标签：loc 面试题 Linux 0.0 offset 面试官 shader egl display
- atan(pos.y,pos.x) - phase ); \
} \
";
// handle to the shader
void print_shader_info_log (GLuint shader){
GLint length;
glGetShaderiv ( shader , GL_INFO_LOG_LENGTH , &length );
if ( length ) {
char* buffer = new char [ length ];
glGetShaderInfoLog ( shader , length , NULL , buffer );
cout << "shader info: " << buffer << flush;
delete [] buffer;
GLint success;
glGetShaderiv( shader, GL_COMPILE_STATUS, &success );
if ( success != GL_TRUE ) exit ( 1 );
}
}
GLuint load_shader ( const char *shader_source, GLenum type){
GLuint shader = glCreateShader( type );
glShaderSource ( shader , 1 , &shader_source , NULL );
glCompileShader ( shader );
print_shader_info_log ( shader );
return shader;
}
Display *x_display;
Window win;
EGLDisplay egl_display;
EGLContext egl_context;
EGLSurface egl_surface;
GLfloat
norm_x = 0.0,
norm_y = 0.0,
offset_x = 0.0,
offset_y = 0.0,
p1_pos_x = 0.0,
p1_pos_y = 0.0;
GLint phase_loc, offset_loc, position_loc;
bool update_pos = false;
const float vertexArray[] = {
0.0, 0.5, 0.0,
-0.5, 0.0, 0.0,
0.0, -0.5, 0.0,
0.5, 0.0, 0.0,
0.0, 0.5, 0.0
};
void render(){
static float phase = 0;
static int donesetup = 0;
static XWindowAttributes gwa;
draw
if ( !donesetup ) {
XWindowAttributes gwa;
XGetWindowAttributes ( x_display , win , &gwa );
glViewport ( 0 , 0 , gwa.width , gwa.height );
glClearColor ( 0.08 , 0.06 , 0.07 , 1.); // background color
donesetup = 1;
}
glClear ( GL_COLOR_BUFFER_BIT );
glUniform1f ( phase_loc , phase ); // write the value of phase to the shaders phase
phase = fmodf ( phase + 0.5f , 2.f * 3.141f ); // and update the local variable
if ( update_pos ) { // if the position of the texture has changed due to user action
GLfloat old_offset_x = offset_x;
GLfloat old_offset_y = offset_y;
offset_x = norm_x - p1_pos_x;
offset_y = norm_y - p1_pos_y;
p1_pos_x = norm_x;
p1_pos_y = norm_y;
offset_x += old_offset_x;
offset
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_y += old_offset_y;
update_pos = false;
}
glUniform4f ( offset_loc , offset_x , offset_y , 0.0 , 0.0 );
glVertexAttribPointer ( position_loc, 3, GL_FLOAT, false, 0, vertexArray );
glEnableVertexAttribArray ( position_loc );
glDrawArrays ( GL_TRIANGLE_STRIP, 0, 5 );
eglSwapBuffers ( egl_display, egl_surface ); // get the rendered buffer to the screen
}
int main(){
/// the X11 part //
// in the first part the program opens a connection to the X11 window manager
//
x_display = XOpenDisplay ( NULL ); // open the standard display (the primary screen)
if ( x_display == NULL ) {
cerr << “cannot connect to X server” << endl;
return 1;
}
Window root = DefaultRootWindow( x_display ); // get the root window (usually the whole screen)
XSetWindowAttributes swa;
swa.event_mask = ExposureMask | PointerMotionMask | KeyPressMask;
win = XCreateWindow ( // create a window with the provided parameters
x_display, root,
0, 0, 800, 480, 0,
CopyFromParent, InputOutput,
CopyFromParent, CWEventMask,
&swa );
XSetWindowAttributes xattr;
Atom atom;
int one = 1;
xattr.override_redirect = False;
XChangeWindowAttributes ( x_display, win, CWOverrideRedirect, &xattr );
atom = XInternAtom ( x_display, “_NET_WM_STATE_FULLSCREEN”, True );
XChangeProperty (
x_display, win,
XInternAtom ( x_display, “_NET_WM_STATE”, True ),
XA_ATOM, 32, PropModeReplace,
(unsigned char*) &atom, 1 );
XChangeProperty (
x_display, win,
XInternAtom ( x_display, “_HILDON_NON_COMPOSITED_WINDOW”, False ),
