178 строки
4.9 KiB
C
178 строки
4.9 KiB
C
// Built from glbook/hello triange and sdl_ogl, see details there
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#include "SDL/SDL.h"
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#include "SDL/SDL_image.h"
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#include "SDL/SDL_opengl.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <assert.h>
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#include <string.h>
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GLuint programObject;
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int width = 512;
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int height = 256;
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GLuint LoadShader ( GLenum type, const char *shaderSrc )
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{
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GLuint shader;
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GLint compiled;
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shader = glCreateShader ( type );
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if ( shader == 0 )
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return 0;
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glShaderSource ( shader, 1, &shaderSrc, NULL );
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glCompileShader ( shader );
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glGetShaderiv ( shader, GL_COMPILE_STATUS, &compiled );
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if ( !compiled )
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{
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GLint infoLen = 0;
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glGetShaderiv ( shader, GL_INFO_LOG_LENGTH, &infoLen );
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if ( infoLen > 1 )
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{
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char* infoLog = malloc (sizeof(char) * infoLen );
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glGetShaderInfoLog ( shader, infoLen, NULL, infoLog );
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printf ( "Error compiling shader:\n%s\n", infoLog );
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free ( infoLog );
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}
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glDeleteShader ( shader );
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return 0;
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}
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return shader;
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}
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int Init ()
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{
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GLbyte vShaderStr[] =
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"attribute vec4 vPosition; \n"
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"void main() \n"
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"{ \n"
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" gl_Position = vPosition; \n"
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"} \n";
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GLbyte fShaderStr[] =
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"precision mediump float;\n"\
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"void main() \n"
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"{ \n"
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" gl_FragColor = vec4 ( 0.0, 0.0, 1.0, 1.0 );\n"
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"} \n";
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GLuint vertexShader;
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GLuint fragmentShader;
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GLint linked;
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vertexShader = LoadShader ( GL_VERTEX_SHADER, (const char *)vShaderStr );
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fragmentShader = LoadShader ( GL_FRAGMENT_SHADER, (const char *)fShaderStr );
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programObject = glCreateProgram ( );
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if ( programObject == 0 )
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return 0;
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glAttachShader ( programObject, vertexShader );
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glAttachShader ( programObject, fragmentShader );
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glBindAttribLocation ( programObject, 0, "vPosition" );
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glLinkProgram ( programObject );
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glGetProgramiv ( programObject, GL_LINK_STATUS, &linked );
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if ( !linked )
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{
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GLint infoLen = 0;
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glGetProgramiv ( programObject, GL_INFO_LOG_LENGTH, &infoLen );
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if ( infoLen > 1 )
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{
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char* infoLog = malloc (sizeof(char) * infoLen );
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glGetProgramInfoLog ( programObject, infoLen, NULL, infoLog );
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printf ( "Error linking program:\n%s\n", infoLog );
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free ( infoLog );
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}
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glDeleteProgram ( programObject );
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return GL_FALSE;
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}
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glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
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return GL_TRUE;
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}
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///
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// Draw a triangle using the shader pair created in Init()
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//
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void Draw ()
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{
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void *buffer;
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GLfloat vVertices[] = { 0.0f, 0.5f, 0.0f,
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-0.5f, -0.5f, 0.0f,
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0.5f, -0.5f, 0.0f };
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// No clientside arrays, so do this in a webgl-friendly manner
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GLuint vertexPosObject;
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glGenBuffers(1, &vertexPosObject);
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glBindBuffer(GL_ARRAY_BUFFER, vertexPosObject);
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glBufferData(GL_ARRAY_BUFFER, sizeof(vVertices), NULL, GL_STATIC_DRAW);
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buffer = glMapBufferRange(
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GL_ARRAY_BUFFER,
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0,
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sizeof(vVertices),
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GL_MAP_FLUSH_EXPLICIT_BIT | GL_MAP_INVALIDATE_BUFFER_BIT | GL_MAP_WRITE_BIT
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);
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if (buffer == NULL) {
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fprintf(stderr, "Could not map buffer: %x\n", glGetError());
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exit(1);
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}
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memcpy(buffer, vVertices, sizeof(vVertices));
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glFlushMappedBufferRange(GL_ARRAY_BUFFER, 0, sizeof(vVertices));
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glUnmapBuffer(GL_ARRAY_BUFFER);
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glViewport ( 0, 0, width, height );
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glClear ( GL_COLOR_BUFFER_BIT );
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glUseProgram ( programObject );
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glBindBuffer(GL_ARRAY_BUFFER, vertexPosObject);
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glVertexAttribPointer(0 /* ? */, 3, GL_FLOAT, 0, 0, 0);
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glEnableVertexAttribArray(0);
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glDrawArrays ( GL_TRIANGLES, 0, 3 );
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}
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void Verify() {
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unsigned char *data = malloc(width*height*4 + 16);
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int *last = (int*)(data + width*height*4 - 4);
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int *after = (int*)(data + width*height*4);
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*last = 0xdeadbeef;
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*after = 0x12345678;
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glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
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assert(*last != 0xdeadbeef); // should overwrite the buffer to the end
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assert(*after == 0x12345678); // nothing should be written afterwards!
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// Should see some blue, and nothing else
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int seen = 0;
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int ok = 1;
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for (int x = 0; x < width*height; x++) {
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seen = seen || data[x*4+2] != 0;
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ok = ok && (data[x*4+0] == 0);
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ok = ok && (data[x*4+1] == 0);
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}
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int result = seen && ok;
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REPORT_RESULT();
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}
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int main(int argc, char *argv[])
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{
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SDL_Surface *screen;
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if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
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printf("Unable to initialize SDL: %s\n", SDL_GetError());
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return 1;
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}
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screen = SDL_SetVideoMode(width, height, 32, SDL_OPENGL);
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if (!screen) {
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printf("Unable to set video mode: %s\n", SDL_GetError());
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return 1;
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}
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Init();
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Draw();
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Verify();
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return 0;
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}
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