[sysprof/wip/visualizers] line-visualizer-row: use cairo_curve_to()

[Christian Hergert <chergert src gnome org>]

commit 573ba7bf511bee0b855fc6d47af25c1360677f9f
Author: Christian Hergert <chergert redhat com>
Date:   Mon Sep 26 21:57:33 2016 -0700

    line-visualizer-row: use cairo_curve_to()
    
    This makes our line graph match more closely to the design
    coming from Builder's cpu graph.

 lib/sp-line-visualizer-row.c |   52 ++++++++++++++++++++---------------------
 1 files changed, 25 insertions(+), 27 deletions(-)
---
diff --git a/lib/sp-line-visualizer-row.c b/lib/sp-line-visualizer-row.c
index 2841ade..4c7ac70 100644
--- a/lib/sp-line-visualizer-row.c
+++ b/lib/sp-line-visualizer-row.c
@@ -778,47 +778,45 @@ sp_line_visualizer_row_render_worker (GTask        *task,
       goto cleanup;
     }
 
-  /*
-   * Flip the coordinate space so that we can just use the x,y pairs
-   * as our position between 0.0 and 1.0 and have both the direction
-   * and the placement correct.
-   */
+  /* Flip the coordinate space so that 0,0 is in the bottom left. */
   cairo_translate (cr, 0, render->height);
-  cairo_scale (cr, render->width, -render->height);
+  cairo_scale (cr, 1.0, -1.0);
 
   for (guint i = 0; i < render->lines->len; i++)
     {
-      const LineInfo *info = &g_array_index (render->lines, LineInfo, i);
+      const LineInfo *line_info = &g_array_index (render->lines, LineInfo, i);
       const Point *points;
       guint n_points;
 
-      points = point_cache_get_points (render->cache, info->id, &n_points);
-
-      cairo_move_to (cr, 0, 0);
+      points = point_cache_get_points (render->cache, line_info->id, &n_points);
 
-      for (guint j = 0; j < n_points; j++)
+      if (n_points > 0)
         {
-          const Point *p = &points[i];
+          gdouble last_x = points[0].x * render->width;
+          gdouble last_y = points[0].y * render->height;
 
-          cairo_line_to (cr, p->x, p->y);
+          cairo_move_to (cr, last_x, last_y);
 
-          if G_UNLIKELY (j + 1 == n_points)
+          for (guint j = 1; j < n_points; j++)
             {
-              gdk_cairo_set_source_rgba (cr, &info->foreground);
-              cairo_set_line_width (cr, info->line_width / (gdouble)render->height);
-              cairo_stroke_preserve (cr);
-              cairo_line_to (cr, p->x, 0.0);
+              gdouble x = points[j].x * render->width;
+              gdouble y = points[j].y * render->height;
+
+              cairo_curve_to (cr,
+                              last_x + ((x - last_x) / 2),
+                              last_y,
+                              last_x + ((x - last_x) / 2),
+                              y,
+                              x,
+                              y);
+
+              last_x = x;
+              last_y = y;
             }
-        }
 
-      if (n_points > 0 && info->background.alpha > 0)
-        {
-          /*
-           * Close the path and fill if nencessary.
-           */
-          cairo_line_to (cr, 0, 0);
-          gdk_cairo_set_source_rgba (cr, &info->background);
-          cairo_fill (cr);
+          cairo_set_line_width (cr, line_info->line_width);
+          gdk_cairo_set_source_rgba (cr, &line_info->foreground);
+          cairo_stroke (cr);
         }
     }