108 lines
2.5 KiB
C
108 lines
2.5 KiB
C
#define GINT_NEED_VRAM
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#include <gint/defs/util.h>
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#include <gint/display.h>
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/* dhline() - optimized drawing of a horizontal line
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@x1 @x2 @y Coordinates of endpoints of line (both included)
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@color Any R5G6B5 color */
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static void dhline(int x1, int x2, int y, uint16_t color)
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{
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/* Order and bounds */
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if((uint)y >= 224) return;
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if(x1 > x2) swap(x1, x2);
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if(x1 < 0) x1 = 0;
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if(x2 >= 396) x2 = 395;
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int offset = 396 * y;
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/* Use longwords to do the copy, but first paint the endpoints to heed
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for odd x1 and x2. Checking the parity may be a waste of time. */
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vram[offset + x1] = color;
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vram[offset + x2] = color;
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/* Now round to longword boundaries and copy everything in-between with
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longwords */
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x1 = x1 + (x1 & 1);
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x2 = (x2 + 1) & ~1;
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uint32_t *start = (void *)(vram + offset + x1);
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uint32_t *end = (void *)(vram + offset + x2);
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uint32_t op = (color << 16) | color;
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while(end > start) *--end = op;
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}
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/* dvline() - optimized drawing of a vertical line
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@y1 @y2 @x Coordinates of endpoints of line (both included)
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@color Any R5G6B5 color */
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static void dvline(int y1, int y2, int x, uint16_t color)
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{
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/* Order and bounds */
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if((uint)x >= 395) return;
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if(y1 > y2) swap(y1, y2);
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if(y1 < 0) y1 = 0;
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if(y2 >= 224) y2 = 223;
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uint16_t *v = vram + 396 * y1 + x;
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int height = y2 - y1 + 1;
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while(height--) *v = color, v += 396;
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}
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/* dline() - Bresenham line drawing algorithm
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Remotely adapted from MonochromeLib code by Pierre "PerriotLL" Le Gall.
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Relies on dhline() and dvline() for optimized situations.
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@x1 @y1 @x2 @y2 Coordinates of endpoints of line (included)
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@color Any R5G6B5 color */
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void dline(int x1, int y1, int x2, int y2, uint16_t color)
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{
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/* Possible optimizations */
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if(y1 == y2)
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{
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dhline(x1, x2, y1, color);
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return;
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}
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if(x1 == x2)
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{
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dvline(y1, y2, x1, color);
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return;
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}
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/* Brensenham line drawing algorithm */
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int i, x = x1, y = y1, cumul;
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int dx = x2 - x1, dy = y2 - y1;
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int sx = sgn(dx), sy = sgn(dy);
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dx = abs(dx), dy = abs(dy);
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dpixel(x1, y1, color);
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if(dx >= dy)
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{
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/* Start with a non-zero cumul to even the overdue between the
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two ends of the line (for more regularity) */
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cumul = dx >> 1;
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for(i = 1; i < dx; i++)
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{
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x += sx;
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cumul += dy;
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if(cumul > dx) cumul -= dx, y += sy;
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dpixel(x, y, color);
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}
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}
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else
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{
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cumul = dy >> 1;
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for(i = 1; i < dy; i++)
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{
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y += sy;
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cumul += dx;
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if(cumul > dy) cumul -= dy, x += sx;
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dpixel(x, y, color);
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}
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}
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dpixel(x2, y2, color);
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}
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