src/objectrenderer.cpp

   1 /**
   2  * @file objectrenderer.cpp
   3  * @brief Implements ObjectRenderer and derived classes
   4  */
   5
   6 #include "objectrenderer.h"
   7 #include "view.h"
   8 #include <list>
   9
  10 using namespace std;
  11
  12 namespace IPDF
  13 {
  14
  15 /**
  16  * ObjectRenderer constructor
  17  * Note we cannot compile the shaders in the ShaderProgram constructor
  18  *  because the Screen class needs to initialise GL first and it has a
  19  *      ShaderProgram member
  20  */
  21 ObjectRenderer::ObjectRenderer(const ObjectType & type,
  22                 const char * vert_glsl_file, const char * frag_glsl_file, const char * geom_glsl_file)
  23                 : m_type(type), m_shader_program(), m_indexes(), m_buffer_builder(NULL)
  24 {
  25         m_shader_program.InitialiseShaders(vert_glsl_file, frag_glsl_file, geom_glsl_file);
  26         m_shader_program.Use();
  27         glUniform4f(m_shader_program.GetUniformLocation("colour"), 0,0,0,1); //TODO: Allow different colours
  28 }
  29
  30 /**
  31  * Render using GPU
  32  */
  33 void ObjectRenderer::RenderUsingGPU(unsigned first_obj_id, unsigned last_obj_id)
  34 {
  35         // If we don't have anything to render, return.
  36         if (first_obj_id == last_obj_id) return;
  37         // If there are no objects of this type, return.
  38         if (m_indexes.empty()) return;
  39         unsigned first_index = 0;
  40         while (m_indexes.size() > first_index && m_indexes[first_index] < first_obj_id) first_index ++;
  41         unsigned last_index = first_index;
  42         while (m_indexes.size() > last_index && m_indexes[last_index] < last_obj_id) last_index ++;
  43
  44         m_shader_program.Use();
  45         m_ibo.Bind();
  46         glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(2*first_index*sizeof(uint32_t)));
  47 }
  48
  49
  50 /**
  51  * Default implementation for rendering using CPU
  52  */
  53 void ObjectRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
  54 {
  55         Error("Cannot render objects of type %d on CPU", m_type);
  56         //TODO: Render a rect or something instead?
  57 }
  58
  59 /**
  60  * Prepare index buffers for both CPU and GPU rendering to receive indexes (but don't add any yet!)
  61  */
  62 void ObjectRenderer::PrepareBuffers(unsigned max_objects)
  63 {
  64         if (m_buffer_builder != NULL) // We already have a BufferBuilder
  65         {
  66                 Fatal("Has been called before, without FinaliseBuffers being called since!");
  67         }
  68         // Empty and reserve the indexes vector (for CPU rendering)
  69         m_indexes.clear();
  70         m_indexes.reserve(max_objects); //TODO: Can probably make this smaller? Or leave it out? Do we care?
  71
  72         // Initialise and resize the ibo (for GPU rendering)
  73         m_ibo.Invalidate();
  74         m_ibo.SetUsage(GraphicsBuffer::BufferUsageStaticDraw);
  75         m_ibo.SetType(GraphicsBuffer::BufferTypeIndex);
  76         m_ibo.Resize(max_objects * 2 * sizeof(uint32_t));
  77         // BufferBuilder is used to construct the ibo
  78         m_buffer_builder = new BufferBuilder<uint32_t>(m_ibo.Map(false, true, true), m_ibo.GetSize()); // new matches delete in ObjectRenderer::FinaliseBuffers
  79
  80 }
  81
  82 /**
  83  * Add object index to the buffers for CPU and GPU rendering
  84  */
  85 void ObjectRenderer::AddObjectToBuffers(unsigned index)
  86 {
  87         if (m_buffer_builder == NULL) // No BufferBuilder!
  88         {
  89                 Fatal("Called without calling PrepareBuffers");
  90         }
  91         m_buffer_builder->Add(2*index); // ibo for GPU rendering
  92         m_buffer_builder->Add(2*index+1);
  93         m_indexes.push_back(index); // std::vector of indices for CPU rendering
  94 }
  95
  96 /**
  97  * Finalise the index buffers for CPU and GPU rendering
  98  */
  99 void ObjectRenderer::FinaliseBuffers()
 100 {
 101         if (m_buffer_builder == NULL) // No BufferBuilder!
