Files
plotter/include/plot/render/vertex_array.hpp
T
Martino Ferrari 3c0e7763ab fix(render): one fence per frame for the vertex ring; two qt6 adapter fixes
The persistent-mapped instance ring had three slots and recorded a fence per
upload, so a frame recycled a slot whose fence was recorded a few draws earlier
*in that same frame*: from the fourth of the demos' nine uploads on, each one
waited on the frame's own work. It is free on a driver that retires draws
promptly (the GLFW host, 1.07 ms/frame) and ~4 ms of the Qt widget's 7.11 ms
under llvmpipe, and it grows with the trace and cursor counts this library
exists for.

* The ring grows to cover a frame's upload count, the frame's write cursor is
  the ring index (so a frame writes 0, 1, 2, ... and never a slot twice), one
  fence is recorded after the frame's last draw, and the only wait is at the
  start of the next frame. A wait that times out, or a slot written with no
  fence ever recorded behind it, drops the store to the orphan path -- the
  treatment a refused fence already had -- so nothing is ever written into
  storage the GPU may still be reading.
* New test-only counters (PLOT_RING_STATS, the PLOT_PYRAMID_COUNT_* pattern:
  free functions, no member, so no consumer's layout changes) pin a frame's
  upload and wait counts. The new tests assert the frame's slot offsets are
  distinct, that the ring grew past its floor to cover the frame, and that a
  frame waits at most once per store -- read from the counters and from
  glClientWaitSync itself.
* qt6: print the unresolved entry-point names before the load-failure branch,
  which used to return first and leave the one failure this widget can have
  reporting nothing but a generic message.
* qt6: the cached pointer anchor is now in logical pixels and a move's delta is
  the logical difference scaled by the DPR in effect, so a scale change between
  two move events (the window dragged onto another monitor mid-drag) is no
  longer a cross-scale jump applied as a pan. The anchor moved into a
  toolkit-free unit (adapters/qt6/qt_pointer.hpp) with its own test.

GLFW demo headless: 1.07 -> 0.73 ms/frame. Qt widget under xvfb/llvmpipe:
7.1 -> 3.8 ms at dpr 1.0, 6.7 -> 3.6 ms at 1.25, with both upload paths still
rendering and the demo's scripted pan/box-zoom checks passing at both scales.
2026-09-28 01:38:09 +02:00

85 lines
3.6 KiB
C++

#pragma once
#include <plot/core/status.hpp>
#include <plot/core/types.hpp>
#include <plot/gl/handle.hpp>
#include <plot/render/buffer.hpp>
namespace plot::render {
/// Vertex array plus instance buffer of the line pipeline.
///
/// The attribute layout is fixed by the line shader (see shaders.hpp): `a_p0` at
/// location 0 and `a_p1` at location 1, two floats each, advancing once per
/// instance. A caller never writes a location, stride or offset; it stages a
/// `LineBatch` and uploads its `data()`.
///
/// The instance buffer may sit behind either transfer strategy (see
/// `UploadMode`). Only the mapped one moves the instances between slots, so
/// `upload()` re-points the attributes when `InstanceStore::epoch()` changes and
/// otherwise leaves them alone; the caller never has to know which path is live.
class LineVertexArray {
public:
/// Creates the vertex array, the instance buffer and the attribute layout.
/// `mode` selects the instance buffer's transfer strategy and defaults to the
/// GL 3.3 baseline; a caller asking for `UploadMode::PersistentMapped` must
/// have checked the context can do it (see `Renderer::init()`).
bool create(Status* st = nullptr, UploadMode mode = UploadMode::Orphan) noexcept;
/// Uploads `segments` instances from interleaved `x0,y0,x1,y1` floats and
/// records how many the next draw should rasterise.
void upload(const f32* interleaved, u32 segments) noexcept;
void bind() const noexcept { vao_.bind(); }
/// Waits, once, for the previous frame's draws to retire the ring before any
/// slot of this frame is written (see `InstanceStore::begin_frame`). False when
/// the store had to drop to the baseline path; the caller reports it.
bool begin_frame() noexcept { return buffer_.begin_frame(); }
/// Records the frame's single fence, behind every draw that read the ring (see
/// `InstanceStore::mark_drawn`); called once per frame, after its last draw.
/// False only when the driver refused the fence: the buffer has then fallen
/// back to the baseline path, and `persistent()` says so from the next call on.
bool mark_drawn() noexcept { return buffer_.mark_drawn(); }
/// True while this array's instance buffer is the mapped ring (see
/// `UploadMode`); a failure that falls back clears it.
bool persistent() const noexcept { return buffer_.persistent(); }
bool valid() const noexcept { return vao_.id() != 0; }
u32 instance_count() const noexcept { return instances_; }
private:
LineBuffer buffer_;
gl::VertexArray vao_;
u32 instances_ = 0;
/// Instance-buffer generation the attribute pointers currently point into.
u32 epoch_ = 0;
};
/// Vertex array plus instance buffer of the text pipeline: `a_pos` at location 0
/// and the glyph's atlas texel origin `a_uv` at location 1, two floats each,
/// advancing once per instance.
class TextVertexArray {
public:
bool create(Status* st = nullptr, UploadMode mode = UploadMode::Orphan) noexcept;
/// Uploads `glyphs` instances from interleaved `x,y,u,v` floats.
void upload(const f32* interleaved, u32 glyphs) noexcept;
void bind() const noexcept { vao_.bind(); }
/// The line pipeline's frame pair, for the text store (see
/// `LineVertexArray::begin_frame` / `mark_drawn`).
bool begin_frame() noexcept { return buffer_.begin_frame(); }
bool mark_drawn() noexcept { return buffer_.mark_drawn(); }
bool persistent() const noexcept { return buffer_.persistent(); }
bool valid() const noexcept { return vao_.id() != 0; }
u32 instance_count() const noexcept { return instances_; }
private:
TextBuffer buffer_;
gl::VertexArray vao_;
u32 instances_ = 0;
u32 epoch_ = 0;
};
} // namespace plot::render