don't use SDL in Load_surface() anymore

So the init phase does not depend on SDL anymore.

Signed-off-by: Thomas Bernard <miniupnp@free.fr>

src/gfx2surface.c

@@ -0,0 +1,80 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+    Copyright 2018 Thomas Bernard
+    Copyright 1996-2001 Sunset Design (Guillaume Dorme & Karl Maritaud)
+
+    Grafx2 is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; version 2
+    of the License.
+
+    Grafx2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+#include <stdlib.h>
+#include <string.h>
+#include "gfx2surface.h"
+#include "errors.h"
+
+T_GFX2_Surface * New_GFX2_Surface(word width, word height)
+{
+  T_GFX2_Surface * surface;
+  size_t size;
+
+  surface = malloc(sizeof(T_GFX2_Surface));
+  if (surface == NULL)
+    return NULL;
+  size = width * height;
+  if (size > 0)
+  {
+    surface->pixels = malloc(size);
+    if(surface->pixels == NULL)
+    {
+      free(surface);
+      return NULL;
+    }
+  }
+  else
+  {
+    surface->pixels = NULL;
+  }
+  memset(surface->palette, 0, sizeof(surface->palette));
+  surface->w = width;
+  surface->h = height;
+  return surface;
+}
+
+void Free_GFX2_Surface(T_GFX2_Surface * surface)
+{
+  free(surface->pixels);
+  free(surface);
+}
+
+byte Get_GFX2_Surface_pixel(const T_GFX2_Surface * surface, int x, int y)
+{
+  if (surface == NULL) return 0;
+  if (x<0 || x>=surface->w || y<0 || y>=surface->h)
+  {
+    Warning("Get_GFX2_Surface_pixel() out of bound access");
+    return 0;
+  }
+  return surface->pixels[x + surface->w * y];
+}
+
+void Set_GFX2_Surface_pixel(T_GFX2_Surface * surface, int x, int y, byte value)
+{
+  if (surface == NULL) return;
+  if (x<0 || x>=surface->w || y<0 || y>=surface->h)
+  {
+    Warning("Set_GFX2_Surface_pixel() out of bound access");
+    return;
+  }
+  surface->pixels[x + surface->w * y] = value;
+}