Add basic testgles2_sdf program to demonstrate sign distance field with opengles2

test/Makefile.in

@@ -170,6 +170,9 @@ testgles$(EXE): $(srcdir)/testgles.c
 testgles2$(EXE): $(srcdir)/testgles2.c
 	$(CC) -o $@ $^ $(CFLAGS) $(LIBS) @MATHLIB@
 
+testgles2_sdf$(EXE): $(srcdir)/testgles2_sdf.c
+	$(CC) -o $@ $^ $(CFLAGS) $(LIBS) @MATHLIB@
+
 testhaptic$(EXE): $(srcdir)/testhaptic.c
 	$(CC) -o $@ $^ $(CFLAGS) $(LIBS)
 

test/testgles2_sdf.c

@@ -0,0 +1,802 @@
+/*
+  Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely.
+*/
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+#ifdef __EMSCRIPTEN__
+#include <emscripten/emscripten.h>
+#endif
+
+#include "SDL_test_common.h"
+
+#if defined(__IPHONEOS__) || defined(__ANDROID__) || defined(__EMSCRIPTEN__) || defined(__NACL__) \
+    || defined(__WINDOWS__) || defined(__LINUX__)
+#define HAVE_OPENGLES2
+#endif
+
+#ifdef HAVE_OPENGLES2
+
+#include "SDL_opengles2.h"
+
+typedef struct GLES2_Context
+{
+#define SDL_PROC(ret,func,params) ret (APIENTRY *func) params;
+#include "../src/render/opengles2/SDL_gles2funcs.h"
+#undef SDL_PROC
+} GLES2_Context;
+
+
+static SDL_Surface *g_surf_sdf = NULL;
+GLenum g_texture;
+GLenum g_texture_type = GL_TEXTURE_2D;
+GLfloat g_verts[24];
+typedef enum
+{
+    GLES2_ATTRIBUTE_POSITION = 0,
+    GLES2_ATTRIBUTE_TEXCOORD = 1,
+    GLES2_ATTRIBUTE_ANGLE = 2,
+    GLES2_ATTRIBUTE_CENTER = 3,
+} GLES2_Attribute;
+
+typedef enum
+{
+    GLES2_UNIFORM_PROJECTION,
+    GLES2_UNIFORM_TEXTURE,
+    GLES2_UNIFORM_COLOR,
+} GLES2_Uniform;
+
+
+GLuint g_uniform_locations[16];
+
+
+
+static SDLTest_CommonState *state;
+static SDL_GLContext *context = NULL;
+static int depth = 16;
+static GLES2_Context ctx;
+
+static int LoadContext(GLES2_Context * data)
+{
+#if SDL_VIDEO_DRIVER_UIKIT
+#define __SDL_NOGETPROCADDR__
+#elif SDL_VIDEO_DRIVER_ANDROID
+#define __SDL_NOGETPROCADDR__
+#elif SDL_VIDEO_DRIVER_PANDORA
+#define __SDL_NOGETPROCADDR__
+#endif
+
+#if defined __SDL_NOGETPROCADDR__
+#define SDL_PROC(ret,func,params) data->func=func;
+#else
+#define SDL_PROC(ret,func,params) \
+    do { \
+        data->func = SDL_GL_GetProcAddress(#func); \
+        if ( ! data->func ) { \
+            return SDL_SetError("Couldn't load GLES2 function %s: %s", #func, SDL_GetError()); \
+        } \
+    } while ( 0 );
+#endif /* __SDL_NOGETPROCADDR__ */
+
+#include "../src/render/opengles2/SDL_gles2funcs.h"
+#undef SDL_PROC
+    return 0;
+}
+
+/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
+static void
+quit(int rc)
+{
+    int i;
+
+    if (context != NULL) {
+        for (i = 0; i < state->num_windows; i++) {
+            if (context[i]) {
+                SDL_GL_DeleteContext(context[i]);
+            }
+        }
+
+        SDL_free(context);
+    }
+
+    SDLTest_CommonQuit(state);
+    exit(rc);
+}
+
+#define GL_CHECK(x) \
+        x; \
+        { \
+          GLenum glError = ctx.glGetError(); \
+          if(glError != GL_NO_ERROR) { \
+            SDL_Log("glGetError() = %i (0x%.8x) at line %i\n", glError, glError, __LINE__); \
+            quit(1); \
+          } \
+        }
+
+
+/* 
+ * Create shader, load in source, compile, dump debug as necessary.
