsigned long backgroundColor = (0x33 << 16 | 0x33 << 8 | 0x33);
+	Window rootWindow = 0;
+};
diff -r 000000000000 -r bb715a82a8f1 EPoll.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/EPoll.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,116 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdexcept>
+#include <string>
+
+#include <signal.h>
+#include <sys/signalfd.h>
+#include <sys/epoll.h>
+#include <unistd.h>
+#include <sys/fcntl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <stdexcept>
+#include <string>
+
+class EPoll {
+private:
+	int epollEventCount;
+	epoll_event* epollEvents;
+	int epollFD;
+
+	void static log(const std::string& message) {
+		std::cout << message << std::endl;
+	}
+public:
+
+	class Exception : public std::logic_error {
+	public:
+
+		Exception(const std::string& msg) : logic_error(msg) {
+		}
+
+		Exception(const std::string& msg, int errNo) :
+				logic_error(msg + strerror(errNo)) {
+		}
+
+	};
+
+	EPoll(int eventCount = 5) : epollEventCount(eventCount) {
+		epollEvents = (epoll_event*) malloc(sizeof (*epollEvents) * eventCount);
+		epollFD = epoll_create1(0);
+		log("EPoll(): epoll_create() = " + std::to_string(epollFD));
+	}
+
+	virtual ~EPoll() {
+		::close(epollFD);
+		free(epollEvents);
+	}
+
+	EPoll(const EPoll&) = delete;
+	EPoll& operator=(const EPoll&) = delete;
+
+	static void processSignal(int signal) {
+		log("got signal: " + std::to_string(signal));
+	}
+
+	int addSignals() {
+		::signal(SIGTERM, EPoll::processSignal);
+		::signal(SIGINT, EPoll::processSignal);
+
+		sigset_t mask;
+		::sigemptyset(&mask);
+		::sigaddset(&mask, SIGTERM);
+		::sigaddset(&mask, SIGINT);
+		int signalFD = ::signalfd(-1, &mask, 0);
+		add(signalFD, EPOLLIN | EPOLLET | EPOLLHUP);
+		log("signalFD=" + std::to_string(signalFD));
+		return signalFD;
+	}
+
+	void add(int fd, uint32_t events = EPOLL_EVENTS::EPOLLIN) {
+		struct epoll_event ev;
+		ev.data.fd = fd;
+		ev.events = events;
+		int err = epoll_ctl(epollFD, EPOLL_CTL_ADD, ev.data.fd, &ev);
+		if (err) throw Exception("EPoll::add() failed (a file?):", errno);
+		// Regular files can not be monitored this way, thus:
+		//   cat Makefile | opengl-pdf      # works
+		//   opengl-pdf < Makefile          # does not work
+	}
+
+	void del(int fd) {
+		int err = epoll_ctl(epollFD, EPOLL_CTL_DEL, fd, nullptr);
+		if (err) throw Exception("EPoll::del() failed: ", errno);
+	}
+
+	int wait(int timeout = 1000) {
+		int count = epoll_wait(epollFD, epollEvents, epollEventCount, timeout);
+		if (count >= 0) return count;
+		else throw Exception("EPoll::wait() failed: ", errno);
+	}
+
+	const epoll_event& operator[](std::size_t index) const {
+		if (index < epollEventCount) return epollEvents[index];
+		else throw std::out_of_range("invalid index of epollEvents");
+	}
+
+};
diff -r 000000000000 -r bb715a82a8f1 Logger.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Logger.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,58 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <ostream>
+#include <string>
+
+#define LOG_LEVEL(XX) \
+	XX(OFF, 0, "OFF") \
+	XX(SEVERE, 1, "SEVERE") \
+	XX(WARNING, 2, "WARNING") \
+	XX(INFO, 3, "INFO") \
+	XX(CONFIG, 4, "CONFIG") \
+	XX(FINE, 5, "FINE") \
+	XX(FINER, 6, "FINER") \
+	XX(FINEST, 7, "FINEST") \
+	XX(ALL, 8, "ALL")
+
+enum class LogLevel {
+#define XX(a, b, c) a = (1 << b),
+	LOG_LEVEL(XX)
+#undef XX
+};
+
+static const char* LOG_LEVELS[] = {
+#define XX(a, b, c) [b] = c,
+	LOG_LEVEL(XX)
+#undef XX
+};
+
+#undef LOG_LEVEL
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+inline const char* getLogLevelName(LogLevel l) {
+	auto count = ARRAY_SIZE(LOG_LEVELS);
+	for (int i = 0; i < count; i++) if ((int) l == 1 << i) return LOG_LEVELS[i];
+	return nullptr;
+}
+
+inline void log(std::ostream& out, LogLevel level, std::string message) {
+	out << getLogLevelName(level) << ": " << message << std::endl;
+}
diff -r 000000000000 -r bb715a82a8f1 Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,37 @@
+# ShaderShark
+# Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+all: build/shader-shark
+
+.PHONY: all clean run
+
+clean:
+	rm -rf build
+
+run: build/shader-shark build/jazz.rgba
+	$(<) --texture build/jazz.rgba
+
+build:
+	mkdir -p $(@)
+	
+SRC=Shark.cpp shader-shark.cpp
+
+build/shader-shark: $(SRC) build *.h
