501 lines
15 KiB
C
Executable File
501 lines
15 KiB
C
Executable File
/*
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Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely.
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*/
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/* This is a simple example of using GLSL shaders with SDL */
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#include "SDL.h"
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#ifdef HAVE_OPENGL
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#include "SDL_opengl.h"
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static SDL_bool shaders_supported;
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static int current_shader = 0;
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enum {
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SHADER_COLOR,
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SHADER_TEXTURE,
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SHADER_TEXCOORDS,
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NUM_SHADERS
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};
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typedef struct {
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GLhandleARB program;
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GLhandleARB vert_shader;
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GLhandleARB frag_shader;
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const char *vert_source;
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const char *frag_source;
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} ShaderData;
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static ShaderData shaders[NUM_SHADERS] = {
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/* SHADER_COLOR */
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{ 0, 0, 0,
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/* vertex shader */
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"varying vec4 v_color;\n"
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"\n"
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"void main()\n"
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"{\n"
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" gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
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" v_color = gl_Color;\n"
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"}",
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/* fragment shader */
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"varying vec4 v_color;\n"
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"\n"
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"void main()\n"
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"{\n"
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" gl_FragColor = v_color;\n"
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"}"
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},
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/* SHADER_TEXTURE */
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{ 0, 0, 0,
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/* vertex shader */
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"varying vec4 v_color;\n"
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"varying vec2 v_texCoord;\n"
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"\n"
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"void main()\n"
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"{\n"
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" gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
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" v_color = gl_Color;\n"
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" v_texCoord = vec2(gl_MultiTexCoord0);\n"
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"}",
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/* fragment shader */
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"varying vec4 v_color;\n"
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"varying vec2 v_texCoord;\n"
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"uniform sampler2D tex0;\n"
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"\n"
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"void main()\n"
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"{\n"
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" gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
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"}"
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},
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/* SHADER_TEXCOORDS */
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{ 0, 0, 0,
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/* vertex shader */
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"varying vec2 v_texCoord;\n"
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"\n"
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"void main()\n"
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"{\n"
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" gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
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" v_texCoord = vec2(gl_MultiTexCoord0);\n"
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"}",
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/* fragment shader */
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"varying vec2 v_texCoord;\n"
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"\n"
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"void main()\n"
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"{\n"
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" vec4 color;\n"
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" vec2 delta;\n"
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" float dist;\n"
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"\n"
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" delta = vec2(0.5, 0.5) - v_texCoord;\n"
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" dist = dot(delta, delta);\n"
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"\n"
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" color.r = v_texCoord.x;\n"
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" color.g = v_texCoord.x * v_texCoord.y;\n"
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" color.b = v_texCoord.y;\n"
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" color.a = 1.0 - (dist * 4.0);\n"
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" gl_FragColor = color;\n"
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"}"
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},
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};
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static PFNGLATTACHOBJECTARBPROC glAttachObjectARB;
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static PFNGLCOMPILESHADERARBPROC glCompileShaderARB;
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static PFNGLCREATEPROGRAMOBJECTARBPROC glCreateProgramObjectARB;
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static PFNGLCREATESHADEROBJECTARBPROC glCreateShaderObjectARB;
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static PFNGLDELETEOBJECTARBPROC glDeleteObjectARB;
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static PFNGLGETINFOLOGARBPROC glGetInfoLogARB;
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static PFNGLGETOBJECTPARAMETERIVARBPROC glGetObjectParameterivARB;
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static PFNGLGETUNIFORMLOCATIONARBPROC glGetUniformLocationARB;
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static PFNGLLINKPROGRAMARBPROC glLinkProgramARB;
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static PFNGLSHADERSOURCEARBPROC glShaderSourceARB;
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static PFNGLUNIFORM1IARBPROC glUniform1iARB;
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static PFNGLUSEPROGRAMOBJECTARBPROC glUseProgramObjectARB;
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static SDL_bool CompileShader(GLhandleARB shader, const char *source)
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{
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GLint status;
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glShaderSourceARB(shader, 1, &source, NULL);
