Fixed crash if initialization of EGL failed but was tried again later.

The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().

src/video/emscripten/SDL_emscriptenframebuffer.c

@@ -0,0 +1,136 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2015 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, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "../../SDL_internal.h"
+
+#if SDL_VIDEO_DRIVER_EMSCRIPTEN
+
+#include "SDL_emscriptenvideo.h"
+#include "SDL_emscriptenframebuffer.h"
+
+
+int Emscripten_CreateWindowFramebuffer(_THIS, SDL_Window * window, Uint32 * format, void ** pixels, int *pitch)
+{
+    SDL_Surface *surface;
+    const Uint32 surface_format = SDL_PIXELFORMAT_BGR888;
+    int w, h;
+    int bpp;
+    Uint32 Rmask, Gmask, Bmask, Amask;
+
+    /* Free the old framebuffer surface */
+    SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
+    surface = data->surface;
+    SDL_FreeSurface(surface);
+
+    /* Create a new one */
+    SDL_PixelFormatEnumToMasks(surface_format, &bpp, &Rmask, &Gmask, &Bmask, &Amask);
+    SDL_GetWindowSize(window, &w, &h);
+
+    surface = SDL_CreateRGBSurface(0, w, h, bpp, Rmask, Gmask, Bmask, Amask);
+    if (!surface) {
+        return -1;
+    }
+
+    /* Save the info and return! */
+    data->surface = surface;
+    *format = surface_format;
+    *pixels = surface->pixels;
+    *pitch = surface->pitch;
+    return 0;
+}
+
+int Emscripten_UpdateWindowFramebuffer(_THIS, SDL_Window * window, const SDL_Rect * rects, int numrects)
+{
+    SDL_Surface *surface;
+
+    SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
+    surface = data->surface;
+    if (!surface) {
+        return SDL_SetError("Couldn't find framebuffer surface for window");
+    }
+
+    /* Send the data to the display */
+
+    EM_ASM_INT({
+        //TODO: don't create context every update
+        var ctx = Module['canvas'].getContext('2d');
+
+        //library_sdl.js SDL_UnlockSurface
+        var image = ctx.createImageData($0, $1);
+        var data = image.data;
+        var src = $2 >> 2;
+        var dst = 0;
+        var isScreen = true;
+        var num;
+        if (typeof CanvasPixelArray !== 'undefined' && data instanceof CanvasPixelArray) {
+            // IE10/IE11: ImageData objects are backed by the deprecated CanvasPixelArray,
+            // not UInt8ClampedArray. These don't have buffers, so we need to revert
+            // to copying a byte at a time. We do the undefined check because modern
+            // browsers do not define CanvasPixelArray anymore.
+            num = data.length;
+            while (dst < num) {
+                var val = HEAP32[src]; // This is optimized. Instead, we could do {{{ makeGetValue('buffer', 'dst', 'i32') }}};
+                data[dst  ] = val & 0xff;
+                data[dst+1] = (val >> 8) & 0xff;
+                data[dst+2] = (val >> 16) & 0xff;
+                data[dst+3] = isScreen ? 0xff : ((val >> 24) & 0xff);
+                src++;
+                dst += 4;
+            }
+        } else {
+            var data32 = new Uint32Array(data.buffer);
+            num = data32.length;
+            if (isScreen) {
+                while (dst < num) {
+                    // HEAP32[src++] is an optimization. Instead, we could do {{{ makeGetValue('buffer', 'dst', 'i32') }}};
+                    data32[dst++] = HEAP32[src++] | 0xff000000;
+                }
+            } else {
+                while (dst < num) {
+                    data32[dst++] = HEAP32[src++];
+                }
+            }
+        }
+
+        ctx.putImageData(image, 0, 0);
+        return 0;
+    }, surface->w, surface->h, surface->pixels);
+
+    /*if (SDL_getenv("SDL_VIDEO_Emscripten_SAVE_FRAMES")) {
+        static int frame_number = 0;
+        char file[128];
+        SDL_snprintf(file, sizeof(file), "SDL_window%d-%8.8d.bmp",
+                     SDL_GetWindowID(window), ++frame_number);
+        SDL_SaveBMP(surface, file);
+    }*/
+    return 0;
+}
+
+void Emscripten_DestroyWindowFramebuffer(_THIS, SDL_Window * window)
+{
+    SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
+
+    SDL_FreeSurface(data->surface);
+    data->surface = NULL;
+}
+
+#endif /* SDL_VIDEO_DRIVER_EMSCRIPTEN */
+
+/* vi: set ts=4 sw=4 expandtab: */