+	$(CXX) -std=c++20 -g -o $(@) $(SRC) $$(pkg-config --cflags --libs \
+	    epoxy x11 glu glm)
+
+build/jazz.rgba: textures/jazz.png
+	mkdir -p build
+	convert -format rgba $(<) $(@)
diff -r 000000000000 -r bb715a82a8f1 MappedFile.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MappedFile.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,57 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <sys/mman.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "Buffer.h"
+
+class MappedFile : public Buffer {
+private:
+	int fd = -1;
+public:
+
+	MappedFile(const std::string& fileName) {
+		struct stat stat;
+		fd = open(fileName.c_str(), O_RDONLY);
+		if (fd < 0) throw std::invalid_argument("unable to open file");
+
+		int result = fstat(fd, &stat);
+		if (result) throw std::invalid_argument("unable to stat file");
+
+		size = stat.st_size;
+		data = static_cast<char*> (
+				mmap(nullptr, size, PROT_READ, MAP_SHARED, fd, 0));
+		if (data == MAP_FAILED) throw std::invalid_argument("unable to mmap");
+		// std::cerr << "MappedFile() / mmap()" << std::endl;
+	}
+
+	virtual ~MappedFile() {
+		int result = munmap(data, size);
+		// std::cerr << "~MappedFile() / munmap() = " << result << std::endl;
+		result = close(fd);
+		// std::cerr << "~MappedFile() / close() = " << result << std::endl;
+	}
+
+	MappedFile(const MappedFile&) = delete;
+	MappedFile& operator=(const MappedFile&) = delete;
+
+};
diff -r 000000000000 -r bb715a82a8f1 Shark.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Shark.cpp	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,438 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Shark.h"
+
+Shark::Shark(const Configuration& configuration) :
+cfg(configuration) {
+}
+
+Shark::~Shark() {
+}
+
+void Shark::run() {
+	Display* dpy = XOpenDisplay(NULL);
+
+	if (dpy == NULL) throw std::logic_error("Unable to connect to X server");
+
+	GLint att[] = {GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None};
+	XVisualInfo* vi = glXChooseVisual(dpy, 0, att);
+	Window root = DefaultRootWindow(dpy);
+	Window parent = cfg.rootWindow ? cfg.rootWindow : root;
+
+	XSetWindowAttributes swa;
+	swa.colormap = XCreateColormap(dpy, parent, vi->visual, AllocNone);
+	swa.event_mask = ExposureMask | KeyPressMask | PointerMotionMask
+			| ButtonPressMask
+			| StructureNotifyMask;
+
+	bool full = false;
+	unsigned int width = 1600;
+	unsigned int height = 1200;
+	if (parent != root) {
+		XWindowAttributes parentAttr;
+		XGetWindowAttributes(dpy, parent, &parentAttr);
+		width = parentAttr.width;
+		height = parentAttr.height;
+	}
+
+	Window win = XCreateWindow(
+			dpy, parent, 0, 0, width, height, 0,
+			vi->depth, InputOutput, vi->visual,
+			CWColormap | CWEventMask, &swa);
+
+	XMapWindow(dpy, win);
+	XStoreName(dpy, win, "ShaderShark");
+	setX11PID(dpy, win);
+	// XSetWindowBackground(dpy, win, 0) vs. glClearColor()
+
+	GLXContext glc = glXCreateContext(dpy, vi, NULL, GL_TRUE);
+	glXMakeCurrent(dpy, win, glc);
+
+	// Load GLSL shaders:
+	GLuint shaderProgram = loadShaders();
+	loadVertices();
+	loadTextures(shaderProgram);
+
+	auto toggleFullscreen = [&]() {
+		full = setFullscreen(dpy, win, !full);
+	};
+
+	auto resetView = [&]() {
+		ctx = initialCtx;
+		ctx.updateCameraFrontAndUp();
+	};
+
+	// root can reize our window
+	// or we can listen to root resize and then resize our window ourselves
+	bool listenToRootResizes = true;
+	if (listenToRootResizes) XSelectInput(dpy, parent, StructureNotifyMask);
+
+	bool keepRunningX11 = true;
+	int x11fd = XConnectionNumber(dpy);
+	EPoll epoll;
+	epoll.add(x11fd);
+	try {
+		epoll.add(setNonBlocking(STDIN_FILENO));
+	} catch (const EPoll::Exception& e) {
+		logOutput << "Will not monitor events on STDIN: " << e.what() << "\n";
+	}
+
+	// rended the 3D scene even before the first event:
+	runShaders(shaderProgram);
+	glXSwapBuffers(dpy, win);
+
+	for (XEvent xev; keepRunningX11;) {
+		int epollEventCount = epoll.wait();
+		//std::cout << "trace: epoll.wait() = " << epollEventCount << std::endl;
+		for (int epollEvent = 0; epollEvent < epollEventCount; epollEvent++) {
+			if (epoll[epollEvent].data.fd == x11fd) {
+				if (!XPending(dpy)) {
+					// otherwise STDIN events are held until the first X11 event
+					logOutput << "trace: no pending X11 event" << std::endl;
+					break;
+				}
