Use a unified pointer emulation model

The existing kernel MT devices together use a handful of different
pointer emulation strategies, each with its own subtlety. This creates
a problem for grail, which needs to rebuild pointer emulation during
gesture recognition; relying on the correct pointer information to be
available at the right time becomes almost impossible.

This patch implements a common pointer emulation model for grail,
following a strategy recently discussed on LKML. This resolves the
problems stemming from different emulation strategies, and results
in a common pointer emulation experience for all devices.

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

2 files changed, 57 insertions, 4 deletions

diff --git a/src/grail-api.c b/src/grail-api.c
index 9cc94df..f013aa3 100644
--- a/src/grail-api.c
+++ b/src/grail-api.c
@@ -36,10 +36,6 @@ static void tp_event(struct touch_dev *dev,
         struct grail *ge = dev->priv;
         struct grail_impl *x = ge->impl;
         if (ev->type == EV_ABS) {
-                if (ev->code == ABS_X)
-                        x->pointer_x = ev->value;
-                if (ev->code == ABS_Y)
-                        x->pointer_y = ev->value;
                 return;
         }
         if (ev->type == EV_KEY) {
@@ -80,6 +76,60 @@ static void report_up(struct grail_impl *impl, const struct input_event *syn)
         impl->report_status = 0;
 }
 
+#define SYSCALL(call) while (((call) == -1) && (errno == EINTR))
+
+static int getabs(struct input_absinfo *abs, int key, int fd)
+{
+        int rc;
+        SYSCALL(rc = ioctl(fd, EVIOCGABS(key), abs));
+        return rc >= 0;
+}
+
+static void set_emulation_caps(struct grail_impl *impl, int fd)
+{
+        struct touch_caps *emu = &impl->emu;
+        struct input_absinfo info;
+
+        memset(emu, 0, sizeof(*emu));
+
+        if (getabs(&info, ABS_X, fd)) {
+                emu->min_x = info.minimum;
+                emu->max_x = info.maximum;
+        }
+        if (getabs(&info, ABS_Y, fd)) {
+                emu->min_y = info.minimum;
+                emu->max_y = info.maximum;
+        }
+}
+
+static void set_pointer(struct grail_impl *impl)
+{
+        struct touch_dev *dev = &impl->dev;
+        struct touch_caps *caps = &dev->caps;
+        struct touch_caps *emu = &impl->emu;
+        struct touch_frame *frame = &dev->frame;
+        int best_x, best_y, best_d = -1;
+        int i;
+
+        for (i = 0; i < frame->nactive; i++) {
+                struct touch *t = frame->active[i];
+                float u = (t->x - caps->min_x) / (caps->max_x - caps->min_x);
+                float v = (t->y - caps->min_y) / (caps->max_y - caps->min_y);
+                int x = emu->min_x + u * (emu->max_x - emu->min_x);
+                int y = emu->min_y + v * (emu->max_y - emu->min_y);
+                int d = abs(x - impl->pointer_x) + abs(y - impl->pointer_y);
+                if (best_d < 0 || d < best_d) {
+                        best_x = x;
+                        best_y = y;
+                        best_d = d;
+                }
+        }
+        if (best_d >= 0) {
+                impl->pointer_x = best_x;
+                impl->pointer_y = best_y;
+        }
+}
+
 static void handle_abs_events(struct grail *ge, const struct input_event *syn)
 {
         static const int fm_mask = 0x03;
@@ -95,6 +145,7 @@ static void handle_abs_events(struct grail *ge, const struct input_event *syn)
         int ishold = pointer && tap->active && !used_move;
         int istap = gru->tapping.tap == 1 && !used_tap;
 
+        set_pointer(impl);
         if (!impl->pointer_status && pointer) {
                 impl->report_x = impl->pointer_x;
                 impl->report_y = impl->pointer_y;
@@ -175,6 +226,7 @@ int grail_open(struct grail *ge, int fd)
         ret = touch_dev_open(&x->dev, fd);
         if (ret)
                 goto freemem;
+        set_emulation_caps(x, fd);
         x->dev.event = tp_event;
         x->dev.sync = tp_sync;
         x->dev.priv = ge;
diff --git a/src/grail-impl.h b/src/grail-impl.h
index 6093a0f..dc3b425 100644
--- a/src/grail-impl.h
+++ b/src/grail-impl.h
@@ -28,6 +28,7 @@
 
 struct grail_impl {
         struct touch_dev dev;
+        struct touch_caps emu;
         struct evbuf evbuf;
         int filter_abs;
         int pointer_status;