+ *
+ * shader: Pointer to return created shader ID.
+ * source: Passed-in shader source code.
+ * shader_type: Passed to GL, e.g. GL_VERTEX_SHADER.
+ */
+void 
+process_shader(GLuint *shader, const char * source, GLint shader_type)
+{
+    GLint status = GL_FALSE;
+    const char *shaders[1] = { NULL };
+    char buffer[1024];
+    GLsizei length;
+
+    /* Create shader and load into GL. */
+    *shader = GL_CHECK(ctx.glCreateShader(shader_type));
+
+    shaders[0] = source;
+
+    GL_CHECK(ctx.glShaderSource(*shader, 1, shaders, NULL));
+
+    /* Clean up shader source. */
+    shaders[0] = NULL;
+
+    /* Try compiling the shader. */
+    GL_CHECK(ctx.glCompileShader(*shader));
+    GL_CHECK(ctx.glGetShaderiv(*shader, GL_COMPILE_STATUS, &status));
+
+    /* Dump debug info (source and log) if compilation failed. */
+    if(status != GL_TRUE) {
+        ctx.glGetProgramInfoLog(*shader, sizeof(buffer), &length, &buffer[0]);
+        buffer[length] = '\0';
+        SDL_Log("Shader compilation failed: %s", buffer);fflush(stderr);
+        quit(-1);
+    }
+}
+
+/* Notes on a_angle:
+   * It is a vector containing sin and cos for rotation matrix
+   * To get correct rotation for most cases when a_angle is disabled cos
+     value is decremented by 1.0 to get proper output with 0.0 which is
+     default value
+*/
+static const Uint8 GLES2_VertexSrc_Default_[] = " \
+    uniform mat4 u_projection; \
+    attribute vec2 a_position; \
+    attribute vec2 a_texCoord; \
+    attribute vec2 a_angle; \
+    attribute vec2 a_center; \
+    varying vec2 v_texCoord; \
+    \
+    void main() \
+    { \
+        float s = a_angle[0]; \
+        float c = a_angle[1] + 1.0; \
+        mat2 rotationMatrix = mat2(c, -s, s, c); \
+        vec2 position = rotationMatrix * (a_position - a_center) + a_center; \
+        v_texCoord = a_texCoord; \
+        gl_Position = u_projection * vec4(position, 0.0, 1.0);\
+        gl_PointSize = 1.0; \
+    } \
+";
+
+static const Uint8 GLES2_FragmentSrc_TextureABGRSrc_[] = " \
+    precision mediump float; \
+    uniform sampler2D u_texture; \
+    uniform vec4 u_color; \
+    varying vec2 v_texCoord; \
+    \
+    void main() \
+    { \
+        gl_FragColor = texture2D(u_texture, v_texCoord); \
+        gl_FragColor *= u_color; \
+    } \
+";
+
+/* RGB to ABGR conversion */
+static const Uint8 GLES2_FragmentSrc_TextureABGRSrc_SDF[] = " \
+    #extension GL_OES_standard_derivatives : enable\n\
+    \
+    precision mediump float; \
+    uniform sampler2D u_texture; \
+    uniform vec4 u_color; \
+    varying vec2 v_texCoord; \
+    \
+    void main() \
+    { \
+        vec4 abgr = texture2D(u_texture, v_texCoord); \
+\
+        float sigDist = abgr.a; \
+        \
+        float w = fwidth( sigDist );\
+        float alpha = clamp(smoothstep(0.5 - w, 0.5 + w, sigDist), 0.0, 1.0); \
+\
+        gl_FragColor = vec4(abgr.rgb, abgr.a * alpha); \
+        gl_FragColor.rgb *= gl_FragColor.a; \
+        gl_FragColor *= u_color; \
+    } \
+";
+
+/* RGB to ABGR conversion DEBUG */
+static const char *GLES2_FragmentSrc_TextureABGRSrc_SDF_dbg = " \
+    #extension GL_OES_standard_derivatives : enable\n\
+    \
+    precision mediump float; \
+    uniform sampler2D u_texture; \
+    uniform vec4 u_color; \
+    varying vec2 v_texCoord; \
+    \
+    void main() \
+    { \
+        vec4 abgr = texture2D(u_texture, v_texCoord); \
+\
+        float a = abgr.a; \
+        gl_FragColor = vec4(a, a, a, 1.0); \
+    } \
+";
+
+
+static float g_val = 1.0f;
+static int   g_use_SDF = 1;
+static int   g_use_SDF_debug = 0;
