[RFC weston 04/16] zoom: Use pixels instead of GL coordinates

[Derek Foreman]

From: Jason Ekstrand <jason at jlekstrand.net>

Previously, the zoom functions used GL coordinates natively which doesn't
work with the new output matrix calculations.  This changes zoom to work in
pixel coordinates to match the new output matrix format.  This also cleans
up the math in the zoom code substantially.
---
 src/zoom.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/src/zoom.c b/src/zoom.c
index 7553849..cbff2f3 100644
--- a/src/zoom.c
+++ b/src/zoom.c
@@ -106,8 +106,8 @@ zoom_area_center_from_pointer(struct weston_output *output,
 	wl_fixed_t w = wl_fixed_from_int(output->width);
 	wl_fixed_t h = wl_fixed_from_int(output->height);
 
-	*x -= ((((*x - offset_x) / (float) w) - 0.5) * (w * (1.0 - level)));
-	*y -= ((((*y - offset_y) / (float) h) - 0.5) * (h * (1.0 - level)));
+	*x = (*x - offset_x) * level + w / 2;
+	*y = (*y - offset_y) * level + h / 2;
 }
 
 static void
@@ -116,11 +116,9 @@ weston_output_update_zoom_transform(struct weston_output *output)
 	float global_x, global_y;
 	wl_fixed_t x = output->zoom.current.x;
 	wl_fixed_t y = output->zoom.current.y;
-	float trans_min, trans_max;
-	float ratio, level;
+	float level;
 
 	level = output->zoom.spring_z.current;
-	ratio = 1 / level;
 
 	if (!output->zoom.active || level > output->zoom.max_level ||
 	    level == 0.0f)
@@ -132,25 +130,17 @@ weston_output_update_zoom_transform(struct weston_output *output)
 	global_x = wl_fixed_to_double(x);
 	global_y = wl_fixed_to_double(y);
 
-	output->zoom.trans_x =
-		((((global_x - output->x) / output->width) *
-		(level * 2)) - level) * ratio;
-	output->zoom.trans_y =
-		((((global_y - output->y) / output->height) *
-		(level * 2)) - level) * ratio;
-
-	trans_max = level * 2 - level;
-	trans_min = -trans_max;
-
-	/* Clip zoom area to output */
-	if (output->zoom.trans_x > trans_max)
-		output->zoom.trans_x = trans_max;
-	else if (output->zoom.trans_x < trans_min)
-		output->zoom.trans_x = trans_min;
-	if (output->zoom.trans_y > trans_max)
-		output->zoom.trans_y = trans_max;
-	else if (output->zoom.trans_y < trans_min)
-		output->zoom.trans_y = trans_min;
+	output->zoom.trans_x = global_x - (output->x + output->width / 2);
+	output->zoom.trans_y = global_y - (output->y + output->height / 2);
+
+	if (output->zoom.trans_x < 0)
+		output->zoom.trans_x = 0;
+	if (output->zoom.trans_y < 0)
+		output->zoom.trans_y = 0;
+	if (output->zoom.trans_x > level * output->width)
+		output->zoom.trans_x = level * output->width;
+	if (output->zoom.trans_y > level * output->height)
+		output->zoom.trans_y = level * output->height;
 }
 
 static void
-- 
2.1.0