| /******************************************************************* |
| * * |
| * Using SDL With OpenGL * |
| * * |
| * Tutorial by Kyle Foley (sdw) * |
| * * |
| * http://gpwiki.org/index.php/SDL:Tutorials:Using_SDL_with_OpenGL * |
| * * |
| *******************************************************************/ |
| |
| /* |
| THIS WORK, INCLUDING THE SOURCE CODE, DOCUMENTATION |
| AND RELATED MEDIA AND DATA, IS PLACED INTO THE PUBLIC DOMAIN. |
| |
| THE ORIGINAL AUTHOR IS KYLE FOLEY. |
| |
| THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY |
| OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF |
| MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE, |
| ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE |
| RESULTING FROM THE USE, MODIFICATION, OR |
| REDISTRIBUTION OF THIS SOFTWARE. |
| */ |
| |
| #ifndef __EMSCRIPTEN__ |
| #define USE_GLEW 1 |
| #endif |
| |
| #if USE_GLEW |
| #include "GL/glew.h" |
| #endif |
| |
| #include "SDL/SDL.h" |
| #include "SDL/SDL_image.h" |
| #if !USE_GLEW |
| #include "SDL/SDL_opengl.h" |
| #endif |
| |
| #include <stdio.h> |
| #include <string.h> |
| #include <assert.h> |
| |
| void shaders() { |
| #if USE_GLEW |
| glewInit(); |
| #endif |
| |
| GLint ok; |
| |
| const char *vertexShader = "void main(void) \n" |
| "{ \n" |
| " gl_Position = ftransform(); \n" |
| " gl_TexCoord[0] = gl_MultiTexCoord0; \n" |
| " gl_FrontColor = gl_Color; \n" |
| "} \n"; |
| const char *fragmentShader = "uniform sampler2D tex0; \n" |
| "void main(void) \n" |
| "{ \n" |
| " gl_FragColor = gl_Color * texture2D(tex0, gl_TexCoord[0].xy); \n" |
| "} \n"; |
| |
| GLuint vs = glCreateShader(GL_VERTEX_SHADER); |
| glShaderSource(vs, 1, &vertexShader, NULL); |
| glCompileShader(vs); |
| glGetShaderiv(vs, GL_COMPILE_STATUS, &ok); |
| assert(ok); |
| |
| GLuint fs = glCreateShader(GL_FRAGMENT_SHADER); |
| glShaderSource(fs, 1, &fragmentShader, NULL); |
| glCompileShader(fs); |
| glGetShaderiv(fs, GL_COMPILE_STATUS, &ok); |
| assert(ok); |
| |
| GLuint program = glCreateProgram(); |
| |
| glAttachShader(program, vs); |
| glAttachShader(program, fs); |
| glLinkProgram(program); |
| glGetProgramiv(program, GL_LINK_STATUS, &ok); |
| assert(ok); |
| assert(glIsProgram(program)); |
| assert(!glIsProgram(0)); |
| assert(!glIsProgram(program+1)); // a number that can't be a real shader |
| |
| glUseProgram(program); |
| |
| { |
| // Also, check getting the error log |
| const char *fakeVertexShader = "atbute ve4 blarg; ### AAA\n"; |
| GLuint vs = glCreateShader(GL_VERTEX_SHADER); |
| glShaderSource(vs, 1, &fakeVertexShader, NULL); |
| glCompileShader(vs); |
| glGetShaderiv(vs, GL_COMPILE_STATUS, &ok); |
| assert(!ok); |
| GLint infoLen = 0; |
| glGetShaderiv(vs, GL_INFO_LOG_LENGTH, &infoLen); |
| assert(infoLen > 1); |
| } |
| } |
| |
| int main(int argc, char *argv[]) |
| { |
| SDL_Surface *screen; |
| |
| // Slightly different SDL initialization |
| if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) { |
| printf("Unable to initialize SDL: %s\n", SDL_GetError()); |
| return 1; |
| } |
| |
| SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new* |
| |
| screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL ); // *changed* |
| if ( !screen ) { |
| printf("Unable to set video mode: %s\n", SDL_GetError()); |
| return 1; |
| } |
