src/video/gl_renderer.cpp

   1 //  $Id: gl_renderer.cpp 5063 2007-05-27 11:32:00Z matzeb $
   2 //
   3 //  SuperTux
   4 //  Copyright (C) 2006 Matthias Braun <matze@braunis.de>
   5 //
   6 //  This program is free software; you can redistribute it and/or
   7 //  modify it under the terms of the GNU General Public License
   8 //  as published by the Free Software Foundation; either version 2
   9 //  of the License, or (at your option) any later version.
  10 //
  11 //  This program is distributed in the hope that it will be useful,
  12 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 //  GNU General Public License for more details.
  15 //
  16 //  You should have received a copy of the GNU General Public License
  17 //  along with this program; if not, write to the Free Software
  18 //  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  19 #include <config.h>
  20
  21 #ifdef HAVE_OPENGL
  22
  23 #include <functional>
  24 #include <algorithm>
  25 #include <cassert>
  26 #include <math.h>
  27 #include <iostream>
  28 #include <SDL_image.h>
  29 #include <sstream>
  30 #include <iomanip>
  31 #include <physfs.h>
  32
  33 #include "glutil.hpp"
  34 #include "gl_renderer.hpp"
  35 #include "gl_texture.hpp"
  36 #include "gl_surface_data.hpp"
  37 #include "drawing_context.hpp"
  38 #include "drawing_request.hpp"
  39 #include "surface.hpp"
  40 #include "font.hpp"
  41 #include "main.hpp"
  42 #include "gameconfig.hpp"
  43 #include "texture.hpp"
  44 #include "texture_manager.hpp"
  45 #include "obstack/obstackpp.hpp"
  46 #define LIGHTMAP_DIV 5
  47
  48 #ifdef GL_VERSION_ES_CM_1_0
  49 #  define glOrtho glOrthof
  50 #endif
  51
  52 namespace
  53 {
  54
  55 inline void intern_draw(float left, float top, float right, float bottom,
  56                         float uv_left, float uv_top,
  57                         float uv_right, float uv_bottom,
  58                         float angle, float alpha,
  59                         const Color& color,
  60                         const Blend& blend,
  61                         DrawingEffect effect)
  62 {
  63   if(effect & HORIZONTAL_FLIP)
  64     std::swap(uv_left, uv_right);
  65
  66   if(effect & VERTICAL_FLIP)
  67     std::swap(uv_top, uv_bottom);
  68
  69   // unrotated blit
  70   glBlendFunc(blend.sfactor, blend.dfactor);
  71   glColor4f(color.red, color.green, color.blue, color.alpha * alpha);
  72
  73   if (angle == 0.0f) {
  74     float vertices[] = {
  75       left, top,
  76       right, top,
  77       right, bottom,
  78       left, bottom,
  79     };
  80     glVertexPointer(2, GL_FLOAT, 0, vertices);
  81
  82     float uvs[] = {
  83       uv_left, uv_top,
  84       uv_right, uv_top,
  85       uv_right, uv_bottom,
  86       uv_left, uv_bottom,
  87     };
  88     glTexCoordPointer(2, GL_FLOAT, 0, uvs);
  89
  90     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
  91   } else {
  92     // rotated blit
  93     float center_x = (left + right) / 2;
  94     float center_y = (top + bottom) / 2;
  95
  96     float sa = sinf(angle/180.0f*M_PI);
  97     float ca = cosf(angle/180.0f*M_PI);
  98
  99     left  -= center_x;
 100     right -= center_x;
 101
 102     top    -= center_y;
 103     bottom -= center_y;
 104
 105     float vertices[] = {
 106         left*ca - top*sa + center_x, left*sa + top*ca + center_y,
 107         right*ca - top*sa + center_x, right*sa + top*ca + center_y,
 108         right*ca - bottom*sa + center_x, right*sa + bottom*ca + center_y,
 109         left*ca - bottom*sa + center_x, left*sa + bottom*ca + center_y
 110     };
 111     glVertexPointer(2, GL_FLOAT, 0, vertices);
 112
 113     float uvs[] = {
 114       uv_left, uv_top,
 115       uv_right, uv_top,
 116       uv_right, uv_bottom,
 117       uv_left, uv_bottom,
 118     };
 119     glTexCoordPointer(2, GL_FLOAT, 0, uvs);
 120
 121     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 122   }
 123
 124   // FIXME: find a better way to restore the blend mode
 125   glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
 126   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 127 }
 128
 129 }
 130
 131 namespace GL {
 132
 133 Renderer::Renderer()
 134   : desktop_width(-1),
 135     desktop_height(-1)
 136 {
 137   ::Renderer::instance_ = this;
 138
 139 #if SDL_MAJOR_VERSION > 1 || SDL_MINOR_VERSION > 2 || (SDL_MINOR_VERSION == 2 && SDL_PATCHLEVEL >= 10)
 140   // unfortunately only newer SDLs have these infos.