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glCompileShaderARB(shader);
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glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
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if (status == 0) {
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GLint length;
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char *info;
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glGetObjectParameterivARB(shader, GL_OBJECT_INFO_LOG_LENGTH_ARB, &length);
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info = SDL_stack_alloc(char, length+1);
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glGetInfoLogARB(shader, length, NULL, info);
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to compile shader:\n%s\n%s", source, info);
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SDL_stack_free(info);
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return SDL_FALSE;
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} else {
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return SDL_TRUE;
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}
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}
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static SDL_bool CompileShaderProgram(ShaderData *data)
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{
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const int num_tmus_bound = 4;
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int i;
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GLint location;
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glGetError();
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/* Create one program object to rule them all */
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data->program = glCreateProgramObjectARB();
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/* Create the vertex shader */
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data->vert_shader = glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
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if (!CompileShader(data->vert_shader, data->vert_source)) {
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return SDL_FALSE;
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}
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/* Create the fragment shader */
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data->frag_shader = glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
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if (!CompileShader(data->frag_shader, data->frag_source)) {
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return SDL_FALSE;
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}
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/* ... and in the darkness bind them */
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glAttachObjectARB(data->program, data->vert_shader);
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glAttachObjectARB(data->program, data->frag_shader);
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glLinkProgramARB(data->program);
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/* Set up some uniform variables */
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glUseProgramObjectARB(data->program);
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for (i = 0; i < num_tmus_bound; ++i) {
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char tex_name[5];
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SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
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location = glGetUniformLocationARB(data->program, tex_name);
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if (location >= 0) {
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glUniform1iARB(location, i);
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}
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}
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glUseProgramObjectARB(0);
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return (glGetError() == GL_NO_ERROR) ? SDL_TRUE : SDL_FALSE;
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}
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static void DestroyShaderProgram(ShaderData *data)
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{
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if (shaders_supported) {
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glDeleteObjectARB(data->vert_shader);
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glDeleteObjectARB(data->frag_shader);
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glDeleteObjectARB(data->program);
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}
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}
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static SDL_bool InitShaders()
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{
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int i;
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/* Check for shader support */
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shaders_supported = SDL_FALSE;
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if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
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SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
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SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
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SDL_GL_ExtensionSupported("GL_ARB_fragment_shader")) {
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glAttachObjectARB = (PFNGLATTACHOBJECTARBPROC) SDL_GL_GetProcAddress("glAttachObjectARB");
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glCompileShaderARB = (PFNGLCOMPILESHADERARBPROC) SDL_GL_GetProcAddress("glCompileShaderARB");
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glCreateProgramObjectARB = (PFNGLCREATEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glCreateProgramObjectARB");
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glCreateShaderObjectARB = (PFNGLCREATESHADEROBJECTARBPROC) SDL_GL_GetProcAddress("glCreateShaderObjectARB");
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glDeleteObjectARB = (PFNGLDELETEOBJECTARBPROC) SDL_GL_GetProcAddress("glDeleteObjectARB");
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glGetInfoLogARB = (PFNGLGETINFOLOGARBPROC) SDL_GL_GetProcAddress("glGetInfoLogARB");
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glGetObjectParameterivARB = (PFNGLGETOBJECTPARAMETERIVARBPROC) SDL_GL_GetProcAddress("glGetObjectParameterivARB");
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glGetUniformLocationARB = (PFNGLGETUNIFORMLOCATIONARBPROC) SDL_GL_GetProcAddress("glGetUniformLocationARB");
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glLinkProgramARB = (PFNGLLINKPROGRAMARBPROC) SDL_GL_GetProcAddress("glLinkProgramARB");
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glShaderSourceARB = (PFNGLSHADERSOURCEARBPROC) SDL_GL_GetProcAddress("glShaderSourceARB");
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glUniform1iARB = (PFNGLUNIFORM1IARBPROC) SDL_GL_GetProcAddress("glUniform1iARB");
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glUseProgramObjectARB = (PFNGLUSEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glUseProgramObjectARB");
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if (glAttachObjectARB &&
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glCompileShaderARB &&
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glCreateProgramObjectARB &&
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glCreateShaderObjectARB &&
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glDeleteObjectARB &&
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glGetInfoLogARB &&
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glGetObjectParameterivARB &&
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glGetUniformLocationARB &&
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glLinkProgramARB &&
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glShaderSourceARB &&
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glUniform1iARB &&
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glUseProgramObjectARB) {
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shaders_supported = SDL_TRUE;