XA_INTEGER, 32, PropModeReplace,
(unsigned char*) &one, 1);
XWMHints hints;
hints.input = True;
hints.flags = InputHint;
XSetWMHints(x_display, win, &hints);
XMapWindow ( x_display , win ); // make the window visible on the screen
XStoreName ( x_display , win , “GL test” ); // give the window a name
get identifiers for the provided atom name strings
Atom wm_state = XInternAtom ( x_display, “_NET_WM_STATE”, False );
Atom fullscreen = XInternAtom ( x_display, “_NET_WM_STATE_FULLSCREEN”, False );
XEvent xev;
memset ( &xev, 0, sizeof(xev) );
xev.type = ClientMessage;
xev.xclient.window = win;
xev.xclient.message_type = wm_state;
xev.xclient.format = 32;
xev.xclient.data.l[0] = 1;
xev.xclient.data.l[1] = fullscreen;
XSendEvent ( // send an event mask to the X-server
x_display,
DefaultRootWindow ( x_display ),
False,
SubstructureNotifyMask,
&xev );
/// the egl part //
// egl provides an interface to connect the graphics related functionality of openGL ES
// with the windowing interface and functionality of the native operation system (X11
// in our case.
egl_display = eglGetDisplay( (EGLNativeDisplayType) x_display );
if ( egl_display == EGL_NO_DISPLAY ) {
cerr << “Got no EGL display.” << endl;
return 1;
}
if ( !eglInitialize( egl_display, NULL, NULL ) ) {
cerr << “Unable to initialize EGL” << endl;
return 1;
}
EGLint attr[] = { // some attributes to set up our egl-interface
EGL_BUFFER_SIZE, 16,
EGL_RENDERABLE_TYPE,
EGL_OPENGL_ES2_BIT,
EGL_NONE
};
EGLConfig ecfg;
EGLint num_config;
if ( !eglChooseConfig( egl_display, attr, &ecfg, 1, &num_config ) ) {
cerr << "Failed to choose config (eglError: " << eglGetError() << “)” << endl;
return 1;
}
if ( num_config != 1 ) {
cerr << "Didn’t get exactly one config, but " << num_config << endl;
return 1;
}
egl_surface = eglCreateWindowSurface ( egl_display, ecfg, win, NULL );
if ( egl_surface == EGL_NO_SURFACE ) {
cerr << "Unable to create EGL surface (eglError: " << eglGetError() << “)” << endl;
return 1;
}
egl-contexts collect all state descriptions needed required for operation
EGLint ctxattr[] = {
EGL_CONTEXT_CLIENT_VERSION, 2,
EGL_NONE
};
egl_context = eglCreateContext ( egl_display, ecfg, EGL_NO_CONTEXT, ctxattr );
if ( egl_context == EGL_NO_CONTEXT ) {
cerr << "Unable to create EGL context (eglError: " << eglGetError() << “)” << endl;
return 1;
}
associate the egl-context with the egl-surface
eglMakeCurrent( egl_display, egl_surface, egl_surface, egl_context );
/// the openGL part ///
GLuint vertexShader = load_shader ( vertex_src , GL_VERTEX_SHADER ); // load vertex shader
GLuint fragmentShader = load_shader ( fragment_src , GL_FRAGMENT_SHADER ); // load fragment shader
GLuint shaderProgram = glCreateProgram (); // create program object
glAttachShader ( shaderProgram, vertexShader ); // and attach both…
glAttachShader ( shaderProgram, fragmentShader ); // … shaders to it
glLinkProgram ( shaderProgram ); // link the program
glUseProgram ( shaderProgram ); // and select it for usage
now get the locations (kind of handle) of the shaders variables
position_loc = glGetAttribLocation ( shaderProgram , “position” );
phase_loc = glGetUniformLocation ( shaderProgram , “phase” );
offset_loc = glGetUniformLocation ( shaderProgram , “offset” );
if ( position_loc < 0 || phase_loc < 0 || offset_loc < 0 ) {
标签：loc,面试题,Linux,0.0,offset,面试官,shader,egl,display 来源： https://blog.csdn.net/m0_65146387/article/details/122027537
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