Use event bbox for collision detection

Consider the bounding box of an event for collision detection instead
of only its vertical position and height.  This allows multiple events
per line if they don't overlap.

diff --git a/libass/ass_render.c b/libass/ass_render.c
index 7922825e17a5671f2e024f65a781e48dfc714d73..eea91bb285da9f26769d15c9cb059c25bc0283df 100644 (file)
--- a/libass/ass_render.c
+++ b/libass/ass_render.c
@@ -2988,6 +2988,8 @@ ass_render_event(ASS_Renderer *render_priv, ASS_Event *event,
     memset(event_images, 0, sizeof(*event_images));
     event_images->top = device_y - text_info->lines[0].asc;
     event_images->height = text_info->height;
+    event_images->left = device_x + bbox.xMin + 0.5;
+    event_images->width = bbox.xMax - bbox.xMin + 0.5;
     event_images->detect_collisions = render_priv->state.detect_collisions;
     event_images->shift_direction = (valign == VALIGN_TOP) ? 1 : -1;
     event_images->event = event;
@@ -3204,7 +3206,7 @@ static int cmp_event_layer(const void *p1, const void *p2)
 }
 
 static ASS_RenderPriv *get_render_priv(ASS_Renderer *render_priv,
-                                      ASS_Event *event)
+                                       ASS_Event *event)
 {
     if (!event->render_priv)
         event->render_priv = calloc(1, sizeof(ASS_RenderPriv));
@@ -3218,7 +3220,8 @@ static ASS_RenderPriv *get_render_priv(ASS_Renderer *render_priv,
 
 static int overlap(Segment *s1, Segment *s2)
 {
-    if (s1->a >= s2->b || s2->a >= s1->b)
+    if (s1->a >= s2->b || s2->a >= s1->b ||
+        s1->ha >= s2->hb || s2->ha >= s1->hb)
         return 0;
     return 1;
 }
@@ -3263,18 +3266,22 @@ static int fit_segment(Segment *s, Segment *fixed, int *cnt, int dir)
 
     if (dir == 1)               // move down
         for (i = 0; i < *cnt; ++i) {
-            if (s->b + shift <= fixed[i].a || s->a + shift >= fixed[i].b)
+            if (s->b + shift <= fixed[i].a || s->a + shift >= fixed[i].b ||
+                s->hb <= fixed[i].ha || s->ha >= fixed[i].hb)
                 continue;
             shift = fixed[i].b - s->a;
     } else                      // dir == -1, move up
         for (i = *cnt - 1; i >= 0; --i) {
-            if (s->b + shift <= fixed[i].a || s->a + shift >= fixed[i].b)
+            if (s->b + shift <= fixed[i].a || s->a + shift >= fixed[i].b ||
+                s->hb <= fixed[i].ha || s->ha >= fixed[i].hb)
                 continue;
             shift = fixed[i].a - s->b;
         }
 
     fixed[*cnt].a = s->a + shift;
     fixed[*cnt].b = s->b + shift;
+    fixed[*cnt].ha = s->ha;
+    fixed[*cnt].hb = s->hb;
     (*cnt)++;
     qsort(fixed, *cnt, sizeof(Segment), cmp_segment);
 
@@ -3298,20 +3305,28 @@ fix_collisions(ASS_Renderer *render_priv, EventImages *imgs, int cnt)
             Segment s;
             s.a = priv->top;
             s.b = priv->top + priv->height;
+            s.ha = priv->left;
+            s.hb = priv->left + priv->width;
             if (priv->height != imgs[i].height) {       // no, it's not
                 ass_msg(render_priv->library, MSGL_WARN,
                         "Warning! Event height has changed");
                 priv->top = 0;
                 priv->height = 0;
+                priv->left = 0;
+                priv->width = 0;
             }
             for (j = 0; j < cnt_used; ++j)
                 if (overlap(&s, used + j)) {    // no, it's not
                     priv->top = 0;
                     priv->height = 0;
+                    priv->left = 0;
+                    priv->width = 0;
                 }
             if (priv->height > 0) {     // still a fixed event
                 used[cnt_used].a = priv->top;
                 used[cnt_used].b = priv->top + priv->height;
+                used[cnt_used].ha = priv->left;
+                used[cnt_used].hb = priv->left + priv->width;
                 cnt_used++;
                 shift_event(render_priv, imgs + i, priv->top - imgs[i].top);
             }
@@ -3330,13 +3345,16 @@ fix_collisions(ASS_Renderer *render_priv, EventImages *imgs, int cnt)
             Segment s;
             s.a = imgs[i].top;
             s.b = imgs[i].top + imgs[i].height;
-            shift =
-                fit_segment(&s, used, &cnt_used, imgs[i].shift_direction);
+            s.ha = imgs[i].left;
+            s.hb = imgs[i].left + imgs[i].width;
+            shift = fit_segment(&s, used, &cnt_used, imgs[i].shift_direction);
             if (shift)
                 shift_event(render_priv, imgs + i, shift);
             // make it fixed
             priv->top = imgs[i].top;
             priv->height = imgs[i].height;
+            priv->left = imgs[i].left;
+            priv->width = imgs[i].width;
         }
 
     }

diff --git a/libass/ass_render.h b/libass/ass_render.h
index 6e16db92ec06fb1a264be2ca2c41ef6564ada497..1b07cfe208a23708a4b64f78f086fd00ac2be7ec 100644 (file)
--- a/libass/ass_render.h
+++ b/libass/ass_render.h
@@ -77,7 +77,7 @@ typedef struct {
 // a rendered event
 typedef struct {
     ASS_Image *imgs;
-    int top, height;
+    int top, height, left, width;
     int detect_collisions;
     int shift_direction;
     ASS_Event *event;
@@ -240,7 +240,7 @@ struct ass_renderer {
 };
 
 typedef struct render_priv {
-    int top, height;
+    int top, height, left, width;
     int render_id;
 } RenderPriv;
 
@@ -253,6 +253,7 @@ typedef struct {
 
 typedef struct {
     int a, b;                   // top and height
+    int ha, hb;                 // left and width
 } Segment;
 
 #endif /* LIBASS_RENDER_H */