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}
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}
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if (!shaders_supported) {
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return SDL_FALSE;
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}
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/* Compile all the shaders */
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for (i = 0; i < NUM_SHADERS; ++i) {
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if (!CompileShaderProgram(&shaders[i])) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to compile shader!\n");
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return SDL_FALSE;
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}
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}
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/* We're done! */
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return SDL_TRUE;
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}
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static void QuitShaders()
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{
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int i;
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for (i = 0; i < NUM_SHADERS; ++i) {
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DestroyShaderProgram(&shaders[i]);
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}
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}
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/* Quick utility function for texture creation */
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static int
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power_of_two(int input)
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{
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int value = 1;
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while (value < input) {
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value <<= 1;
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}
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return value;
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}
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GLuint
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SDL_GL_LoadTexture(SDL_Surface * surface, GLfloat * texcoord)
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{
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GLuint texture;
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int w, h;
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SDL_Surface *image;
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SDL_Rect area;
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SDL_BlendMode saved_mode;
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/* Use the surface width and height expanded to powers of 2 */
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w = power_of_two(surface->w);
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h = power_of_two(surface->h);
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texcoord[0] = 0.0f; /* Min X */
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texcoord[1] = 0.0f; /* Min Y */
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texcoord[2] = (GLfloat) surface->w / w; /* Max X */
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texcoord[3] = (GLfloat) surface->h / h; /* Max Y */
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image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 32,
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#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
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0x000000FF,
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0x0000FF00, 0x00FF0000, 0xFF000000
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#else
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0xFF000000,
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0x00FF0000, 0x0000FF00, 0x000000FF
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#endif
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);
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if (image == NULL) {
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return 0;
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}
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/* Save the alpha blending attributes */
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SDL_GetSurfaceBlendMode(surface, &saved_mode);
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SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE);
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/* Copy the surface into the GL texture image */
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area.x = 0;
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area.y = 0;
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area.w = surface->w;
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area.h = surface->h;
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SDL_BlitSurface(surface, &area, image, &area);
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/* Restore the alpha blending attributes */
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SDL_SetSurfaceBlendMode(surface, saved_mode);
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/* Create an OpenGL texture for the image */
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glGenTextures(1, &texture);
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glBindTexture(GL_TEXTURE_2D, texture);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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glTexImage2D(GL_TEXTURE_2D,
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0,
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GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
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SDL_FreeSurface(image); /* No longer needed */
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return texture;
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}
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/* A general OpenGL initialization function. Sets all of the initial parameters. */
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void InitGL(int Width, int Height) /* We call this right after our OpenGL window is created. */
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{
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GLdouble aspect;
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glViewport(0, 0, Width, Height);
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glClearColor(0.0f, 0.0f, 0.0f, 0.0f); /* This Will Clear The Background Color To Black */
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glClearDepth(1.0); /* Enables Clearing Of The Depth Buffer */
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glDepthFunc(GL_LESS); /* The Type Of Depth Test To Do */
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glEnable(GL_DEPTH_TEST); /* Enables Depth Testing */
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glShadeModel(GL_SMOOTH); /* Enables Smooth Color Shading */
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity(); /* Reset The Projection Matrix */
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aspect = (GLdouble)Width / Height;
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glOrtho(-3.0, 3.0, -3.0 / aspect, 3.0 / aspect, 0.0, 1.0);
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glMatrixMode(GL_MODELVIEW);
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}
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/* The main drawing function. */
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void DrawGLScene(SDL_Window *window, GLuint texture, GLfloat * texcoord)
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{
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/* Texture coordinate lookup, to make it simple */
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enum {
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MINX,
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MINY,
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MAXX,
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MAXY
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};
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glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); /* Clear The Screen And The Depth Buffer */