 141   // This must be called before SDL_SetVideoMode() or it will return
 142   // the window size instead of the desktop size.
 143   const SDL_VideoInfo *info = SDL_GetVideoInfo();
 144   if (info)
 145     {
 146       desktop_width  = info->current_w;
 147       desktop_height = info->current_h;
 148     }
 149 #endif
 150
 151   if(texture_manager != 0)
 152     texture_manager->save_textures();
 153
 154 #ifndef GP2X
 155   //FIXME: This is not supported on the GP2X
 156   if(config->try_vsync) {
 157     /* we want vsync for smooth scrolling */
 158     SDL_GL_SetAttribute(SDL_GL_SWAP_CONTROL, 1);
 159   }
 160 #endif
 161
 162   SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
 163
 164   // FIXME: Hu? 16bit rendering?
 165   SDL_GL_SetAttribute(SDL_GL_RED_SIZE,   5);
 166   SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 5);
 167   SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE,  5);
 168
 169   int flags = SDL_OPENGL;
 170   int width;
 171   int height;
 172
 173   if(config->use_fullscreen)
 174     {
 175       flags |= SDL_FULLSCREEN;
 176       width  = config->fullscreen_width;
 177       height = config->fullscreen_height;
 178     }
 179   else
 180     {
 181       flags |= SDL_RESIZABLE;
 182       width  = config->window_width;
 183       height = config->window_height;
 184     }
 185
 186   int bpp = 0;
 187   SDL_Surface *screen = SDL_SetVideoMode(width, height, bpp, flags);
 188
 189   if(screen == 0) {
 190     std::stringstream msg;
 191     msg << "Couldn't set video mode (" << width << "x" << height
 192         << "-" << bpp << "bpp): " << SDL_GetError();
 193     throw std::runtime_error(msg.str());
 194   }
 195
 196   // setup opengl state and transform
 197   glDisable(GL_DEPTH_TEST);
 198   glDisable(GL_CULL_FACE);
 199   glEnable(GL_TEXTURE_2D);
 200   glEnable(GL_BLEND);
 201   glEnableClientState(GL_VERTEX_ARRAY);
 202   glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 203   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 204
 205   // Init the projection matrix, viewport and stuff
 206   apply_config();
 207
 208   if(texture_manager == 0)
 209     texture_manager = new TextureManager();
 210   else
 211     texture_manager->reload_textures();
 212 }
 213
 214 Renderer::~Renderer()
 215 {
 216 }
 217
 218 void
 219 Renderer::draw_surface(const DrawingRequest& request)
 220 {
 221   const Surface* surface = (const Surface*) request.request_data;
 222   GL::Texture *gltexture = dynamic_cast<GL::Texture *>(surface->get_texture());
 223   GL::SurfaceData *surface_data = reinterpret_cast<GL::SurfaceData *>(surface->get_surface_data());
 224
 225   glBindTexture(GL_TEXTURE_2D, gltexture->get_handle());
 226   intern_draw(request.pos.x, request.pos.y,
 227               request.pos.x + surface->get_width(),
 228               request.pos.y + surface->get_height(),
 229               surface_data->get_uv_left(),
 230               surface_data->get_uv_top(),
 231               surface_data->get_uv_right(),