+				XWindowAttributes gwa;
+				XNextEvent(dpy, &xev);
+				bool redraw = false;
+
+				if (xev.type == Expose) {
+					std::cout << "XEvent: Expose" << std::endl;
+					XGetWindowAttributes(dpy, win, &gwa);
+					glViewport(0, 0, gwa.width, gwa.height);
+					redraw = true;
+				} else if (xev.type == KeyPress) {
+					DecodedKey key = decodeKeycode(dpy, xev.xkey.keycode);
+					std::cout << "XEvent: KeyPress:"
+							<< " keycode=" << key.code
+							<< " key=" << key.name
+							<< std::endl;
+
+					const float cSp = 0.05f; // camera speed
+					const float aSp = 5.f; // angle speed
+
+					if (key.matches(XK_q, XK_Escape)) keepRunningX11 = false;
+					else if (key.matches(XK_Left, XK_s)) ctx.turnLeft(aSp);
+					else if (key.matches(XK_Right, XK_f)) ctx.turnRight(aSp);
+					else if (key.matches(XK_Up, XK_e)) ctx.moveForward(cSp);
+					else if (key.matches(XK_Down, XK_d)) ctx.moveBackward(cSp);
+					else if (key.matches(XK_w)) ctx.rollLeft(aSp);
+					else if (key.matches(XK_r)) ctx.rollRight(aSp);
+					else if (key.matches(XK_t)) ctx.turnUp(aSp);
+					else if (key.matches(XK_g)) ctx.turnDown(aSp);
+					else if (key.matches(XK_m)) ctx.moveLeft(cSp);
+					else if (key.matches(XK_comma)) ctx.moveRight(cSp);
+					else if (key.matches(XK_l)) ctx.moveUp(cSp);
+					else if (key.matches(XK_period)) ctx.moveDown(cSp);
+					else if (key.matches(XK_j)) ctx.moveLeft(cSp * 5);
+					else if (key.matches(XK_k)) ctx.moveRight(cSp * 5);
+					else if (key.matches(XK_u)) ctx.moveLeft(cSp * 10);
+					else if (key.matches(XK_i)) ctx.moveRight(cSp * 10);
+					else if (key.matches(XK_x)) resetView();
+					else if (key.matches(XK_F11, XK_y)) toggleFullscreen();
+					redraw = true;
+				} else if (xev.type == ButtonPress) {
+					std::cout << "XEvent: ButtonPress:"
+							<< " button=" << xev.xbutton.button
+							<< std::endl;
+					if (xev.xbutton.button == 1);
+					else if (xev.xbutton.button == 4) ctx.adjustFov(+1.0);
+					else if (xev.xbutton.button == 5) ctx.adjustFov(-1.0);
+					else if (xev.xbutton.button == 8) resetView();
+					else if (xev.xbutton.button == 9) keepRunningX11 = false;
+					redraw = true;
+				} else if (xev.type == MotionNotify) {
+					// printCursorInfo(xev.xmotion);
+				} else if (xev.type == ConfigureNotify) {
+					std::cout << "XEvent: ConfigureNotify:"
+							<< " window=" << xev.xconfigure.window
+							<< " height=" << xev.xconfigure.height
+							<< " width=" << xev.xconfigure.width
+							<< std::endl;
+					if (listenToRootResizes
+							&& xev.xconfigure.window == parent) {
+						XResizeWindow(dpy, win,
+								xev.xconfigure.width, xev.xconfigure.height);
+					}
+				} else if (xev.type == UnmapNotify) {
+					std::cout << "XEvent: UnmapNotify" << std::endl;
+				} else if (xev.type == DestroyNotify) {
+					std::cout << "XEvent: DestroyNotify → finish" << std::endl;
+					break;
+				} else {
+					std::cout << "XEvent: type=" << xev.type << std::endl;
+				}
+
+				if (redraw) {
+					runShaders(shaderProgram);
+					glXSwapBuffers(dpy, win);
+				}
+			} else if (epoll[epollEvent].data.fd == STDIN_FILENO) {
+				int epollFD = epoll[epollEvent].data.fd;
+				logOutput << "other event: fd=" << epollFD << " data=";
+				for (char ch; read(epollFD, &ch, 1) > 0;) {
+					std::stringstream msg;
+					msg
+							<< std::hex
+							<< std::setfill('0')
+							<< std::setw(2)
+							<< (int) ch;
+					logOutput << msg.str();
+				}
+				logOutput << std::endl;
+
+			} else {
+				logOutput
+						<< "error: event on an unexpected FD: "
+						<< epoll[epollEvent].data.fd
+						<< std::endl;
+			}
+		}
+	}
+
+	XFree(vi);
+	// for (auto page : pdfTextures) glDeleteTextures(1, &page.texture);
+
+	glXMakeCurrent(dpy, None, NULL);
+	glXDestroyContext(dpy, glc);
+	XDestroyWindow(dpy, win);
+	XCloseDisplay(dpy);
+}
+
+void Shark::runShaders(GLuint program) {
+	std::cerr << "GLSL: runShaders(" << program << ")" << std::endl;
+	std::cerr << "background color: " << cfg.backgroundColor << std::endl;
+	glUseProgram(program);
+	checkError(&std::cerr);
+
+	glClearColor(
+			(cfg.backgroundColor >> 16 & 0xFF) / 256.,
+			(cfg.backgroundColor >> 8 & 0xFF) / 256.,
+			(cfg.backgroundColor & 0xFF) / 256.,
+			1.0);
+	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+	GLint viewport[4];
+	glGetIntegerv(GL_VIEWPORT, viewport);