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glLoadIdentity(); /* Reset The View */
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glTranslatef(-1.5f,0.0f,0.0f); /* Move Left 1.5 Units */
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/* draw a triangle (in smooth coloring mode) */
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glBegin(GL_POLYGON); /* start drawing a polygon */
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glColor3f(1.0f,0.0f,0.0f); /* Set The Color To Red */
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glVertex3f( 0.0f, 1.0f, 0.0f); /* Top */
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glColor3f(0.0f,1.0f,0.0f); /* Set The Color To Green */
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glVertex3f( 1.0f,-1.0f, 0.0f); /* Bottom Right */
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glColor3f(0.0f,0.0f,1.0f); /* Set The Color To Blue */
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glVertex3f(-1.0f,-1.0f, 0.0f); /* Bottom Left */
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glEnd(); /* we're done with the polygon (smooth color interpolation) */
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glTranslatef(3.0f,0.0f,0.0f); /* Move Right 3 Units */
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/* Enable blending */
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glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
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glEnable(GL_BLEND);
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glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
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/* draw a textured square (quadrilateral) */
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glEnable(GL_TEXTURE_2D);
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glBindTexture(GL_TEXTURE_2D, texture);
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glColor3f(1.0f,1.0f,1.0f);
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if (shaders_supported) {
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glUseProgramObjectARB(shaders[current_shader].program);
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}
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glBegin(GL_QUADS); /* start drawing a polygon (4 sided) */
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glTexCoord2f(texcoord[MINX], texcoord[MINY]);
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glVertex3f(-1.0f, 1.0f, 0.0f); /* Top Left */
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glTexCoord2f(texcoord[MAXX], texcoord[MINY]);
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glVertex3f( 1.0f, 1.0f, 0.0f); /* Top Right */
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glTexCoord2f(texcoord[MAXX], texcoord[MAXY]);
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glVertex3f( 1.0f,-1.0f, 0.0f); /* Bottom Right */
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glTexCoord2f(texcoord[MINX], texcoord[MAXY]);
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glVertex3f(-1.0f,-1.0f, 0.0f); /* Bottom Left */
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glEnd(); /* done with the polygon */
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if (shaders_supported) {
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glUseProgramObjectARB(0);
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}
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glDisable(GL_TEXTURE_2D);
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/* swap buffers to display, since we're double buffered. */
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SDL_GL_SwapWindow(window);
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}
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int main(int argc, char **argv)
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{
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int done;
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SDL_Window *window;
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SDL_Surface *surface;
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GLuint texture;
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GLfloat texcoords[4];
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/* Enable standard application logging */
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SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
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/* Initialize SDL for video output */
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if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to initialize SDL: %s\n", SDL_GetError());
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exit(1);
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}
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/* Create a 640x480 OpenGL screen */
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window = SDL_CreateWindow( "Shader Demo", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL );
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if ( !window ) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL window: %s\n", SDL_GetError());
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SDL_Quit();
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exit(2);
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}
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if ( !SDL_GL_CreateContext(window)) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL context: %s\n", SDL_GetError());
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SDL_Quit();
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exit(2);
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}
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surface = SDL_LoadBMP("icon.bmp");
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if ( ! surface ) {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to load icon.bmp: %s\n", SDL_GetError());
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SDL_Quit();
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exit(3);
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}
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texture = SDL_GL_LoadTexture(surface, texcoords);
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SDL_FreeSurface(surface);
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/* Loop, drawing and checking events */
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InitGL(640, 480);
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if (InitShaders()) {
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SDL_Log("Shaders supported, press SPACE to cycle them.\n");
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} else {
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SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Shaders not supported!\n");
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}
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done = 0;
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while ( ! done ) {
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DrawGLScene(window, texture, texcoords);
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/* This could go in a separate function */
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{ SDL_Event event;
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while ( SDL_PollEvent(&event) ) {
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if ( event.type == SDL_QUIT ) {
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done = 1;
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}
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if ( event.type == SDL_KEYDOWN ) {
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if ( event.key.keysym.sym == SDLK_SPACE ) {
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current_shader = (current_shader + 1) % NUM_SHADERS;
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|
}
|
|
if ( event.key.keysym.sym == SDLK_ESCAPE ) {
|
|
done = 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
QuitShaders();
|
|
SDL_Quit();
|
|
return 1;
|
|
}
|
|
|
|
#else /* HAVE_OPENGL */
|
|
|
|
int
|
|
main(int argc, char *argv[])
|
|
{
|
|
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "No OpenGL support on this system\n");
|
|
return 1;
|
|
}
|
|
|
|
#endif /* HAVE_OPENGL */
|
|
|
|
/* vi: set ts=4 sw=4 expandtab: */
|