Draw a line from the grab start point to the current one.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 89 insertions, 0 deletions

diff --git a/multitouch.c b/multitouch.c
index 232fbe6..1e44c86 100644
--- a/multitouch.c
+++ b/multitouch.c
@@ -32,6 +32,13 @@ struct touchpoint {
     double x, y;   /* last recorded x/y position */
 };
 
+struct grabpoint {
+    enum TouchState state;
+    uint32_t touchid;
+    double startx, starty; /* x/y of TouchBegin */
+    double x, y;           /* last recorded x/y position */
+};
+
 struct multitouch {
     Display *dpy;
     int screen_no;
@@ -50,11 +57,16 @@ struct multitouch {
 
     cairo_t *cr;
     cairo_t *cr_win;
+    cairo_t *cr_grabs;
     cairo_surface_t *surface;
     cairo_surface_t *surface_win;
+    cairo_surface_t *surface_grabs;
 
     struct touchpoint touches[MAX_TOUCHES];
     int ntouches;
+
+    struct grabpoint grabs[MAX_TOUCHES];
+    size_t ngrabs;
 };
 
 static void expose(struct multitouch *mt, int x1, int y1, int x2, int y2);
@@ -281,10 +293,65 @@ static void paint_touch_end(struct multitouch *mt, XIDeviceEvent *event)
 
 }
 
+static void handle_grabbed_event(struct multitouch *mt, XIDeviceEvent *event)
+{
+    struct grabpoint *grab = NULL;
+    const int radius = 50;
+
+    int i;
+    for (i = 0; i < mt->ngrabs; i++)
+    {
+        grab = &mt->grabs[i];
+        if (event->evtype == XI_TouchBegin && grab->state == TSTATE_END)
+        {
+                grab->state = TSTATE_BEGIN;
+                grab->touchid = event->detail;
+                grab->startx = event->event_x;
+                grab->starty = event->event_y;
+                break;
+        } else if (event->evtype != XI_TouchBegin) {
+            if (grab->state != TSTATE_END && grab->touchid == event->detail)
+                break;
+        }
+    }
+    if (!grab) {
+        error("oops, touchpoint for %d (touchid %d) not found\n",
+                event->evtype, event->detail);
+        return;
+    }
+
+    /* clear the whole area */
+    cairo_save(mt->cr_grabs);
+    cairo_save(mt->cr_grabs);
+    cairo_set_operator(mt->cr_grabs, CAIRO_OPERATOR_CLEAR);
+    cairo_paint(mt->cr_grabs);
+    cairo_restore(mt->cr_grabs);
+
+    /* draw starting circle */
+    cairo_set_source_rgba(mt->cr_grabs, 0, 0, 1, 1);
+    cairo_arc(mt->cr_grabs, grab->startx, grab->starty, radius, 0, 2 * M_PI);
+    cairo_stroke(mt->cr_grabs);
+
+    grab->x = event->event_x;
+    grab->y = event->event_y;
+
+    /* draw line to current point */
+    cairo_set_source_rgba(mt->cr_grabs, 0, 0, 1, 1);
+    cairo_move_to(mt->cr_grabs, grab->startx, grab->starty);
+    cairo_line_to(mt->cr_grabs, grab->x, grab->y);
+    cairo_stroke(mt->cr_grabs);
+    cairo_restore(mt->cr_grabs);
+
+    expose(mt, grab->startx, grab->starty, grab->x, grab->y);
+}
+
 static void paint_event(struct multitouch *mt, XIDeviceEvent *event)
 {
     if (event->event == mt->toolbar)
+    {
+        handle_grabbed_event(mt, event);
         return;
+    }
 
     switch(event->evtype)
     {
@@ -313,6 +380,21 @@ static int init_cairo(struct multitouch *mt)
 
     mt->cr_win = cr;
 
+    /* grab drawing backbuffer */
+    surface = cairo_surface_create_similar(surface,
+                                           CAIRO_CONTENT_COLOR_ALPHA,
+                                           mt->width, mt->height);
+    if (!surface)
+        return error("Failed to create cairo surface\n");
+
+    mt->surface_grabs = surface;
+
+    cr = cairo_create(surface);
+    if (!cr)
+        return error("Failed to create cairo context\n");
+
+    mt->cr_grabs = cr;
+
     /* backbuffer */
     surface = cairo_surface_create_similar(surface,
                                            CAIRO_CONTENT_COLOR_ALPHA,
@@ -345,6 +427,12 @@ static void expose(struct multitouch *mt, int x1, int y1, int x2, int y2)
 {
     cairo_set_source_surface(mt->cr_win, mt->surface, 0, 0);
     cairo_paint(mt->cr_win);
+
+    cairo_save(mt->cr_win);
+    cairo_set_source_surface(mt->cr_win, mt->surface_grabs, 0, 0);
+    cairo_mask_surface(mt->cr_win, mt->surface_grabs, 0, 0);
+    cairo_restore(mt->cr_win);
+
 }
 
 static int main_loop(struct multitouch *mt)
@@ -390,6 +478,7 @@ static void init(struct multitouch *mt)
     memset(mt, 0, sizeof(*mt));
 
     mt->ntouches = MAX_TOUCHES;
+    mt->ngrabs = MAX_TOUCHES;
 }
 
 int main(int argc, char **argv)