 102         {
 103                 Fatal("Called without calling PrepareBuffers");
 104         }
 105         // For GPU rendering, UnMap the ibo
 106         m_ibo.UnMap();
 107         // ... and delete the BufferBuilder used to create it
 108         delete m_buffer_builder; // delete matches new in ObjectRenderer::PrepareBuffers
 109         m_buffer_builder = NULL;
 110
 111         // Nothing is necessary for CPU rendering
 112 }
 113
 114
 115 /**
 116  * Rectangle (filled)
 117  */
 118 void RectFilledRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
 119 {
 120         for (unsigned i = 0; i < m_indexes.size(); ++i)
 121         {
 122                 if (m_indexes[i] < first_obj_id) continue;
 123                 if (m_indexes[i] >= last_obj_id) continue;
 124                 PixelBounds bounds(CPURenderBounds(objects.bounds[m_indexes[i]], view, target));
 125                 for (int64_t x = max((int64_t)0, bounds.x); x <= min(bounds.x+bounds.w, target.w-1); ++x)
 126                 {
 127                         for (int64_t y = max((int64_t)0, bounds.y); y <= min(bounds.y+bounds.h, target.h-1); ++y)
 128                         {
 129                                 int index = (x+target.w*y)*4;
 130                                 target.pixels[index+0] = 0;
 131                                 target.pixels[index+1] = 0;
 132                                 target.pixels[index+2] = 0;
 133                                 target.pixels[index+3] = 255;
 134                         }
 135                 }
 136         }
 137 }
 138
 139 /**
 140  * Rectangle (outine)
 141  */
 142 void RectOutlineRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
 143 {
 144         //Debug("Render %u outlined rectangles on CPU", m_indexes.size());
 145         for (unsigned i = 0; i < m_indexes.size(); ++i)
 146         {
 147                 if (m_indexes[i] < first_obj_id) continue;
 148                 if (m_indexes[i] >= last_obj_id) continue;
 149                 PixelBounds bounds(CPURenderBounds(objects.bounds[m_indexes[i]], view, target));
 150
 151                 // Using bresenham's lines now mainly because I want to see if they work
 152                 // top
 153                 ObjectRenderer::RenderLineOnCPU(bounds.x, bounds.y, bounds.x+bounds.w, bounds.y, target);
 154                 // bottom
 155                 ObjectRenderer::RenderLineOnCPU(bounds.x, bounds.y+bounds.h, bounds.x+bounds.w, bounds.y+bounds.h, target);
 156                 // left
 157                 ObjectRenderer::RenderLineOnCPU(bounds.x, bounds.y, bounds.x, bounds.y+bounds.h, target);
 158                 // right
 159                 ObjectRenderer::RenderLineOnCPU(bounds.x+bounds.w, bounds.y, bounds.x+bounds.w, bounds.y+bounds.h, target);
 160
 161                 // Diagonal for testing (from bottom left to top right)
 162                 //ObjectRenderer::RenderLineOnCPU(bounds.x,bounds.y+bounds.h, bounds.x+bounds.w, bounds.y,target, C_BLUE);
 163                 //ObjectRenderer::RenderLineOnCPU(bounds.x+bounds.w, bounds.y+bounds.h, bounds.x, bounds.y, target,C_GREEN);
 164         }
 165 }
 166
 167 /**
 168  * Circle (filled)
 169  */
 170 void CircleFilledRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
 171 {
 172         for (unsigned i = 0; i < m_indexes.size(); ++i)
 173         {
 174                 if (m_indexes[i] < first_obj_id) continue;
 175                 if (m_indexes[i] >= last_obj_id) continue;
 176                 PixelBounds bounds(CPURenderBounds(objects.bounds[m_indexes[i]], view, target));
 177                 int64_t centre_x = bounds.x + bounds.w / 2;
 178                 int64_t centre_y = bounds.y + bounds.h / 2;
 179
 180                 //Debug("Centre is %d, %d", centre_x, centre_y);