+	GLfloat width = viewport[2];
+	GLfloat height = viewport[3];
+
+	glm::mat4 projection = glm::perspective(
+			glm::radians(ctx.fov),
+			width / height,
+			0.1f, 100.0f);
+	glUniformMatrix4fv(ProgAttr.projection, 1, GL_FALSE, &projection[0][0]);
+
+	glm::mat4 view = glm::lookAt(
+			ctx.cameraPos,
+			ctx.cameraPos + ctx.cameraFront,
+			ctx.cameraUp);
+	glUniformMatrix4fv(ProgAttr.view, 1, GL_FALSE, &view[0][0]);
+
+	// glBindVertexArray(vao);
+
+	glm::mat4 model = glm::mat4(1.0f); // identity matrix
+	// model = glm::translate(model, glm::vec3(0., 0., 0.));
+	// float angle = 20.0f;
+	// glm::vec3 xxx = glm::vec3(1.0f, 0.3f, 0.5f);
+	// model = glm::rotate(model, glm::radians(angle), xxx);
+	glUniformMatrix4fv(ProgAttr.model, 1, GL_FALSE, &model[0][0]);
+
+	glDrawArrays(GL_TRIANGLES, 0, 2 * 3); // viz loadVertices() kde plníme data
+	std::cerr << "GLSL: glDrawArrays()" << std::endl;
+}
+
+void Shark::log(LogLevel level, std::string message) {
+	::log(logOutput, level, message);
+}
+
+int Shark::setNonBlocking(int fd) {
+	int flags = fcntl(fd, F_GETFL, 0);
+	fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+	return fd;
+}
+
+void Shark::loadVertices() {
+	const std::vector<GLfloat> vertices = {
+		// Vertex XYZ                          Texture XY
+		-0.80f * TEX.ratio, +0.80f, +0.0, /**/ 0.0, 0.0,
+		+0.80f * TEX.ratio, +0.80f, +0.0, /**/ 1.0, 0.0,
+		-0.80f * TEX.ratio, -0.80f, +0.0, /**/ 0.0, 1.0,
+
+		-0.80f * TEX.ratio, -0.80f, +0.0, /**/ 0.0, 1.0,
+		+0.80f * TEX.ratio, -0.80f, +0.0, /**/ 1.0, 1.0,
+		+0.80f * TEX.ratio, +0.80f, +0.0, /**/ 1.0, 0.0,
+
+		// viz glDrawArrays(), kde vybereme počátek a počet hodnot
+	};
+
+	// Vertex data:
+	glVertexAttribPointer(ProgAttr.vertexXYZ, 3, // vertex items
+			GL_FLOAT, GL_FALSE, 5 * sizeof (float),
+			(void*) 0);
+	glEnableVertexAttribArray(ProgAttr.vertexXYZ);
+
+	// Texture positions:
+	glVertexAttribPointer(ProgAttr.textureXY, 2, // texture items
+			GL_FLOAT, GL_FALSE, 5 * sizeof (float),
+			(void*) (3 * sizeof (float)));
+	glEnableVertexAttribArray(ProgAttr.textureXY);
+
+	glBufferData(GL_ARRAY_BUFFER,
+			vertices.size() * sizeof (vertices[0]),
+			vertices.data(),
+			GL_STATIC_DRAW);
+	// GL_STATIC_DRAW:
+	//   The vertex data will be uploaded once
+	//   and drawn many times(e.g. the world).
+	// GL_DYNAMIC_DRAW:
+	//   The vertex data will be created once, changed from
+	// 	 time to time, but drawn many times more than that.
+	// GL_STREAM_DRAW:
+	//   The vertex data will be uploaded once and drawn once.
+
+	// see also glBindBuffer(GL_ARRAY_BUFFER, vbo); where we set current VBO
+}
+
+GLuint Shark::loadTexture(const std::string& fileName, int width, int height) {
+	MappedFile file(fileName);
+	if (file.getSize() == width * height * 4) {
+		GLuint textureID;
+		glGenTextures(1, &textureID);
+		glBindTexture(GL_TEXTURE_2D, textureID);
+		auto GLT2D = GL_TEXTURE_2D;
+		glTexImage2D(GLT2D, 0, GL_RGBA,
+				width, height,
+				0, GL_RGBA, GL_UNSIGNED_BYTE,
+				file.getData());
+		glTexParameteri(GLT2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
+		glTexParameteri(GLT2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+		glTexParameteri(GLT2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+		glTexParameteri(GLT2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+		glGenerateMipmap(GLT2D);
+		std::cerr << "loadTexture(\"" << fileName.c_str() << "\", "
+				<< width << ", " << height << ") = " << textureID << std::endl;
+		checkError(&std::cerr);
+		return textureID;
+	} else {
+		throw std::invalid_argument("wrong texture file size");
+	}
+}
+
+void Shark::loadTextures(GLuint shaderProgram) {
+	for (const Configuration::Texture& tex : cfg.textures) {
+		GLuint jazz = loadTexture(tex.fileName, TEX.width, TEX.height);
+		// FIXME: decode PNG, JPEG etc. formats
+		// FIXME: read width and height from the file
+		// TODO: review texture loading and binding
+		// works even without this - default texture
+		// glUniform1i(ProgAttr.jazz, jazz);
+		// checkError(&std::cerr);
+	}
+}
+
+GLuint Shark::loadShaders() {
+	try {
+		// Vertex Array Object (VAO)
+		GLuint vao;
+		glGenVertexArrays(1, &vao);
+		glBindVertexArray(vao);
+		// VAO - something like context for bound data/variables
+		// We can switch multiple VAOs. VAO can contain multiple VBOs.