| |
| // Set the OpenGL state after creating the context with SDL_SetVideoMode |
| |
| glClearColor( 0, 0, 0, 0 ); |
| |
| #ifndef __EMSCRIPTEN__ |
| glEnable( GL_TEXTURE_2D ); // Need this to display a texture XXX unnecessary in OpenGL ES 2.0/WebGL |
| #endif |
| |
| glViewport( 0, 0, 640, 480 ); |
| |
| glMatrixMode( GL_PROJECTION ); |
| GLfloat matrixData[] = { 2.0/640, 0, 0, 0, |
| 0, -2.0/480, 0, 0, |
| 0, 0, -1, 0, |
| -1, 1, 0, 1 }; |
| glLoadMatrixf(matrixData); // test loadmatrix |
| |
| glMatrixMode( GL_MODELVIEW ); |
| glLoadIdentity(); |
| |
| // Load the OpenGL texture |
| |
| GLuint texture; // Texture object handle |
| SDL_Surface *surface; // Gives us the information to make the texture |
| |
| if ( (surface = IMG_Load("screenshot.png")) ) { |
| |
| // Check that the image's width is a power of 2 |
| if ( (surface->w & (surface->w - 1)) != 0 ) { |
| printf("warning: image.bmp's width is not a power of 2\n"); |
| } |
| |
| // Also check if the height is a power of 2 |
| if ( (surface->h & (surface->h - 1)) != 0 ) { |
| printf("warning: image.bmp's height is not a power of 2\n"); |
| } |
| |
| // Have OpenGL generate a texture object handle for us |
| glGenTextures( 1, &texture ); |
| |
| // Bind the texture object |
| glBindTexture( GL_TEXTURE_2D, texture ); |
| |
| // Set the texture's stretching properties |
| glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR ); |
| glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); |
| |
| //SDL_LockSurface(surface); |
| |
| // Add some greyness |
| memset(surface->pixels, 0x66, surface->w*surface->h); |
| |
| // Edit the texture object's image data using the information SDL_Surface gives us |
| glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, surface->w, surface->h, 0, |
| GL_RGBA, GL_UNSIGNED_BYTE, surface->pixels ); |
| |
| //SDL_UnlockSurface(surface); |
| } |
| else { |
| printf("SDL could not load image.bmp: %s\n", SDL_GetError()); |
| SDL_Quit(); |
| return 1; |
| } |
| |
| // Free the SDL_Surface only if it was successfully created |
| if ( surface ) { |
| SDL_FreeSurface( surface ); |
| } |
| |
| // Clear the screen before drawing |
| glClear( GL_COLOR_BUFFER_BIT ); |
| |
| shaders(); |
| |
| // Bind the texture to which subsequent calls refer to |
| glBindTexture( GL_TEXTURE_2D, texture ); |
| |
| // Use clientside vertex pointers to render two items |
| GLfloat vertexData[] = { 0, 0, 10, 10, // texture2, position2 |
| 1, 0, 300, 10, |
| 1, 1, 300, 128, |
| 0, 1, 10, 128, |
| 0, 0.5, 410, 10, |
| 1, 0.5, 600, 10, |
| 1, 1, 630, 200, |
| 0.5, 1, 310, 250, |
| 0, 0, 100, 300, |
| 1, 0, 300, 300, |
| 1, 1, 300, 400, |
| 0, 1, 100, 400 }; |
| |
| glEnableClientState(GL_TEXTURE_COORD_ARRAY); |
| glTexCoordPointer(2, GL_FLOAT, 4*4, &vertexData[0]); |
| glEnableClientState(GL_VERTEX_ARRAY); |
| glVertexPointer(2, GL_FLOAT, 4*4, &vertexData[2]); |
| |
| glDrawArrays(GL_QUADS, 0, 12); |
| |
| glDisableClientState(GL_TEXTURE_COORD_ARRAY); |
| glDisableClientState(GL_VERTEX_ARRAY); |
| |
| SDL_GL_SwapBuffers(); |
| |
| #ifndef __EMSCRIPTEN__ |
| // Wait for 3 seconds to give us a chance to see the image |
| SDL_Delay(3000); |
| #endif |
| |
| // Now we can delete the OpenGL texture and close down SDL |
| glDeleteTextures( 1, &texture ); |
| |
| SDL_Quit(); |
| |
| return 0; |
| } |