+static float g_angle = 0.0f;
+static float matrix_mvp[4][4];
+
+
+
+
+typedef struct shader_data
+{
+    GLuint shader_program, shader_frag, shader_vert;
+
+    GLint attr_position;
+    GLint attr_color, attr_mvp;
+
+} shader_data;
+
+static void
+Render(unsigned int width, unsigned int height, shader_data* data)
+{
+    ctx.glViewport(0, 0, 640, 480);
+
+    GL_CHECK(ctx.glClear(GL_COLOR_BUFFER_BIT));
+
+    GL_CHECK(ctx.glUniformMatrix4fv(g_uniform_locations[GLES2_UNIFORM_PROJECTION], 1, GL_FALSE, (const float *)matrix_mvp));
+    GL_CHECK(ctx.glUniform4f(g_uniform_locations[GLES2_UNIFORM_COLOR], 1.0f, 1.0f, 1.0f, 1.0f));
+
+    float *verts = g_verts;
+
+    GL_CHECK(ctx.glVertexAttribPointer(GLES2_ATTRIBUTE_ANGLE,    2, GL_FLOAT, GL_FALSE, 0, (const GLvoid *) (verts + 16)));
+    GL_CHECK(ctx.glVertexAttribPointer(GLES2_ATTRIBUTE_TEXCOORD, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid *) (verts + 8)));
+    GL_CHECK(ctx.glVertexAttribPointer(GLES2_ATTRIBUTE_POSITION, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid *) verts));
+
+    GL_CHECK(ctx.glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
+}
+
+
+void renderCopy_angle(float degree_angle) 
+{
+    const float radian_angle = (float)(3.141592 * degree_angle) / 180.0;
+    const GLfloat s = (GLfloat) SDL_sin(radian_angle);
+    const GLfloat c = (GLfloat) SDL_cos(radian_angle) - 1.0f;
+    GLfloat *verts = g_verts + 16;
+    *(verts++) = s;
+    *(verts++) = c;
+    *(verts++) = s;
+    *(verts++) = c;
+    *(verts++) = s;
+    *(verts++) = c;
+    *(verts++) = s;
+    *(verts++) = c;
+}
+
+
+void renderCopy_position(SDL_Rect *srcrect, SDL_Rect *dstrect) 
+{
+    GLfloat minx, miny, maxx, maxy;
+    GLfloat minu, maxu, minv, maxv;
+    GLfloat *verts = g_verts;
+
+    minx = dstrect->x;
+    miny = dstrect->y;
+    maxx = dstrect->x + dstrect->w;
+    maxy = dstrect->y + dstrect->h;
+
+    minu = (GLfloat) srcrect->x / g_surf_sdf->w;
+    maxu = (GLfloat) (srcrect->x + srcrect->w) / g_surf_sdf->w;
+    minv = (GLfloat) srcrect->y / g_surf_sdf->h;
+    maxv = (GLfloat) (srcrect->y + srcrect->h) / g_surf_sdf->h;
+
+    *(verts++) = minx;
+    *(verts++) = miny;
+    *(verts++) = maxx;
+    *(verts++) = miny;
+    *(verts++) = minx;
+    *(verts++) = maxy;
+    *(verts++) = maxx;
+    *(verts++) = maxy;
+
+    *(verts++) = minu;
+    *(verts++) = minv;
+    *(verts++) = maxu;
+    *(verts++) = minv;
+    *(verts++) = minu;
+    *(verts++) = maxv;
+    *(verts++) = maxu;
+    *(verts++) = maxv;
+}
+
+int done;
+Uint32 frames;
+shader_data *datas;
+
+void loop()
+{
+    SDL_Event event;
+    int i;
+    int status;
+
+    /* Check for events */
+    ++frames;
+    while (SDL_PollEvent(&event) && !done) {
+        switch (event.type) {
+        case SDL_KEYDOWN:
+            {
+                const int sym = event.key.keysym.sym;
+
+                if (sym == SDLK_TAB) {
+                    SDL_Log("Tab");
+
+
+                }
+
+
+                if (sym == SDLK_LEFT)  g_val -= 0.05;
+                if (sym == SDLK_RIGHT) g_val += 0.05;
+                if (sym == SDLK_UP)    g_angle -= 1;
+                if (sym == SDLK_DOWN)  g_angle += 1;
+ 
+
+                break;
+            }
+
+        case SDL_WINDOWEVENT:
+            switch (event.window.event) {
+                case SDL_WINDOWEVENT_RESIZED:
+                    for (i = 0; i < state->num_windows; ++i) {
+                        if (event.window.windowID == SDL_GetWindowID(state->windows[i])) {
+                            int w, h;
+                            status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