 181                 //Debug("Bounds are %d,%d,%d,%d", bounds.x, bounds.y, bounds.w, bounds.h);
 182                 //Debug("Windos is %d,%d", target.w, target.h);
 183                 for (int64_t x = max((int64_t)0, bounds.x); x <= min(bounds.x+bounds.w, target.w-1); ++x)
 184                 {
 185                         for (int64_t y = max((int64_t)0, bounds.y); y <= min(bounds.y + bounds.h, target.h-1); ++y)
 186                         {
 187                                 Real dx(2); dx *= Real(x - centre_x)/Real(bounds.w);
 188                                 Real dy(2); dy *= Real(y - centre_y)/Real(bounds.h);
 189                                 int64_t index = (x+target.w*y)*4;
 190
 191                                 if (dx*dx + dy*dy <= Real(1))
 192                                 {
 193                                         target.pixels[index+0] = 0;
 194                                         target.pixels[index+1] = 0;
 195                                         target.pixels[index+2] = 0;
 196                                         target.pixels[index+3] = 255;
 197                                 }
 198                         }
 199                 }
 200         }
 201 }
 202
 203 Rect ObjectRenderer::CPURenderBounds(const Rect & bounds, const View & view, const CPURenderTarget & target)
 204 {
 205         Rect result = view.TransformToViewCoords(bounds);
 206         result.x *= Real(target.w);
 207         result.y *= Real(target.h);
 208         result.w *= Real(target.w);
 209         result.h *= Real(target.h);
 210         return result;
 211 }
 212
 213
 214 /**
 215  * Bezier curve
 216  * Not sure how to apply De'Casteljau, will just use a bunch of Bresnham lines for now.
 217  */
 218 void BezierRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
 219 {
 220         //Warn("Rendering Beziers on CPU. Things may explode.");
 221         for (unsigned i = 0; i < m_indexes.size(); ++i)
 222         {
 223                 if (m_indexes[i] < first_obj_id) continue;
 224                 if (m_indexes[i] >= last_obj_id) continue;
 225                 const Rect & bounds = objects.bounds[m_indexes[i]];
 226                 PixelBounds pix_bounds(CPURenderBounds(bounds,view,target));
 227
 228                 Bezier control(objects.beziers[objects.data_indices[m_indexes[i]]].ToAbsolute(bounds),CPURenderBounds(Rect(0,0,1,1), view, target));
 229                 //Debug("%s -> %s via %s", objects.beziers[objects.data_indices[m_indexes[i]]].Str().c_str(), control.Str().c_str(), bounds.Str().c_str());
 230                 // Draw a rectangle around the bezier for debugging the bounds rectangle calculations
 231                 if (view.ShowingObjectBounds())
 232                 {
 233                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y, pix_bounds.x+pix_bounds.w, pix_bounds.y, target, Colour(1,0,0,1));
 234                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y+pix_bounds.h, pix_bounds.x+pix_bounds.w, pix_bounds.y+pix_bounds.h, target, Colour(0,1,0,1));
 235                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y, pix_bounds.x, pix_bounds.y+pix_bounds.h, target, Colour(1,0,0,1));
 236                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x+pix_bounds.w, pix_bounds.y, pix_bounds.x+pix_bounds.w, pix_bounds.y+pix_bounds.h, target, Colour(0,1,0,1));
 237                 }
 238                 // Draw lines between the control points for debugging
 239                 //ObjectRenderer::RenderLineOnCPU((int64_t)control.x0, (int64_t)control.y0, (int64_t)control.x1, (int64_t)control.y1,target);
 240                 //ObjectRenderer::RenderLineOnCPU((int64_t)control.x1, (int64_t)control.y1, (int64_t)control.x2, (int64_t)control.y2,target);