+		// See also https://stackoverflow.com/questions/11821336/
+		// what-are-vertex-array-objects
+
+		// Vertex Buffer Object (VBO):
+		GLuint vbo;
+		glGenBuffers(1, &vbo);
+		glBindBuffer(GL_ARRAY_BUFFER, vbo);
+
+		std::vector<std::string> fileNames = {
+			"shaders/first.vert",
+			"shaders/first.frag",
+		};
+
+		std::vector<GLuint> shaders;
+
+		GLuint program = glCreateProgram();
+
+		// glBindFragDataLocation(program, 0, "outColor");
+		// glBindAttribLocation(program, LOC.input, "vertices");
+
+		for (const std::string& fileName : fileNames) {
+			MappedFile file(fileName);
+			GLuint shader = glCreateShader(toShaderType(fileName));
+			auto fileData = file.getData();
+			GLint fileSize = file.getSize();
+			glShaderSource(shader, 1, &fileData, &fileSize);
+			glCompileShader(shader);
+
+			GLint compileStatus;
+			glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);
+			std::cerr << "GLSL shader compile status: "
+					<< compileStatus
+					<< (compileStatus == GL_TRUE ? " = OK" : " = ERROR")
+					<< std::endl;
+
+			if (compileStatus != GL_TRUE) {
+				char error[512];
+				glGetShaderInfoLog(shader, sizeof (error), NULL, error);
+				std::cerr << "GLSL shader error: " << error;
+				throw std::logic_error("GLSL: shader failed to compile");
+			}
+
+			glAttachShader(program, shader);
+			shaders.push_back(shader);
+			std::cerr << "GLSL loaded: " << fileName.c_str() << std::endl;
+		}
+
+		// GLSL compiler does very efficient / aggressive optimization.
+		// Attributes and uniforms that are not used in the shader are deleted.
+		// And even if we e.g. read color from a texture and overwrite it,
+		// the variable is still deleted and considered „inactive“.
+		// Functions glGetAttribLocation() and glGetUniformLocation() return -1.
+
+		glLinkProgram(program);
+
+		ProgAttr.vertexXYZ = glGetAttribLocation(program, "vertices");
+		ProgAttr.textureXY = glGetAttribLocation(program, "textureCoordinates");
+		ProgAttr.model = glGetUniformLocation(program, "model");
+		ProgAttr.view = glGetUniformLocation(program, "view");
+		ProgAttr.projection = glGetUniformLocation(program, "projection");
+		ProgAttr.jazz = glGetUniformLocation(program, "jazz");
+		ProgAttr.color = glGetFragDataLocation(program, "outColor");
+		glBindFragDataLocation(program, ProgAttr.color, "outColor");
+		// listVariables(program);
+		GLint linkStatus;
+		glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
+		if (linkStatus != GL_TRUE) {
+			char error[512];
+			glGetProgramInfoLog(program, sizeof (error), NULL, error);
+			std::cerr << "GLSL program error: " << error;
+			throw std::logic_error("GLSL: program failed to link");
+		}
+		std::cerr << "GLSL shader count: " << shaders.size() << std::endl;
+
+		return program;
+	} catch (const std::exception& e) {
+		std::cerr << "Error while loading shaders: " << e.what() << std::endl;
+	} catch (...) {
+		std::cerr << "Error while loading shaders: unknown" << std::endl;
+	}
+	throw std::logic_error("GLSL: loadShaders() failed");
+}
+
diff -r 000000000000 -r bb715a82a8f1 Shark.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Shark.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,182 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <iostream>
+#include <iomanip>
+#include <string>
+#include <memory>
+#include <functional>
+#include <sstream>
+#include <vector>
+#include <chrono>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "Configuration.h"
+#include "x11.h"
+#include "opengl.h"
+#include "EPoll.h"
+#include "Logger.h"
+#include "MappedFile.h"
+
+class Shark {
+private:
+
+	struct {
+		GLint vertexXYZ = -2;
+		GLint textureXY = -2;
+
+		GLint color = -2;
+
+		GLint model = -2;
+		GLint view = -2;
+		GLint projection = -2;
+		GLint jazz = -2;
+	} ProgAttr;
+
+	struct {
+		float yaw = -90.f;
+		float pitch = 0.f;
+		float roll = 0.f;
+		float fov = 45.0f;
+		glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 3.0f);
+		glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);
+		glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);
+
+		void adjustFov(float diff) {
+			fov += diff;
+			if (fov < 1.0f) fov = 1.0f;
+			else if (fov > 120.0f) fov = 120.0f;
+			std::cerr << "field of view: " << fov << " °" << std::endl;
+		}
+
+		void moveForward(const float cameraSpeed) {
+			cameraPos += cameraSpeed * cameraFront;
+		}
+
+		void moveBackward(const float cameraSpeed) {
+			cameraPos -= cameraSpeed * cameraFront;
+		}
+
+		void moveLeft(const float cameraSpeed) {
+			cameraPos -= glm::normalize(
+					glm::cross(cameraFront, cameraUp)) * cameraSpeed;
+		}
+
+		void moveRight(const float cameraSpeed) {
+			cameraPos += glm::normalize(
+					glm::cross(cameraFront, cameraUp)) * cameraSpeed;
+		}
+
+		void moveUp(const float cameraSpeed) {
+			cameraPos += cameraSpeed * glm::normalize(cameraUp);
+		}
+
+		void moveDown(const float cameraSpeed) {
+			cameraPos -= cameraSpeed * glm::normalize(cameraUp);
+		}
+
+		void updateCameraFrontAndUp() {
+			std::cerr << "--- updateCameraFrontAndUp() --------" << std::endl;
+			dump("pitch, yaw, roll", glm::vec3(pitch, yaw, roll));
+			dump("cameraPos", cameraPos);
+			dump("cameraFront", cameraFront);
+			const auto pitchR = glm::radians(pitch); // around X axis
+			const auto yawR = glm::radians(yaw); //     around Y axis