+                            if (status) {
+                                SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());
+                                break;
+                            }
+                            /* Change view port to the new window dimensions */
+                            SDL_GL_GetDrawableSize(state->windows[i], &w, &h);
+                            ctx.glViewport(0, 0, w, h);
+                            state->window_w = event.window.data1;
+                            state->window_h = event.window.data2;
+                            /* Update window content */
+                            Render(event.window.data1, event.window.data2, &datas[i]);
+                            SDL_GL_SwapWindow(state->windows[i]);
+                            break;
+                        }
+                    }
+                    break;
+            }
+        }
+        SDLTest_CommonEvent(state, &event, &done);
+    }
+
+
+    matrix_mvp[3][0] = -1.0f;
+    matrix_mvp[3][3] = 1.0f;
+
+    matrix_mvp[0][0] = 2.0f / 640.0;
+    matrix_mvp[1][1] = -2.0f / 480.0;
+    matrix_mvp[3][1] = 1.0f;
+    
+    if (0)
+    {
+        float *f = matrix_mvp;
+        SDL_Log("-----------------------------------");
+        SDL_Log("[ %f, %f, %f, %f ]", *f++, *f++, *f++, *f++);
+        SDL_Log("[ %f, %f, %f, %f ]", *f++, *f++, *f++, *f++);
+        SDL_Log("[ %f, %f, %f, %f ]", *f++, *f++, *f++, *f++);
+        SDL_Log("[ %f, %f, %f, %f ]", *f++, *f++, *f++, *f++);
+        SDL_Log("-----------------------------------");
+    }
+
+    renderCopy_angle(g_angle);
+
+    int w, h;
+    SDL_GL_GetDrawableSize(state->windows[0], &w, &h);
+    SDL_Rect rs, rd;
+    rs.x = 0; rs.y = 0; rs.w = g_surf_sdf->w; rs.h = g_surf_sdf->h;
+    rd.w = g_surf_sdf->w * g_val; rd.h = g_surf_sdf->h * g_val;
+    rd.x = (w - rd.w) / 2; rd.y = (h - rd.h) / 2;
+    renderCopy_position(&rs, &rd);
+    
+
+    if (!done) {
+      for (i = 0; i < state->num_windows; ++i) {
+          status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
+          if (status) {
+              SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());
+
+              /* Continue for next window */
+              continue;
+          }
+          Render(state->window_w, state->window_h, &datas[i]);
+          SDL_GL_SwapWindow(state->windows[i]);
+      }
+    }
+#ifdef __EMSCRIPTEN__
+    else {
+        emscripten_cancel_main_loop();
+    }
+#endif
+}
+
+int
+main(int argc, char *argv[])
+{
+    int fsaa, accel;
+    int value;
+    int i;
+    SDL_DisplayMode mode;
+    Uint32 then, now;
+    int status;
+    shader_data *data;
+
+    /* Initialize parameters */
+    fsaa = 0;
+    accel = 0;
+
+    /* Initialize test framework */
+    state = SDLTest_CommonCreateState(argv, SDL_INIT_VIDEO);
+    if (!state) {
+        return 1;
+    }
+    for (i = 1; i < argc;) {
+        int consumed;
+
+        consumed = SDLTest_CommonArg(state, i);
+        if (consumed == 0) {
+            if (SDL_strcasecmp(argv[i], "--fsaa") == 0) {
+                ++fsaa;
+                consumed = 1;
+            } else if (SDL_strcasecmp(argv[i], "--accel") == 0) {
+                ++accel;
+                consumed = 1;
+            } else if (SDL_strcasecmp(argv[i], "--zdepth") == 0) {
+                i++;
+                if (!argv[i]) {
+                    consumed = -1;
+                } else {
+                    depth = SDL_atoi(argv[i]);
+                    consumed = 1;
+                }
+            } else {