 232               surface_data->get_uv_bottom(),
 233               request.angle,
 234               request.alpha,
 235               request.color,
 236               request.blend,
 237               request.drawing_effect);
 238 }
 239
 240 void
 241 Renderer::draw_surface_part(const DrawingRequest& request)
 242 {
 243   const SurfacePartRequest* surfacepartrequest
 244     = (SurfacePartRequest*) request.request_data;
 245   const Surface *surface = surfacepartrequest->surface;
 246   GL::Texture *gltexture = dynamic_cast<GL::Texture *>(surface->get_texture());
 247   GL::SurfaceData *surface_data = reinterpret_cast<GL::SurfaceData *>(surface->get_surface_data());
 248
 249   float uv_width = surface_data->get_uv_right() - surface_data->get_uv_left();
 250   float uv_height = surface_data->get_uv_bottom() - surface_data->get_uv_top();
 251
 252   float uv_left = surface_data->get_uv_left() + (uv_width * surfacepartrequest->source.x) / surface->get_width();
 253   float uv_top = surface_data->get_uv_top() + (uv_height * surfacepartrequest->source.y) / surface->get_height();
 254   float uv_right = surface_data->get_uv_left() + (uv_width * (surfacepartrequest->source.x + surfacepartrequest->size.x)) / surface->get_width();
 255   float uv_bottom = surface_data->get_uv_top() + (uv_height * (surfacepartrequest->source.y + surfacepartrequest->size.y)) / surface->get_height();
 256
 257   glBindTexture(GL_TEXTURE_2D, gltexture->get_handle());
 258   intern_draw(request.pos.x, request.pos.y,
 259               request.pos.x + surfacepartrequest->size.x,
 260               request.pos.y + surfacepartrequest->size.y,
 261               uv_left,
 262               uv_top,
 263               uv_right,
 264               uv_bottom,
 265               0.0,
 266               request.alpha,
 267               Color(1.0, 1.0, 1.0),
 268               Blend(),
 269               request.drawing_effect);
 270 }
 271
 272 void
 273 Renderer::draw_gradient(const DrawingRequest& request)
 274 {
 275   const GradientRequest* gradientrequest
 276     = (GradientRequest*) request.request_data;
 277   const Color& top = gradientrequest->top;
 278   const Color& bottom = gradientrequest->bottom;
 279
 280   glDisable(GL_TEXTURE_2D);
 281   glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 282   glEnableClientState(GL_COLOR_ARRAY);
 283
 284   float vertices[] = {
 285     0, 0,
 286     SCREEN_WIDTH, 0,
 287     SCREEN_WIDTH, SCREEN_HEIGHT,
 288     0, SCREEN_HEIGHT
 289   };
 290   glVertexPointer(2, GL_FLOAT, 0, vertices);
 291
 292   float colors[] = {
 293     top.red, top.green, top.blue, top.alpha,
 294     top.red, top.green, top.blue, top.alpha,
 295     bottom.red, bottom.green, bottom.blue, bottom.alpha,
 296     bottom.red, bottom.green, bottom.blue, bottom.alpha,
 297   };
 298   glColorPointer(4, GL_FLOAT, 0, colors);
 299
 300   glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 301
 302   glDisableClientState(GL_COLOR_ARRAY);
