77 lines
2.3 KiB
C++
77 lines
2.3 KiB
C++
#include <plot/render/vertex_array.hpp>
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#include <plot/gl/api.hpp>
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#include <cstddef>
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namespace plot::render {
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namespace {
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/// Instance data advances one step per instance, never per vertex: both
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/// pipelines draw one quad per instance with corners synthesised from
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/// `gl_VertexID`, so every attribute has a divisor of 1 (core since GL 3.3).
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constexpr gl::GLuint kPerInstance = 1;
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} // namespace
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bool LineVertexArray::create(Status* st) noexcept {
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if (!vao_.create(st)) {
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return false;
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}
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if (!buffer_.create(st)) {
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vao_.reset(); // do not leave a vertex array behind on the failure path
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return false;
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}
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// Attribute pointers capture the bound GL_ARRAY_BUFFER, so bind both first.
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vao_.bind();
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buffer_.bind();
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// Offsets come from the struct, not from counting floats: the layout is the
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// one shaders.hpp declares, and it stays in step with LineInstance.
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vao_.attrib(0u, 2, sizeof(LineInstance), offsetof(LineInstance, x0));
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vao_.attrib(1u, 2, sizeof(LineInstance), offsetof(LineInstance, x1));
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gl::glVertexAttribDivisor(0u, kPerInstance);
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gl::glVertexAttribDivisor(1u, kPerInstance);
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gl::glBindVertexArray(0); // leave the binding as we found it
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return true;
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}
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void LineVertexArray::upload(const f32* interleaved, u32 segments) noexcept {
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// An array that was never created reports nothing to draw, so a caller that
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// ignored create()'s status rasterises nothing instead of stale memory.
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if (interleaved == nullptr || vao_.id() == 0) {
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instances_ = 0;
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return;
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}
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buffer_.upload(interleaved, segments);
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instances_ = segments;
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}
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bool TextVertexArray::create(Status* st) noexcept {
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if (!vao_.create(st)) {
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return false;
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}
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if (!buffer_.create(st)) {
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vao_.reset();
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return false;
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}
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vao_.bind();
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buffer_.bind();
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vao_.attrib(0u, 2, sizeof(TextInstance), offsetof(TextInstance, x));
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vao_.attrib(1u, 2, sizeof(TextInstance), offsetof(TextInstance, u));
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gl::glVertexAttribDivisor(0u, kPerInstance);
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gl::glVertexAttribDivisor(1u, kPerInstance);
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gl::glBindVertexArray(0);
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return true;
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}
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void TextVertexArray::upload(const f32* interleaved, u32 glyphs) noexcept {
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if (interleaved == nullptr || vao_.id() == 0) {
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instances_ = 0;
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return;
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}
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buffer_.upload(interleaved, glyphs);
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instances_ = glyphs;
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}
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} // namespace plot::render
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