+                consumed = -1;
+            }
+        }
+        if (consumed < 0) {
+            static const char *options[] = { "[--fsaa]", "[--accel]", "[--zdepth %d]", NULL };
+            SDLTest_CommonLogUsage(state, argv[0], options);
+            quit(1);
+        }
+        i += consumed;
+    }
+
+    /* Set OpenGL parameters */
+    state->window_flags |= SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE;
+    state->gl_red_size = 5;
+    state->gl_green_size = 5;
+    state->gl_blue_size = 5;
+    state->gl_depth_size = depth;
+    state->gl_major_version = 2;
+    state->gl_minor_version = 0;
+    state->gl_profile_mask = SDL_GL_CONTEXT_PROFILE_ES;
+
+    if (fsaa) {
+        state->gl_multisamplebuffers=1;
+        state->gl_multisamplesamples=fsaa;
+    }
+    if (accel) {
+        state->gl_accelerated=1;
+    }
+    if (!SDLTest_CommonInit(state)) {
+        quit(2);
+        return 0;
+    }
+
+    context = (SDL_GLContext *)SDL_calloc(state->num_windows, sizeof(context));
+    if (context == NULL) {
+        SDL_Log("Out of memory!\n");
+        quit(2);
+    }
+    
+    /* Create OpenGL ES contexts */
+    for (i = 0; i < state->num_windows; i++) {
+        context[i] = SDL_GL_CreateContext(state->windows[i]);
+        if (!context[i]) {
+            SDL_Log("SDL_GL_CreateContext(): %s\n", SDL_GetError());
+            quit(2);
+        }
+    }
+
+    /* Important: call this *after* creating the context */
+    if (LoadContext(&ctx) < 0) {
+        SDL_Log("Could not load GLES2 functions\n");
+        quit(2);
+        return 0;
+    }
+
+    SDL_memset(matrix_mvp, 0, sizeof (matrix_mvp));
+    
+    {
+        char *f;
+        g_use_SDF = 1;
+        g_use_SDF_debug = 0;
+
+        if (g_use_SDF) {
+            f = "testgles2_sdf_img_sdf.bmp";
+        } else {
+            f = "testgles2_sdf_img_normal.bmp";
+        }
+            
+        SDL_Log("SDF is %s", g_use_SDF ? "enabled" : "disabled");
+
+        /* Load SDF BMP image */
+#if 1
+        SDL_Surface *tmp = SDL_LoadBMP(f);
+        if  (tmp == NULL) {
+            SDL_Log("missing image file: %s", f);
+            exit(-1);
+        } else {
+            SDL_Log("Load image file: %s", f);
+        }
+
+#else
+        /* Generate SDF image using SDL_ttf */
+
+        #include "SDL_ttf.h"
+        char *font_file = "./font/DroidSansFallback.ttf";
+        char *str = "Abcde";
+        SDL_Color color = {  0, 0,0,  255};
+
+        TTF_Init();
+        TTF_Font *font = TTF_OpenFont(font_file, 72);
+
+        if (font == NULL) {
+            SDL_Log("Cannot open font %s", font_file);
+        }
+
+        TTF_SetFontSDF(font, g_use_SDF);
+        SDL_Surface *tmp = TTF_RenderUTF8_Blended(font, str, color);
+
+        SDL_Log("err: %s", SDL_GetError());
+        if (tmp == NULL) {
+            SDL_Log("can't render text");
+            return -1;
+        }
+
+        SDL_SaveBMP(tmp, f);
+
+        TTF_CloseFont(font);
+        TTF_Quit();
+#endif
+        g_surf_sdf = SDL_ConvertSurfaceFormat(tmp, SDL_PIXELFORMAT_ABGR8888, 0);
+
+        SDL_SetSurfaceBlendMode(g_surf_sdf, SDL_BLENDMODE_BLEND);
+    }
+
+
+    if (state->render_flags & SDL_RENDERER_PRESENTVSYNC) {
+        SDL_GL_SetSwapInterval(1);
+    } else {
+        SDL_GL_SetSwapInterval(0);
+    }
+
+    SDL_GetCurrentDisplayMode(0, &mode);
+    SDL_Log("Screen bpp: %d\n", SDL_BITSPERPIXEL(mode.format));
+    SDL_Log("\n");
+    SDL_Log("Vendor     : %s\n", ctx.glGetString(GL_VENDOR));
+    SDL_Log("Renderer   : %s\n", ctx.glGetString(GL_RENDERER));
+    SDL_Log("Version    : %s\n", ctx.glGetString(GL_VERSION));
