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[draw] precise line drawing using antialiasing 

Antialiasing also has the advantage, that the path get's drawn now precisely -
there have been some issues without ... depending on the line-angle, some
pixels weren't filled on some y coordinates etc.

Signed-off-by: Julien Danjou <julien@danjou.info>
This commit is contained in:
marco candrian 2008-04-18 23:54:55 +02:00 committed by Julien Danjou
parent cad79c2e64
commit 37f05a8277
1 changed files with 28 additions and 11 deletions
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39
common/draw.c
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@ -408,7 +408,8 @@ draw_graph_setup(DrawCtx *ctx)
{ {
cairo_set_antialias(ctx->cr, CAIRO_ANTIALIAS_NONE); cairo_set_antialias(ctx->cr, CAIRO_ANTIALIAS_NONE);
cairo_set_line_width(ctx->cr, 1.0); cairo_set_line_width(ctx->cr, 1.0);
/* without it, it can draw over the path on sharp angles (...too long lines) */ /* without it, it can draw over the path on sharp angles
* ...too long lines * (...graph_line) */
cairo_set_miter_limit(ctx->cr, 0.0); cairo_set_miter_limit(ctx->cr, 0.0);
cairo_set_line_join(ctx->cr, CAIRO_LINE_JOIN_MITER); cairo_set_line_join(ctx->cr, CAIRO_LINE_JOIN_MITER);
} }
@ -493,32 +494,44 @@ draw_graph_line(DrawCtx *ctx, area_t rect, int *to, int cur_index,
Position grow, area_t patt_rect, Position grow, area_t patt_rect,
XColor *pcolor, XColor *pcolor_center, XColor *pcolor_end) XColor *pcolor, XColor *pcolor_center, XColor *pcolor_end)
{ {
int i, x, w; int i, w;
float y; float x, y;
cairo_pattern_t *pat; cairo_pattern_t *pat;
/* some stuff below is based on 'try and error' */ /* NOTE: without, it sometimes won't draw to some path (centered in a pixel)
* ... it won't fill some pixels! It also looks much nicer so.
* (since line-drawing is the last on the graph, no need to reset to _NONE) */
/* Not much difference to CAIRO_ANTIALIAS_DEFAULT, but recommend for LCD */
cairo_set_antialias(ctx->cr, CAIRO_ANTIALIAS_SUBPIXEL);
pat = draw_setup_cairo_color_source(ctx, patt_rect, pcolor, pcolor_center, pcolor_end); pat = draw_setup_cairo_color_source(ctx, patt_rect, pcolor, pcolor_center, pcolor_end);
x = rect.x; /* path through the centers of pixels */
y = rect.y + 0.5; /* center of a pixel */ x = rect.x + 0.5;
y = rect.y + 0.5;
w = rect.width; w = rect.width;
/* if grow == Right, go through the values from old to new. Setup the oldest below */ if(grow == Right)
if(grow == Right && ++cur_index > w - 1) {
/* go through the values from old to new. Begin with the oldest. */
if(++cur_index > w - 1)
cur_index = 0; cur_index = 0;
cairo_move_to(ctx->cr, x, y - to[cur_index]); cairo_move_to(ctx->cr, x, y - to[cur_index]);
}
else
/* on the left border: fills a pixel also when there's only one value */
cairo_move_to(ctx->cr, x - 1.0, y - to[cur_index]);
for(i = 0; i < w; i++) for(i = 0; i < w; i++)
{ {
cairo_line_to(ctx->cr, ++x, y - to[cur_index]); cairo_line_to(ctx->cr, x, y - to[cur_index]);
x += 1.0;
/* cycles around the index */ /* cycles around the index */
if(grow == Right) if(grow == Right)
{ {
if (++cur_index > w-1) if (++cur_index > w - 1)
cur_index = 0; cur_index = 0;
} }
else else
@ -528,6 +541,10 @@ draw_graph_line(DrawCtx *ctx, area_t rect, int *to, int cur_index,
} }
} }
/* onto the right border: fills a pixel also when there's only one value */
if(grow == Right)
cairo_line_to(ctx->cr, x, y - to[cur_index]);
cairo_stroke(ctx->cr); cairo_stroke(ctx->cr);
if(pat) if(pat)