+			const auto rollR = glm::radians(roll); //   around Z axis
+
+			cameraFront.x = cos(pitchR) * cos(yawR);
+			cameraFront.y = sin(pitchR);
+			cameraFront.z = cos(pitchR) * sin(yawR);
+			cameraFront = glm::normalize(cameraFront);
+			dump("cameraFront", cameraFront);
+			dump("cameraUp", cameraUp);
+
+			// TODO: review ROLL rotation and default angle
+			glm::mat4 rollMatrix = glm::rotate(
+					glm::mat4(1.0f), rollR, cameraFront);
+			cameraUp = glm::mat3(rollMatrix) * glm::vec3(0., 1., 0.);
+			dump("cameraUp", cameraUp);
+			std::cerr << "-------------------------------------" << std::endl;
+		}
+
+		void limitPitch() {
+			if (pitch > +89.0f) pitch = +89.0f;
+			if (pitch < -89.0f) pitch = -89.0f;
+		}
+
+		void turnLeft(const float angleSpeed) {
+			yaw -= angleSpeed;
+			updateCameraFrontAndUp();
+		}
+
+		void turnRight(const float angleSpeed) {
+			yaw += angleSpeed;
+			updateCameraFrontAndUp();
+		}
+
+		void turnUp(const float angleSpeed) {
+			pitch += angleSpeed;
+			limitPitch();
+			updateCameraFrontAndUp();
+		}
+
+		void turnDown(const float angleSpeed) {
+			pitch -= angleSpeed;
+			limitPitch();
+			updateCameraFrontAndUp();
+		}
+
+		void rollLeft(const float angleSpeed) {
+			roll += angleSpeed;
+			updateCameraFrontAndUp();
+		}
+
+		void rollRight(const float angleSpeed) {
+			roll -= angleSpeed;
+			updateCameraFrontAndUp();
+		}
+
+	} initialCtx, ctx;
+
+	const struct {
+		int width = 640;
+		int height = 398;
+		GLfloat ratio = (GLfloat) width / (GLfloat) height;
+	} TEX;
+
+	Configuration cfg;
+	std::ostream& logOutput = std::cerr;
+
+	void renderImmediateMode();
+	void runShaders(GLuint program);
+	Window getRootWindow(Window defaultValue);
+	void log(LogLevel level, std::string message);
+	int setNonBlocking(int fd);
+	void loadVertices();
+	GLuint loadTexture(const std::string& fileName, int width, int height);
+	void loadTextures(GLuint shaderProgram);
+	GLuint loadShaders();
+public:
+	Shark(const Configuration& cfg);
+	virtual ~Shark();
+	Shark(const Shark&) = delete;
+	Shark& operator=(const Shark&) = delete;
+	void run();
+};
diff -r 000000000000 -r bb715a82a8f1 bash-completion.sh
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bash-completion.sh	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,45 @@
+# ShaderShark
+# Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+_shader_shark_completion() {
+	local w0 w1 w2 w3
+
+	COMPREPLY=()
+	w0=${COMP_WORDS[COMP_CWORD]}
+	w1=${COMP_WORDS[COMP_CWORD-1]}
+	w2=${COMP_WORDS[COMP_CWORD-2]}
+	w3=${COMP_WORDS[COMP_CWORD-3]}
+
+	local COLOR=(
+		"333333"
+		"345678"
+		"147258"
+	)
+
+	if   [[ "$w1" == "--texture" ]]; then
+		COMPREPLY=($(compgen -f -- "$w0"; compgen -d -S / -- "$w0"))
+	elif [[ "$w1" == "--background-color" ]]; then
+		COMPREPLY=($(compgen -W "${COLOR[*]}" -- "$w0"))
+	else
+		local OPTIONS=(
+			"--texture"
+			"--background-color"
+			"--root-window"
+		)
+		COMPREPLY=($(compgen -W "${OPTIONS[*]}" -- "$w0"))
+	fi
+}
+
+complete -F _shader_shark_completion shader-shark
diff -r 000000000000 -r bb715a82a8f1 license/gpl.txt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/license/gpl.txt	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
+certain responsibilities if you distribute copies of the software, or if
+you modify it: responsibilities to respect the freedom of others.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must pass on to the recipients the same
+freedoms that you received.  You must make sure that they, too, receive
+or can get the source code.  And you must show them these terms so they
+know their rights.
+
+  Developers that use the GNU GPL protect your rights with two steps:
+(1) assert copyright on the software, and (2) offer you this License
+giving you legal permission to copy, distribute and/or modify it.
+
+  For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software.  For both users' and
+authors' sake, the GPL requires that modified versions be marked as
+changed, so that their problems will not be attributed erroneously to
+authors of previous versions.
+
+  Some devices are designed to deny users access to install or run
+modified versions of the software inside them, although the manufacturer
+can do so.  This is fundamentally incompatible with the aim of
+protecting users' freedom to change the software.  The systematic
+pattern of such abuse occurs in the area of products for individuals to
+use, which is precisely where it is most unacceptable.  Therefore, we
+have designed this version of the GPL to prohibit the practice for those
+products.  If such problems arise substantially in other domains, we
+stand ready to extend this provision to those domains in future versions
+of the GPL, as needed to protect the freedom of users.
+
+  Finally, every program is threatened constantly by software patents.
+States should not allow patents to restrict development and use of
+software on general-purpose computers, but in those that do, we wish to
+avoid the special danger that patents applied to a free program could
+make it effectively proprietary.  To prevent this, the GPL assures that
+patents cannot be used to render the program non-free.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                       TERMS AND CONDITIONS
+
+  0. Definitions.
