gui_toolkit 0.30.0

Fixes from the review of font, ui and platform (0.26.0). 0.29.0 is the version of another branch (render and draw).

Added

• Grapheme clusters (font/grapheme.odin): font.grapheme_next, grapheme_prev, is_grapheme_boundary, grapheme_count (UAX #29: ZWJ and modifier sequences, flags, tags, keycaps, Hangul, Indic conjuncts, CR LF), a boundary after or before any byte index.
• font.selection_spans / x_spans_of_range: the stretches of a line that a range of characters occupies on screen (several in bidirectional text).
• font.raster_size_limit(s): the largest size glyphs are rasterized at (half an atlas page).
• Colr_Params.surface_limit and work_limit, COLR_MAX_COMPOSITES, COLR_SURFACE_LIMIT, COLR_WORK_*: the bounds of the COLR interpreter's memory and work. gsub_ligate is bounded by GSUB_BUDGET.
• ui.wake_within(s, ms): asks for a wake within ms, keeping the soonest of all the requests. ui.TIMER_KEEP_BUILDS.
• tests/window (windows and messages; needs a desktop, not in CI), tests/ui_robust (in CI), tests/colr/hostile_test.odin (COLR and GSUB tables built by hand), tests/text/grapheme_test.odin.

Changed

• Font_Id carries a generation (slot index in the low 20 bits): the slot of an unloaded font is reused by the next one, so loading and unloading no longer runs out of ids at 65 536; the id of an unloaded font reaches nothing, even once its slot is taken. Ids of the first font in a slot are the same numbers as before. Code that stores Font_Id as an opaque number is not affected; code that computes with it (index into a table by id) must mask with 1 << 20 - 1.
• Caret, arrows, Backspace, Delete, clicks (hit_index), the cut of a toast and the line breaks of wrap_lines work on grapheme clusters, not on code points. Word movement keeps its code point steps.
• platform.poll_events / wait_handle drop only the events they returned before (they used to clear the whole list, losing what a poll of another window had queued for its window).
• platform: the mouse stays captured until the last button is up; a lost capture makes the missing Mouse_Release. A repaint of a window that is not itself polled, arriving while another window of the thread polls, no longer runs on_frame inside that poll: it sets paint_requested (take_paint_request). A move and a menu now get frames (a 16 ms timer, WM_ENTERSIZEMOVE .. WM_EXITSIZEMOVE) as the documentation said.
• platform.open_window returns nil when the system cannot make the window; inject_event of a Close sets is_closed.
• COLR: a glyph over a bound of memory or work is refused (drawn as its outline); PaintComposite nests at most 8 levels; the interpreter draws without the atlas lock. colr_nests_glyph answers "nested" for a graph it cannot read to its end (so that it goes to the interpreter, not to Direct2D), colr_find keeps a base glyph record whose offset is outside the table as an unreadable graph, colr_open accepts any offsets in a v0 header with no records and refuses a table whose base glyph list does not fit; a face with such a table is not drawn in color by Direct2D.
• Atlas: a bitmap bigger than a page makes no page and evicts none; draw.glyph_run caps the rasterization size and stretches the bitmap (text over 1024 px per em was invisible). The Direct2D canvas over 1M pixels is given back after use. Settings.page_size is documented as read by init only.
• ui.menu_item closes the menu when its block ends, not in the middle (the items after the chosen one were built as buttons for a frame). ui.apply_palette keeps the entries an application added to the theme first (Theme.palette_at); theme_add copies its tags. ui.focus_step keeps to the open modal; focused_name is empty for a box not built yet in this build.
• ui.fuzzy_find returns positions in the text it was given (a dotted capital I made them one byte off).
• Timers, scrollbar owners and a virtual list's measured heights of rows that are gone no longer grow without end.

Fixed

• ui.dropdown with an empty list or a selection outside it, ui.tabs with fewer icons than labels, and ui.segmented with no label panicked or drew an infinite rectangle.
• platform.config_dir with %APPDATA% over 259 characters panicked; the clipboard is read up to the size of its block, freed when it cannot be given to the system, and GlobalLock is checked.
• The wake-ups of the caret blink and of a tooltip delay no longer replace each other.