Map device coordinates onto target surface

The current implementation outputs most touch attributes in device
coordinates. However, the primary use case is to map the input device
onto an area on the screen, needed in particular for multihead setups.
Moreover, the XI2.1 backend works with screen coordinates, creating
an unnecessary discrepancy between backends. This patch adds the basic
transformation layer to the utouch surface, thus serving as the master
point of device-to-surface mapping.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/frame.c b/src/frame.c
index 9c4be97..e722adf 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -205,6 +205,25 @@ int utouch_frame_set_current_slot(utouch_frame_handle fh, int slot)
         return 0;
 }
 
+static void transform_slot(struct utouch_contact *slot,
+                           const struct utouch_surface *s)
+{
+        float fx = (s->mapped_max_x - s->mapped_min_x) / (s->max_x - s->min_x);
+        float fy = (s->mapped_max_y - s->mapped_min_y) / (s->max_y - s->min_y);
+        /* assume clipped view for asymmetrical scaling */
+        float f = MAX(fx, fy);
+
+        slot->x = fx * (slot->x - s->min_x) + s->mapped_min_x;
+        slot->y = fy * (slot->y - s->min_y) + s->mapped_min_y;
+        slot->touch_major *= f;
+        slot->touch_minor *= f;
+        slot->width_major *= f;
+        slot->width_minor *= f;
+        slot->orientation *= M_PI_2 / s->max_orient;
+        slot->pressure *= s->mapped_max_pressure / s->max_pressure;
+        slot->distance *= f;
+}
+
 static void copy_contact(utouch_frame_handle fh,
                          struct utouch_contact *a,
                          const struct utouch_contact *b)
@@ -225,6 +244,8 @@ static void copy_contact(utouch_frame_handle fh,
         a->orientation = b->orientation;
         a->pressure = b->pressure;
         a->distance = b->distance;
+
+        transform_slot(a, s);
 }
 
 static int detect_addrem(const struct utouch_contact *a,