+
+  "This License" refers to version 3 of the GNU General Public License.
+
+  "Copyright" also means copyright-like laws that apply to other kinds of
+works, such as semiconductor masks.
+
+  "The Program" refers to any copyrightable work licensed under this
+License.  Each licensee is addressed as "you".  "Licensees" and
+"recipients" may be individuals or organizations.
+
+  To "modify" a work means to copy from or adapt all or part of the work
+in a fashion requiring copyright permission, other than the making of an
+exact copy.  The resulting work is called a "modified version" of the
+earlier work or a work "based on" the earlier work.
+
+  A "covered work" means either the unmodified Program or a work based
+on the Program.
+
+  To "propagate" a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for
+infringement under applicable copyright law, except executing it on a
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+  "Additional permissions" are terms that supplement the terms of this
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+
+  Nothing in this License shall be construed as excluding or limiting
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+
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+
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+  13. Use with the GNU Affero General Public License.
+
+  Notwithstanding any other provision of this License, you have
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+  If the Program specifies that a proxy can decide which future
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+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
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+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
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+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
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+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
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+  To do so, attach the following notices to the program.  It is safest
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+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
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+    This program is free software: you can redistribute it and/or modify
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+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
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+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
diff -r 000000000000 -r bb715a82a8f1 license/header.txt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/license/header.txt	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,16 @@
+/**
+ * OpenGL
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
diff -r 000000000000 -r bb715a82a8f1 nbproject/configurations.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nbproject/configurations.xml	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configurationDescriptor version="100">
+  <logicalFolder name="root" displayName="root" projectFiles="true" kind="ROOT">
+    <df root="." name="0">
+      <in>Shark.cpp</in>
+      <in>shader-shark.cpp</in>
+    </df>
+    <logicalFolder name="ExternalFiles"
+                   displayName="Important Files"
+                   projectFiles="false"
+                   kind="IMPORTANT_FILES_FOLDER">
+      <itemPath>Makefile</itemPath>
+      <itemPath>nbproject/private/launcher.properties</itemPath>
+    </logicalFolder>
+  </logicalFolder>
+  <sourceFolderFilter>^(nbproject)$</sourceFolderFilter>
+  <sourceRootList>
+    <Elem>.</Elem>
+  </sourceRootList>
+  <projectmakefile>Makefile</projectmakefile>
+  <confs>
+    <conf name="Default" type="0">
+      <toolsSet>
+        <compilerSet>default</compilerSet>
+        <dependencyChecking>false</dependencyChecking>
+        <rebuildPropChanged>false</rebuildPropChanged>
+      </toolsSet>
+      <codeAssistance>
+      </codeAssistance>
+      <makefileType>
+        <makeTool>
+          <buildCommandWorkingDir>.</buildCommandWorkingDir>
+          <buildCommand>${MAKE} -f Makefile</buildCommand>
+          <cleanCommand>${MAKE} -f Makefile clean</cleanCommand>
+          <executablePath>build/shader-shark</executablePath>
+        </makeTool>
+        <preBuild>
+          <preBuildCommandWorkingDir>.</preBuildCommandWorkingDir>
+          <preBuildCommand></preBuildCommand>
+        </preBuild>
+      </makefileType>
+      <item path="Shark.cpp" ex="false" tool="1" flavor2="0">
+      </item>
+      <item path="shader-shark.cpp" ex="false" tool="1" flavor2="0">
+      </item>
+    </conf>
+  </confs>
+</configurationDescriptor>
diff -r 000000000000 -r bb715a82a8f1 nbproject/project.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nbproject/project.xml	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://www.netbeans.org/ns/project/1">
+    <type>org.netbeans.modules.cnd.makeproject</type>
+    <configuration>
+        <data xmlns="http://www.netbeans.org/ns/make-project/1">
+            <name>ShaderShark</name>
+            <c-extensions/>
+            <cpp-extensions>cpp</cpp-extensions>
+            <header-extensions>h</header-extensions>
+            <sourceEncoding>UTF-8</sourceEncoding>
+            <make-dep-projects/>
+            <sourceRootList>
+                <sourceRootElem>.</sourceRootElem>
+            </sourceRootList>
+            <confList>
+                <confElem>
+                    <name>Default</name>
+                    <type>0</type>