 303   glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 304
 305   glEnable(GL_TEXTURE_2D);
 306   glColor4f(1, 1, 1, 1);
 307 }
 308
 309 void
 310 Renderer::draw_filled_rect(const DrawingRequest& request)
 311 {
 312   const FillRectRequest* fillrectrequest
 313     = (FillRectRequest*) request.request_data;
 314
 315   if (fillrectrequest->radius != 0.0f)
 316     {
 317       // draw round rect
 318       // Keep radius in the limits, so that we get a circle instead of
 319       // just graphic junk
 320       float radius = std::min(fillrectrequest->radius,
 321                               std::min(fillrectrequest->size.x/2,
 322                                        fillrectrequest->size.y/2));
 323
 324       // inner rectangle
 325       Rect irect(request.pos.x    + radius,
 326                  request.pos.y    + radius,
 327                  request.pos.x + fillrectrequest->size.x - radius,
 328                  request.pos.y + fillrectrequest->size.y - radius);
 329
 330       glDisable(GL_TEXTURE_2D);
 331       glColor4f(fillrectrequest->color.red, fillrectrequest->color.green,
 332                 fillrectrequest->color.blue, fillrectrequest->color.alpha);
 333
 334
 335       int n = 8;
 336       //FIXME: This doesn't work with OpenGL ES
 337       glBegin(GL_QUAD_STRIP);
 338       for(int i = 0; i <= n; ++i)
 339         {
 340           float x = sinf(i * (M_PI/2) / n) * radius;
 341           float y = cosf(i * (M_PI/2) / n) * radius;
 342
 343           glVertex2f(irect.get_left()  - x, irect.get_top() - y);
 344           glVertex2f(irect.get_right() + x, irect.get_top() - y);
 345         }
 346       for(int i = 0; i <= n; ++i)
 347         {
 348           float x = cosf(i * (M_PI/2) / n) * radius;
 349           float y = sinf(i * (M_PI/2) / n) * radius;
 350
 351           glVertex2f(irect.get_left()  - x, irect.get_bottom() + y);
 352           glVertex2f(irect.get_right() + x, irect.get_bottom() + y);
 353         }
 354       glEnd();
 355       glEnable(GL_TEXTURE_2D);
 356       glColor4f(1, 1, 1, 1);
 357     }
 358   else
 359     {
 360       float x = request.pos.x;
 361       float y = request.pos.y;
 362       float w = fillrectrequest->size.x;
 363       float h = fillrectrequest->size.y;
 364
 365       glDisable(GL_TEXTURE_2D);
 366       glColor4f(fillrectrequest->color.red, fillrectrequest->color.green,
 367                 fillrectrequest->color.blue, fillrectrequest->color.alpha);
 368       glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 369
 370       float vertices[] = {
 371         x,   y,
 372         x+w, y,
 373         x+w, y+h,
 374         x,   y+h
 375       };
 376       glVertexPointer(2, GL_FLOAT, 0, vertices);
 377
 378       glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 379
 380       glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 381       glEnable(GL_TEXTURE_2D);
 382       glColor4f(1, 1, 1, 1);
 383     }
 384 }
 385
 386 void
 387 Renderer::draw_inverse_ellipse(const DrawingRequest& request)
 388 {