 241
 242
 243
 244                 Real x[2]; Real y[2];
 245                 control.Evaluate(x[0], y[0], Real(0));
 246                 //Debug("target is (%lu, %lu)", target.w, target.h);
 247                 int64_t blen = min(max((int64_t)2, (int64_t)(target.w/view.GetBounds().w)), (int64_t)100);
 248
 249                 Real invblen(1); invblen /= blen;
 250                 //Debug("Using %li lines, inverse %f", blen, Double(invblen));
 251                 for (int64_t j = 1; j <= blen; ++j)
 252                 {
 253                         control.Evaluate(x[j % 2],y[j % 2], invblen*j);
 254                         ObjectRenderer::RenderLineOnCPU((int64_t)Double(x[0]),(int64_t)Double(y[0]), (int64_t)Double(x[1]),(int64_t)Double(y[1]), target);
 255                 }
 256
 257                 /*
 258                 Real u(0);
 259                 while (u < Real(1))
 260                 {
 261                         u += Real(1e-6);
 262                         Real x; Real y; control.Evaluate(x,y,u);
 263                         int64_t index = ((int64_t)x + (int64_t)y*target.w)*4;
 264                         if (index >= 0 && index < 4*(target.w*target.h))
 265                         {
 266                                 target.pixels[index+0] = 0;
 267                                 target.pixels[index+1] = 0;
 268                                 target.pixels[index+2] = 0;
 269                                 target.pixels[index+3] = 255;
 270                         }
 271                 }
 272                 */
 273
 274         }
 275 }
 276
 277 void BezierRenderer::PrepareBezierGPUBuffer(const Objects& objects)
 278 {
 279         m_bezier_coeffs.SetType(GraphicsBuffer::BufferTypeTexture);
 280         m_bezier_coeffs.SetUsage(GraphicsBuffer::BufferUsageDynamicDraw);
 281         m_bezier_coeffs.Resize(objects.beziers.size()*sizeof(GPUBezierCoeffs));
 282         BufferBuilder<GPUBezierCoeffs> builder(m_bezier_coeffs.Map(false, true, true), m_bezier_coeffs.GetSize());
 283
 284
 285         for (unsigned i = 0; i < objects.beziers.size(); ++i)
 286         {
 287                 const Bezier & bez = objects.beziers[i];
 288
 289                 GPUBezierCoeffs coeffs = {
 290                         Float(bez.x0), Float(bez.y0),
 291                         Float(bez.x1), Float(bez.y1),
 292                         Float(bez.x2), Float(bez.y2),
 293                         Float(bez.x3), Float(bez.y3)
 294                         };
 295                 builder.Add(coeffs);
 296         }
 297         m_bezier_coeffs.UnMap();
 298         glGenTextures(1, &m_bezier_buffer_texture);
 299         glBindTexture(GL_TEXTURE_BUFFER, m_bezier_buffer_texture);
 300         glTexBuffer(GL_TEXTURE_BUFFER, GL_RG32F, m_bezier_coeffs.GetHandle());
 301
 302         m_bezier_ids.SetType(GraphicsBuffer::BufferTypeTexture);
 303         m_bezier_ids.SetUsage(GraphicsBuffer::BufferUsageDynamicDraw);
 304         m_bezier_ids.Upload(objects.data_indices.size() * sizeof(uint32_t), &objects.data_indices[0]);
 305
 306         glGenTextures(1, &m_bezier_id_buffer_texture);
 307         glActiveTexture(GL_TEXTURE1);
 308         glBindTexture(GL_TEXTURE_BUFFER, m_bezier_id_buffer_texture);
 309         glTexBuffer(GL_TEXTURE_BUFFER, GL_R32I, m_bezier_ids.GetHandle());
 310         glActiveTexture(GL_TEXTURE0);
 311 }
 312
 313 void BezierRenderer::RenderUsingGPU(unsigned first_obj_id, unsigned last_obj_id)
 314 {
 315         if (!m_shader_program.Valid())
 316                 Warn("Shader is invalid (objects are of type %d)", m_type);
 317
 318         // If we don't have anything to render, return.
 319         if (first_obj_id == last_obj_id) return;
 320         // If there are no objects of this type, return.
