Don't use margins for events that should not be overridden

libass already does not use the margins for events using \pos. This is
not quite complete: there are other tags that we consider as "not
dialogue", and which should not be overridden. These tags do not use
EVENT_POSITIONED, and thus use the margins, which can mess up rendering.

2 files changed, 14 insertions, 0 deletions

diff --git a/libass/ass_render.c b/libass/ass_render.c
index 97dc119..7085882 100644
--- a/libass/ass_render.c
+++ b/libass/ass_render.c
@@ -245,6 +245,8 @@ static double x2scr_pos(ASS_Renderer *render_priv, double x)
 }
 static double x2scr(ASS_Renderer *render_priv, double x)
 {
+    if (render_priv->state.explicit)
+        return x2scr_pos(render_priv, x);
     return x * render_priv->orig_width_nocrop / render_priv->font_scale_x /
         render_priv->track->PlayResX +
         FFMAX(render_priv->settings.left_margin, 0);
@@ -256,6 +258,8 @@ static double x2scr_pos_scaled(ASS_Renderer *render_priv, double x)
 }
 static double x2scr_scaled(ASS_Renderer *render_priv, double x)
 {
+    if (render_priv->state.explicit)
+        return x2scr_pos_scaled(render_priv, x);
     return x * render_priv->orig_width_nocrop /
         render_priv->track->PlayResX +
         FFMAX(render_priv->settings.left_margin, 0);
@@ -270,6 +274,8 @@ static double y2scr_pos(ASS_Renderer *render_priv, double y)
 }
 static double y2scr(ASS_Renderer *render_priv, double y)
 {
+    if (render_priv->state.explicit)
+        return y2scr_pos(render_priv, y);
     return y * render_priv->orig_height_nocrop /
         render_priv->track->PlayResY +
         FFMAX(render_priv->settings.top_margin, 0);
@@ -278,6 +284,8 @@ static double y2scr(ASS_Renderer *render_priv, double y)
 // the same for toptitles
 static double y2scr_top(ASS_Renderer *render_priv, double y)
 {
+    if (render_priv->state.explicit)
+        return y2scr_pos(render_priv, y);
     if (render_priv->settings.use_margins)
         return y * render_priv->orig_height_nocrop /
             render_priv->track->PlayResY;
@@ -289,6 +297,8 @@ static double y2scr_top(ASS_Renderer *render_priv, double y)
 // the same for subtitles
 static double y2scr_sub(ASS_Renderer *render_priv, double y)
 {
+    if (render_priv->state.explicit)
+        return y2scr_pos(render_priv, y);
     if (render_priv->settings.use_margins)
         return y * render_priv->orig_height_nocrop /
             render_priv->track->PlayResY +
@@ -772,6 +782,8 @@ static ASS_Style *handle_selective_style_overrides(ASS_Renderer *render_priv,
     // script's style that are deemed necessary.
     *new = *rstyle;
 
+    render_priv->state.explicit = explicit;
+
     render_priv->state.apply_font_scale =
         !explicit || !(requested & ASS_OVERRIDE_BIT_SELECTIVE_FONT_SCALE);
 
diff --git a/libass/ass_render.h b/libass/ass_render.h
index d7416e1..8b4698b 100644
--- a/libass/ass_render.h
+++ b/libass/ass_render.h
@@ -275,6 +275,8 @@ typedef struct {
     unsigned overrides;
     // whether to apply font_scale
     int apply_font_scale;
+    // whether this is assumed to be explicitly positioned
+    int explicit;
 
     // used to store RenderContext.style when doing selective style overrides
     ASS_Style override_style_temp_storage;