Add basic shapes to draw things on screen

* Line, Rect Functions
 * Test screen

Makefile

@@ -2,7 +2,7 @@
 # Compiler
 CC=       gcc
 # Compiler flags
-CFLAGS=   -Wall -Os -std=c99
+CFLAGS=   -Wall -std=c99 -ggdb
 # Libraries
 CLIBS=    `sdl-config --cflags` -lSDL -lGL
 ####### Commands

src/draw.c

@@ -1,17 +1,94 @@
 
 #include "SDL.h"
+#include <math.h>
+#include <stdbool.h>
 #include "draw.h"
 #include "config.h"
 
 
 void drawPixel(int x, int y, int color) {
   unsigned int *p = (unsigned int*)screen->pixels;
+
   int lineOffset = y * (screen->pitch/4);
   p[lineOffset+x] = color;
 }
 
-void drawScreen() {
-  Uint32 black = SDL_MapRGB(screen->format, 0xff, 0xff, 0xff);
-  drawPixel(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, black);
+int _sign(float a) {
+  return a > 0 ? 1 : (a < 0 ? -1 : 0);
+}
+
+void drawLine(int x1, int y1, int x2, int y2, int color) {
+  float u, s, v, d1x, d1y, d2x, d2y, m, n;
+  int x = x1, y = y1;
+
+  u = x2-x1;
+  v = y2-y1;
+
+  d1x = d2x = _sign(u);
+  d1y = _sign(v);
+  d2y = 0;
+  m = abs(u);
+  n = abs(v);
+
+  if (m <= n) {
+    d2x = 0;
+    d2y = _sign(v);
+    m = abs(v);
+    n = abs(u);
+  }
+
+  s = (int)(m/2);
+
+  for (int i=0; i<round(m); i++) {
+    drawPixel(x, y, color);
+    s += n;
+    if (s >= m) {
+      s -= m;
+      x += d1x;
+      y += d1y;
+    } else {
+      x += d2x;
+      y += d2y;
+    }
+  }
+}
+
+void drawRect(int x1, int y1, int x2, int y2, int color, bool filled) {
+  int tmp;
+
+  if (x1 > x2) { tmp = x1; x2 = x1; x1 = tmp; }
+  if (y1 > y2) { tmp = y1; y2 = y1; y1 = tmp; }
+  
+  if (filled) {
+    for (int i=y1; i<=y2; i++) drawLine(x1, i, x2, i, color);
+  } else {
+    drawLine(x1, y1, x2, y1, color);
+    drawLine(x1, y1, x1, y2, color);
+    drawLine(x2, y1, x2, y2, color);
+    drawLine(x1, y2, x2, y2, color);
+  }
+}
+
+// TODO: Write some code in here!
+void drawCircle(int x, int y, int radius, int color, bool filled) {
+}
+
+void drawScreen() {
+  Uint32 white = SDL_MapRGB(screen->format, 255, 255, 255);
+  drawPixel(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, white);
+  for (int i=0; i<250; i+=1)
+    drawLine(200, 300-i, 600, 300+i, SDL_MapRGB(screen->format, 0, 0, i));
+
+  drawRect(0, 50, 200, 300, white, true);
+  drawRect(600, 300, 799, 550, white, false);
+
+  // Random dots
+  for (int i=0; i<100; i++)
+    drawPixel(rand()%200+600, rand()%250+300, white);
+
+  drawCircle(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, 100, white, true);
+  drawCircle(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, 104, white, false);
+
+  for (int i=0; i<=600; i++) drawLine(0, i, 799, i, white);
 }
 

src/main.c

@@ -19,6 +19,7 @@ int main(int argc, char **argv) {
     }
 
     // Draw the stuff on the screen and "flip" th the next frame
+    SDL_FillRect(screen, NULL, 0x000000);
     drawScreen();
     SDL_Flip(screen);
   }