Review of the atlas refactor found one Important and three Minor issues:
- Important: TextAtlas::sync called glGetIntegerv before any available() check,
so a host that synced before plot::gl::load() -- which is legal for a public
class Tasks 2 and 8 build backends on -- segfaulted on a null entry point
instead of receiving the Status the interface promises. It now follows the
handle-constructor convention (available(), then the entry point itself) and
reports Unsupported.
- empty() no longer means "a GL name exists": releasing one is a
glDeleteTextures call, so the no-atlas path forgets the atlas and only resets
the texture when there is a table to release it with.
- end_frame's comment still claimed the frame hands back the unpack alignment
init() set, contradicting the code below it and renderer.hpp.
- The orientation case's texel probe mapped the atlas' u along the cell's +v
axis and vice versa, which is a no-op for its two diagonal probes -- so it
could not fail on a transposed UV mapping, and its own comment misstated the
rule. Probes now follow the shader's rule and include an off-diagonal pair.
- The null-glyph path of add_text (and its twin in walk_text_clipped) was
unreached by any case.
Cases: text_atlas_reports_a_status_when_the_entry_points_are_missing,
add_text_skips_a_codepoint_the_backend_cannot_draw.
The text pipeline stages a glyph's rect *origin* per instance and carries the
rect's *size* once per draw, so a backend whose glyphs have differing rect sizes
-- a TrueType packing trimmed to ink, which is Task 8's shape -- would have drawn
every glyph at whichever size it happened to be told, with nothing downstream
able to tell. Make that constraint structural rather than documented:
- TextBackend::cell_uv() declares the one cell size, and the contract (an atlas
is a fixed-cell grid; a proportional face draws its glyphs *into* a uniform
cell instead of trimming each rect to its ink, and why the pipeline needs it)
is stated on the atlas accessors.
- glyph_is_cell() is the check; add_text()/set_cell() declare the cell from the
backend, and the staging path asserts it for every glyph in a debug build.
A release build draws on with the cell it was told, as before.
- Renderer::flush_text() takes u_glyph_uv from the backend, not from the batch,
so the draw's one rect size can never come from whichever glyph was staged
first.
Martino Ferrari