cache: construct cache values only from corresponding keys

This commit forces construction of cache values using only data
available in its companion keys. That ensures logical correctness:
keys are guaranteed to have all the necessary data, and prevents
accidental collisions.

Most fixes of cache logic correspond to minor problem
when rendering is done with double parameter but cache key stores
its approximate fixed-point representation. The only serious problem
is missing scale of clip drawing. Also this commit removes unused
scale parameters from glyph metrics cache key.

Due to missing scale clip shapes that differed only in scale
treated by cache system as identical. That can lead to incorrect reuse
of cached bitmap of different scale instead of correct one.

The only hack left is in glyph metrics cache with its
unicode >= VERTICAL_LOWER_BOUND check.

1 files changed, 19 insertions, 22 deletions

diff --git a/libass/ass_font.c b/libass/ass_font.c
index 6b369aa..2c488cc 100644
--- a/libass/ass_font.c
+++ b/libass/ass_font.c
@@ -224,26 +224,28 @@ static int add_face(ASS_FontSelector *fontsel, ASS_Font *font, uint32_t ch)
 /**
  * \brief Create a new ASS_Font according to "desc" argument
  */
-ASS_Font *ass_font_new(Cache *font_cache, ASS_Library *library,
-                       FT_Library ftlibrary, ASS_FontSelector *fontsel,
-                       ASS_FontDesc *desc)
+ASS_Font *ass_font_new(ASS_Renderer *render_priv, ASS_FontDesc *desc)
 {
-    ASS_Font *font;
-    if (ass_cache_get(font_cache, desc, &font)) {
-        if (font->desc.family)
-            return font;
-        ass_cache_dec_ref(font);
-        return NULL;
-    }
+    ASS_Font *font = ass_cache_get(render_priv->cache.font_cache, desc, render_priv);
     if (!font)
         return NULL;
+    if (font->desc.family)
+        return font;
+    ass_cache_dec_ref(font);
+    return NULL;
+}
+
+size_t ass_font_construct(void *key, void *value, void *priv)
+{
+    ASS_Renderer *render_priv = priv;
+    ASS_FontDesc *desc = key;
+    ASS_Font *font = value;
 
-    font->library = library;
-    font->ftlibrary = ftlibrary;
+    font->library = render_priv->library;
+    font->ftlibrary = render_priv->ftlibrary;
     font->shaper_priv = NULL;
     font->n_faces = 0;
-    ASS_FontDesc *new_desc = ass_cache_key(font);
-    font->desc.family = new_desc->family;
+    font->desc.family = desc->family;
     font->desc.bold = desc->bold;
     font->desc.italic = desc->italic;
     font->desc.vertical = desc->vertical;
@@ -251,15 +253,10 @@ ASS_Font *ass_font_new(Cache *font_cache, ASS_Library *library,
     font->scale_x = font->scale_y = 1.;
     font->size = 0.;
 
-    int error = add_face(fontsel, font, 0);
-    if (error == -1) {
+    int error = add_face(render_priv->fontselect, font, 0);
+    if (error == -1)
         font->desc.family = NULL;
-        ass_cache_commit(font, 1);
-        ass_cache_dec_ref(font);
-        return NULL;
-    }
-    ass_cache_commit(font, 1);
-    return font;
+    return 1;
 }
 
 /**