compositor: use weston_matrix_transform for weston_output_transform_coordinate

We can greatly simplify weston_output_transform_coordinate now by simply
multiplying by the output matrix and converting the result to fixed point.

This patch fixes zoomed input behaviour on the nested backends (x11,
wayland) which use absolute input coordinates. And probably also
absolute input devices. The patch that broke this was "zoom: Use pixels
instead of GL coordinates".

Signed-off-By: Derek Foreman <derekf@osg.samsung.com>
[Pekka: adjusted coding style and message]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compositor.c

@@ -3947,66 +3947,16 @@ weston_output_transform_coordinate(struct weston_output *output,
 				   wl_fixed_t device_x, wl_fixed_t device_y,
 				   wl_fixed_t *x, wl_fixed_t *y)
 {
-	wl_fixed_t tx, ty;
-	wl_fixed_t width, height;
-	float zoom_scale, zx, zy;
+	struct weston_vector p = { {
+		wl_fixed_to_double(device_x),
+		wl_fixed_to_double(device_y),
+		0.0,
+		1.0 } };
 
-	width = wl_fixed_from_int(output->width * output->current_scale - 1);
-	height = wl_fixed_from_int(output->height * output->current_scale - 1);
+	weston_matrix_transform(&output->matrix, &p);
 
-	switch(output->transform) {
-	case WL_OUTPUT_TRANSFORM_NORMAL:
-	default:
-		tx = device_x;
-		ty = device_y;
-		break;
-	case WL_OUTPUT_TRANSFORM_90:
-		tx = device_y;
-		ty = height - device_x;
-		break;
-	case WL_OUTPUT_TRANSFORM_180:
-		tx = width - device_x;
-		ty = height - device_y;
-		break;
-	case WL_OUTPUT_TRANSFORM_270:
-		tx = width - device_y;
-		ty = device_x;
-		break;
-	case WL_OUTPUT_TRANSFORM_FLIPPED:
-		tx = width - device_x;
-		ty = device_y;
-		break;
-	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
-		tx = width - device_y;
-		ty = height - device_x;
-		break;
-	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
-		tx = device_x;
-		ty = height - device_y;
-		break;
-	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
-		tx = device_y;
-		ty = device_x;
-		break;
-	}
-
-	tx /= output->current_scale;
-	ty /= output->current_scale;
-
-	if (output->zoom.active) {
-		zoom_scale = output->zoom.spring_z.current;
-		zx = (wl_fixed_to_double(tx) * (1.0f - zoom_scale) +
-		      output->width / 2.0f *
-		      (zoom_scale + output->zoom.trans_x));
-		zy = (wl_fixed_to_double(ty) * (1.0f - zoom_scale) +
-		      output->height / 2.0f *
-		      (zoom_scale + output->zoom.trans_y));
-		tx = wl_fixed_from_double(zx);
-		ty = wl_fixed_from_double(zy);
-	}
-
-	*x = tx + wl_fixed_from_int(output->x);
-	*y = ty + wl_fixed_from_int(output->y);
+	*x = wl_fixed_from_double(p.f[0] / p.f[3]);
+	*y = wl_fixed_from_double(p.f[1] / p.f[3]);
 }
 
 static void