Martino Ferrari
ffc060d6ca
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.
69 lines
2.6 KiB
C++
69 lines
2.6 KiB
C++
#pragma once
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#include <plot/core/color.hpp>
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#include <plot/core/status.hpp>
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#include <plot/gl/handle.hpp>
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#include <plot/math/vec2.hpp>
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namespace plot::render {
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/// Linked line program and its uniform surface.
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///
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/// It owns the `plot::gl::Program` and knows the GLSL pair (shaders.hpp), so no
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/// caller spells out a uniform name that could drift from the shader. Creating
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/// it propagates what the GL layer reports: `ErrorCode::Unsupported` while
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/// `plot::gl::available()` is false, `GLFailure` plus the driver's log when the
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/// GLSL does not compile or link.
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class LineProgram {
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public:
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bool create(Status* st = nullptr) noexcept;
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bool valid() const noexcept { return program_.id() != 0; }
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void bind() const noexcept { program_.use(); }
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/// `u_scale`: data space to pixels.
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void set_scale(Vec2 data_to_px) const noexcept;
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/// `u_offset`: pixel offset added after `set_scale`.
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void set_offset(Vec2 px) const noexcept;
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/// `u_viewport`: render target size in pixels.
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void set_viewport(Vec2 px) const noexcept;
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/// `u_width`: stroke width in pixels.
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void set_width(f32 px) const noexcept;
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/// `u_color`: stroke colour, alpha included.
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void set_color(Color color) const noexcept;
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private:
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gl::Program program_;
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};
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/// Linked text program and its uniform surface. It fails exactly the way
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/// `LineProgram::create()` does, propagating `Unsupported` and `GLFailure`.
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///
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/// `create()` also points the `u_atlas` sampler at texture unit 0, which is the
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/// unit `plot::gl::Texture::bind()` defaults to, and leaves this program bound.
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/// The atlas itself stays with the caller, who owns its lifetime.
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class TextProgram {
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public:
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bool create(Status* st = nullptr) noexcept;
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bool valid() const noexcept { return program_.id() != 0; }
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void bind() const noexcept { program_.use(); }
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/// `u_viewport`: render target size in pixels.
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void set_viewport(Vec2 px) const noexcept;
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/// `u_px_range`: the glyph cell's size on screen, in pixels (width and
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/// height -- a cell need not be square).
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void set_px_range(Vec2 px) const noexcept;
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/// `u_glyph_uv`: the glyph cell's size in the atlas, normalised. It is the
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/// rect every staged glyph is read through, so it is one size per draw -- and
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/// it is the *backend's* (`TextBackend::cell_uv`), never a glyph's, because a
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/// draw may stage glyphs whose origins differ even when their size cannot.
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void set_glyph_uv(Vec2 uv) const noexcept;
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/// `u_tex_size`: atlas size in texels.
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void set_texture_size(Vec2 texels) const noexcept;
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/// `u_color`: tint colour, alpha included.
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void set_color(Color color) const noexcept;
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private:
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gl::Program program_;
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};
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} // namespace plot::render
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