 321         if (m_indexes.empty()) return;
 322
 323         unsigned first_index = 0;
 324         while (m_indexes.size() > first_index && m_indexes[first_index] < first_obj_id) first_index ++;
 325         unsigned last_index = first_index;
 326         while (m_indexes.size() > last_index && m_indexes[last_index] < last_obj_id) last_index ++;
 327
 328         m_shader_program.Use();
 329         glUniform1i(m_shader_program.GetUniformLocation("bezier_buffer_texture"), 0);
 330         glUniform1i(m_shader_program.GetUniformLocation("bezier_id_buffer_texture"), 1);
 331         m_ibo.Bind();
 332         glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(2*first_index*sizeof(uint32_t)));
 333 }
 334
 335 inline bool IsBlack(uint8_t * pixels, int64_t index)
 336 {
 337         bool result = (pixels[index+0] == 0 && pixels[index+1] == 0 && pixels[index+2] == 0 && pixels[index+3] == 255);
 338         //pixels[index+3] = 254; // hax
 339         return result;
 340 }
 341
 342 /**
 343  * Render Group (shading)
 344  */
 345 void GroupRenderer::RenderUsingCPU(const Objects & objects, const View & view, const CPURenderTarget & target, unsigned first_obj_id, unsigned last_obj_id)
 346 {
 347         if (!view.ShowingObjectBounds() && !view.PerformingShading())
 348                 return;
 349
 350         for (unsigned i = 0; i < m_indexes.size(); ++i)
 351         {
 352                 if (m_indexes[i] < first_obj_id) continue;
 353                 if (m_indexes[i] >= last_obj_id) continue;
 354
 355
 356                 Rect bounds(CPURenderBounds(objects.bounds[m_indexes[i]], view, target));
 357                 PixelBounds pix_bounds(bounds);
 358
 359                 const Group & group = objects.groups[objects.data_indices[m_indexes[i]]];
 360                 if (group.m_fill.a == 0 || !view.PerformingShading())
 361                         continue;
 362
 363                 // make the bounds just a little bit bigger
 364                 pix_bounds.x-=1;
 365                 pix_bounds.w+=2;
 366                 pix_bounds.y-=1;
 367                 pix_bounds.h+=2;
 368
 369                 // Attempt to shade the region
 370                 // Assumes the outline has been drawn first...
 371                 //#ifdef SHADING_DUMB
 372                 for (int64_t y = max((int64_t)0, pix_bounds.y); y <= min(pix_bounds.y+pix_bounds.h, target.h-1); ++y)
 373                 {
 374                         struct Segment
 375                         {
 376                                 int64_t first;
 377                                 int64_t second;
 378                                 bool all_black;
 379                         };
 380                         list<Segment> segments;
 381                         int64_t min_x = max((int64_t)0, pix_bounds.x);
 382                         int64_t max_x = min(pix_bounds.x+pix_bounds.w, target.w-1);
 383                         int64_t yy = y*target.w;
 384
 385                         int64_t x = min_x;
 386                         while (x <= max_x)
 387                         {
 388                                 bool start_black = IsBlack(target.pixels, 4*(x+yy));
 389                                 bool black = start_black;
 390                                 segments.push_back({x,x,start_black});
 391                                 while (black == start_black && ++x <= max_x)
 392                                 {
 393                                         black = IsBlack(target.pixels, 4*(x+yy));
 394                                 }
 395                                 segments.back().second = x-1;
 396                         }
 397
 398                         // Keep only the interior segments
 399                         list<Segment>::iterator j = segments.begin();
 400                         //TODO: Magically delete unneeded segments here...
