[英]Can't render to GtkGLArea
我尝试将一个三角形渲染到 GtkGLArea,但我只能看到我使用 glClearColor() 清除帧的颜色。
请注意:
可能导致问题的事情:
我目前没有刷新帧或交换帧缓冲区,因为文档( https://developer.gnome.org/gtk3/stable/GtkGLArea.html )没有提到我必须这样做。 我试过 glFlush() 但它也没有帮助。
我假设屏幕坐标在所有轴上从 -1 到 1,就像在普通 OpenGL 中一样。 也许那是错误的,但我在那里的文档中也找不到任何内容。
有人可以帮助我吗?
这是我编译它的方式:
g++ -O3 -s -o main main.cpp -isystem include -Llibs -DNDEBUG `pkg-config --cflags gtk+-3.0` `pkg-config --libs gtk+-3.0` -lepoxy -lm
这是我的代码:
#include <gtk/gtk.h>
#include <epoxy/gl.h>
#include <epoxy/glx.h>
#include <iostream>
#include <vector>
GLuint LoadShaders(char const* vertex, char const* fragment){
// Create the shaders
GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
GLint Result = GL_FALSE;
int InfoLogLength;
// Compile Vertex Shader
glShaderSource(VertexShaderID, 1, &vertex , NULL);
glCompileShader(VertexShaderID);
// Check Vertex Shader
glGetShaderiv(VertexShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(VertexShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> VertexShaderErrorMessage(InfoLogLength+1);
glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
printf("%s\n", &VertexShaderErrorMessage[0]);
}
// Compile Fragment Shader
glShaderSource(FragmentShaderID, 1, &fragment , NULL);
glCompileShader(FragmentShaderID);
// Check Fragment Shader
glGetShaderiv(FragmentShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(FragmentShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> FragmentShaderErrorMessage(InfoLogLength+1);
glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
printf("%s\n", &FragmentShaderErrorMessage[0]);
}
// Link the program
GLuint ProgramID = glCreateProgram();
glAttachShader(ProgramID, VertexShaderID);
glAttachShader(ProgramID, FragmentShaderID);
glLinkProgram(ProgramID);
// Check the program
glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> ProgramErrorMessage(InfoLogLength+1);
glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
printf("%s\n", &ProgramErrorMessage[0]);
}
glDetachShader(ProgramID, VertexShaderID);
glDetachShader(ProgramID, FragmentShaderID);
glDeleteShader(VertexShaderID);
glDeleteShader(FragmentShaderID);
return ProgramID;
}
char const* vertShader = R"GLSL(
#version 330 core
void main(){
gl_Position.z = 0.0;
gl_Position.w = 1.0;
if (0 == gl_VertexID) {
gl_Position.x = -100.0;
gl_Position.y = -100.0;
}
if (2 == gl_VertexID) {
gl_Position.x = 0.0;
gl_Position.y = 100.0;
}
if (1 == gl_VertexID) {
gl_Position.x = 100.0;
gl_Position.y = -100.0;
}
}
)GLSL";
char const* fragShader = R"GLSL(
#version 330 core
layout(location = 0) out vec4 color;
void main(){
color = vec4(1.0, 0.0, 0.0, 1.0);
}
)GLSL";
gboolean
render(GtkGLArea*, GdkGLContext*, gpointer) {
glClearColor(0.5, 0.5, 0.5, 0);
glClear(GL_COLOR_BUFFER_BIT);
GLuint programID;
programID = LoadShaders(vertShader, fragShader);
glUseProgram(programID);
glDrawArrays(GL_TRIANGLES, 0, 3);
//glFlush();
glDeleteProgram(programID);
return TRUE;
}
int
main(int argc, char** argv) {
gtk_init(&argc, &argv);
auto window{gtk_window_new(GTK_WINDOW_TOPLEVEL)};
auto glWidget{gtk_gl_area_new()};
gtk_container_add(GTK_CONTAINER(window), glWidget);
g_signal_connect (glWidget, "render", G_CALLBACK(render), nullptr);
gtk_widget_show_all(window);
gtk_main();
return EXIT_SUCCESS;
}
我能想到的两件事:
create-context
& create + return a gdk_gl_context_set_required_version
'd GdkGLContext
。RE:缺少 VAO:
用这个 GLFW 程序和 VAO 创建/绑定注释掉:
#include <glad/glad.h>
#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
#include <iostream>
void CheckStatus( GLuint obj, bool isShader )
{
GLint status = GL_FALSE, log[ 1 << 11 ] = { 0 };
( isShader ? glGetShaderiv : glGetProgramiv )( obj, isShader ? GL_COMPILE_STATUS : GL_LINK_STATUS, &status );
( isShader ? glGetShaderInfoLog : glGetProgramInfoLog )( obj, sizeof( log ), NULL, (GLchar*)log );
if( status == GL_TRUE ) return;
std::cerr << (GLchar*)log << "\n";
std::exit( EXIT_FAILURE );
}
void AttachShader( GLuint program, GLenum type, const char* src )
{
GLuint shader = glCreateShader( type );
glShaderSource( shader, 1, &src, NULL );
glCompileShader( shader );
CheckStatus( shader, true );
glAttachShader( program, shader );
glDeleteShader( shader );
}
const char* vert = 1 + R"GLSL(
#version 330 core
void main(){
gl_Position.z = 0.0;
gl_Position.w = 1.0;
if (0 == gl_VertexID) {
gl_Position.x = -100.0;
gl_Position.y = -100.0;
}
if (2 == gl_VertexID) {
gl_Position.x = 0.0;
gl_Position.y = 100.0;
}
if (1 == gl_VertexID) {
gl_Position.x = 100.0;
gl_Position.y = -100.0;
}
}
)GLSL";
const char* frag = 1 + R"GLSL(
#version 330 core
layout(location = 0) out vec4 color;
void main(){
color = vec4(1.0, 0.0, 0.0, 1.0);
}
)GLSL";
int main( int, char** )
{
glfwSetErrorCallback( []( int, const char* desc ) { std::cerr << desc << "\n"; std::exit( EXIT_FAILURE ); } );
glfwInit();
glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 3 );
glfwWindowHint( GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE );
glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
GLFWwindow* window = glfwCreateWindow( 640, 480, "GLFW", NULL, NULL );
glfwMakeContextCurrent( window );
gladLoadGLLoader( (GLADloadproc)glfwGetProcAddress );
//GLuint vao = 0;
//glGenVertexArrays( 1, &vao );
//glBindVertexArray( vao );
GLuint prog = glCreateProgram();
AttachShader( prog, GL_VERTEX_SHADER, vert );
AttachShader( prog, GL_FRAGMENT_SHADER, frag );
glLinkProgram( prog );
CheckStatus( prog, false );
while( !glfwWindowShouldClose( window ) )
{
glfwPollEvents();
int w, h;
glfwGetFramebufferSize( window, &w, &h );
glViewport( 0, 0, w, h );
glClearColor( 0.5, 0.5, 0.5, 0 );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glUseProgram( prog );
glDrawArrays( GL_TRIANGLES, 0, 3 );
glfwSwapBuffers( window );
}
glfwTerminate();
}
在 Linux 上运行 Mesa 13.0.6 的 llvmpipe 后端和MESA_DEBUG=1
envvar给我一个灰色窗口和 stdout 上的这条消息:
Mesa: User error: GL_INVALID_OPERATION in glDrawArrays(no VAO bound)
恢复 VAO 会提供预期的红色窗口。
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