+                </confElem>
+            </confList>
+            <formatting>
+                <project-formatting-style>false</project-formatting-style>
+            </formatting>
+        </data>
+    </configuration>
+</project>
diff -r 000000000000 -r bb715a82a8f1 opengl.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/opengl.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,61 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <string>
+#include <stdexcept>
+
+#include <epoxy/gl.h>
+#include <epoxy/glx.h>
+#include <GL/glu.h>
+
+#include <glm/glm.hpp>
+#include <glm/ext.hpp>
+
+inline
+void quads(GLfloat tx, GLfloat ty, GLfloat x, GLfloat y, GLfloat z) {
+	glTexCoord2f(tx, ty);
+	glVertex3f(x, y, z);
+}
+
+inline
+void checkError(std::ostream* out) {
+	GLenum code = glGetError();
+	if (code == GL_NO_ERROR) {
+		if (out) *out << "GL check: OK" << std::endl;
+	} else {
+		const char* string = (const char*) gluErrorString(code);
+		if (out) *out << "GL check: " << string << std::endl;
+		else throw std::logic_error(std::string("GL error: ") + string);
+	}
+}
+
+inline
+GLenum toShaderType(const std::string& fileName) {
+	if (fileName.ends_with(".vert")) return GL_VERTEX_SHADER;
+	else if (fileName.ends_with(".frag")) return GL_FRAGMENT_SHADER;
+	else throw std::invalid_argument("Expecting *.vert or *.frag file");
+}
+
+inline
+void dump(const char* name, const glm::vec3& value) {
+	std::cerr << "dump: " << name << " = ["
+			<< value.x << ", "
+			<< value.y << ", "
+			<< value.z << "]" << std::endl;
+}
\ No newline at end of file
diff -r 000000000000 -r bb715a82a8f1 shader-shark.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shader-shark.cpp	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,50 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <iostream>
+#include <locale>
+#include <stdexcept>
+#include <vector>
+#include <string>
+
+#include "CLIParser.h"
+#include "Shark.h"
+
+int main(int argc, char** argv) {
+	setlocale(LC_ALL, "");
+	std::cout << "ShaderShark for OpenGL" << std::endl;
+	int result = 0;
+
+	try {
+		std::vector<std::string> arguments;
+		for (int i = 1; i < argc; i++) arguments.push_back(argv[i]);
+
+		CLIParser cliParser;
+		Configuration cfg = cliParser.parse(arguments);
+
+		Shark shaderShark(cfg);
+		shaderShark.run();
+	} catch (const std::exception& e) {
+		std::cerr << "Exception: " << e.what() << std::endl;
+		result = 1;
+	} catch (...) {
+		std::cerr << "Exception: unexpected" << std::endl;
+		result = 2;
+	}
+
+	return result;
+}
diff -r 000000000000 -r bb715a82a8f1 shaders/first.frag
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shaders/first.frag	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,10 @@
+#version 330 core
+
+uniform sampler2D jazz;
+in vec2 textureCoordinate;
+out vec3 outColor; 
+
+void main(){
+	outColor = texture(jazz, textureCoordinate).xyz;
+	// outColor *= vec3(0.8, 1., 0.2);
+}
diff -r 000000000000 -r bb715a82a8f1 shaders/first.vert
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shaders/first.vert	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,13 @@
+#version 330 core
+
+uniform mat4 model;
+uniform mat4 view;
+uniform mat4 projection;
+in vec3 vertices;
+in vec2 textureCoordinates;
+out vec2 textureCoordinate;
+
+void main() {
+	gl_Position = projection * view * model * vec4(vertices, 1.0f);
+	textureCoordinate = textureCoordinates;
+}
diff -r 000000000000 -r bb715a82a8f1 textures/jazz.png
Binary file textures/jazz.png has changed
diff -r 000000000000 -r bb715a82a8f1 x11.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/x11.h	Sun Nov 26 16:27:50 2023 +0100
@@ -0,0 +1,90 @@
+/**
+ * ShaderShark
+ * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <cstring>
+
+#include <X11/Xatom.h>
+#include <X11/XKBlib.h>
+#include <X11/keysymdef.h>
+
+/**
+ * Publish our PID (process ID) through the X11 window property.
+ */
+inline
+void setX11PID(Display* dpy, Window win) {
+	Atom _NET_WM_PID = XInternAtom(dpy, "_NET_WM_PID", False);
+	pid_t pid = getpid();
+	XChangeProperty(dpy, win, _NET_WM_PID, XA_CARDINAL,
+			32, PropModeReplace, (unsigned char *) &pid, 1);
+}
+
+inline
+bool setFullscreen(Display* dpy, Window win, bool fullscreen) {
+	XEvent ev;
+	Atom wmState = XInternAtom(dpy, "_NET_WM_STATE", False);
+	Atom wmFullscreen = XInternAtom(dpy, "_NET_WM_STATE_FULLSCREEN", False);
+	ev.xclient.type = ClientMessage;
+	ev.xclient.serial = 0; // TODO: serial?
+	ev.xclient.send_event = True;
+	ev.xclient.display = dpy;
+	ev.xclient.window = win;
+	ev.xclient.message_type = wmState;
+	ev.xclient.format = 32;
+	ev.xclient.data.l[0] = fullscreen;
+	ev.xclient.data.l[1] = wmFullscreen;
+	ev.xclient.data.l[2] = None;
+	XSendEvent(dpy, DefaultRootWindow(dpy), False, SubstructureNotifyMask, &ev);
+	return fullscreen;
+}
+
+class DecodedKey {
+public:
+	unsigned int code;
+	KeySym symbol;
+	const char* name;
+
+	bool matches(
+			KeySym s1,
+			KeySym s2 = XK_VoidSymbol,
+			KeySym s3 = XK_VoidSymbol,
+			KeySym s4 = XK_VoidSymbol,
+			KeySym s5 = XK_VoidSymbol,
+			KeySym s6 = XK_VoidSymbol,
+			KeySym s7 = XK_VoidSymbol,
+			KeySym s8 = XK_VoidSymbol
+			) {
+		return symbol == s1
+				|| symbol == s2
+				|| symbol == s3
+				|| symbol == s4
+				|| symbol == s5
+				|| symbol == s6
+				|| symbol == s7
+				|| symbol == s8;
+	}
+};
+
+inline
+const DecodedKey decodeKeycode(Display * dpy, KeyCode keyCode) {
+	DecodedKey dk = {};
+	dk.code = keyCode;
+	dk.symbol = XkbKeycodeToKeysym(dpy, keyCode, 0, 0);
+	dk.name = XKeysymToString(dk.symbol);
+	return dk;
+}