gui_toolkit 0.9.0

Text on DirectWrite (shaping, fallback, bidi, color glyphs, atlas pages) merged with retained drawing (0.7.0).

Retained text

• Glyph runs record into pictures: draw.glyph_run (and text / text_ex on top of it) records shaped glyphs
  (positions from the shaper, subpixel positions, color glyphs) like direct drawing; text is rasterized for the
  picture's raster_scale times the slot's scale (within TEXT_RASTER_TOLERANCE the bitmap is stretched), baked only
  at the picture's own scale. Batches switch between gray and color pages inside a picture as in a frame.
• Staleness per atlas page: a picture remembers the pages its glyphs are on and their epoch (font.Page_Ref,
  Picture.pages); it is .Stale when one of them was reused for other glyphs, or when the rendering settings changed
  (font.atlas_settings_generation), not on every eviction. A replayed picture marks its pages as used by the current
  frame (font.atlas_pages_hold): they are not reused under it. Batch_Bounds.gray / .color: the pages a picture
  batch samples, bound to the replaying context's textures (a picture can be replayed by another context).
• Device loss: the atlas pages upload again whole from their CPU copy (same texture handles); pictures with text
  stay valid and replay without recording (before: the atlas was reset and every picture with text went stale).
• font.Glyph_Image.epoch, font.Page_Ref, font.atlas_pages_hold, font.atlas_settings_generation.
• tests/retained: the scene has color emoji and shaped Arabic (system fallback) next to Latin text, rotated glyphs
  with an emoji; a page reuse with tiny pages makes only the picture on it stale while a picture drawn every frame
  keeps its page and replays exactly; new rendering settings and clear_atlas make a picture stale; after a device
  loss a picture with text replays identically without recording.

Changed (retained text)

• font.set_settings with new rendering settings (subpixel steps, rendering mode, grid fit, color glyphs) forgets the
  cached bitmaps (they were made with the old settings; with other subpixel steps their keys meant other positions)
  and bumps the settings generation.
• Text under a GPU transform at its layout size (rotation, skew) is placed at subpixel positions in local units, as
  text at a uniform scale: a picture recorded at its own scale and replayed rotated draws what direct drawing draws.
• Picture.atlas_generation and font.reset_atlas are gone (font.clear_atlas clears the pages: pictures on them go
  stale).

Fixed (merge)

• font.shape of one right-to-left run of several words (one_run, a layout fragment) left its clusters in visual
  word order: the caret of the logical end and hit testing landed inside the text. Clusters are sorted back to logical
  order (O(n log n)).

Changed

• font is rebuilt on DirectWrite (stb_truetype is gone): faces from the system collection
  (font.load_system, font.has_system_family), files (load_from_file) and memory (load_memory,
  load_from_memory, load_embedded: a custom font file loader, keys never reused). Same Font_Id, metrics,
  text_width, x_from_index, index_from_x, glyph (now outline metrics) and kern (a pair shaped together minus
  apart) as before, so existing callers get fallback and shaping unchanged. See docs/text.md.
• font.Metrics gains x_height, cap_height, underline_offset / _thickness, strike_offset / _thickness.
• draw.text shapes (fallback, ligatures, kerning, bidi in the string's direction) and draws through draw.glyph_run;
  it moved to draw/text.odin with TEXT_RASTER_TOLERANCE. draw.Context.glyphs holds the textures of the atlas
  pages; draw.init / begin_frame / end_frame / destroy call into it (text.odin).
• font.State no longer has pending / pending_pixels / glyphs / fonts: the atlas is in pages uploaded per
  draw context (font.atlas_sync_page).

Added

• Cascades: font.cascade(entries, features, no_system_fallback): per-character fallback through the entries
  (ranges = CSS unicode-range), then the system fallback (IDWriteFontFallback::MapCharacters); clusters stay
  in one face (marks, selectors, ZWJ emoji sequences). OpenType features on every face.
• font.with_simulations (synthetic bold / oblique), font.axes, font.with_variations (variable fonts),
  font.unload, font.valid, font.primary_face, font.set_settings, font.clear_atlas, font.clear_word_cache.
• Shaping: font.shape -> Shaped{glyphs (visual order), clusters (logical order), width} (Glyph_Pos,
  Cluster), Shape_Options{direction, one_run, letter_spacing, word_spacing, justify}, font.measure,
  font.caret_x, font.hit_index, font.shaped_destroy. Words shaped once and cached (sharded, bounded, per-thread
  front cache): measuring is thread-safe without a global lock.
• Analyses: font.bidi_levels, bidi_runs, runs_of_levels, visual_order, reorder (UAX #9);
  font.line_breaks (UAX #14, dictionaries for Thai...); font.maybe_rtl, font.first_strong_rtl.
• Glyph bitmaps: font.glyph_image (grayscale, Settings.subpixel_steps horizontal positions, rendering mode and
  grid fitting from Settings), color glyphs (COLR / CPAL layers composited to RGBA, drawn as images: emoji),
  atlas pages of both kinds with LRU reuse that never clears a page a current frame uses (atlas_begin_frame,
  atlas_remove_user, atlas_page_count, atlas_page_info, atlas_evictions).
• draw.glyph_run(dc, size, pos, color, glyphs) (the painter's entry point), draw.text_ex(..., opts).
• font.Settings / font.DEFAULT_SETTINGS (font.init(s, settings)).
• tests/text: faces, memory faces, fallback (U+2190 in a Latin font), ligatures and kerning, Arabic joining,
  Devanagari, bidi, line breaks, color emoji pixels, atlas stress with a tiny atlas, measuring from 8 threads, and a
  WARP pixel test of drawn text.

Fixed

• A full atlas no longer resets in the middle of a frame (glyphs drawn earlier in the frame showed the glyphs
  rasterized over them: "20 ☒ 7 minutes").