 401
 402                         // Fill in remaining segments
 403                         for (j=segments.begin(); j != segments.end(); ++j)
 404                         {
 405                                 Colour c(group.m_fill);
 406                                 if (j->all_black)
 407                                 {
 408                                         c.r = 1;//1; // Change to debug the outline scanning
 409                                         c.g = 0;
 410                                         c.b = 0;
 411                                         c.a = 1;
 412                                 }
 413                                 for (x = max(min_x, j->first); x <= min(max_x, j->second); ++x)
 414                                 {
 415                                         int64_t index = 4*(x+yy);
 416                                         target.pixels[index+0] = 255*c.r;
 417                                         target.pixels[index+1] = 255*c.g;
 418                                         target.pixels[index+2] = 255*c.b;
 419                                         target.pixels[index+3] = 255*c.a;
 420                                 }
 421                         }
 422                 }
 423                 //#endif //SHADING_DUMB
 424                 if (view.ShowingObjectBounds())
 425                 {
 426                         const Colour & c = group.m_fill;
 427                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y, pix_bounds.x+pix_bounds.w, pix_bounds.y, target, c);
 428                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y+pix_bounds.h, pix_bounds.x+pix_bounds.w, pix_bounds.y+pix_bounds.h, target, c);
 429                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x, pix_bounds.y, pix_bounds.x, pix_bounds.y+pix_bounds.h, target, c);
 430                         ObjectRenderer::RenderLineOnCPU(pix_bounds.x+pix_bounds.w, pix_bounds.y, pix_bounds.x+pix_bounds.w, pix_bounds.y+pix_bounds.h, target, c);
 431                 }
 432
 433
 434         }
 435 }
 436
 437 /**
 438  * For debug, save pixels to bitmap
 439  */
 440 void ObjectRenderer::SaveBMP(const CPURenderTarget & target, const char * filename)
 441 {
 442         SDL_Surface * surf = SDL_CreateRGBSurfaceFrom(target.pixels, target.w, target.h, 8*4, target.w*4,
 443         #if SDL_BYTEORDER == SDL_LIL_ENDIAN
 444                 0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000
 445         #else
 446                 0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff
 447         #endif //SDL_BYTEORDER
 448         );
 449         if (surf == NULL)
 450                 Fatal("SDL_CreateRGBSurfaceFrom(pixels...) failed - %s", SDL_GetError());
 451         if (SDL_SaveBMP(surf, filename) != 0)
 452                 Fatal("SDL_SaveBMP failed - %s", SDL_GetError());
 453
 454         // Cleanup
 455         SDL_FreeSurface(surf);
 456 }
 457
 458 /**
 459  * Bresenham's lines
 460  */
 461 void ObjectRenderer::RenderLineOnCPU(int64_t x0, int64_t y0, int64_t x1, int64_t y1, const CPURenderTarget & target, const Colour & colour, bool transpose)
 462 {
 463         int64_t dx = x1 - x0;
 464         int64_t dy = y1 - y0;
 465         bool neg_m = (dy*dx < 0);
 466         dy = abs(dy);
 467         dx = abs(dx);
 468
 469         // If positive slope > 1, just swap x and y
 470         if (dy > dx)
 471         {
 472                 RenderLineOnCPU(y0,x0,y1,x1,target,colour,!transpose);
 473                 return;
 474         }
 475
 476         int64_t two_dy = 2*dy;
 477         int64_t p = two_dy - dx;
 478         int64_t two_dxdy = 2*(dy-dx);
 479         int64_t x; int64_t y; int64_t x_end;
 480         int64_t width = (transpose ? target.h : target.w);
 481         int64_t height = (transpose ? target.w : target.h);
 482
 483         uint8_t rgba[4];
 484         rgba[0] = 255*colour.r;
 485         rgba[1] = 255*colour.g;
 486         rgba[2] = 255*colour.b;
 487         rgba[3] = 255*colour.a;
 488
 489         if (x0 > x1)
 490         {
 491                 x = x1;
 492                 y = y1;
 493                 x_end = x0;
 494         }
 495         else
 496         {
 497                 x = x0;
 498                 y = y0;
 499                 x_end = x1;
 500         }
 501
 502         if (x < 0)
 503         {
 504                 if (x_end < 0) return;
 505                 y = (neg_m ? y - (dy*-x)/dx : y + (dy*-x)/dx);
 506                 x = 0;
 507         }
 508
 509         if (x_end > width)
 510         {
 511                 if (x > width) return;
 512                 x_end = width-1;
 513         }
 514
 515         // TODO: Avoid extra inner conditionals
 516         do
 517         {
 518                 if (x >= 0 && x < width && y >= 0 && y < height)
 519                 {
 520                         int64_t index = (transpose ? (y + x*target.w)*4 : (x + y*target.w)*4);
 521                         for (int i = 0; i < 4; ++i)
 522                                 target.pixels[index+i] = rgba[i];
 523                 }
 524                 if (p < 0)
 525                         p += two_dy;
 526                 else
 527                 {
 528                         if (neg_m) --y; else ++y;
 529                         p += two_dxdy;
 530                 }
 531         } while (++x <= x_end);
 532 }
 533
 534 }