+    SDL_Log("Extensions : %s\n", ctx.glGetString(GL_EXTENSIONS));
+    SDL_Log("\n");
+
+    status = SDL_GL_GetAttribute(SDL_GL_RED_SIZE, &value);
+    if (!status) {
+        SDL_Log("SDL_GL_RED_SIZE: requested %d, got %d\n", 5, value);
+    } else {
+        SDL_Log( "Failed to get SDL_GL_RED_SIZE: %s\n",
+                SDL_GetError());
+    }
+    status = SDL_GL_GetAttribute(SDL_GL_GREEN_SIZE, &value);
+    if (!status) {
+        SDL_Log("SDL_GL_GREEN_SIZE: requested %d, got %d\n", 5, value);
+    } else {
+        SDL_Log( "Failed to get SDL_GL_GREEN_SIZE: %s\n",
+                SDL_GetError());
+    }
+    status = SDL_GL_GetAttribute(SDL_GL_BLUE_SIZE, &value);
+    if (!status) {
+        SDL_Log("SDL_GL_BLUE_SIZE: requested %d, got %d\n", 5, value);
+    } else {
+        SDL_Log( "Failed to get SDL_GL_BLUE_SIZE: %s\n",
+                SDL_GetError());
+    }
+    status = SDL_GL_GetAttribute(SDL_GL_DEPTH_SIZE, &value);
+    if (!status) {
+        SDL_Log("SDL_GL_DEPTH_SIZE: requested %d, got %d\n", depth, value);
+    } else {
+        SDL_Log( "Failed to get SDL_GL_DEPTH_SIZE: %s\n",
+                SDL_GetError());
+    }
+    if (fsaa) {
+        status = SDL_GL_GetAttribute(SDL_GL_MULTISAMPLEBUFFERS, &value);
+        if (!status) {
+            SDL_Log("SDL_GL_MULTISAMPLEBUFFERS: requested 1, got %d\n", value);
+        } else {
+            SDL_Log( "Failed to get SDL_GL_MULTISAMPLEBUFFERS: %s\n",
+                    SDL_GetError());
+        }
+        status = SDL_GL_GetAttribute(SDL_GL_MULTISAMPLESAMPLES, &value);
+        if (!status) {
+            SDL_Log("SDL_GL_MULTISAMPLESAMPLES: requested %d, got %d\n", fsaa,
+                   value);
+        } else {
+            SDL_Log( "Failed to get SDL_GL_MULTISAMPLESAMPLES: %s\n",
+                    SDL_GetError());
+        }
+    }
+    if (accel) {
+        status = SDL_GL_GetAttribute(SDL_GL_ACCELERATED_VISUAL, &value);
+        if (!status) {
+            SDL_Log("SDL_GL_ACCELERATED_VISUAL: requested 1, got %d\n", value);
+        } else {
+            SDL_Log( "Failed to get SDL_GL_ACCELERATED_VISUAL: %s\n",
+                    SDL_GetError());
+        }
+    }
+
+    datas = (shader_data *)SDL_calloc(state->num_windows, sizeof(shader_data));
+
+    /* Set rendering settings for each context */
+    for (i = 0; i < state->num_windows; ++i) {
+
+        int w, h;
+        status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
+        if (status) {
+            SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());
+
+            /* Continue for next window */
+            continue;
+        }
+
+        {
+            int format = GL_RGBA;
+            int type = GL_UNSIGNED_BYTE;
+
+            GL_CHECK(ctx.glGenTextures(1, &g_texture));
+
+            ctx.glActiveTexture(GL_TEXTURE0);
+            ctx.glPixelStorei(GL_PACK_ALIGNMENT, 1);
+            ctx.glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+            ctx.glBindTexture(g_texture_type, g_texture);
+
+            ctx.glTexParameteri(g_texture_type, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+            ctx.glTexParameteri(g_texture_type, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+            ctx.glTexParameteri(g_texture_type, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+            ctx.glTexParameteri(g_texture_type, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+            GL_CHECK(ctx.glTexImage2D(g_texture_type, 0, format, g_surf_sdf->w, g_surf_sdf->h, 0, format, type, NULL));