 389   const InverseEllipseRequest* ellipse = (InverseEllipseRequest*)request.request_data;
 390
 391   glDisable(GL_TEXTURE_2D);
 392   glColor4f(ellipse->color.red,  ellipse->color.green,
 393             ellipse->color.blue, ellipse->color.alpha);
 394
 395   float x = request.pos.x;
 396   float y = request.pos.y;
 397   float w = ellipse->size.x/2.0f;
 398   float h = ellipse->size.y/2.0f;
 399
 400   static const int slices = 16;
 401   static const int points = (slices+1) * 12;
 402
 403   float vertices[points * 2];
 404   int   p = 0;
 405
 406   // Bottom
 407   vertices[p++] = SCREEN_WIDTH; vertices[p++] = SCREEN_HEIGHT;
 408   vertices[p++] = 0;            vertices[p++] = SCREEN_HEIGHT;
 409   vertices[p++] = x;            vertices[p++] = y+h;
 410
 411   // Top
 412   vertices[p++] = SCREEN_WIDTH; vertices[p++] = 0;
 413   vertices[p++] = 0;            vertices[p++] = 0;
 414   vertices[p++] = x;            vertices[p++] = y-h;
 415
 416   // Left
 417   vertices[p++] = SCREEN_WIDTH; vertices[p++] = 0;
 418   vertices[p++] = SCREEN_WIDTH; vertices[p++] = SCREEN_HEIGHT;
 419   vertices[p++] = x+w;          vertices[p++] = y;
 420
 421   // Right
 422   vertices[p++] = 0;            vertices[p++] = 0;
 423   vertices[p++] = 0;            vertices[p++] = SCREEN_HEIGHT;
 424   vertices[p++] = x-w;          vertices[p++] = y;
 425
 426   for(int i = 0; i < slices; ++i)
 427     {
 428       float ex1 = sinf(M_PI/2 / slices * i) * w;
 429       float ey1 = cosf(M_PI/2 / slices * i) * h;
 430
 431       float ex2 = sinf(M_PI/2 / slices * (i+1)) * w;
 432       float ey2 = cosf(M_PI/2 / slices * (i+1)) * h;
 433
 434       // Bottom/Right
 435       vertices[p++] = SCREEN_WIDTH; vertices[p++] = SCREEN_HEIGHT;
 436       vertices[p++] = x + ex1;      vertices[p++] = y + ey1;
 437       vertices[p++] = x + ex2;      vertices[p++] = y + ey2;
 438
 439       // Top/Left
 440       vertices[p++] = 0;            vertices[p++] = 0;
 441       vertices[p++] = x - ex1;      vertices[p++] = y - ey1;
 442       vertices[p++] = x - ex2;      vertices[p++] = y - ey2;
 443
 444       // Top/Right
 445       vertices[p++] = SCREEN_WIDTH; vertices[p++] = 0;
 446       vertices[p++] = x + ex1;      vertices[p++] = y - ey1;
 447       vertices[p++] = x + ex2;      vertices[p++] = y - ey2;
 448
 449       // Bottom/Left
 450       vertices[p++] = 0;            vertices[p++] = SCREEN_HEIGHT;
 451       vertices[p++] = x - ex1;      vertices[p++] = y + ey1;
 452       vertices[p++] = x - ex2;      vertices[p++] = y + ey2;
 453     }
 454
 455   glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 456   glVertexPointer(2, GL_FLOAT, 0, vertices);
 457
 458   glDrawArrays(GL_TRIANGLES, 0, points);
 459
 460   glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 461
 462   glEnable(GL_TEXTURE_2D);
 463   glColor4f(1, 1, 1, 1);
 464 }
 465
 466 void
 467 Renderer::do_take_screenshot()
 468 {
 469   // [Christoph] TODO: Yes, this method also takes care of the actual disk I/O. Split it?
