From a7105addcbd924297e077d7203b94139f37224d7 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@openmoko.org>
Date: Fri, 24 Sep 2010 18:24:10 -0300
Subject: [PATCH] Like rotations, shifts can now be accelerated by changing the
 mouse position.

- solidify/overlap.c (do_shift, shift): instead of passing an integer
  direction, pass a floating-point distance
- solidify/overlap.c (scroll_event): weight shifts as well. Closer to the
  circle means faster.
- solidify/style.h (DIST_STEPS): acceleration factor for shifts
---
 solidify/overlap.c | 26 +++++++++++++++++---------
 solidify/style.h   |  1 +
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/solidify/overlap.c b/solidify/overlap.c
index a8c7805..e47e13a 100644
--- a/solidify/overlap.c
+++ b/solidify/overlap.c
@@ -309,14 +309,14 @@ static void rotate(struct matrix *m, double r)
 }
 
 
-static void do_shift(struct matrix *m, int dx, int dy)
+static void do_shift(struct matrix *m, double dx, double dy)
 {
 	m->b[0] += dx;
 	m->b[1] += dy;
 }
 
 
-static void shift(struct matrix *m, int dx, int dy, int dir)
+static void shift(struct matrix *m, int dx, int dy, double dist)
 {
 	/*
 	 * Wheeling "up" in each quadrant shifts in the respective direction,
@@ -328,13 +328,13 @@ static void shift(struct matrix *m, int dx, int dy, int dir)
 	 */
 
 	if (dx > 0 && dy < dx && dy > -dx)
-		do_shift(m, dir, 0);
+		do_shift(m, dist, 0);
 	if (dx < 0 && dy < -dx && dy > dx)
-		do_shift(m, -dir, 0);
+		do_shift(m, -dist, 0);
 	if (dy > 0 && dx < dy && dx > -dy)
-		do_shift(m, 0, dir);
+		do_shift(m, 0, dist);
 	if (dy < 0 && dx < -dy && dx > dy)
-		do_shift(m, 0, dir);	/* exception ! */
+		do_shift(m, 0, dist);	/* exception ! */
 }
 
 
@@ -362,7 +362,7 @@ static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *event,
 	int dy = event->y-sy(s)/2;
 	double r = hypot(dx, dy);
 	double rc = r_center(s);
-	double rs, rot;
+	double rs, rot, dist;
 	int center = r < rc;
 	int osd = osd_proximity(s, dx, dy);
 
@@ -386,17 +386,25 @@ static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *event,
 	rot = (r-rc)/(rs-rc);
 	rot = SLOWEST_ROT*rs*exp(-rot*log(SLOWEST_ROT*rs/FASTEST_ROT));
 
+	/*
+	 * dist stays at 1 from 0...rc/DIST_STEPS, then linearly goes up to
+	 * DIST_STEPS from rc/DIST_STEPS...rc
+	 */
+	dist = r/rc*DIST_STEPS;
+	if (dist < 0)
+		dist = 1;
+
 	switch (event->direction) {
 	case GDK_SCROLL_UP:
 		if (center)
-			shift(&s->a->m, dx, dy, 1);
+			shift(&s->a->m, dx, dy, dist);
 		else
 			rotate(&s->a->m, dx > 0 ? rot : -rot);
 		draw_image(darea, s, osd);
 		break;
 	case GDK_SCROLL_DOWN:
 		if (center)
-			shift(&s->a->m, dx, dy, -1);
+			shift(&s->a->m, dx, dy, -dist);
 		else
 			rotate(&s->a->m, dx > 0 ? -rot : rot);
 		draw_image(darea, s, osd);
diff --git a/solidify/style.h b/solidify/style.h
index e678b15..39085fb 100644
--- a/solidify/style.h
+++ b/solidify/style.h
@@ -25,6 +25,7 @@ extern GdkGC *gc_osd;
 #define	OVERLAP_CENTER_DIV	5	/* fraction of diagonal */
 #define	SLOWEST_ROT		3	/* thrice the half-diagonal */
 #define	FASTEST_ROT		2	/* one pixel in distance of 2 pixels */
+#define	DIST_STEPS		5	/* fastest shift is 5 px/wheel step */
 
 
 void init_style(GdkDrawable *da);