+            GL_CHECK(ctx.glTexSubImage2D(g_texture_type, 0, 0 /* xoffset */, 0 /* yoffset */, g_surf_sdf->w, g_surf_sdf->h, format, type, g_surf_sdf->pixels));
+        }
+
+
+        SDL_GL_GetDrawableSize(state->windows[i], &w, &h);
+        ctx.glViewport(0, 0, w, h);
+
+        data = &datas[i];
+
+        /* Shader Initialization */
+        process_shader(&data->shader_vert, GLES2_VertexSrc_Default_, GL_VERTEX_SHADER);
+
+        if (g_use_SDF) {
+            if (g_use_SDF_debug == 0) {
+                process_shader(&data->shader_frag, GLES2_FragmentSrc_TextureABGRSrc_SDF, GL_FRAGMENT_SHADER);
+            } else {
+                process_shader(&data->shader_frag, GLES2_FragmentSrc_TextureABGRSrc_SDF_dbg, GL_FRAGMENT_SHADER);
+            }
+        } else {
+            process_shader(&data->shader_frag, GLES2_FragmentSrc_TextureABGRSrc_, GL_FRAGMENT_SHADER);
+        }
+
+        /* Create shader_program (ready to attach shaders) */
+        data->shader_program = GL_CHECK(ctx.glCreateProgram());
+
+        /* Attach shaders and link shader_program */
+        GL_CHECK(ctx.glAttachShader(data->shader_program, data->shader_vert));
+        GL_CHECK(ctx.glAttachShader(data->shader_program, data->shader_frag));
+        GL_CHECK(ctx.glLinkProgram(data->shader_program));
+
+        ctx.glBindAttribLocation(data->shader_program, GLES2_ATTRIBUTE_POSITION, "a_position");
+        ctx.glBindAttribLocation(data->shader_program, GLES2_ATTRIBUTE_TEXCOORD, "a_texCoord");
+        ctx.glBindAttribLocation(data->shader_program, GLES2_ATTRIBUTE_ANGLE, "a_angle");
+        ctx.glBindAttribLocation(data->shader_program, GLES2_ATTRIBUTE_CENTER, "a_center");
+
+        /* Predetermine locations of uniform variables */
+        g_uniform_locations[GLES2_UNIFORM_PROJECTION] = ctx.glGetUniformLocation(data->shader_program, "u_projection");
+        g_uniform_locations[GLES2_UNIFORM_TEXTURE] = ctx.glGetUniformLocation(data->shader_program, "u_texture");
+        g_uniform_locations[GLES2_UNIFORM_COLOR] = ctx.glGetUniformLocation(data->shader_program, "u_color");
+
+        GL_CHECK(ctx.glUseProgram(data->shader_program));
+
+        ctx.glEnableVertexAttribArray((GLenum) GLES2_ATTRIBUTE_ANGLE);
+        ctx.glDisableVertexAttribArray((GLenum) GLES2_ATTRIBUTE_CENTER);
+        ctx.glEnableVertexAttribArray(GLES2_ATTRIBUTE_POSITION);
+        ctx.glEnableVertexAttribArray((GLenum) GLES2_ATTRIBUTE_TEXCOORD);
+
+
+    ctx.glUniform1i(g_uniform_locations[GLES2_UNIFORM_TEXTURE], 0);  /* always texture unit 0. */
+    ctx.glActiveTexture(GL_TEXTURE0);
+    ctx.glBindTexture(g_texture_type, g_texture);
+     GL_CHECK(ctx.glClearColor(1, 1, 1, 1));
+
+    // SDL_BLENDMODE_BLEND
+    GL_CHECK(ctx.glEnable(GL_BLEND));
+    ctx.glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+    ctx.glBlendEquationSeparate(GL_FUNC_ADD, GL_FUNC_ADD);
+
+
+    }
+
+    /* Main render loop */
+    frames = 0;
+    then = SDL_GetTicks();
+    done = 0;
+
+#ifdef __EMSCRIPTEN__
+    emscripten_set_main_loop(loop, 0, 1);
+#else
+    while (!done) {
+        loop();
+    }
+#endif
+
+    /* Print out some timing information */
+    now = SDL_GetTicks();
+    if (now > then) {
+        SDL_Log("%2.2f frames per second\n",
+               ((double) frames * 1000) / (now - then));
+    }
+#if !defined(__ANDROID__) && !defined(__NACL__)  
+    quit(0);
+#endif    
+    return 0;
+}
+
+#else /* HAVE_OPENGLES2 */
+
+int
+main(int argc, char *argv[])
+{
+    SDL_Log("No OpenGL ES support on this system\n");
+    return 1;
+}
+
+#endif /* HAVE_OPENGLES2 */
+
+/* vi: set ts=4 sw=4 expandtab: */