 470
 471   SDL_Surface *shot_surf;
 472   // create surface to hold screenshot
 473 #if SDL_BYTEORDER == SDL_BIG_ENDIAN
 474   shot_surf = SDL_CreateRGBSurface(SDL_SWSURFACE, SCREEN_WIDTH, SCREEN_HEIGHT, 24, 0x00FF0000, 0x0000FF00, 0x000000FF, 0);
 475 #else
 476   shot_surf = SDL_CreateRGBSurface(SDL_SWSURFACE, SCREEN_WIDTH, SCREEN_HEIGHT, 24, 0x000000FF, 0x0000FF00, 0x00FF0000, 0);
 477 #endif
 478   if (!shot_surf) {
 479     log_warning << "Could not create RGB Surface to contain screenshot" << std::endl;
 480     return;
 481   }
 482
 483   // read pixels into array
 484   char* pixels = new char[3 * SCREEN_WIDTH * SCREEN_HEIGHT];
 485   if (!pixels) {
 486     log_warning << "Could not allocate memory to store screenshot" << std::endl;
 487     SDL_FreeSurface(shot_surf);
 488     return;
 489   }
 490   glReadPixels(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, GL_RGB, GL_UNSIGNED_BYTE, pixels);
 491
 492   // copy array line-by-line
 493   for (int i = 0; i < SCREEN_HEIGHT; i++) {
 494     char* src = pixels + (3 * SCREEN_WIDTH * (SCREEN_HEIGHT - i - 1));
 495     if(SDL_MUSTLOCK(shot_surf))
 496       {
 497         SDL_LockSurface(shot_surf);
 498       }
 499     char* dst = ((char*)shot_surf->pixels) + i * shot_surf->pitch;
 500     memcpy(dst, src, 3 * SCREEN_WIDTH);
 501     if(SDL_MUSTLOCK(shot_surf))
 502       {
 503         SDL_UnlockSurface(shot_surf);
 504       }
 505   }
 506
 507   // free array
 508   delete[](pixels);
 509
 510   // save screenshot
 511   static const std::string writeDir = PHYSFS_getWriteDir();
 512   static const std::string dirSep = PHYSFS_getDirSeparator();
 513   static const std::string baseName = "screenshot";
 514   static const std::string fileExt = ".bmp";
 515   std::string fullFilename;
 516   for (int num = 0; num < 1000; num++) {
 517     std::ostringstream oss;
 518     oss << baseName;
 519     oss << std::setw(3) << std::setfill('0') << num;
 520     oss << fileExt;
 521     std::string fileName = oss.str();
 522     fullFilename = writeDir + dirSep + fileName;
 523     if (!PHYSFS_exists(fileName.c_str())) {
 524       SDL_SaveBMP(shot_surf, fullFilename.c_str());
 525       log_debug << "Wrote screenshot to \"" << fullFilename << "\"" << std::endl;
 526       SDL_FreeSurface(shot_surf);
 527       return;
 528     }
 529   }
 530   log_warning << "Did not save screenshot, because all files up to \"" << fullFilename << "\" already existed" << std::endl;
 531   SDL_FreeSurface(shot_surf);
 532 }
 533
 534 void
 535 Renderer::flip()
 536 {
 537   assert_gl("drawing");
 538   SDL_GL_SwapBuffers();
 539 }
 540
 541 void
 542 Renderer::resize(int w, int h)
 543 {
 544   // This causes the screen to go black, which is annoying, but seems
 545   // unavoidable with SDL at the moment
 546   SDL_SetVideoMode(w, h, 0, SDL_OPENGL | SDL_RESIZABLE);
 547
 548   config->window_width  = w;
 549   config->window_height = h;
 550
 551   apply_config();
 552 }
 553
 554 void
 555 Renderer::apply_config()
 556 {
 557   if (0)
 558     {
 559       std::cout << "Applying Config:"
 560                 << "\n  Desktop: " << desktop_width << "x" << desktop_height
 561                 << "\n  Window:  " << config->window_width << "x" << config->window_height
 562                 << "\n  FullRes: " << config->fullscreen_width << "x" << config->fullscreen_height
 563                 << "\n  Aspect:  " << config->aspect_width << ":" << config->aspect_height
 564                 << "\n  Magnif:  " << config->magnification
 565                 << std::endl;
 566     }
 567
 568   int w,h;
 569   float target_aspect = float(desktop_width) / desktop_height;
 570
 571   if (config->aspect_width != 0 && config->aspect_height != 0)
 572     target_aspect = float(config->aspect_width) / float(config->aspect_height);
 573
 574   float desktop_aspect = 4.0f / 3.0f; // random default fallback guess
 575
 576   if (desktop_width != -1 && desktop_height != -1)
 577     {
 578       desktop_aspect = float(desktop_width) / float(desktop_height);
 579     }
 580
 581   // Get the screen width
 582   if (config->use_fullscreen)
 583     {
 584       w = config->fullscreen_width;
 585       h = config->fullscreen_height;
 586       desktop_aspect = float(w) / float(h);
 587     }
 588   else
 589     {
 590       w = config->window_width;
 591       h = config->window_height;
 592     }
 593
 594   if (target_aspect > 1.0f)
 595     {
 596       SCREEN_WIDTH  = static_cast<int>(w * (target_aspect / desktop_aspect));
 597       SCREEN_HEIGHT = static_cast<int>(h);
 598     }
 599   else
 600     {
 601       SCREEN_WIDTH  = static_cast<int>(w);
 602       SCREEN_HEIGHT = static_cast<int>(h  * (target_aspect / desktop_aspect));
 603     }
 604
 605   int max_width  = 1600; // FIXME: Maybe 1920 is ok too
 606   int max_height = 1200;
 607
 608   if (config->magnification == 0.0f) // Magic value that means 'minfill'
 609     {
 610       // This scales SCREEN_WIDTH/SCREEN_HEIGHT so that they never excede
 611       // max_width/max_height
 612       if (SCREEN_WIDTH > max_width || SCREEN_HEIGHT > max_height)
 613         {
 614           float scale1  = float(max_width)/SCREEN_WIDTH;
 615           float scale2  = float(max_height)/SCREEN_HEIGHT;
 616           float scale   = (scale1 < scale2) ? scale1 : scale2;
 617           SCREEN_WIDTH  = static_cast<int>(SCREEN_WIDTH  * scale);
 618           SCREEN_HEIGHT = static_cast<int>(SCREEN_HEIGHT * scale);
 619         }
 620
 621       glViewport(0, 0, w, h);
 622     }
 623   else
 624     {
 625       SCREEN_WIDTH  = static_cast<int>(SCREEN_WIDTH  / config->magnification);
 626       SCREEN_HEIGHT = static_cast<int>(SCREEN_HEIGHT / config->magnification);
 627
 628       // This works by adding black borders around the screen to limit
 629       // SCREEN_WIDTH/SCREEN_HEIGHT to max_width/max_height
 630       int nw = w;
 631       int nh = h;
 632
 633       if (SCREEN_WIDTH > max_width)
 634         {
 635           nw = static_cast<int>((float) nw * float(max_width)/SCREEN_WIDTH);
 636           SCREEN_WIDTH = static_cast<int>(max_width);
 637         }
 638
 639       if (SCREEN_HEIGHT > max_height)
 640         {
 641           nh = static_cast<int>((float) nh * float(max_height)/SCREEN_HEIGHT);
 642           SCREEN_HEIGHT = static_cast<int>(max_height);
 643         }
 644
 645       // Clear both buffers so that we get a clean black border without junk
 646       glClear(GL_COLOR_BUFFER_BIT);
 647       SDL_GL_SwapBuffers();
 648       glClear(GL_COLOR_BUFFER_BIT);
 649       SDL_GL_SwapBuffers();
 650
 651       if (0)
 652         std::cout << (w-nw)/2 << " "
 653                   << (h-nh)/2 << " "
 654                   << nw << "x" << nh << std::endl;
 655
 656       glViewport(std::max(0, (w-nw)/2),
 657                  std::max(0, (h-nh)/2),
 658                  std::min(nw, w),
 659                  std::min(nh, h));
 660     }
 661
 662   if (0)
 663     std::cout << "  -> " << SCREEN_WIDTH << "x" << SCREEN_HEIGHT << std::endl;
 664
 665   glMatrixMode(GL_PROJECTION);
 666   glLoadIdentity();
 667
 668   glOrtho(0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, -1, 1);
 669
 670   glMatrixMode(GL_MODELVIEW);
 671   glLoadIdentity();
 672   glTranslatef(0, 0, 0);
 673   check_gl_error("Setting up view matrices");
 674 }
 675
 676 } // namespace GL
 677
 678 #endif